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Sample records for vo2 peak increased

  1. Lvad pump speed increase is associated with increased peak exercise cardiac output and vo2, postponed anaerobic threshold and improved ventilatory efficiency.

    Science.gov (United States)

    Vignati, Carlo; Apostolo, Anna; Cattadori, Gaia; Farina, Stefania; Del Torto, Alberico; Scuri, Silvia; Gerosa, Gino; Bottio, Tomaso; Tarzia, Vincenzo; Bejko, Jonida; Sisillo, Erminio; Nicoli, Flavia; Sciomer, Susanna; Alamanni, Francesco; Paolillo, Stefania; Agostoni, Piergiuseppe

    2017-03-01

    Peak exercise cardiac output (CO) increase is associated with an increase of peak oxygen uptake (VO2), provided that arteriovenous O2 difference [Δ(Ca-Cv)O2] does not decrease. At anaerobic threshold, VO2, is related to CO. We tested the hypothesis that, in heart failure (HF) patients with left ventricular assistance device (LVAD), an acute increase of CO obtained through changes in LVAD pump speed is associated with peak exercise and anaerobic threshold VO2 increase. Fifteen of 20 patients bearing LVAD (Jarvik 2000) enrolled in the study successfully performed peak exercise evaluation. All patients had severe HF as shown by clinical evaluation, laboratory tests, echocardiography, spirometry with alveolar-capillary diffusion, and maximal cardiopulmonary exercise testing (CPET). CPETs with non-invasive CO measurements at rest and peak exercise were done on 2days at LVAD pump speed set randomly at 2 and 4. Increasing LVAD pump speed from 2 to 4 increased CO from 3.4±0.9 to 3.8±1.0L/min (ΔCO 0.4±0.6L/min, p=0.04) and from 5.3±1.3 to 5.9±1.4L/min (ΔCO 0.6±0.7L/min, pincreased from 788±169 to 841±152mL/min (ΔVO2 52±76mL/min, p=0.01) and from 568±116 to 619±124mL/min (ΔVO2 69±96mL/min, p=0.02) at peak exercise and at anaerobic threshold, respectively. Δ(Ca-Cv)O2 did not change significantly, while ventilatory efficiency improved (VE/VCO2 slope from 39.9±5.4 to 34.9±8.3, ΔVE/VCO2 -5.0±6.4, pincrease in CO with a higher LVAD pump speed is associated with increased peak VO2, postponed anaerobic threshold, and improved ventilatory efficiency. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  2. Low-intensity training increases peak arm VO2 by enhancing both convective and diffusive O2 delivery

    DEFF Research Database (Denmark)

    Boushel, R; Ara, I; Gnaiger, E;

    2014-01-01

    It is an ongoing discussion the extent to which oxygen delivery and oxygen extraction contribute to an increased muscle oxygen uptake during dynamic exercise. It has been proposed that local muscle factors including the capillary bed and mitochondrial oxidative capacity play a large role in prolo...

  3. Expression of VO2peak in Children and Youth, with Special Reference to Allometric Scaling.

    Science.gov (United States)

    Loftin, Mark; Sothern, Melinda; Abe, Takashi; Bonis, Marc

    2016-10-01

    The aim of this review was to highlight research that has focused on examining expressions of peak oxygen uptake (VO2peak) in children and youth, with special reference to allometric scaling. VO2peak is considered the highest VO2 during an increasing workload treadmill or bicycle ergometer test until volitional termination. We have reviewed scholarly works identified from PubMed, One Search, EBSCOhost and Google Scholar that examined VO2peak in absolute units (L·min(-1)), relative units [body mass, fat-free mass (FFM)], and allometric expressions [mass, height, lean body mass (LBM) or LBM of the legs raised to a power function] through July 2015. Often, the objective of measuring VO2peak is to evaluate cardiorespiratory function and fitness level. Since body size (body mass and height) frequently vary greatly in children and youth, expressing VO2peak in dimensionless units is often inappropriate for comparative or explanatory purposes. Consequently, expressing VO2peak in allometric units has gained increased research attention over the past 2 decades. In our review, scaling mass was the most frequent variable employed, with coefficients ranging from approximately 0.30 to over 1.0. The wide variance is probably due to several factors, including mass, height, LBM, sex, age, physical training, and small sample size. In summary, we recommend that since skeletal muscle is paramount for human locomotion, an allometric expression of VO2peak relative to LBM is the best expression of VO2peak in children and youth.

  4. Effects of muscle electrical stimulation on peak VO2 in cardiac transplant patients.

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    Vaquero, A F; Chicharro, J L; Gil, L; Ruiz, M P; Sánchez, V; Lucía, A; Urrea, S; Gómez, M A

    1998-07-01

    Peak oxygen consumption (peak VO2) has become a critical component in the evaluation of heart transplant recipients (HTR). In these patients, peak VO2 remains low after cardiac transplantation mainly because of persisting peripheral limitations in the working muscles. Muscular electrical stimulation, on the other hand, has been shown to enhance the oxidative capacity of healthy muscle. It was the purpose of our investigation to study the effects of ES on the peak VO2 of HTR. Fourteen (11 males and 3 females) HTR (age: 57+/-7yr, mean +/- SD; height: 163+/-7 cm, weight: 70.5+/-8.6 kg) were selected as subjects and each of them was randomly assigned to one of two groups: (a) group EXP (n = 7), receiving electrical stimulation on both quadriceps muscles during a period of 8 weeks, and (b) group CONT (n = 7), not receiving electrical stimulation. Before (PRE) and after (POST) the aforementioned 8-week period, respectively, all the subjects performed a cardiopulmonary exercise test (ramp protocol) on a cycle ergometer for peak VO2 determination. PRE values of peak VO2 were similar in both groups (17.1+/-2.0 vs 16.9+/-3.8ml x kg(-1) x min(-1) in EXP and CONT, respectively). However, peak values of VO2 significantly increased in EXP (p < 0.05) after the period of electrical stimulation (POST peak VO2: 18.7+/-2.0ml x kg(-1)), whereas no change was observed in CONT (POST peak VO2: 16.2+/-3.2 ml x kg(-1) x min(-1)). In conclusion, electrical stimulation could therefore be used to improve the functional capacity of HTR, and might be included in the rehabilitation programs of this population group.

  5. Contributions of Astronauts Aerobic Exercise Intensity and Time on Change in VO2peak during Spaceflight

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    Downs, Meghan E.; Buxton, Roxanne; Moore, Alan; Ploutz-Snyder, Robert; Ploutz-Snyder, Lori

    2014-01-01

    There is considerable variability among astronauts with respect to changes in maximal aerobic capacity (VO2peak) during International Space Station (ISS) missions, ranging from a 5% increase to 30% decline. Individual differences may be due to in-flight aerobic exercise time and intensity. PURPOSE: To evaluate the effects of in-flight aerobic exercise time and intensity on change in VO2peak during ISS missions. METHODS: Astronauts (N=11) performed peak cycle tests approx 60 days before flight (L-60), on flight day (FD) approx 14, and every approx 30 days thereafter. Metabolic gas analysis and heart rate (HR) were measured continuously during the test using the portable pulmonary function system. HR and duration of each in-flight cycle ergometer and treadmill (TM) session were recorded and averaged in time segments corresponding to each peak test. Mixed effects linear regression with exercise mode (TM or cycle) as a categorical variable was used to assess the contributions of exercise intensity (%time >70% peak HR or %time >90% peak HR) and time (min/wk), adjusted for body weight, on %change in VO2peak during the mission, and incorporating the repeated-measures experimental design. RESULTS: 110 observations were included in the model (4-6 peak cycle tests per astronaut, 2 exercise devices). VO2peak was reduced from preflight throughout the mission (FD14: 13+/-13% and FD 105: 8+/-10%). Exercise intensity (%peak HR: FD14=66+/-14; FD105=75+/-8) and time (min/wk: FD14=82+/-46; FD105=158+/-40) increased during flight. The models showed main effects for exercise time and intensity with no interactions between time, intensity, and device (70% peak HR: time [z-score=2.39; P=0.017], intensity [z-score=3.51; P=0.000]; 90% peak HR: time [zscore= 3.31; P=0.001], intensity [z-score=2.24; P=0.025]). CONCLUSION: Exercise time and intensity independently contribute to %change in VO2peak during ISS missions, indicating that there are minimal values for exercise time and intensity

  6. Predicting VO2peak from Submaximal- and Peak Exercise Models: The HUNT 3 Fitness Study, Norway.

    Directory of Open Access Journals (Sweden)

    Henrik Loe

    Full Text Available Peak oxygen uptake (VO2peak is seldom assessed in health care settings although being inversely linked to cardiovascular risk and all-cause mortality. The aim of this study was to develop VO2peak prediction models for men and women based on directly measured VO2peak from a large healthy population.VO2peak prediction models based on submaximal- and peak performance treadmill work were derived from multiple regression analysis. 4637 healthy men and women aged 20-90 years were included. Data splitting was used to generate validation and cross-validation samples.The accuracy for the peak performance models were 10.5% (SEE = 4.63 mL⋅kg(-1⋅min(-1 and 11.5% (SEE = 4.11 mL⋅kg(-1⋅min(-1 for men and women, respectively, with 75% and 72% of the variance explained. For the submaximal performance models accuracy were 14.1% (SEE = 6.24 mL⋅kg(-1⋅min(-1 and 14.4% (SEE = 5.17 mL⋅kg(-1⋅min(-1 for men and women, respectively, with 55% and 56% of the variance explained. The validation and cross-validation samples displayed SEE and variance explained in agreement with the total sample. Cross-classification between measured and predicted VO2peak accurately classified 91% of the participants within the correct or nearest quintile of measured VO2peak.Judicious use of the exercise prediction models presented in this study offers valuable information in providing a fairly accurate assessment of VO2peak, which may be beneficial for risk stratification in health care settings.

  7. Predictors of VO2Peak in children age 6- to 7-years-old

    DEFF Research Database (Denmark)

    Dencker, Magnus; Hermansen, Bianca; Bugge, Anna

    2011-01-01

    This study investigated the predictors of aerobic fitness (VO2PEAK) in young children on a population-base. Participants were 436 children (229 boys and 207 girls) aged 6.7 ± 0.4 yrs. VO2PEAK was measured during a maximal treadmill exercise test. Physical activity was assessed by accelerometers....... Total body fat and total fat free mass were estimated from skinfold measurements. Regression analyses indicated that significant predictors for VO2PEAK per kilogram body mass were total body fat, maximal heart rate, sex, and age. Physical activity explained an additional 4-7%. Further analyses showed...... the main contributing factors for absolute values of VO2PEAK were fat free mass, maximal heart rate, sex, and age. Physical activity explained an additional 3-6%....

  8. The relationship among HRpeak, RERpeak, and VO2peak during treadmill testing in girls.

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    Peyer, Karissa; Pivarnik, James M; Coe, Dawn Podulka

    2011-12-01

    Clear criteria for maximal oxygen consumption (VO2max) determination in youth are not available, and no studies have examined this issue in girls. Our purpose was to determine whether different peak heart rate (HRpeak) and peak respiratory exchange ratio (RERpeak) cut points affect girls' (N = 453; M age = 13.3 years, SD = .1) VO2max during a maximal treadmill test. A multivariate analysis of variance revealed VO2max (ml kg(-1) min(-1) differed significantly among HRpeak, 180-189 b min(-1) = 34 (SD = .8), 190-194 bmin(-1) = 35 (SD = .9), 195-199 b min(-1) = 38 (SD = .8), 200-204 b min(-1) = 40 ml kg1 x min(-1) (SD = .8), and > or = 205 bmin(-1) = 42 ml kg1 x min(-1) (SD = .7) but not RERpeak. In studies where evidence of a VO2 plateau was examined, peak oxygen consumption (VO2peak) did not differ between plateau and no-plateau groups. Although our results suggest the association between lower VO2peak and lower peak heart rate is a true cardiovascular limit to aerobic energy production, we cannot rule out participant effort.

  9. Body fat, abdominal fat and body fat distribution related to VO(2PEAK) in young children

    DEFF Research Database (Denmark)

    Dencker, Magnus; Wollmer, Per; Karlsson, Magnus K

    2011-01-01

    -based level. Methods. Cross-sectional study of 225 children (128 boys and 97 girls) aged 8-11 years, recruited from a population-based cohort. Total lean body mass (LBM), total fat mass (TBF), and abdominal fat mass (AFM) were measured by dual-energy x-ray absorptiometry. Body fat was also calculated...... as a percentage of body mass (BF%) and body fat distribution as AFM/TBF. VO(2PEAK) was assessed by indirect calorimetry during maximal exercise test. Results. Significant relationships existed between body fat measurements and VO(2PEAK) in both boys and girls, with Pearson correlation coefficients for absolute...... values of VO(2PEAK) (0.22-0.36, Pmass (-0.38 - -0.70, P...

  10. Assessment of measurement properties of peak VO2 in children with pulmonary arterial hypertension

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    Cappelleri Joseph C

    2012-09-01

    Full Text Available Abstract Background The 6-minute walk test evaluates the effect of pharmacologic intervention in adults with pulmonary arterial hypertension (PAH but, for reasons of compliance or reliability, may not be appropriate for children at all ages. Thus, peak oxygen consumption (VO2, maximal exercise test was used instead in a pediatric PAH trial (STARTS-1 to evaluate pharmacologic intervention with sildenafil. This was the first large placebo-controlled trial to use the peak VO2 endpoint in this population. Our working hypothesis was that, as with other populations, percentage changes in peak VO2 in pediatric patients with PAH are reliable and are associated with changes in other clinical endpoints. Methods Using data from the subpopulation of 106 patients who were developmentally and physically able to perform exercise testing, all of whom were World Health Organization Functional Class (WHO FC I, II, or III, reliability was assessed using the intraclass correlation coefficient and Bland-Altman plot on screening and baseline data. Relationships between percentage change in peak VO2 from baseline to end of treatment and other endpoints were evaluated using correlation coefficients and regression analyses. Results The intraclass correlation was 0.79 between screening and baseline peak VO2, an agreement that was supported by the Bland-Altman plot. Percentage change in peak VO2 correlated well (r ≥0.40 and showed responsiveness to a physician global assessment of change and with change in WHO FC (for baseline classes I and III. Percentage change in peak VO2 did not correlate with change in the Family Cohesion of the Child Health Questionnaire (r = 0.04 or with a subject global assessment of change (r = 0.12. The latter may have been influenced by child and parental-proxy response and instrument administration. Conclusion In pediatric PAH patients who are developmentally and physically able to perform exercise testing, peak VO2 measurements

  11. Peak treadmill running velocity during the VO2 max test predicts running performance.

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    Noakes, T D; Myburgh, K H; Schall, R

    1990-01-01

    Twenty specialist marathon runners and 23 specialist ultra-marathon runners underwent maximal exercise testing to determine the relative value of maximum oxygen consumption (VO2max), peak treadmill running velocity, running velocity at the lactate turnpoint, VO2 at 16 km h-1, % VO2max at 16 km h-1, and running time in other races, for predicting performance in races of 10-90 km. Race time at 10 or 21.1 km was the best predictor of performance at 42.2 km in specialist marathon runners and at 42.2 and 90 km in specialist ultra-marathon runners (r = 0.91-0.97). Peak treadmill running velocity was the best laboratory-measured predictor of performance (r = -0.88(-)-0.94) at all distances in ultra-marathon specialists and at all distances except 42.2 km in marathon specialists. Other predictive variables were running velocity at the lactate turnpoint (r = -0.80(-)-0.92); % VO2max at 16 km h-1 (r = 0.76-0.90) and VO2max (r = 0.55(-)-0.86). Peak blood lactate concentrations (r = 0.68-0.71) and VO2 at 16 km h-1 (r = 0.10-0.61) were less good predictors. These data indicate: (i) that in groups of trained long distance runners, the physiological factors that determine success in races of 10-90 km are the same; thus there may not be variables that predict success uniquely in either 10 km, marathon or ultra-marathon runners, and (ii) that peak treadmill running velocity is at least as good a predictor of running performance as is the lactate turnpoint. Factors that determine the peak treadmill running velocity are not known but are not likely to be related to maximum rates of muscle oxygen utilization.

  12. Predictors of VO2Peak in children age 6- to 7-years-old

    DEFF Research Database (Denmark)

    Dencker, Magnus; Hermansen, Bianca; Bugge, Anna

    2011-01-01

    . Total body fat and total fat free mass were estimated from skinfold measurements. Regression analyses indicated that significant predictors for VO2PEAK per kilogram body mass were total body fat, maximal heart rate, sex, and age. Physical activity explained an additional 4-7%. Further analyses showed...

  13. Maintained peak leg and pulmonary VO2 despite substantial reduction in muscle mitochondrial capacity.

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    Boushel, R; Gnaiger, E; Larsen, F J; Helge, J W; González-Alonso, J; Ara, I; Munch-Andersen, T; van Hall, G; Søndergaard, H; Saltin, B; Calbet, J A L

    2015-12-01

    We recently reported the circulatory and muscle oxidative capacities of the arm after prolonged low-intensity skiing in the arctic (Boushel et al., 2014). In the present study, leg VO2 was measured by the Fick method during leg cycling while muscle mitochondrial capacity was examined on a biopsy of the vastus lateralis in healthy volunteers (7 male, 2 female) before and after 42 days of skiing at 60% HR max. Peak pulmonary VO2 (3.52 ± 0.18 L.min(-1) pre vs 3.52 ± 0.19 post) and VO2 across the leg (2.8 ± 0.4L.min(-1) pre vs 3.0 ± 0.2 post) were unchanged after the ski journey. Peak leg O2 delivery (3.6 ± 0.2 L.min(-1) pre vs 3.8 ± 0.4 post), O2 extraction (82 ± 1% pre vs 83 ± 1 post), and muscle capillaries per mm(2) (576 ± 17 pre vs 612 ± 28 post) were also unchanged; however, leg muscle mitochondrial OXPHOS capacity was reduced (90 ± 3 pmol.sec(-1) .mg(-1) pre vs 70 ± 2 post, P VO2 can be sustained with a substantial reduction in mitochondrial OXPHOS capacity. This is achieved at a similar O2 delivery and a higher relative ADP-stimulated mitochondrial respiration at a higher mitochondrial p50. These findings support the concept that muscle mitochondrial respiration is submaximal at VO2max , and that mitochondrial volume can be downregulated by chronic energy demand.

  14. COMPARISON OF VO2 PEAK DURING TREADMILL AND CYCLE ERGOMETRY IN SEVERELY OVERWEIGHT YOUTH

    Directory of Open Access Journals (Sweden)

    John Udall

    2004-12-01

    Full Text Available The purpose of this study was to compare peak cardiorespiratory parameters during treadmill and cycle ergometry in severely overweight youth. Twenty-one participants from the Committed to Kids Pediatric Weight Management program at the Louisiana State University Health Sciences Center volunteered. Participants completed peak treadmill and cycle ergometer tests on separate days. In order to examine reliability, six subjects completed a second treadmill test and seven subjects a second cycle test. Physical characteristics included the following: Age (yrs 12.5 ¡À 2.8; Body weight (BW (kg 78.5 ¡À 27.0, Height (m 1.56 ¡À 0.13; and % fat 42.8 ¡À 7.5. No statistical significant differences (p ¡Ü 0.05 were found between treadmill and cycle peak tests. Treadmill VO2 peak (l¡¤min-1 averaged 1.57 ¡À 0.40 and cycle 1.46 ¡À 0.30 and VO2 peak relative to BW 21.5 ¡À 4.1 and 20.3 ¡À 5.5 for treadmill and cycle ergometry, respectively. Therefore treadmill values were 7.0% and 5.6% higher than cycle values. In normal weight or children and adolescents at risk for overweight, treadmill values typically average from 7 to 12% higher than cycle values. Reliability of VO2 peak as indicated by intraclass correlation coefficients ranged from 0.70 to 0.96 for a single or repeated tests. Intra individual variability averaged 0.5% for VO2 peak (l¡¤min-1 during treadmill ergometry and 5.7% for cycle ergometry. Also, standard errors of measurement were low (40 to 90 ml min or 1.0 to 1.7 ml.kg-1. min-1 for the peak treadmill or cycle tests. In summary, our data suggest that both treadmill and cycle ergometry provide reliable methods for determining VO2 peak in overweight youth.

  15. Evaluation of cardiorespiratory fitness using three field tests in obese adolescents: validity, sensitivity and prediction of peak VO2.

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    Quinart, Sylvain; Mougin, Fabienne; Simon-Rigaud, Marie-Laure; Nicolet-Guénat, Marie; Nègre, Véronique; Regnard, Jacques

    2014-09-01

    Evaluation of cardiorespiratory fitness in obese adolescents is necessary to develop personalised retraining programmes. We aimed to measure cardiorespiratory fitness using 3 field tests, and to evaluate their validity and sensitivity compared to values obtained by laboratory tests. Longitudinal interventional study in obese adolescents admitted to a rehabilitation centre for a 9-month programme of obesity management. A 12-min walk/run test, an adapted 20 m shuttle walk-run test (starting speed 4 km h(-1), increments of 0.5 km h(-1)min(-1)) and a 4-level submaximal cycle ergometer test were performed to estimate respectively distance covered in 12 min, maximum speed and maximal aerobic power. Thirty adolescents aged 14.2 ± 1.6 years were included. After 9 months intervention, we observed a significant reduction in body mass index, and an increase in peak VO2 and field test results. We observed significant correlations between pre- and post-intervention values of peak VO2 and distance covered in 12 min (r=0.70 pre; r=0.82 post), maximum speed (r=0.80 pre; r=0.83 post) and maximal aerobic power (r=0.71 pre; r=0.84 post). Multiple linear regression made it possible to estimate peak VO2 based on results from the 3 field tests using prediction equations specific to a population of obese adolescents. These field tests, including the adapted 20 m shuttle walk-run test, adequately assess cardiorespiratory fitness in obese adolescents, and are sensitive to changes over time. Predictive equations including BMI are useful in clinical practice to predict peak VO2 in these patients. Copyright © 2013 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

  16. PREDICTION OF VO2PEAK USING OMNI RATINGS OF PERCEIVED EXERTION FROM A SUBMAXIMAL CYCLE EXERCISE TEST

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    Mays, Ryan J.; Goss, Fredric L.; Nagle-Stilley, Elizabeth F.; Gallagher, Michael; Schafer, Mark A.; Kim, Kevin H.; Robertson, Robert J.

    2015-01-01

    Summary The primary aim of this study was to develop statistical models to predict peak oxygen consumption (VO2peak) using OMNI Ratings of Perceived Exertion measured during submaximal cycle ergometry. Men (mean ± standard error: 20.90 ± 0.42 yrs) and women (21.59 ± 0.49 yrs) participants (n = 81) completed a load-incremented maximal cycle ergometer exercise test. Simultaneous multiple linear regression was used to develop separate VO2peak statistical models using submaximal ratings of perceived exertion for the overall body, legs, and chest/breathing as predictor variables. VO2peak (L·min−1) predicted for men and women from ratings of perceived exertion for the overall body (3.02 ± 0.06; 2.03 ± 0.04), legs (3.02 ± 0.06; 2.04 ± 0.04) and chest/breathing (3.02 ± 0.05; 2.03 ± 0.03) were similar with measured VO2peak (3.02 ± 0.10; 2.03 ± 0.06, ps > .05). Statistical models based on submaximal OMNI Ratings of Perceived Exertion provide an easily administered and accurate method to predict VO2peak. PMID:25068750

  17. Effects of ATP-induced leg vasodilation on VO2 peak and leg O2 extraction during maximal exercise in humans

    DEFF Research Database (Denmark)

    Calbet, J A L; Lundby, C; Sander, M

    2006-01-01

    During maximal whole body exercise VO2 peak is limited by O2 delivery. In turn, it is though that blood flow at near-maximal exercise must be restrained by the sympathetic nervous system to maintain mean arterial pressure. To determine whether enhancing vasodilation across the leg results in higher...... O2 delivery and leg VO2 during near-maximal and maximal exercise in humans, seven men performed two maximal incremental exercise tests on the cycle ergometer. In random order, one test was performed with and one without (control exercise) infusion of ATP (8 mg in 1 ml of isotonic saline solution......) into the right femoral artery at a rate of 80 microg.kg body mass-1.min-1. During near-maximal exercise (92% of VO2 peak), the infusion of ATP increased leg vascular conductance (+43%, P...

  18. Validity of a taekwondo specific test to measure vo2peak and the heart rate deflection point.

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    Sant'Ana, Jader; Franchini, Emerson; Murias, Juan; Diefenthaeler, Fernando

    2017-07-19

    This study investigated whether the progressive specific taekwondo test (PSTT) is a valid test to measure peak oxygen consumption (VO2PEAK) and the heart rate deflection point (HRDP) in taekwondo athletes. Eighteen male black belt athletes (25.3 ± 4.8 years; 8.2 ± 4.7 years of practice; 171.8 ± 4.7 cm; 76.1 ± 8.2 kg, and 13.1 ± 2.9% body fat) involved in regional and national level competitions performed the PSTT and an incremental treadmill test (IT). The following variables were analyzed: VO2PEAK, respiratory quotient, oxygen consumption at the HRDP (VO2HRDP), peak heart rate (HRPEAK), HRDP, and peak post-test blood lactate concentration. During the PSTT the peak kick frequency (FKPEAK) and kick frequency at the HRDP (FKHRDP) was also obtained. During the IT, the peak speed and the speed at the HRDP were identified by the DMAX method (the first and last points of the curve were connected by a straight line and the most distant point of the curve to the line was considered as the heart rate deflection point). No differences were observed between VO2 responses during the PSTT and IT (p>0.05). VO2PEAK and VO2HRDP presented bias (1.3 ml·kg·min and -0.78 ml·kg·min, respectively) derived from the Bland & Altman plots, with the 95% limits of agreement indicating that the differences between the two measures can reach 11% for VO2PEAK and 17% for VO2HRDP. The PSTT is a valid tool to assess aerobic power and capacity in taekwondo athletes based on direct comparisons to a treadmill test. The test presents more specific variables for the assessment and training of taekwondo athletes, such as FKPEAK and FKHRDP, which can be used to determine and control the effects of training and help coaches in prescribing training programs.

  19. Comparing the effects of two in-flight aerobic exercise protocols on standing heart rates and VO(2peak) before and after space flight

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    Siconolfi, S. F.; Charles, J. B.; Moore, A. D. Jr; Barrows, L. H.

    1994-01-01

    The effects of regular aerobic exercise on orthostatic tolerance have been the subject of a long-standing controversy that will influence the use of exercise during space flight. To examine these effects, astronauts performed continuous (CE) aerobic exercise (n = 8), interval (IE) aerobic exercise (n = 4), or no (NE) exercise (n = 5) during flights of 7 to 11 days. Heart rate (HR) responses to an orthostatic challenge (stand test) were measured 10 days before flight and on landing day. VO(2peak) (graded treadmill exercise) was measured 7 to 21 days before and 2 days after flight. No significant differences across the groups were observed in standing HRs before or after flight. However, the within-group mean HRs significantly increased in the NE (71-89 beats/min) and CE (60-85 beats/min) groups after space flight. The HRs for the IE group did not significantly increase (75-86 beats/min) after space flight. VO(2peak) decreased (P < .05) in the NE (-9.5%) group, but did not change in the CE (-2.4%) and IE (1%) groups. The relationship (r = 0.237) between the delta HR and delta VO(2peak) was not significant. These preliminary results indicate that: (1) continuous exercise does not affect the orthostatic HR response after space flight; (2) interval exercise may minimize an increase in the postflight orthostatic HR; and (3) both exercise protocols can maintain VO(2peak).

  20. High-intensity interval training improves VO(2peak), maximal lactate accumulation, time trial and competition performance in 9-11-year-old swimmers.

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    Sperlich, Billy; Zinner, Christoph; Heilemann, Ilka; Kjendlie, Per-Ludvik; Holmberg, Hans-Christer; Mester, Joachim

    2010-11-01

    Training volume in swimming is usually very high when compared to the relatively short competition time. High-intensity interval training (HIIT) has been demonstrated to improve performance in a relatively short training period. The main purpose of the present study was to examine the effects of a 5-week HIIT versus high-volume training (HVT) in 9-11-year-old swimmers on competition performance, 100 and 2,000 m time (T(100 m) and T(2,000 m)), VO(2peak) and rate of maximal lactate accumulation (Lac(max)). In a 5-week crossover study, 26 competitive swimmers with a mean (SD) age of 11.5 ± 1.4 years performed a training period of HIIT and HVT. Competition (P effect size = 0.48) and T(2,000 m) (P = 0.04; effect size = 0.21) performance increased following HIIT. No changes were found in T(100 m) (P = 0.20). Lac(max) increased following HIIT (P effect size = 0.43) and decreased after HVT (P effect size = 0.51). VO(2peak) increased following both interventions (P effect sizes = 0.46-0.57). The increases in competition performance, T(2,000 m), Lac(max) and VO(2peak) following HIIT were achieved in significantly less training time (~2 h/week).

  1. Comparing the effects of two in-flight aerobic exercise protocols on standing heart rates and VO(2peak) before and after space flight

    Science.gov (United States)

    Siconolfi, S. F.; Charles, J. B.; Moore, A. D. Jr; Barrows, L. H.

    1994-01-01

    The effects of regular aerobic exercise on orthostatic tolerance have been the subject of a long-standing controversy that will influence the use of exercise during space flight. To examine these effects, astronauts performed continuous (CE) aerobic exercise (n = 8), interval (IE) aerobic exercise (n = 4), or no (NE) exercise (n = 5) during flights of 7 to 11 days. Heart rate (HR) responses to an orthostatic challenge (stand test) were measured 10 days before flight and on landing day. VO(2peak) (graded treadmill exercise) was measured 7 to 21 days before and 2 days after flight. No significant differences across the groups were observed in standing HRs before or after flight. However, the within-group mean HRs significantly increased in the NE (71-89 beats/min) and CE (60-85 beats/min) groups after space flight. The HRs for the IE group did not significantly increase (75-86 beats/min) after space flight. VO(2peak) decreased (P exercise does not affect the orthostatic HR response after space flight; (2) interval exercise may minimize an increase in the postflight orthostatic HR; and (3) both exercise protocols can maintain VO(2peak).

  2. Plasma volume expansion does not increase maximal cardiac output or VO2 max in lowlanders acclimatized to altitude.

    Science.gov (United States)

    Calbet, José A L; Rådegran, Göran; Boushel, Robert; Søndergaard, Hans; Saltin, Bengt; Wagner, Peter D

    2004-09-01

    With altitude acclimatization, blood hemoglobin concentration increases while plasma volume (PV) and maximal cardiac output (Qmax) decrease. This investigation aimed to determine whether reduction of Qmax at altitude is due to low circulating blood volume (BV). Eight Danish lowlanders (3 females, 5 males: age 24.0 +/- 0.6 yr; mean +/- SE) performed submaximal and maximal exercise on a cycle ergometer after 9 wk at 5,260 m altitude (Mt. Chacaltaya, Bolivia). This was done first with BV resulting from acclimatization (BV = 5.40 +/- 0.39 liters) and again 2-4 days later, 1 h after PV expansion with 1 liter of 6% dextran 70 (BV = 6.32 +/- 0.34 liters). PV expansion had no effect on Qmax, maximal O2 consumption (VO2), and exercise capacity. Despite maximal systemic O2 transport being reduced 19% due to hemodilution after PV expansion, whole body VO2 was maintained by greater systemic O2 extraction (P VO2 during exercise regardless of PV. Pulmonary ventilation, gas exchange, and acid-base balance were essentially unaffected by PV expansion. Sea level Qmax and exercise capacity were restored with hyperoxia at altitude independently of BV. Low BV is not a primary cause for reduction of Qmax at altitude when acclimatized. Furthermore, hemodilution caused by PV expansion at altitude is compensated for by increased systemic O2 extraction with similar peak muscular O2 delivery, such that maximal exercise capacity is unaffected.

  3. A high blood lactate induced by heavy exercise does not affect the increase in submaximal VO2 with hyperoxia.

    Science.gov (United States)

    Favier, F B; Prieur, F; Grataloup, O; Busso, T; Castells, J; Denis, C; Geyssant, A; Benoit, H

    2005-05-01

    Few studies evidenced an enhancement in oxygen uptake (VO2) during submaximal exercise in hyperoxia. This O2 "overconsumption" seems to increase above the lactate threshold. The aim of this study was to determine whether the hyperoxia-induced enhancement in VO2 may be related to a higher metabolism of lactate. Nine healthy males (aged 23.1 years, mean VO2 max= 53.8 ml min-1 kg-1) were randomized to two series of exercise in either normoxia or hyperoxia corresponding to an inspired O2 fraction (FIO2) of 30%. Each series consisted of 6 min cycling at 50% VO2 max (Moderate1), 5 min cycling at 95%VO2 max (Near Max) and then 6 min at 50% VO2 max (Moderate2). In both series Near Max was performed in normoxia. VO2 was significantly greater under hyperoxia than in normoxia during Moderate1 (2192 +/- 189 vs. 2025 +/- 172 ml min-1) and during Moderate2 (2352 +/- 173 vs. 2180+ /- 193 ml min-1). However, the effect of the high FIO2 was not significantly different on VO2Moderate2 (+172+/-137 ml min-1 with [La] approximately 6 mmol l-1) compared to VO2Moderate1 (+166 +/- 133 ml min-1 with [La] approximately 2.4 mmol l-1). [La] at the onset of Moderate2 was not different between normoxia and hyperoxia (10.1 +/- 2.2 vs. 10.9 +/- 1.6 mmol l-1). The results show that VO2 is significantly increased during moderate exercise in hyperoxia. But this O2 overconsumption was not modified by a high [La] induced by a prior heavy exercise. It could be concluded that lactate accumulation is not directly responsible for the increase in O2 overconsumption with intensity during exercise in hyperoxia.

  4. Escala de VO2pico em adolescentes obesos e não-Obesos por diferentes métodos Escala de VO2pico en adolescentes obesos y no obesos por diferentes métodos Scale of VO2peak in obese and non-obese adolescents by different methods

    Directory of Open Access Journals (Sweden)

    Gerusa Eisfeld Milano

    2009-12-01

    estrategia atractiva para comparar individuos con grandes diferencias en la masa corporal. OBJETIVO: Investigar el VO2pico en individuos obesos y no obesos usando el método de corrección de masa corporal (convencional y la escala alométrica (método alométrico y cómo esos métodos se aplican cuando individuos de ambos sexos se ejercitan en una cinta ergométrica. MÉTODOS: El VO2pico relativo al peso corporal y por el método alométrico fue comparado en 54 adolescentes obesos y 33 no obesos (10-16 años. Para evaluar el VO2pico durante un test máximo se utilizó calorimetría indirecta. El exponente alométrico fue calculado considerando la masa corporal individual. Así, el VO2pico fue corregido mediante el exponente alométrico. Las comparaciones se realizaron utilizando two-way ANOVA para medidas repetidas (p0,05. Sin embargo, el VO2pico calculado por el método convencional fue mayor (p0.05 entre los grupos. CONCLUSIÓN: Los individuos obesos presentaron VO2pico más bajo que los no obesos, al ser evaluados mediante el método convencional. Sin embargo, las diferencias desaparecieron cuando se aplicó el método de la escala alométrica.BACKGROUND: Peak oxygen uptake (VO2peak can be defined as the highest oxygen rate consumed during exhaustive or maximal exercise. The evaluation of the aerobic fitness can be expressed as relative to body mass, but this procedure may not fully remove differences when heavy subjects are assessed. Thus, the allometric scaling procedure is an attractive strategy to compare individuals with large differences in body mass. OBJECTIVE: Investigate VO2peak in obese and non-obese individuals using body mass correction (conventional and allometric scaling (allometric methods and how these methods apply when subjects of different genders exercise on a treadmill. METHODS: VO2peak relative to body weight and measured by the allometric method were compared in 54 obese and 33 non-obese adolescents (10 a 16 years. Indirect calorimetry was used to

  5. Cardiopulmonary Exercise Testing in Patients with Chronic Heart Failure: Prognostic Comparison from Peak VO2 and VE/VCO2 Slope.

    Science.gov (United States)

    Sarullo, Filippo Maria; Fazio, Giovanni; Brusca, Ignazio; Fasullo, Sergio; Paterna, Salvatore; Licata, Pamela; Novo, Giuseppina; Novo, Salvatore; Di Pasquale, Pietro

    2010-05-26

    Cardiopulmonary exercise testing with ventilatory expired gas analysis (CPET) has proven to be a valuable tool for assessing patients with chronic heart failure (CHF). The maximal oxygen uptake (peak V02) is used in risk stratification of patients with CHF. The minute ventilation-carbon dioxide production relationship (VE/VCO2 slope) has recently demonstrated prognostic significance in patients with CHF. Between January 2006 and December 2007 we performed CPET in 184 pts (146 M, 38 F, mean age 59.8 +/- 12.9 years), with stable CHF (96 coronary artery disease, 88 dilated cardiomyopathy), in NYHA functional class II (n.107) - III (n.77), with left ventricular ejection fraction (LVEF) /= 35.6 and 25% in those with VE/VCO2 slope 12.2 ml/kg/min (log rank chi2: 50.98, p /= 32.5 and 23% in those with VE/VCO2 slope 12.3 ml/kg/min (log rank chi2: 72.86, p < 0.0001). The VE/VCO2 slope was demonstrated with receiver operating characteristic curve analysis to be equivalent to peak VO2 in predicting cardiac-related mortality (0.89 vs. 0.89). Although area under the receiver operating characteristic curve for the VE/VCO2 slope was greater than peak VO2 in predicting cardiac-related hospitalization (0.88 vs 0.82), the difference was no statistically significant (p = 0.13). These results add to the present body of knowledge supporting the use of CPET in CHF patients. The VE/VCO2 slope, as an index of ventilatory response to exercise, is an excellent prognostic parameter and improves the risk stratification of CHF patients. It is easier to obtain than parameters of maximal exercise capacity and is of equivalent prognostic importance than peak VO2.

  6. 吸气肌力量训练对大学生VO2peak的影响%Effects of Inspiratory Muscle Strength Training on VO2peak in University Students

    Institute of Scientific and Technical Information of China (English)

    赵敬国; 朱同乐; 曹丽凤

    2010-01-01

    探讨吸气肌力量训练是否会影响以主观感觉为主要判定标准的VO2peak值.观察了为期4周的吸气肌力量训练(训练负荷为80% MIP,30次/30分/天,5天/周,共20个训练周期)过程中VO2peak值及运动能力的动态改变.VO2peak测定采用德国耶格公司生产的MasterScreen CPX 运动肺功能仪.随吸气肌训练周期的延长,吸气肌力量、GXT运动持续时间及完成的最大负荷值以及VO2peak的绝对值和相对值均呈显著性意义的增加(P0.05);而对照组则没有显著性意义的改变(P>0.05).说明4周吸气肌力量训练可显著性提高以主观感觉为主要判定标准的VO2peak值以及递增负荷运动试验(GXT)的运动能力.

  7. Time limit and time at VO2max' during a continuous and an intermittent run.

    Science.gov (United States)

    Demarie, S; Koralsztein, J P; Billat, V

    2000-06-01

    The purpose of this study was to verify, by track field tests, whether sub-elite runners (n=15) could (i) reach their VO2max while running at v50%delta, i.e. midway between the speed associated with lactate threshold (vLAT) and that associated with maximal aerobic power (vVO2max), and (ii) if an intermittent exercise provokes a maximal and/or supra maximal oxygen consumption longer than a continuous one. Within three days, subjects underwent a multistage incremental test during which their vVO2max and vLAT were determined; they then performed two additional testing sessions, where continuous and intermittent running exercises at v50%delta were performed up to exhaustion. Subject's gas exchange and heart rate were continuously recorded by means of a telemetric apparatus. Blood samples were taken from fingertip and analysed for blood lactate concentration. In the continuous and the intermittent tests peak VO2 exceeded VO2max values, as determined during the incremental test. However in the intermittent exercise, peak VO2, time to exhaustion and time at VO2max reached significantly higher values, while blood lactate accumulation showed significantly lower values than in the continuous one. The v50%delta is sufficient to stimulate VO2max in both intermittent and continuous running. The intermittent exercise results better than the continuous one in increasing maximal aerobic power, allowing longer time at VO2max and obtaining higher peak VO2 with lower lactate accumulation.

  8. VO2 pico e inclinação VE/VCO2 na era dos betabloqueadores na insuficiência cardíaca: uma experiência brasileira Peak VO2 and VE/VCO2 slope in betablockers era in patients with heart failure: a brazilian experience

    Directory of Open Access Journals (Sweden)

    Guilherme Veiga Guimarães

    2008-07-01

    Full Text Available FUNDAMENTO: Estudos têm demonstrado que o consumo de oxigênio de pico (VO2 pico e a inclinação VE/VCO2 são preditores de sobrevida em pacientes com insuficiência cardíaca (IC. Entretanto, com a adição do betabloqueador no tratamento da IC, os valores de prognóstico do VO2 pico e da Inclinação VE/VCO2 não estão totalmente estabelecidos. OBJETIVO: Avaliar o efeito dos betabloqueadores no valor de prognóstico do VO2 pico e da inclinação VE/VCO2 em pacientes com IC. MÉTODOS: Estudamos 391 pacientes com insuficiência cardíaca, com idade de 49 ± 14 anos e fração de ejeção do ventrículo esquerdo de 38 ± 10%. Total de pacientes que usavam (grupo I - GI e não usavam (grupo II - GII betabloqueadores: 229 e 162, respectivamente. Todos os pacientes foram submetidos a teste de esforço cardiopulmonar, em esteira, usando o protocolo de Naughton. RESULTADOS: O VO2 pico 16 ml.kg-1.min-1 categorizaram pacientes com melhor prognóstico em médio prazo. A faixa do VO2 pico entre > 10 e BACKGROUND: Studies have demonstrated that peak oxygen consumption (peak VO2 and the VE/VCO2 slope are predictors of survival in patients with heart failure (HF. However, with the advent of betablockers in the treatment of HF, the prognostic values of peak VO2 and VE/VCO2 slope have not been fully established. OBJECTIVE: To evaluate the effect of betablocker use on the prognostic value of peak VO2 and VE/VCO2 slope in patients with HF. METHODS: We studied 391 patients with heart failure, aged 49 ± 14 years and presenting a left ventricular ejection fraction of 38 ± 10%. The total number of patients that used (Group I - GI or did not use (Group II - GII betablockers was 229 and 162, respectively. All patients were submitted to a cardiopulmonary stress test on a treadmill, using the Naughton protocol. RESULTS: A peak VO2 16 ml.kg-1.min-1 categorizes patients with a better mid-term prognosis. Peak VO2 values between > 10 and < 16 ml.kg-1.min-1 indicated

  9. VO2 max in an Indian population: a study to understand the role of factors determining VO2 max.

    Science.gov (United States)

    Nitin, Y M; Sucharita, S; Madhura, M; Thomas, T; Sandhya, T A

    2013-01-01

    VO2 max is the maximum amount of oxygen a person can consume and the value does not change despite an increase in workload. There is lack of data evaluating the impact of factors, which could affect VO2 max measurement, particularly in Indian population. The objectives of the present study were (i) to estimate VO2 max in a young healthy Indian population and to compare it with available prediction equations for Indian population (ii) to correlate time to achieve VO2 max with the relative VO2 max (iii) to assess the factors affecting the time to achieve VO2 max measurement (body composition and physical activity level). Twenty healthy adult males (18-30 years) underwent detailed anthropometry, physical activity level and modified Bruce protocol for VO2 max assessment. Breath by breath VO2, VCO2, oxygen saturation, heart rate, blood pressure were measured continuously and following exercise protocol. There was an internal validity between the estimated VO2 max and the maximum heart rate (MHR) (r = 0.51, P VO2 max P VO2 max. Out of the 3 prediction equations computed to estimate VO2 max, 2 equations significantly overestimated VO2 max. In Conclusion, physical activity level emerged to be a strong predictor of time to VO2 max. Time to achieve VO2 max is an important factor to be considered when determining VO2 max. There was an overestimation in the VO2 max values derived from predicted equations.

  10. Validation of a Ramp Running Protocol for Determination of the True VO2max in Mice

    Science.gov (United States)

    Ayachi, Mohamed; Niel, Romain; Momken, Iman; Billat, Véronique L.; Mille-Hamard, Laurence

    2016-01-01

    In the field of comparative physiology, it remains to be established whether the concept of VO2max is valid in the mouse and, if so, how this value can be accurately determined. In humans, VO2max is generally considered to correspond to the plateau observed when VO2 no longer rises with an increase in workload. In contrast, the concept of VO2peak tends to be used in murine studies. The objectives of the present study were to determine whether (i) a continuous ramp protocol yielded a higher VO2peak than a stepwise, incremental protocol, and (ii) the VO2peak measured in the ramp protocol corresponded to VO2max. The three protocols (based on intensity-controlled treadmill running until exhaustion with eight female FVB/N mice) were performed in random order: (a) an incremental protocol that begins at 10 m.min−1 speed and increases by 3 m.min−1 every 3 min. (b) a ramp protocol with slow acceleration (3 m.min−2), and (c) a ramp protocol with fast acceleration (12 m.min−2). Each protocol was performed with two slopes (0 and 25°). Hence, each mouse performed six exercise tests. We found that the value of VO2peak was protocol-dependent (p VO2max plateau was associated with the fulfillment of two secondary criteria (a blood lactate concentration >8 mmol.l−1 and a respiratory exchange ratio >1). The total duration of the 3 m.min−2 0° ramp protocol was shorter than that of the incremental protocol. Taken as a whole, our results suggest that VO2max in the mouse is best determined by applying a ramp exercise protocol with slow acceleration and no treadmill slope. PMID:27621709

  11. Effect of nonstoichiometry on Raman scattering of VO2 films

    Institute of Scientific and Technical Information of China (English)

    Yuan Hong-Tao; Feng Ke-Cheng; Wang Xue-Jin; Li Chao; He Chen-Juan; Nie Yu-Xin

    2004-01-01

    @@ We report on Raman scattering of VO2 films prepared by radio frequency magnetron sputtering under different conditions. Our investigations revealed that the dominated Raman peaks shift towards high frequency for both V-rich and O-rich VO2 films, compared with the stoichiometry VO2 films. The experimental evidence is presented and the cause for nonstoichiometry dependence of Raman spectra of VO2 films is discussed.

  12. Escala de VO2pico em adolescentes obesos e não-Obesos por diferentes métodos Escala de VO2pico en adolescentes obesos y no obesos por diferentes métodos Scale of VO2peak in obese and non-obese adolescents by different methods

    OpenAIRE

    2009-01-01

    FUNDAMENTO: O consumo de oxigênio de pico (VO2pico) pode ser definido como a maior taxa de consumo de oxigênio durante exercício exaustivo ou máximo. A avaliação da aptidão aeróbica pode ser expressa como relativa à massa corporal, mas esse procedimento pode não remover completamente as diferenças quando indivíduos pesados são avaliados. Assim, o procedimento com escala alométrica é uma estratégia atraente para comparar indivíduos com grandes diferenças em massa corporal. OBJETIVO: Investigar...

  13. Effects of high-intensity interval training on the VO2 response during severe exercise.

    Science.gov (United States)

    Duffield, Rob; Edge, Johann; Bishop, David

    2006-06-01

    This study examined the effect of high-intensity interval training on the VO2 response during severe, constant-load exercise. Prior to, and following training, 10 females (V O2 peak 37.4+/-6.0 mL kg-1 min-1) performed a graded exercise test to determine VO2 peak and lactate threshold (LT) and a 6 min cycle test (CT) at the pre-training VO2 peak intensity. Training involved high-intensity intervals (2 min work, 1 min rest) performed 3x week for 8 weeks. Breath-by-breath data from 0 to 6 min during the CT were smoothed using 5s averages and fit to a bi-exponential model starting from 20s. Training resulted in significant improvements in VO2 max (2.34+/-0.37-2.78+/-0.30 L min-1), power at VO2 max (170+/-26-204+/-25 W) and power at LT (113+/-17-136+/-20 W) (pVO2 response showed a significant increase in the amplitude of the primary phase (A1) (1396+/-103-1695+/-100 mL min-1; pVO2 (VO2 EE), with no difference (p>0.05) in the time constants of either phase or the amplitude of the slow component (318+/-67-380+/-48 mL; p=0.15). In conjunction, accumulated oxygen deficit (AOD) (43.7+/-9.8-17.2+/-2.8 mL O2 eq kg-1) and anaerobic contribution to the CT (19.4+/-4.4-7.2+/-1.2%) were significantly reduced. In contrast to previous moderate-intensity research, a high-intensity interval training program increased A1 and VO2 EE for the same absolute exercise intensity, decreasing the AOD during a severe-intensity CT.

  14. Training effects on peak (VO2)-O-center dot, specific of the mode of movement, in rehabilitation of patients with coronary artery disease

    NARCIS (Netherlands)

    Nieuwland, W; Berkhuysen, MA; Landsman, MLJ; Lie, KI; Rispens, P

    1998-01-01

    Training effects on peak oxygen consumption ((V) over dot O-2), specific to the mode of movement, are well-known in exercise training of young, healthy adults. However, these specific training effects were never studied in patients with coronary artery disease, but may be important in the evaluation

  15. Kinetics of VO(2) in professional cyclists.

    Science.gov (United States)

    Lucía, Alejandro; Hoyos, Jesús; Santalla, Alfredo; Pérez, Margarita; Chicharro, José L

    2002-02-01

    To analyze the kinetics of oxygen uptake (VO(2)) in professional road cyclists during a ramp cycle ergometer test and to compare the results with those derived from well-trained amateur cyclists. Twelve professional cyclists (P group; 25 +/- 1 yr; maximal power output (W(max)), 508.3 +/- 9.3 watts) and 10 amateur cyclists (A group; 22 +/- 1 y; W(max), 429.9 +/- 8.6 watts) performed a ramp test until exhaustion (power output increases of 25 watts x min(-1)). The regression lines of the VO(2):power output (W) relationship were calculated for the following three phases: phase I (below the lactate threshold (LT)), phase II (between LT and the respiratory compensation point (RCP)), and phase III (above RCP). In group P, the mean slope (Delta VO(2):Delta W) of the VO(2):W relationship decreased significantly (P 0.05) were found between phases I and II (P > 0.05) in group A, whereas Delta VO(2):Delta W significantly increased in phase III (P < 0.01), compared with phase II (10.2 +/- 0.3, 9.2 +/- 0.4, and 10.1 +/- 1.1 mL O(2) x watts(-1) x min(-1) in phases I, II, and III, respectively). The mean value of Delta VO(2):Delta W for phase III was significantly lower in group P than in group A (P < 0.01). Contrary to the case in amateur riders, the rise in VO(2) in professional cyclists is attenuated at moderate to high workloads. This is possibly an adaptation to the higher demands of their training/competition schedule.

  16. Increased steady-state VO2 and larger O2 deficit with CO2 inhalation during exercise

    DEFF Research Database (Denmark)

    Østergaard, Lars; Kjær, Kirsten; Jensen, Kurt

    2012-01-01

    Abstract Aim:  To examine whether inhalation of CO2-enriched gas would increase steady-state during exercise and enlarge O2 deficit. Methods:  Ten physically active men ( 53.7 ± 3.6 mL min−1 kg−1; ± SD) performed transitions from low-load cycling (baseline; 40 W) to work rates representing light...... respiratory acidosis with increases in PCO2 and decreases in capillary blood pH (P exercise, presumably because of increased cost of breathing (ΔVE 40–50 L min−1; P ... with hypercapnia in heavy exercise (2.24 ± 0.51 L vs. 1.91 ± 0.45 L; P respiratory acidosis increase steady-state in both light and heavy exercise and enlarges O2 deficit in heavy exercise....

  17. [Effect of 4 weeks of training on the limit time at VO2 max].

    Science.gov (United States)

    Heubert, Richard; Bocquet, Valéry; Koralsztein, Jean Pierre; Billat, Véronique

    2003-10-01

    The purpose of this study was to examine the effect of 4 weeks training in running on the time spent at VO2max (tlim VO2max). Eight athletes carried out, before and after an aerobic training, an incremental and five exhaustive tests at 90, 95, 100, 115% vVO2max and at the critical power at VO2max (CV'; slope of the linear relation between the tlim VO2max and the distance limit at VO2max). This training did not significantly improve VO2max (p = 0.17) or tlim VO2max (p = 0.72). However, the "tlim VO2max-intensity" curve was shifted toward the right, meaning that the athlete had to run at a higher intensity after training to obtain the same tlim VO2max. Tlim VO2max at CV' before training was significantly higher than tlim VO2max at 90, 95, 100, and 115% vVO2max (p max; p = 0.9). In conclusion, in spite of the shift of the "tlim VO2max-intensity" curve, tlim VO2max was not significantly increased by this training. Furthermore, CV' allowed subjects to spend the longest time of exercise at VO2max during a continuous exercise with constant speed, but CV', expressed in % vVO2max, did not improve with this training.

  18. Plasma volume expansion does not increase maximal cardiac output or VO2 max in lowlanders acclimatized to altitude

    DEFF Research Database (Denmark)

    Calbet, José A L; Rådegran, Göran; Boushel, Robert Christopher

    2004-01-01

    With altitude acclimatization, blood hemoglobin concentration increases while plasma volume (PV) and maximal cardiac output (Qmax) decrease. This investigation aimed to determine whether reduction of Qmax at altitude is due to low circulating blood volume (BV). Eight Danish lowlanders (3 females, 5...... males: age 24.0 +/- 0.6 yr; mean +/- SE) performed submaximal and maximal exercise on a cycle ergometer after 9 wk at 5,260 m altitude (Mt. Chacaltaya, Bolivia). This was done first with BV resulting from acclimatization (BV = 5.40 +/- 0.39 liters) and again 2-4 days later, 1 h after PV expansion with 1...... level Qmax and exercise capacity were restored with hyperoxia at altitude independently of BV. Low BV is not a primary cause for reduction of Qmax at altitude when acclimatized. Furthermore, hemodilution caused by PV expansion at altitude is compensated for by increased systemic O2 extraction...

  19. The ergogenic effect of recombinant human erythropoietin on VO2max depends on the severity of arterial hypoxemia.

    Directory of Open Access Journals (Sweden)

    Paul Robach

    Full Text Available Treatment with recombinant human erythropoietin (rhEpo induces a rise in blood oxygen-carrying capacity (CaO(2 that unequivocally enhances maximal oxygen uptake (VO(2max during exercise in normoxia, but not when exercise is carried out in severe acute hypoxia. This implies that there should be a threshold altitude at which VO(2max is less dependent on CaO(2. To ascertain which are the mechanisms explaining the interactions between hypoxia, CaO(2 and VO(2max we measured systemic and leg O(2 transport and utilization during incremental exercise to exhaustion in normoxia and with different degrees of acute hypoxia in eight rhEpo-treated subjects. Following prolonged rhEpo treatment, the gain in systemic VO(2max observed in normoxia (6-7% persisted during mild hypoxia (8% at inspired O(2 fraction (F(IO(2 of 0.173 and was even larger during moderate hypoxia (14-17% at F(IO(2 = 0.153-0.134. When hypoxia was further augmented to F(IO(2 = 0.115, there was no rhEpo-induced enhancement of systemic VO(2max or peak leg VO(2. The mechanism highlighted by our data is that besides its strong influence on CaO(2, rhEpo was found to enhance leg VO(2max in normoxia through a preferential redistribution of cardiac output toward the exercising legs, whereas this advantageous effect disappeared during severe hypoxia, leaving augmented CaO(2 alone insufficient for improving peak leg O(2 delivery and VO(2. Finally, that VO(2max was largely dependent on CaO(2 during moderate hypoxia but became abruptly CaO(2-independent by slightly increasing the severity of hypoxia could be an indirect evidence of the appearance of central fatigue.

  20. Effects of Inspiratory Muscle Training on VO2peak,Lung Function and Exercise Performance in Healthy University Students%吸气肌训练对健康大学生VO2peak、肺功能及运动能力的影响

    Institute of Scientific and Technical Information of China (English)

    赵敬国; 朱同乐; 曹丽凤

    2010-01-01

    探讨呼吸肌训练能否影响以主观感觉为主要判定标准的VO2peak值以及肺功能和运动能力.方法:观察了为期4周的吸气肌力量训练过程中VO2peak值、肺功能及运动能力的动态改变.结果:随吸气肌训练周期的延长,吸气肌力量、GXT运动持续时间及完成的最大负荷值以及、VO2peak的绝对值和相对值均呈显著性意义的增加(P0.05).MV、VCmax和FEV1均没有显著性意义的差异(P>0.05).结论:4周吸气肌力量训练可显著性提高以主观感觉为主要判定标准的VO2peak值以及递增负荷运动试验(GXT)的运动能力.

  1. Improving the electrocatalytic performance of carbon nanotubes for VO2+/VO2+ redox reaction by KOH activation

    Science.gov (United States)

    Dai, Lei; Jiang, Yingqiao; Meng, Wei; Zhou, Huizhu; Wang, Ling; He, Zhangxing

    2017-04-01

    In this paper, carbon nanotubes (CNTs) was activated by KOH treatment at high temperature and investigated as catalyst for VO2+/VO2+ redox reaction for vanadium redox flow battery (VRFB). X-ray photoelectron spectroscopy results suggest that the oxygen-containing groups can be introduced on CNTs by KOH activation. The mass transfer of vanadium ions can be accelerated by chemical etching by KOH activation and improved wettability due to the introduction of hydrophilic groups. The electrochemical properties of VO2+/VO2+ redox reaction can be enhanced by introduced oxygen-containing groups as active sites. The sample treated at 900 °C with KOH/CNTs mass ratio of 3:1 (CNTs-3) exhibits the highest electrocatalytic activity for VO2+/VO2+ redox reaction. The cell using CNTs-3 as positive catalyst demonstrates the smallest electrochemical polarization, the highest capacity and efficiency among the samples. Using KOH-activated CNTs-3 can increase the average energy efficiency of the cell by 4.4%. This work suggests that KOH-activated CNTs is a low-cost, efficient and promising catalyst for VO2+/VO2+ redox reaction for VRFB system.

  2. Assessment of anaerobic power to verify VO2max attainment.

    Science.gov (United States)

    Astorino, Todd A; White, Ailish C

    2010-07-01

    Across various populations, verification testing is used to confirm VO(2)max attainment and has repeatedly shown similar VO(2)max values to those obtained from incremental exercise. Yet, many individuals show meaningful differences in VO(2)max between protocols, and an explanation for this is unknown. The aim of the study was to elucidate this phenomenon in 30 men and women of similar age, fitness, and physical activity using assessment of anaerobic power. On day 1, they completed the Wingate test, and returned at least 48 h later to complete incremental cycle ergometry followed by a verification protocol. During exercise, ventilation, pulmonary gas exchange data, and heart rate (HR) were continuously measured. Mean VO(2)max was similar (P > 0.05) between protocols (42.05 +/- 5.88 ml kg(-1) per min versus 42.03 +/- 5.75 ml kg(-1) per min, respectively), although seven subjects (23%) revealed a VO(2)max that was not 'verified' by the supramaximal protocol. Indices of power output and gas exchange data were similar (P > 0.05) between subjects who revealed a 'true' VO(2)max compared to those who did not, although peak and mean power was consistently higher in persons whose VO(2)max was not 'verified.' A previously established HRmax criterion for verification testing was not met in 17% of subjects. Additional study is merited to identify alternate determinants of VO(2)max, such as muscle activation via assessment of motor unit recruitment, and to investigate utility of verification testing to confirm VO(2)max attainment in elite athletes and the elderly.

  3. Could peak oxygen uptake be estimated from proposed equations based on the six-minute walk test in chronic heart failure subjects?

    Science.gov (United States)

    Ribeiro-Samora, Giane A; Montemezzo, Dayane; Pereira, Danielle A G; Tagliaferri, Thaysa L; Vieira, Otávia A; Britto, Raquel R

    To evaluate the agreement between the measured peak oxygen uptake (VO2peak) and the VO2peak estimated by four prediction equations based on the six-minute walk test (6MWT) in chronic heart failure patients. Thirty-six chronic heart failure patients underwent cardiopulmonary exercise testing and the 6MWT to assess their VO2peak. Four previously published equations that include the variable six-minute walk distance were used to estimate the VO2peak: Cahalin, 1996a (1); Cahalin, 1996b (2); Ross, 2010 (3); and Adedoyin, 2010 (4). The agreement between the VO2peak in the cardiopulmonary exercise testing and the estimated values was assessed using the Bland-Altman method. A p-value of <0.05 was considered statistically significant. All estimated VO2peak values presented moderate correlation (ranging from 0.55 to 0.70; p<0.001) with measured VO2peak values. Equations 2, 3, and 4 underestimated the VO2peak by 30%, 15.2%, and 51.2%, respectively, showing significant differences from the actual VO2peak measured in the cardiopulmonary exercise testing (p<0.0001 for all), and the limits of agreement were elevated. The VO2peak estimated by equation 1 was similar to that measured by the cardiopulmonary exercise testing, and despite the agreement, bias increased as VO2peak increased. Only equation 1 showed estimated VO2peak similar to the measured VO2peak; however, a large limits of agreement range (∼3 METs) does not allow its use to estimate maximal VO2peak. Copyright © 2017 Associação Brasileira de Pesquisa e Pós-Graduação em Fisioterapia. Publicado por Elsevier Editora Ltda. All rights reserved.

  4. The Effect of Habitual Smoking on VO2max

    Science.gov (United States)

    Wier, Larry T.; Suminski, Richard R.; Poston, Walker S.; Randles, Anthony M.; Arenare, Brian; Jackson, Andrew S.

    2008-01-01

    VO2max is associated with many factors, including age, gender, physical activity, and body composition. It is popularly believed that habitual smoking lowers aerobic fitness. PURPOSE: to determine the effect of habitual smoking on VO2max after controlling for age, gender, activity and BMI. METHODS: 2374 men and 375 women employed at the NASA/Johnson Space Center were measured for VO2max by indirect calorimetry (RER>=1.1), activity by the 11 point (0-10) NASA Physical Activity Status Scale (PASS), BMI and smoking pack-yrs (packs day*y of smoking). Age was recorded in years and gender was coded as M=1, W=0. Pack.y was made a categorical variable consisting of four levels as follows: Never Smoked (0), Light (1-10), Regular (11-20), Heavy (>20). Group differences were verified by ANOVA. A General Linear Models (GLM) was used to develop two models to examine the relationship of smoking behavior on VO2max. GLM #1(without smoking) determined the combined effects of age, gender, PASS and BMI on VO2max. GLM #2 (with smoking) determined the added effects of smoking (pack.y groupings) on VO2max after controlling for age, gender, PASS and BMI. Constant errors (CE) were calculated to compare the accuracy of the two models for estimating the VO2max of the smoking subgroups. RESULTS: ANOVA affirmed the mean VO2max of each pack.y grouping decreased significantly (psmoking exposure increased. GLM #1 showed that age, gender, PASS and BMI were independently related with VO2max (R2 = 0.642, SEE = 4.90, pSmoked, the effects on VO2max from Light and Regular smoking habits were -0.83 and -0.85 ml.kg- 1.min-1 respectively (peffect of Heavy smoking on VO2max was -2.56 ml.kg- 1.min-1 (psmoking group in GLM #2 was smaller than the CE s of the smoking group counterparts in GLM #1. CONCLUSIONS: After accounting for the effects of gender, age, PASS and BMI the effect of habitual smoking on reducing VO2max is minimal, about 0.85 ml/kg/min, until the habit exceeds 20 pack.y at which point an

  5. VO2@RER1.0: a novel submaximal cardiopulmonary exercise index.

    Science.gov (United States)

    Chin, Clifford; Kazmucha, Jeffrey; Kim, Nancy; Suryani, Reny; Olson, Inger

    2010-01-01

    Maximal oxygen consumption (VO2max) is the "gold standard" by which to assess functional capacity; however, it is effort dependent. VO2@RER1.0 is defined when VO2 = VCO2. Between December 22, 1997 and November 9, 2004, 305 pediatric subjects underwent cycle ergometer cardiopulmonary exercise testing, exercised to exhaustion, and reached a peak respiratory exchange ratio > or = 1.10. Group 1 subjects achieved a peak VO2 > or = 80% of predicted VO2max; group 2 subjects achieved a peak VO2 equation was created. VO2@RER1.0 data from groups 2 and 3 were plotted onto the normative graph. Contingency table and relative-risk analysis showed that an abnormal VO2@RER1.0 predicted an abnormal peak VO2(positive-predictive value 83%, negative-predictive value 85%, sensitivity 84%, and specificity 84%). VO2@RER1.0 is a highly sensitive, specific, and predictive submaximal index of functional capacity. This submaximal index is easy to identify without subjectivity. This index may aid in the evaluation of subjects who cannot exercise to maximal parameters.

  6. Leg strength and the VO2 max of older men.

    Science.gov (United States)

    Lovell, D; Cuneo, R; Delphinus, E; Gass, G

    2011-04-01

    The purpose of the study was to determine if leg strength limits VO2 max and the ability to reach a plateau during VO2 max test in older men during cycle ergometry. Men aged 70-80 years were randomly selected into a strength training (ST, n=12) 3 times weekly for 16 weeks, followed by 4 weeks detraining or a non-training control group (C, n=12). Leg strength and VO2 max were assessed every 4 weeks for 20 weeks; body composition and cardiac function were assessed before and after 16 weeks training and after 4 weeks detraining. Leg strength, upper leg muscle mass (ULMM), arterial-venous O2 difference (a-v O2 difference) and VO2 max increased in the ST group (95±0.6%, 7±0.7%. 6.2±0.5% and 8±0.8%, respectively; PVO2 max and a-v O2 difference returned to pre-training levels. There was no change in the ability of the participants to reach a plateau during VO2 max testing over the 20-week study. These findings indicate that leg strength may not limit either VO2 max or the ability to plateau during VO2 max tests in older men during cycle ergometry. © Georg Thieme Verlag KG Stuttgart · New York.

  7. Development of a rowing-specific VO2max field test.

    Science.gov (United States)

    Huntsman, Heather D; DiPietro, Loretta; Drury, Daniel G; Miller, Todd A

    2011-06-01

    The purpose of this study was to develop an aerobic capacity test for rowers using minimal equipment that could be used in the field. Thirty rowers (15 men and 15 women) between the ages of 18 and 26 years were recruited on a volunteer basis from the District of Columbia metro area. The testing protocol consisted of a maximum of 7 2-minute stages on a rowing ergometer, separated by 30-second breaks where lactic acid concentrations were analyzed. Starting intensity for men was 200 W, although women started at 150 W, and each stage increased by 50 W. Expired gasses were collected during the test, and athletes were asked to row until maximal volition so that the directly measured VO2max could be compared to predicted values. Peak heart rates from each completed stage were plotted, and regression equations were calculated to predict VO2max. Separate regression equations were calculated for men and women. The predicted VO2max values were approximately 23 and 25% lower than what was actually achieved for men and women, respectively. Heart rate was a stronger correlate of VO2max in men compared with in women. Among men, we observed a moderate and statistically significant correlation (r = 0.55; p = 0.05), whereas among women, no such agreement was observed (r = -0.05; p > 0.85). The principle finding of this study was that the test was adequate in predicting VO2max in men but was inadequate in its prediction in women. With slight modifications to the testing protocol, stronger correlations and a more accurate prediction of VO2max is expected in men.

  8. Determinants of VO(2) kinetics at high power outputs during a ramp exercise protocol.

    Science.gov (United States)

    Lucía, Alejandro; Rivero, José-Luis L; Pérez, Margarita; Serrano, Antonio L; Calbet, José A L; Santalla, Alfredo; Chicharro, José L

    2002-02-01

    To determine the relationship between the additional, nonlinear increase in oxygen uptake (Delta VO(2)) that occurs at high power outputs during a ramp cycle ergometer test, on one hand; and possible explanatory mechanisms of the phenomenon, such as cardiorespiratory work, blood lactate, fitness level, or muscle fiber distribution, on the other. Ten healthy, sedentary young adults (age (mean +/- SEM), 22 +/- 1 yr) were chosen as subjects. A muscle biopsy specimen was taken from the vastus lateralis of the right leg to determine fiber type distribution by immunohistochemical identification of myosin heavy chain (MHC) isoforms. During the ramp tests (power output increases of 5 W every 15-s interval), the ventilatory threshold (VT) and lactate threshold (LT) were measured. We defined Delta VO(2) as the difference between "true" VO(2) values observed at the maximal power output (VO(2)obs) and those expected (VO(2)exp) from the previous linear VO2:power output relationship below the VT. A nonlinear increase was observed in VO2 (Delta VO(2) = 239 +/- 79 mL x min(-1), P < 0.05 for VO(2)obs vs VO(2)exp), which was significantly correlated with the percentage of type IIX fibers (r = 0.80, P < 0.05). No other correlations were found between Delta VO(2) and possible explanatory mechanisms. A greater percentage of type IIX fibers is associated with a higher excess VO(2) at high power outputs (above VT).

  9. VO2 kinetics and metabolic contributions whilst swimming at 95, 100, and 105% of the velocity at VO2max.

    Science.gov (United States)

    Sousa, Ana C; Vilas-Boas, João P; Fernandes, Ricardo J

    2014-01-01

    A bioenergetical analysis of swimming at intensities near competitive distances is inexistent. It was aimed to compare the transient VO2 kinetics responses and metabolic contributions whilst swimming at different velocities around VO2max. 12 trained male swimmers performed (i) an incremental protocol to determine the velocity at VO2max (vVO2max) and (ii) three square wave exercises from rest to 95, 100, and 105% of vVO2max. VO2 was directly measured using a telemetric portable gas analyser and its kinetics analysed through a double-exponential model. Metabolic contributions were assessed through the sum of three energy components. No differences were observed in the fast component response (τ1--15, 18, and 16 s, A1--36, 34, and 37 mL · kg(-1) · min (-1), and Gain--32, 29, and 30 mL · min (-1) at 95, 100, and 105% of the vVO2max, resp.) but A2 was higher in 95 and 100% compared to 105% intensity (480.76 ± 247.01, 452.18 ± 217.04, and 147.04 ± 60.40 mL · min (-1), resp.). The aerobic energy contribution increased with the time sustained (83 ± 5, 74 ± 6, and 59 ± 7% for 95, 100, and 105%, resp.). The adjustment of the cardiovascular and/or pulmonary systems that determine O2 delivery and diffusion to the exercising muscles did not change with changing intensity, with the exception of VO2 slow component kinetics metabolic profiles.

  10. Creative MuVo2

    Institute of Scientific and Technical Information of China (English)

    zdwei

    2004-01-01

    苹果(Apple)与创新(Creative),这两大巨擘在MP3播放器上的造诣可谓各有千秋,前者推出的iPod系列在外形上独领风骚,而后者推出的NOMAND系列则在间效上无人能比。就在苹果最新型iPod3排山倒海般的宣传攻势下,创新也推出了一款以曼妙身材和相对低廉价格为主打的1.5GB硬盘式MP3播放器——NOMAND MuVo2

  11. Effects of Zirconium Ions Doping on the Structural and Thermochromic Properties of VO2 Thin Films

    Science.gov (United States)

    Li, Yuanbao; Liu, Juncheng; Wang, Danping; Dang, Yuanyuan

    2017-07-01

    As an inorganic functional material, VO2 thin films are expected to be used for smart windows. However, these films are not conducive to practical applications when the phase transition temperature (Tc) of the VO2 is approximately 68°C, which is greater than room temperature. To decrease Tc, the effect of Zr4+ doping on the structure and properties of VO2 films were investigated. The films were prepared using a sol-gel process, spin-coating on quartz glasses, and annealing at 525°C in a tube furnace within a nitrogen atmosphere. The results demonstrate that these films have a highly preferential crystalline orientation on the substrate; however, the primary two x-ray diffraction pattern peaks shift slightly toward the small angle, and when 7 at.% Zr4+ was doped in the VO2 film, the deviation angle was 0.16°, and the crystallite size was approximately 98 nm. A large number of grains were found on the surface of the pure VO2 films, but all the Zr4+ doped films had a layered structure, and the thickness of the films was approximately 200 nm. The Tc of these films was characterized using differential scanning calorimetry, and the luminous and solar transmittance was characterized using a UV-Vis-NIR spectrophotometer, which demonstrated that the effect of Zr4+ doping decreased Tc by approximately 1°C per 1 at.% on average, and the Tc of the 7 at.% film was slightly greater than that of the 5 at.% film, the phase transition temperature of which was 61.4°C. The transmittance decreased as the doping concentration increased, and 1 at.% Zr4+ doping increased the luminous regulation efficiency (ΔT lum) and solar modulation efficiency (ΔT sol). The ΔT lum of the pure VO2 film and the 1 at.% Zr4+-doped VO2 films was 10.9% and 11.2%, and ΔT sol was 14.4 and 15.2%, respectively.

  12. Curvilinear VO(2):power output relationship in a ramp test in professional cyclists: possible association with blood hemoglobin concentration.

    Science.gov (United States)

    Lucía, Alejandro; Hoyos, Jesús; Santalla, Alfredo; Pérez, Margarita; Chicharro, José L

    2002-02-01

    The purpose of this study was to determine (1) if there exists an additional, nonlinear increase (DeltaVO(2)) in the oxygen uptake observed (VO2 (obs)) at the maximal power output reached during a ramp cycle ergometer test and that expected (VO2 (exp)) from the linear relationship between VO(2) and power output below the lactate threshold (LT) in professional riders, and (2) the relationship between DeltaVO(2) and possible explanatory mechanisms. Each of 12 professional cyclists (25 +/- 1 years; VO(2 max): 71.3 +/- 1.2 ml x kg(-1) x min(-1)) performed a ramp test until exhaustion (power output increases of 25 W x min(-1)) during which several gas-exchange and blood variables were measured (including lactate, HCO(3)(-) and K(+)). VO(2) was linearly related to power output until the LT in all subjects. Afterward, a nonlinear deflection was observed in the VO(2):power output relationship (DeltaVO(2) = 2492 +/- 55 ml x min(-1) and p < 0.05 for VO2 (obs) vs. VO2 (exp)). A significant negative correlation was encountered between DeltaVO(2) and resting hemoglobin levels before the tests (r = 20.61; p < 0.05). In conclusion, professional cyclists exhibit an attenuation of the VO(2) rise above the LT.

  13. Tunable VO2/Au hyperbolic metamaterial

    Science.gov (United States)

    Prayakarao, S.; Mendoza, B.; Devine, A.; Kyaw, C.; van Dover, R. B.; Liberman, V.; Noginov, M. A.

    2016-08-01

    Vanadium dioxide (VO2) is known to have a semiconductor-to-metal phase transition at ˜68 °C. Therefore, it can be used as a tunable component of an active metamaterial. The lamellar metamaterial studied in this work is composed of subwavelength VO2 and Au layers and is designed to undergo a temperature controlled transition from the optical hyperbolic phase to the metallic phase. VO2 films and VO2/Au lamellar metamaterial stacks have been fabricated and studied in electrical conductivity and optical (transmission and reflection) experiments. The observed temperature-dependent changes in the reflection and transmission spectra of the metamaterials and VO2 thin films are in a good qualitative agreement with theoretical predictions. The demonstrated optical hyperbolic-to-metallic phase transition is a unique physical phenomenon with the potential to enable advanced control of light-matter interactions.

  14. Effect of W addition on the electrical switching of VO2 thin films

    Science.gov (United States)

    Rajeswaran, Bharathi; Umarji, Arun M.

    2016-03-01

    Vanadium Oxide has been a frontrunner in the field of oxide electronics because of its metal-insulator transition (MIT). The interplay of different structures of VO2 has played a crucial role in deciding the magnitude of the first order MIT. Substitution doping has been found to introduce different polymorphs of VO2. Hence the role of substitution doping in stabilizing the competing phases of VO2 in the thin film form remains underexplored. Consequently there have been reports both discounting and approving such a stabilization of competing phases in VO2. It is reported in the literature that the bandwidth of the hysteresis and transition temperature of VO2 can be tuned by substitutional doping of VO2 with W. In this work, we have adopted a novel technique called, Ultrasonic Nebulized Spray Pyrolysis of Aqueous Combustion Mixture (UNSPACM) to deposit VO2 and W- doped VO2 as thin films. XRD and Raman spectroscopy were used to investigate the role of tungsten on the structure of VO2 thin films. Morphology of the thin films was found to be consisting of globular and porous nanoparticles of size ˜ 20nm. Transition temperature decreased with the addition of W. We found that for 2.0 at % W doping in VO2, the transition temperature has reduced from 68 o C to 25 o C. It is noted that W-doping in the process of reducing the transition temperature, alters the local structure and also increases room temperature carrier concentration.

  15. Biology of VO2 max: looking under the physiology lamp.

    Science.gov (United States)

    Lundby, C; Montero, D; Joyner, M

    2017-06-01

    In this review, we argue that several key features of maximal oxygen uptake (VO2 max) should underpin discussions about the biological and reductionist determinants of its interindividual variability: (i) training-induced increases in VO2 max are largely facilitated by expansion of red blood cell volume and an associated improvement in stroke volume, which also adapts independent of changes in red blood cell volume. These general concepts are also informed by cross-sectional studies in athletes that have very high values for VO2 max. Therefore, (ii) variations in VO2 max improvements with exercise training are also likely related to variations in these physiological determinants. (iii) All previously untrained individuals will respond to endurance exercise training in terms of improvements in VO2 max provided the stimulus exceeds a certain volume and/or intensity. Thus, genetic analysis and/or reductionist studies performed to understand or predict such variations might focus specifically on DNA variants or other molecular phenomena of relevance to these physiological pathways. © 2016 Scandinavian Physiological Society. Published by John Wiley & Sons Ltd.

  16. Why is VO2 max after altitude acclimatization still reduced despite normalization of arterial O2 content?

    DEFF Research Database (Denmark)

    Calbet, J A L; Boushel, Robert Christopher; Radegran, G

    2003-01-01

    Acute hypoxia (AH) reduces maximal O2 consumption (VO2 max), but after acclimatization, and despite increases in both hemoglobin concentration and arterial O2 saturation that can normalize arterial O2 concentration ([O2]), VO2 max remains low. To determine why, seven lowlanders were studied at VO2...

  17. [VO2 max, a true exercise test].

    Science.gov (United States)

    Saunier, Carole

    2013-01-01

    VO2 max is nowadays an essential examination performed in the monitoring of heart failure. The nurse has a role to play during the test and in supporting the patient, although this test remains highly technical and complex.

  18. VO2max Measured with a Self-selected Work Rate Protocol on an Automated Treadmill.

    Science.gov (United States)

    Scheadler, Cory M; Devor, Steven T

    2015-10-01

    The use of graded maximal exercise tests for measuring maximal oxygen consumption (VO2max) is common practice in both cardiopulmonary rehabilitation settings and in sports medicine research. Recent alterations of common testing protocols to allow for self-selected work rates (SPV) have elicited V˙O2max values similar to or higher than more traditional style protocols (TP). Research is lacking in the delivery of the SPV protocol using a treadmill modality. The purpose of the study was to examine the validity of an SPV using an automated treadmill for measuring cardiorespiratory fitness. Thirteen experienced endurance runners completed three maximal exercise tests on a treadmill. Oxygen consumption was measured using a computerized system and averaged more than 30-s time periods. SPV was completed using an automated treadmill that consisted of a sonar range finder, microcontroller, and customized computer software. Subject deviations from the middle of the treadmill belt resulted in rapid, graded increases or decreases in speed. TP was completed on the same treadmill without the use of the automated software. A verification phase protocol (VP) was used to verify if VO2 was maximal. Peak work rate achieved during SPV was significantly greater than that achieved during TP by 1.2 METs; P VO2max than TP despite higher work rates.

  19. HIGHER PRECISION OF HEART RATE COMPARED WITH VO2 TO PREDICT EXERCISE INTENSITY IN ENDURANCE-TRAINED RUNNERS

    Directory of Open Access Journals (Sweden)

    Victor M. Reis

    2011-03-01

    Full Text Available The aim of the present study was to assess the precision of oxygen uptake with heart rate regression during track running in highly-trained runners. Twelve national and international level male long-distance road runners (age 30.7 ± 5.5 yrs, height 1.71 ± 0.04 m and mass 61.2 ± 5.8 kg with a personal best on the half marathon of 62 min 37 s ± 1 min 22 s participated in the study. Each participant performed, in an all-weather synthetic track five, six min bouts at constant velocity with each bout at an increased running velocity. The starting velocity was 3.33 m·s-1 with a 0.56 m·s-1 increase on each subsequent bout. VO2 and heart rate were measured during the runs and blood lactate was assessed immediately after each run. Mean peak VO2 and mean peak heart rate were, respectively, 76.2 ± 9.7 mL·kg-1·min-1 and 181 ± 13 beats·min-1. The linearity of the regressions between heart rate, running velocity and VO2 were all very high (r > 0.99 with small standard errors of regression (i.e. Sy.x < 5% at the velocity associated with the 2 and 4 mmol·L-1 lactate thresholds. The strong relationships between heart rate, running velocity and VO2 found in this study show that, in highly trained runners, it is possible to have heart rate as an accurate indicator of energy demand and of the running speed. Therefore, in this subject cohort it may be unnecessary to use VO2 to track changes in the subjects' running economy during training periods.

  20. Matching of Male and Female Subjects Using VO2 Max.

    Science.gov (United States)

    Cureton, Kirk J.

    1981-01-01

    The increasing use of various VO2 max expressions as test measures is a problem because the magnitude of sex difference varies considerably with each expression. A valid match of male and female test subjects would consider physical activity history and the amount of endurance exercise done in the previous year. (Author/FG)

  1. VO2 prediction and cardiorespiratory responses during underwater treadmill exercise.

    Science.gov (United States)

    Greene, Nicholas P; Greene, Elizabeth S; Carbuhn, Aaron F; Green, John S; Crouse, Stephen F

    2011-06-01

    We compared cardiorespiratory responses to exercise on an underwater treadmill (UTM) and land treadmill (LTM) and derived an equation to estimate oxygen consumption (VO2) during UTM exercise. Fifty-five men and women completed one LTM and five UTM exercise sessions on separate days. The UTM sessions consisted of chest-deep immersion, with 0, 25, 50, 75, and 100% water-jet resistance. All session treadmill velocities increased every 3 min from 53.6 to 187.8 m x min(-1). Cardiorespiratory responses were similar between LTM and UTM when jet resistance for UTM was 50%. Using multiple regression analysis, weight-relative VO2 could be estimated as: VO2 (mLO2 c kg(-1) x min(-1)) = 0.19248 x height (cm) + 0.17422 x jet resistance (% max) + 0.14092 x velocity (m x min(-1)) -0.12794 x weight (kg)-27.82849, R2 = .82. Our data indicate that similar LTM and UTM cardiorespiratory responses are achievable, and we provide a reasonable estimate of UTM VO2.

  2. Peak Oxygen Uptake during and after Long-duration Space Flight

    Science.gov (United States)

    Moore, Alan D., Jr.; Downs, Meghan E.; Lee, Stuart M. C.; Feiveson, Alan H.; Knudsen, Poul; Evetts, Simon N.; Ploutz-Snyder, Lori

    2014-01-01

    Aerobic capacity (VO2peak) previously has not been measured during or after long-duration spaceflight. PURPOSE: To measure VO2peak and submaximal exercise responses during and after International Space Station (ISS) missions. METHODS: Astronauts (9 M, 5 F: 49 +/- 5 yr, 175 +/- 7 cm, 77.2 +/- 15.1 kg, 40.6 +/- 6.4 mL/kg/min [mean +/-SD]) performed graded peak cycle tests 90 days before spaceflight, 15 d (FD15) after launch and every 30 d thereafter during flight, and 1 (R+1), 10 (R+10), and 30 d (R+30) after landing. Oxygen consumption (VO2) and heart rate (HR) were measured from rest to peak exercise, while cardiac output (Q), stroke volume (SV), and arterial-venous oxygen difference (a-vO2diff) were measured only during rest and submaximal exercise. Data were analyzed using mixed-model linear regression. Body mass contributed significantly to statistical models, and thus results are reported as modeled estimates for an average subject. RESULTS: Early inflight (FD15) VO2peak was 17% lower (95% CI = - 22%, -13%) than preflight. VO2peak increased during spaceflight (0.001 L/min/d, P = 0.02) but did not return to preflight levels. On R+1 VO2peak was 15% (95% CI = -19%, -10%) lower than preflight but recovered to within 2% of preflight by R+30 (95% CI = -6%, +3%). Peak HR was not significantly different from preflight at any time. Inflight submaximal VO2 and a-vO2diff were generally lower than preflight, but the Q vs. VO2 slope was unchanged. In contrast, the SV vs. VO2 slope was lower (P < 0.001), primarily due to elevated SV at rest, and the HR vs. VO2 slope was greater (P < 0.001), largely due to elevated HR during more intense exercise. On R+1 although the relationships between VO2 and Q, SV, and HR were not statistically different than preflight, resting and submaximal exercise SV was lower (P < 0.001), resting and submaximal exercise HR was higher (P < 0.002), and a-vO2diff was unchanged. HR and SV returned to preflight levels by R+30. CONCLUSION: In the average

  3. Validation of a new method for estimating VO2max based on VO2 reserve.

    Science.gov (United States)

    Swain, David P; Parrott, James A; Bennett, Anna R; Branch, J David; Dowling, Elizabeth A

    2004-08-01

    The American College of Sports Medicine's (ACSM) preferred method for estimating maximal oxygen consumption (VO2max) has been shown to overestimate VO2max, possibly due to the short length of the cycle ergometry stages. This study validates a new method that uses a final 6-min stage and that estimates VO2max from the relationship between heart rate reserve (HRR) and VO2 reserve. A cycle ergometry protocol was designed to elicit 65-75% HRR in the fifth and sixth minutes of the final stage. Maximal workload was estimated by dividing the workload of the final stage by %HRR. VO2max was then estimated using the ACSM metabolic equation for cycling. After the 6-min stage was completed, an incremental test to maximal effort was used to measure actual VO2max. Forty-nine subjects completed a pilot study using one protocol to reach the 6-min stage, and 50 additional subjects completed a modified protocol. The pilot study obtained a valid estimate of VO2max (r = 0.91, SEE = 3.4 mL x min(-1) x kg-1) with no over- or underestimation (mean estimated VO2max = 35.3 mL x min(-1) x kg(-1), mean measured VO2max = 36.1 mL x min(-1) x kg(-1)), but the average %HRR achieved in the 6-min stage was 78%, with several subjects attaining heart rates considered too high for submaximal fitness testing. The second study also obtained a valid estimate of VO2max (r = 0.89, SEE = 4.0 mL x min(-1) x kg(-1)) with no over- or underestimation (mean estimated VO2max = 36.7 mL x min(-1) x kg(-1), mean measured VO2max = 36.9 mL x min(-1) x kg(-1), and the average %HRR achieved in the 6-min stage was 64%. A new method for estimating VO2max from submaximal cycling based on VO2 reserve has been found to be valid and more accurate than previous methods.

  4. Infrared Thermochromic Properties of VO2 Thin Films Prepared through Aqueous Sol-gel Process

    Institute of Scientific and Technical Information of China (English)

    LIU Dongqing; CHENG Haifeng; ZHENG Wenwei; ZHANG Chaoyang

    2012-01-01

    The stoichiometric vanadium(Ⅳ) oxide thin films were obtained by controlling the temperature,time and pressure of annealing.The thermochromic phase transition and the IR thermochromic property of 400 nm and 900 nm VO2 thin films in the 7.5 μm-14 μm region were discussed.The derived VO2 thin film samples were characterized by Raman,XRD,XPS,AFM,SEM,and DSC.The resistance and infrared emissivity of VO2 thin films under different temperature were measured,and the thermal images of films were obtained using infrared imager.The results show that the VO2 thin film annealed at 550 ℃ for 10 hours through aqueous sol-gel process is pure and uniform.The 900 nm VO2 thin film exhibits better IR thermochromic property than the 400 nm VO2 thin film.The resistance of 900 nm VO2 film can change by 4orders of magnitude and the emissivity can change by 0.6 during the phase transition,suggesting the outstanding IR thermochromic property.The derived VO2 thin film can control its infrared radiation intensity and lower its apparent temperature actively when the real temperature increases,which may be applied in the field of energy saving,thermal control and camouflage.

  5. Peak Exercise Oxygen Uptake Predicts Recurrent Admissions in Heart Failure With Preserved Ejection Fraction.

    Science.gov (United States)

    Palau, Patricia; Domínguez, Eloy; Núñez, Eduardo; Ramón, José María; López, Laura; Melero, Joana; Sanchis, Juan; Bellver, Alejandro; Santas, Enrique; Bayes-Genis, Antoni; Chorro, Francisco J; Núñez, Julio

    2017-06-27

    Heart failure with preserved ejection fraction (HFpEF) is a highly prevalent syndrome with an elevated risk of morbidity and mortality. To date, there is scarce evidence on the role of peak exercise oxygen uptake (peak VO2) for predicting the morbidity burden in HFpEF. We sought to evaluate the association between peak VO2 and the risk of recurrent hospitalizations in patients with HFpEF. A total of 74 stable symptomatic patients with HFpEF underwent a cardiopulmonary exercise test between June 2012 and May 2016. A negative binomial regression method was used to determine the association between the percentage of predicted peak VO2 (pp-peak VO2) and recurrent hospitalizations. Risk estimates are reported as incidence rate ratios. The mean age was 72.5 ± 9.1 years, 53% were women, and all patients were in New York Heart Association functional class II to III. Mean peak VO2 and median pp-peak VO2 were 10 ± 2.8mL/min/kg and 60% (range, 47-67), respectively. During a median follow-up of 276 days [interquartile range, 153-1231], 84 all-cause hospitalizations in 31 patients (41.9%) were registered. A total of 15 (20.3%) deaths were also recorded. On multivariate analysis, accounting for mortality as a terminal event, pp-peak VO2 was independently and linearly associated with the risk of recurrent admission. Thus, and modeled as continuous, a 10% decrease of pp-peak VO2 increased the risk of recurrent hospitalizations by 32% (IRR, 1.32; 95%CI, 1.03-1.68; P = .028). In symptomatic elderly patients with HFpEF, pp-peak VO2 predicts all-cause recurrent admission. Copyright © 2017 Sociedad Española de Cardiología. Published by Elsevier España, S.L.U. All rights reserved.

  6. .VO2max is not altered by self-pacing during incremental exercise.

    Science.gov (United States)

    Chidnok, Weerapong; Dimenna, Fred J; Bailey, Stephen J; Burnley, Mark; Wilkerson, Daryl P; Vanhatalo, Anni; Jones, Andrew M

    2013-02-01

    We tested the hypothesis that incremental cycling to exhaustion that is paced using clamps of the rating of perceived exertion (RPE) elicits higher .VO2max values compared to a conventional ramp incremental protocol when test duration is matched. Seven males completed three incremental tests to exhaustion to measure .VO2max. The incremental protocols were of similar duration and included: a ramp test at 30 W min(-1) with constant cadence (RAMP1); a ramp test at 30 W min(-1) with cadence free to fluctuate according to subject preference (RAMP2); and a self-paced incremental test in which the power output was selected by the subject according to prescribed increments in RPE (SPT). The subjects also completed a .VO2max 'verification' test at a fixed high-intensity power output and a 3-min all-out test. No difference was found for .VO2max between the incremental protocols (RAMP1 = 4.33 ± 0.60 L min(-1); RAMP2 = 4.31 ± 0.62 L min(-1); SPT = 4.36 ± 0.59 L min(-1); P > 0.05) nor between the incremental protocols and the peak.VO2max measured during the 3-min all-out test (4.33 ± 0.68 L min(-1)) or the .VO2max measured in the verification test (4.32 ± 0.69 L min(-1)). The integrated electromyogram, blood lactate concentration, heart rate and minute ventilation at exhaustion were not different (P > 0.05) between the incremental protocols. In conclusion, when test duration is matched, SPT does not elicit a higher .VO2max compared to conventional incremental protocols. The striking similarity of .VO2max measured across an array of exercise protocols indicates that there are physiological limits to the attainment of .VO2max that cannot be exceeded by self-pacing.

  7. VO2 Kinetics and Metabolic Contributions Whilst Swimming at 95, 100, and 105% of the Velocity at VO2 max

    Directory of Open Access Journals (Sweden)

    Ana C. Sousa

    2014-01-01

    Full Text Available A bioenergetical analysis of swimming at intensities near competitive distances is inexistent. It was aimed to compare the transient VO2 kinetics responses and metabolic contributions whilst swimming at different velocities around VO2max⁡. 12 trained male swimmers performed (i an incremental protocol to determine the velocity at VO2max⁡ (vVO2max⁡ and (ii three square wave exercises from rest to 95, 100, and 105% of vVO2max⁡. VO2 was directly measured using a telemetric portable gas analyser and its kinetics analysed through a double-exponential model. Metabolic contributions were assessed through the sum of three energy components. No differences were observed in the fast component response (τ1—15, 18, and 16 s, A1—36, 34, and 37 mL·kg-1·min⁡-1, and Gain—32, 29, and 30 mL·min⁡-1 at 95, 100, and 105% of the vVO2max⁡, resp. but A2 was higher in 95 and 100% compared to 105% intensity (480.76 ± 247.01, 452.18 ± 217.04, and 147.04 ± 60.40 mL·min⁡-1, resp.. The aerobic energy contribution increased with the time sustained (83 ± 5, 74 ± 6, and 59 ± 7% for 95, 100, and 105%, resp.. The adjustment of the cardiovascular and/or pulmonary systems that determine O2 delivery and diffusion to the exercising muscles did not change with changing intensity, with the exception of VO2 slow component kinetics metabolic profiles.

  8. A theoretical analysis of factors determining VO2 MAX at sea level and altitude.

    Science.gov (United States)

    Wagner, P D

    1996-12-01

    When maximal VO2 (VO2 MAX) is limited by O2 supply, it is generally thought that cardiac output (QT) is mostly responsible, but other O2 transport conductances [ventilation (VA); [Hb]; pulmonary (DLO2) and muscle (DMO2) diffusion capacities] may also influence VO2 MAX. A numerical analysis interactively linking the lungs, circulation and muscles was designed to compare the influences of each conductance component on VO2 MAX at three altitudes: PB = 760, 464 and 253 Torr. For any given set of conductances the analysis simultaneously solved six equations for alveolar, arterial, and venous PO2 and PcO2. The equations represent pulmonary mass balance, pulmonary diffusion, and muscle diffusion for both gases. At PB = 760, [Hb], DLO2 and DMO2 were as influential as QT in limiting VO2 MAX. With increasing altitude, the influence of QT and [Hb] fell while that of VA, DLO2 and DMO2 progressively increased until at PB = 253, VO2 MAX was independent of QT and [Hb]. Neither the fall in maximal QT nor rise in [Hb] with chronic hypoxia therefore appear to affect VO2 MAX. However, high values of ventilation, DLO2 and DMO2 appear to be advantageous for exercise at altitude.

  9. Comparison of intensities and rest periods for VO2max verification testing procedures.

    Science.gov (United States)

    Nolan, P B; Beaven, M L; Dalleck, L

    2014-11-01

    We sought to determine the incidence of 'true' VO2max confirmation with the verification procedure across different protocols. 12 active participants (men n=6, women n=6) performed in random order 4 different maximal graded exercises tests (GXT) and verification bout protocols on 4 separate days. Conditions for the rest period and verification bout intensity were: A - 105% intensity, 20 min rest; B - 105% intensity, 60 min rest; C - 115% intensity, 20 min rest; D - 115% intensity, 60 min rest. VO2max confirmation (difference between peak VO2 GXT and verification trialVO2max confirmation across all exercise test conditions (intensity effect within recovery 20 min (χ(2) (1)=4.800, pVO2max confirmation with different rest periods. We recommend the use of 105% of the maximal GXT workload and 20 min rest periods when using verification trials to confirm VO2max in normally active populations. © Georg Thieme Verlag KG Stuttgart · New York.

  10. Effect of increasing pump speed during exercise on peak oxygen uptake in heart failure patients supported with a continuous-flow left ventricular assist device. A double-blind randomized study

    DEFF Research Database (Denmark)

    Jung, Mette Holme; Hansen, Peter Bo; Sander, Kaare

    2014-01-01

    AIMS: Continuous-flow left ventricular assist device (CF-LVAD) implantation is associated with improved quality of life, but the effect on exercise capacity is less well documented. It is uncertain whether a fixed CF-LVAD pump speed, which allows for sufficient circulatory support at rest, remains...... adequate during exercise. The aim of this study was to evaluate the effects of fixed versus incremental pump speed on peak oxygen uptake (peak VO2) during a maximal exercise test. METHODS AND RESULTS: In CF-LVAD (HeartMate II) patients exercise testing measuring peak oxygen uptake (VO2) was performed...... on an ergometer bike twice in one day: once with fixed pump speed (testfix) and once with incremental pump speed (testinc). The order of testfix and testinc in each patient was determined by randomization. During testinc pump speed was increased from the baseline value by 400 rpm/2 min. Fourteen patients (aged 23...

  11. Enhanced electrochemical performance of orientated VO2(B) raft-like nanobelt arrays through direct lithiation for lithium ion batteries

    Science.gov (United States)

    Liu, Liang; Liu, Qiang; Zhao, Wen; Li, Guochun; Wang, Limei; Shi, Weidong; Chen, Long

    2017-02-01

    Lithiation modification of VO2(B) has been carried out by a facile hydrothermal process, and the compact and locally ordered VO2(B) raft-like nanobelt arrays have been prepared. The synthesis route provides a new approach to elaborate a VO2(B) nanostructure under a mild environment condition. It is found that the growth mechanism of VO2(B) raft-like nanobelt arrays is different from the traditional nucleation-growth process. A novel chemical lithiating-exfoliating-splitting model is proposed. Compared with the bulk counterpart, the lithiated VO2(B) raft-like nanobelt arrays as cathodes exhibit a higher discharge capacity and an enhanced high-rate performance owing to their increased structural anisotropy and decreased polarization. This work indicates that VO2(B) raft-like nanobelt arrays have great potential applications as cathode materials for lithium ion batteries.

  12. The effects of recreational sport on VO₂peak, VO₂ kinetics and submaximal exercise performance in males and females.

    Science.gov (United States)

    Edgett, Brittany A; Ross, Jonathan E D; Green, Alex E; MacMillan, Norah J; Milne, Kevin J; Gurd, Brendon J

    2013-01-01

    The purpose of the present study was to examine changes in VO(2peak), VO(2) kinetics and steady-state exercise performance following 4 weeks of participation in recreational sport. Subjects (male n = 8, female n = 9) participated in recreational sport (basketball, floor hockey and soccer) four times per week for 4 weeks. Both before and after training, VO(2peak) was measured on a cycle ergometer, VO(2) kinetics was determined as the average of three transitions to 80 W, and heart rate (HR) and respiratory exchange ratio (RER) were measured during 60 min at a work rate corresponding to 50 % of pre-training VO(2peak). HR was also monitored during all training sessions. After training, VO(2peak) was increased in females, but not males, while VO(2) kinetics (τVO(2)) were sped in both males and females. HR during constant load exercise was reduced in both males and females, but exercise RER was only reduced in females. Mean HR during participation in sport was higher in males than females and higher during basketball than both floor hockey and soccer. These results demonstrate that training adaptations traditionally associated with endurance exercise can also be obtained through regular participation in recreational sport.

  13. New Methods for Processing and Quantifying VO2 Kinetics to Steady State: VO2 Onset Kinetics

    Directory of Open Access Journals (Sweden)

    Craig R. McNulty

    2017-09-01

    Full Text Available Current methods of oxygen uptake (VO2 kinetics data handling may be too simplistic for the complex physiology involved in the underlying physiological processes. Therefore, the aim of this study was to quantify the VO2 kinetics to steady state across the full range of sub-ventilatory threshold work rates, with a particular focus on the VO2 onset kinetics. Ten healthy, moderately trained males participated in five bouts of cycling. Each bout involved 10 min at a percentage of the subject's ventilation threshold (30, 45, 60, 75, 90% from unloaded cycling. The VO2 kinetics was quantified using the conventional mono-exponential time constant (tau, τ, as well as the new methods for VO2 onset kinetics. Compared to linear modeling, non-linear modeling caused a deterioration of goodness of fit (main effect, p < 0.001 across all exercise intensities. Remainder kinetics were also improved using a modified application of the mono-exponential model (main effect, p < 0.001. Interestingly, the slope from the linear regression of the onset kinetics data is similar across all subjects and absolute exercise intensities, and thereby independent of subject fitness and τ. This could indicate that there are no functional limitations between subjects during this onset phase, with limitations occurring for the latter transition to steady state. Finally, the continuing use of mono-exponential modeling could mask important underlying physiology of more instantaneous VO2 responses to steady state. Consequently, further research should be conducted on this new approach to VO2 onset kinetics.

  14. Speeding of pulmonary VO2 on-kinetics by light-to-moderate-intensity aerobic exercise training in chronic heart failure: clinical and pathophysiological correlates.

    Science.gov (United States)

    Mezzani, Alessandro; Grassi, Bruno; Jones, Andrew M; Giordano, Andrea; Corrà, Ugo; Porcelli, Simone; Della Bella, Silvia; Taddeo, Adriano; Giannuzzi, Pantaleo

    2013-09-01

    Pulmonary VO2 on-kinetics during light-to-moderate-intensity constant-work-rate exercise, an experimental model mirroring energetic transitions during daily activities, has been shown to speed up with aerobic exercise training (AET) in normal subjects, but scant data are available in chronic heart failure (CHF). Thirty CHF patients were randomized to 3 months of light-to-moderate-intensity AET (CHF-AET) or control (CHF-C). Baseline and end-protocol evaluations included i) one incremental cardiopulmonary exercise test with near infrared spectroscopy analysis of peak deoxygenated hemoglobin+myoglobin concentration changes (Δ[deoxy(Hb+Mb)]) in vastus lateralis muscle, ii) 8 light-to-moderate-intensity constant-work-rate exercise tests for VO2 on-kinetics phase I duration, phase II τ, and mean response time (MRT) assessment, and iii) circulating endothelial progenitor cell (EPC) measurement. Reference values were obtained in 7 age-matched normals (N). At end-protocol, phase I duration, phase II τ, and MRT were significantly reduced (-12%, -22%, and -19%, respectively) and peak VO2, peak Δ[deoxy(Hb+Mb)], and EPCs increased (9%, 20%, and 98%, respectively) in CHF-AET, but not in CHF-C. Peak Δ[deoxy(Hb+Mb)] and EPCs relative increase correlated significantly to that of peak VO2 (r=0.61 and 0.64, respectively, pexercise-related risk. The AET-induced simultaneous improvement of phase I and phase II, associated with an increase of peak peripheral oxygen extraction and EPCs, supports microcirculatory O2 delivery impairment as a key factor determining exercise intolerance in CHF. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

  15. Prior Knowledge of Trial Number Influences the Incidence of Plateau at VO2max.

    Science.gov (United States)

    Gordon, Dan; Caddy, Oliver; Merzbach, Viviane; Gernigon, Marie; Baker, James; Scruton, Adrian; Keiller, Don; Barnes, Richard

    2015-03-01

    The purpose of this study was to assess the VO2max plateau response at VO2max during a series of pre-determined trials. Ten male well-trained athletes (age, 23.0 ± 3.2; height, 183.3 ± 5.5 cm; mass 77.5 ± 11.1 Kg; VO2max 66.5 ± 5.0 ml(.)kg(-1,)min(-1)), but who were VO2max testing naïve and with prior-knowledge of trial number completed four incremental tests to volitional exhaustion, separated by ~72-h for the determination of VO2max and gas exchange threshold. Throughout all trials VO2max was recorded on a breath-by-breath basis using a pre-calibrated metabolic cart, using a plateau criterion of Δ VO2 ≤1.5 ml(.)kg(-1.)min(-1) over the final 2 consecutive 30 s sampling periods. A significant difference was observed between trial-1 and trial-4 for plateau incidence (p = 0.0285) rising from 20% in trial-1 to a 70% response rate in trial-4. Furthermore a significant difference was observed for VO2dif (difference between criterion value and Δ VO2) in trial-1, 1.02 ± 1.69 ml(.)kg(-1.)min(-1) (p = 0.038), with non-significant differences observed for all other trials, despite a non-significant difference for VO2max across all trials (p > 0.05). Finally, a significant difference was observed for effort perception (RPE) at volitional exhaustion between trial-1 (17.7 ± 1.3) and trial-4 (19.0 ± 1.4) (p = 0.0052). These data indicate that prior-knowledge of trial number can influence the manifestation of the VO2 plateau in a group of well-trained male athletes, thereby suggesting that a form of effort control is established in order to preserve the finite anaerobic capacity. Key pointsIn well-trained athletes the incidence of plateau at VO2max increases in conjunction with an increase in trial number and the associated sensations of pain and fatigue.By informing the participant of the number of trials to be completed a closed-loop condition is developed whereby effort in all trials is compared to a perceptually developed template.Closed-loop condition leads to a

  16. Hybrid Resonators and Highly Tunable Terahertz Metamaterials Enabled by Vanadium Dioxide (VO2).

    Science.gov (United States)

    Wang, Shengxiang; Kang, Lei; Werner, Douglas H

    2017-06-28

    Hybrid metamaterials that exhibit reconfigurable responses under external stimulus, such as electric fields and light radiation, have only recently been demonstrated by combining active media with patterned metallic structures. Nevertheless, hybrid terahertz (THz) metamaterials whose spectral performance can be dynamically tuned over a large scale remain rare. Compared with most active media (for instance, silicon) that provide limited activity, vanadium dioxide (VO2), which exhibits an insulator-to-metal transition, has been recently explored to facilitate dynamically tunable metamaterials. More importantly, the phase transition yields a three orders of magnitude increase in THz electrical conductivity, which suggests the potential for creating VO2 based hybrid resonators that operate at THz frequencies. Here, we show that an integration of VO2 structures and conventional metallic resonating components can enable a class of highly tunable THz metamaterials. Considering the widely studied phase-transition dynamics in VO2, the proposed hybrid metamaterials are capable of offering ultrafast modulation of THz radiation.

  17. Effects of erythrocyte infusion on VO2max at high altitude

    DEFF Research Database (Denmark)

    Young, Jette Feveile; Sawka, M N; Muza, S R

    1996-01-01

    group received only saline. The VO2max of erythrocyte-infused [54 +/- 1 (SE) ml.kg-1.min-1] and control subjects (52 +/- 2 ml.kg-1.min-1) did not differ at SL before infusion. The decrement in VO2max on HA1 did not differ between groups, averaging 26% overall, despite higher (P arterial...... hematocrit, hemoglobin concentration, and arterial O2 content in the erythrocyte-infused subjects. By HA9, there were no longer any differences in hematocrit, hemoglobin concentration, or arterial O2 content between groups. No change in VO2max occurred between HA1 and HA9 for either group. Thus, despite...... increasing arterial O2-carrying capacity, autologous erythrocyte infusion did not ameliorate the decrement in VO2max at 4,300-m altitude....

  18. Role of right ventricle and dynamic pulmonary hypertension on determining ΔVO2/ΔWork Rate flattening: insights from cardiopulmonary exercise test combined with exercise echocardiography.

    Science.gov (United States)

    Bandera, Francesco; Generati, Greta; Pellegrino, Marta; Donghi, Valeria; Alfonzetti, Eleonora; Gaeta, Maddalena; Villani, Simona; Guazzi, Marco

    2014-09-01

    Several cardiovascular diseases are characterized by an impaired O2 kinetic during exercise. The lack of a linear increase of Δoxygen consumption (VO2)/ΔWork Rate (WR) relationship, as assessed by expired gas analysis, is considered an indicator of abnormal cardiovascular efficiency. We aimed at describing the frequency of ΔVO2/ΔWR flattening in a symptomatic population of cardiac patients, characterizing its functional profile, and testing the hypothesis that dynamic pulmonary hypertension and right ventricular contractile reserve play a major role as cardiac determinants. We studied 136 patients, with different cardiovascular diseases, referred for exertional dyspnoea. Cardiopulmonary exercise test combined with simultaneous exercise echocardiography was performed using a symptom-limited protocol. ΔVO2/ΔWR flattening was observed in 36 patients (group A, 26.5% of population) and was associated with a globally worse functional profile (reduced peak VO2, anaerobic threshold, O2 pulse, impaired VE/VCO2). At univariate analysis, exercise ejection fraction, exercise mitral regurgitation, rest and exercise tricuspid annular plane systolic excursion, exercise systolic pulmonary artery pressure, and exercise cardiac output were all significantly (Pexercise systolic pulmonary artery pressure (odds ratio, 1.06; confidence interval, 1.01-1.11; P=0.01) and exercise tricuspid annular plane systolic excursion (odds ratio, 0.88; confidence interval, 0.80-0.97; P=0.01) as main cardiac determinants of ΔVO2/ΔWR flattening; female sex was strongly associated (odds ratio, 6.10; confidence interval, 2.11-17.7; Pincrease and the reduced peak right ventricular longitudinal systolic function. © 2014 American Heart Association, Inc.

  19. Higher Precision of Heart Rate Compared with VO2 to Predict Exercise Intensity in Endurance-Trained Runners.

    Science.gov (United States)

    Reis, Victor M; den Tillaar, Roland Van; Marques, Mario C

    2011-01-01

    The aim of the present study was to assess the precision of oxygen uptake with heart rate regression during track running in highly-trained runners. Twelve national and international level male long-distance road runners (age 30.7 ± 5.5 yrs, height 1.71 ± 0.04 m and mass 61.2 ± 5.8 kg) with a personal best on the half marathon of 62 min 37 s ± 1 min 22 s participated in the study. Each participant performed, in an all-weather synthetic track five, six min bouts at constant velocity with each bout at an increased running velocity. The starting velocity was 3.33 m·s(-1) with a 0.56 m·s(-1) increase on each subsequent bout. VO2 and heart rate were measured during the runs and blood lactate was assessed immediately after each run. Mean peak VO2 and mean peak heart rate were, respectively, 76.2 ± 9.7 mL·kg(-1)·min(-1) and 181 ± 13 beats·min(-1). The linearity of the regressions between heart rate, running velocity and VO2 were all very high (r > 0.99) with small standard errors of regression (i.e. Sy.x heart rate, running velocity and VO2 found in this study show that, in highly trained runners, it is possible to have heart rate as an accurate indicator of energy demand and of the running speed. Therefore, in this subject cohort it may be unnecessary to use VO2 to track changes in the subjects' running economy during training periods. Key pointsHeart rate is used in the control of exercise intensity in endurance sports.However, few studies have quantified the precision of its relationship with oxygen uptake in highly trained runners.We evaluated twelve elite half-marathon runners during track running at various intensities and established three regressions: oxygen uptake / heart rate; heart rate / running velocity and oxygen uptake / running velocity.The three regressions presented, respectively, imprecision of 4,2%, 2,75% and 4,5% at the velocity associated with the 4 mmol·L(-1) threshold.The results of the present study show that, in highly trained runners

  20. The ergogenic effect of recombinant human erythropoietin on VO2max depends on the severity of arterial hypoxemia

    DEFF Research Database (Denmark)

    Robach, Paul; Calbet, Jose A L; Thomsen, Jonas J;

    2008-01-01

    Treatment with recombinant human erythropoietin (rhEpo) induces a rise in blood oxygen-carrying capacity (CaO(2)) that unequivocally enhances maximal oxygen uptake (VO(2)max) during exercise in normoxia, but not when exercise is carried out in severe acute hypoxia. This implies that there should...... redistribution of cardiac output toward the exercising legs, whereas this advantageous effect disappeared during severe hypoxia, leaving augmented CaO(2) alone insufficient for improving peak leg O(2) delivery and VO(2). Finally, that VO(2)max was largely dependent on CaO(2) during moderate hypoxia but became...

  1. Fitness self-perception and Vo2max in firefighters.

    Science.gov (United States)

    Peate, W F; Lundergan, Linda; Johnson, Jerry J

    2002-06-01

    Firefighters work at maximal levels of exertion. Fitness for such duty requires adequate aerobic capacity (maximum oxygen consumption [Vo2max]). Aerobic fitness can both improve a worker's ability to perform and offer resistance to cardiopulmonary conditions. Inactive firefighters have a 90% greater risk of myocardial infarction than those who are aerobically fit. Participants (101 firefighters) completed a questionnaire that asked them to rank their fitness level from 0 to 7; e.g., Level 0 was low fitness: "I avoid walking or exertion, e.g., always use elevator, drive whenever possible." The level of activity rating increased to Level 7: "I run over 10 miles per week or spend 3 hours per week in comparable physical activity." Each participant then completed two measures of Vo2max: a 5-minute step test and a submaximal treadmill test. There was no association between the firefighters' self-perception of their level of fitness and their aerobic capacity as measured by either step test or submaximal treadmill. Because of the critical job demands of firefighting and the negative consequences of inadequate fitness and aerobic capacity, periodic aerobic capacity testing with individualized exercise prescriptions and work--community support may be advisable for all active-duty firefighters.

  2. VO2max trainability and high intensity interval training in humans: a meta-analysis.

    Science.gov (United States)

    Bacon, Andrew P; Carter, Rickey E; Ogle, Eric A; Joyner, Michael J

    2013-01-01

    Endurance exercise training studies frequently show modest changes in VO2max with training and very limited responses in some subjects. By contrast, studies using interval training (IT) or combined IT and continuous training (CT) have reported mean increases in VO2max of up to ~1.0 L · min(-1). This raises questions about the role of exercise intensity and the trainability of VO2max. To address this topic we analyzed IT and IT/CT studies published in English from 1965-2012. Inclusion criteria were: 1)≥ 3 healthy sedentary/recreationally active humans training duration 6-13 weeks, 3) ≥ 3 days/week, 4) ≥ 10 minutes of high intensity work, 5) ≥ 1:1 work/rest ratio, and 6) results reported as mean ± SD or SE, ranges of change, or individual data. Due to heterogeneity (I(2) value of 70), statistical synthesis of the data used a random effects model. The summary statistic of interest was the change in VO2max. A total of 334 subjects (120 women) from 37 studies were identified. Participants were grouped into 40 distinct training groups, so the unit of analysis was 40 rather than 37. An increase in VO2max of 0.51 L · min(-1) (95% CI: 0.43 to 0.60 L · min(-1)) was observed. A subset of 9 studies, with 72 subjects, that featured longer intervals showed even larger (~0.8-0.9 L · min(-1)) changes in VO2max with evidence of a marked response in all subjects. These results suggest that ideas about trainability and VO2max should be further evaluated with standardized IT or IT/CT training programs.

  3. VO2max trainability and high intensity interval training in humans: a meta-analysis.

    Directory of Open Access Journals (Sweden)

    Andrew P Bacon

    Full Text Available Endurance exercise training studies frequently show modest changes in VO2max with training and very limited responses in some subjects. By contrast, studies using interval training (IT or combined IT and continuous training (CT have reported mean increases in VO2max of up to ~1.0 L · min(-1. This raises questions about the role of exercise intensity and the trainability of VO2max. To address this topic we analyzed IT and IT/CT studies published in English from 1965-2012. Inclusion criteria were: 1≥ 3 healthy sedentary/recreationally active humans <45 yrs old, 2 training duration 6-13 weeks, 3 ≥ 3 days/week, 4 ≥ 10 minutes of high intensity work, 5 ≥ 1:1 work/rest ratio, and 6 results reported as mean ± SD or SE, ranges of change, or individual data. Due to heterogeneity (I(2 value of 70, statistical synthesis of the data used a random effects model. The summary statistic of interest was the change in VO2max. A total of 334 subjects (120 women from 37 studies were identified. Participants were grouped into 40 distinct training groups, so the unit of analysis was 40 rather than 37. An increase in VO2max of 0.51 L · min(-1 (95% CI: 0.43 to 0.60 L · min(-1 was observed. A subset of 9 studies, with 72 subjects, that featured longer intervals showed even larger (~0.8-0.9 L · min(-1 changes in VO2max with evidence of a marked response in all subjects. These results suggest that ideas about trainability and VO2max should be further evaluated with standardized IT or IT/CT training programs.

  4. Effects of electrical stimulation on VO2 kinetics and delta efficiency in healthy young men

    Science.gov (United States)

    Perez, M; Lucia, A; Santalla, A; Chicharro, J

    2003-01-01

    Objective: To determine the effects of electrical stimulation (ES) on oxygen uptake (VO2) kinetics and delta efficiency (DE) during gradual exercise. The hypothesis was that ES would attenuate the VO2-workload relation and improve DE. Methods: Fifteen healthy, untrained men (mean (SD) age 22 (5) years) were selected. Ten were electrostimulated on both quadriceps muscles with a frequency of 45–60 Hz, with 12 seconds of stimulation followed by eight seconds recovery for a total of 30 minutes a day, three days a week for six weeks. The remaining five subjects were assigned to a control group. A standardised exercise test on a cycle ergometer (ramp protocol, workload increases of 20 W/min) was performed by each subject before and after the experimental period. The slope of the VO2-power output (W) relation (ΔVO2/ΔW) and DE were calculated in each subject at moderate to high intensities (above the ventilatory threshold—that is, from 50–60% to 100% VO2max). Results: The mean (SEM) values for ΔVO2/ΔW and DE had significantly decreased and increased respectively after the six week ES programme (p<0.05; 9.8 (0.2) v 8.6 (0.5) ml O2/W/min respectively and 27.7 (0.9) v 31.5 (1.4)% respectively). Conclusions: ES could be used as a supplementary tool to improve two of the main determinants of endurance capacity, namely VO2 kinetics and work efficiency. PMID:12663356

  5. Skeletal muscle-specific expression of PGC-1α-b, an exercise-responsive isoform, increases exercise capacity and peak oxygen uptake.

    Directory of Open Access Journals (Sweden)

    Miki Tadaishi

    Full Text Available BACKGROUND: Maximal oxygen uptake (VO(2max predicts mortality and is associated with endurance performance. Trained subjects have a high VO(2max due to a high cardiac output and high metabolic capacity of skeletal muscles. Peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α, a nuclear receptor coactivator, promotes mitochondrial biogenesis, a fiber-type switch to oxidative fibers, and angiogenesis in skeletal muscle. Because exercise training increases PGC-1α in skeletal muscle, PGC-1α-mediated changes may contribute to the improvement of exercise capacity and VO(2max. There are three isoforms of PGC-1α mRNA. PGC-1α-b protein, whose amino terminus is different from PGC-1α-a protein, is a predominant PGC-1α isoform in response to exercise. We investigated whether alterations of skeletal muscle metabolism by overexpression of PGC-1α-b in skeletal muscle, but not heart, would increase VO(2max and exercise capacity. METHODOLOGY/PRINCIPAL FINDINGS: Transgenic mice showed overexpression of PGC-1α-b protein in skeletal muscle but not in heart. Overexpression of PGC-1α-b promoted mitochondrial biogenesis 4-fold, increased the expression of fatty acid transporters, enhanced angiogenesis in skeletal muscle 1.4 to 2.7-fold, and promoted exercise capacity (expressed by maximum speed by 35% and peak oxygen uptake by 20%. Across a broad range of either the absolute exercise intensity, or the same relative exercise intensities, lipid oxidation was always higher in the transgenic mice than wild-type littermates, suggesting that lipid is the predominant fuel source for exercise in the transgenic mice. However, muscle glycogen usage during exercise was absent in the transgenic mice. CONCLUSIONS/SIGNIFICANCE: Increased mitochondrial biogenesis, capillaries, and fatty acid transporters in skeletal muscles may contribute to improved exercise capacity via an increase in fatty acid utilization. Increases in PGC-1α-b protein or function

  6. Study of Thermal properties of VO2 and multilayer VO2 thin films for application in Thermal Switches

    Science.gov (United States)

    Zhu, Gaohua

    Ultrafast nature of the phase transition near room temperature in VO2 makes it attractive material for applications in electronics and optical devices however utilization of corresponding drastic change in thermo-physical properties are rarely reported. In this study we investigate thermal and electronic properties of VO2 thin films on various substrates across the transition temperature to seek possibility of utilizing VO2 based thermal switches for applications in thermal devices. In addition, the interfacial heat transfer in VO2/metal multilayer thin film is mediated by phonons at low temperature, and when temperature is elevated beyond phase transition temperature, the interface thermal conductance is mediated mainly by both phons and electrons. VO2-multilayers approach is studied to utilize the switching interface thermal conductance in order to obtain higher thermal conductivity switch ratio than what can be achieved in intrinsic VO2. Thermal conductivities and interface thermal conductance of VO2 and VO2 multilayer thin films are measured using the time-domain thermoreflectance (TDTR) method. We will discuss interplay of phononic and electronic component to thermal conductivity in the light of Wiedemann-Franz law across the metal to insulator state of VO2 films.

  7. Atomic layer deposition of VO2 films with Tetrakis-dimethyl-amino vanadium (IV) as vanadium precursor

    Science.gov (United States)

    Lv, Xinrui; Cao, Yunzhen; Yan, Lu; Li, Ying; Song, Lixin

    2017-02-01

    VO2 thin films have been grown on Si(100) (VO2/Si) and fused silica substrates (VO2/SiO2) by atomic layer deposition (ALD) using tetrakis-dimethyl-amino vanadium (IV) (TDMAV) as a novel vanadium precursor and water as reactant gas. The quartz crystal microbalance (QCM) measurement was performed to study the ALD process of VO2 thin film deposition, and a constant growth rate of about 0.95 Å/cycle was obtained at the temperature range of 150-200 °C. XRD measurement was performed to study the influence of deposition temperature and post-annealing condition on the crystallization of VO2 films, which indicated that the films deposited between 150 and 200 °C showed well crystallinity after annealing at 475 °C for 100 min in Ar atmosphere. XPS measurement verified that the vanadium oxidation state was 4+ for both as-deposited film and post-annealed VO2/Si film. AFM was applied to study the surface morphology of VO2/Si films, which showed a dense polycrystalline film with roughness of about 1 nm. The resistance of VO2/Si films deposited between 150 °C and 200 °C as a function of temperature showed similar semiconductor-to-metal transition (SMT) characters with the transition temperature for heating branch (Tc,h) of about 72 °C, a hysteresis width of about 10 °C and the resistance change of two orders of magnitude. The increase of Tc,h compared with the bulk VO2 (68 °C) may be attributed to the tensile stress along the c-axis in the film. Transmittance measurement of VO2/SiO2 films showed typical thermochromic property with a NIR switching efficiency of above 50% at 2 μm across the transition.

  8. Slow VO2 off-kinetics in skeletal muscle is associated with fast PCr off-kinetics--and inversely.

    Science.gov (United States)

    Korzeniewski, Bernard; Zoladz, Jerzy A

    2013-09-01

    The computer model of the bioenergetic system in skeletal muscle, developed previously, was used to study the effect of the characteristic decay time of the parallel activation of oxidative phosphorylation [τ(OFF)] during muscle recovery on the muscle oxygen consumption rate (Vo2) and phosphocreatine (PCr) work-to-rest transition (off)-kinetics and on the relationship between the Vo2 and PCr rest-to-work transition (on)- and off-kinetics in moderate and heavy exercise. An increase in τ(OFF) slows down the initial phase of the muscle Vo2 off-kinetics and accelerates the PCr off-kinetics. As a result, the relationship between the initial phase of the Vo2 off-kinetics (lasting approximately 3-60 s in computer simulations) and the PCr off-kinetics is inverse: the slower the former, the faster the latter. A faster initial phase of the Vo2 off-kinetics is associated with a slower late phase of the Vo2 off-kinetics, and as a result, the integral of Vo2 above baseline during recovery, representing the oxygen debt, is identical in all cases [values of τ(OFF)] for a given PCr decrease. Depending on τ(OFF), the muscle Vo2 on-kinetics was either equally fast or slower than the Vo2 off-kinetics in moderate exercise and always slower in heavy exercise. PCr on-kinetics was always faster than PCr off-kinetics. This study clearly demonstrates that τ(OFF) has a pronounced impact on the mutual relations between the muscle Vo2 and PCr on- and off-kinetics.

  9. Effect of high-intensity interval training on cardiovascular function, VO2max, and muscular force.

    Science.gov (United States)

    Astorino, Todd A; Allen, Ryan P; Roberson, Daniel W; Jurancich, Matt

    2012-01-01

    The purpose of this study was to examine the effects of short-term high-intensity interval training (HIIT) on cardiovascular function, cardiorespiratory fitness, and muscular force. Active, young (age and body fat = 25.3 ± 4.5 years and 14.3 ± 6.4%) men and women (N = 20) of a similar age, physical activity, and maximal oxygen uptake (VO2max) completed 6 sessions of HIIT consisting of repeated Wingate tests over a 2- to 3-week period. Subjects completed 4 Wingate tests on days 1 and 2, 5 on days 3 and 4, and 6 on days 5 and 6. A control group of 9 men and women (age and body fat = 22.8 ± 2.8 years and 15.2 ± 6.9%) completed all testing but did not perform HIIT. Changes in resting blood pressure (BP) and heart rate (HR), VO2max, body composition, oxygen (O2) pulse, peak, mean, and minimum power output, fatigue index, and voluntary force production of the knee flexors and extensors were examined pretraining and posttraining. Results showed significant (p VO2max, O2 pulse, and Wingate-derived power output with HIIT. The magnitude of improvement in VO2max was related to baseline VO2max (r = -0.44, p = 0.05) and fatigue index (r = 0.50, p 0.05) in resting BP, HR, or force production was revealed. Data show that HIIT significantly enhanced VO2max and O2 pulse and power output in active men and women.

  10. Echinacea purpurea supplementation does not enhance VO2max in distance runners.

    Science.gov (United States)

    Baumann, Cory W; Bond, Kelsey L; Rupp, Jeffrey C; Ingalls, Christopher P; Doyle, J Andrew

    2014-05-01

    Oral supplementation of Echinacea purpurea (ECH) has been reported to increase levels of serum erythropoietin and as a result improve endurance performance in untrained subjects. The purpose of this study was to determine if ECH supplementation alters maximal oxygen uptake (VO2max) in trained endurance runners. Using a double-blind design, 16 trained endurance runners (9 ECH and 7 placebo [PLA]) supplemented with either 8,000 mg·d(-1) of ECH or wheat flour (PLA) for 6 weeks. Maximal aerobic treadmill tests and blood samples were measured before and after supplementation to determine VO2max, hematocrit (Hct), and hemoglobin (Hb). VO2max, Hct, and Hb did not differ between the ECH and PLA groups before or after supplementation. Furthermore, supplementation of ECH failed to improve VO2max (67.37 ± 4.62 vs. 67.23 ± 5.82 ml·kg(-1)·min(-1)), Hct (43.57 ± 2.38 vs. 42.85 ± 1.46%), or Hb (14.93 ± 1.27 vs. 15.55 ± 0.80 g·dL(-1)) from baseline measurements. Echinacea purpurea supplementation of 8,000 mg·d(-1) for 6 weeks failed to increase VO2max, Hct, or Hb in trained endurance runners and thus does not seem to influence physiological variables that affect distance running performance.

  11. Fabrication and Characterization of Nanocrystalline VO2 Thin Films

    Institute of Scientific and Technical Information of China (English)

    WANG Hong-Chen; YI Xin-Jian; LAI Jian-Jun; LI Yi

    2005-01-01

    @@ Nanocrystalline VO2 films with phase transition temperature 34℃ have been fabricated on Si3N4-film-coated silicon and quartz substrates by argon-annealing films of metastable VO2(B). The original VO2(B) films are obtained by ion beam sputtering in an argon-oxygen atmosphere at 200 ℃. The nanocrystalline VO2 films exhibit strong changes in electrical and optical properties when a phase transition is completed. The phase transition temperature in the as-fabricated samples is about 34 ℃, which is smaller in comparison with 68 ℃ in the singlecrystalline VO2 material. A lower phase transition temperature is favorable for device applications such as smart window coating and low power consumption optical switching.

  12. AEROBIC FITNESS LEVEL TYPICAL OF ELITE ATHLETES IS NOT ASSOCIATED WITH EVEN FASTER VO2 KINETICS DURING CYCLING EXERCISE

    Directory of Open Access Journals (Sweden)

    Tiago R. Figueira

    2008-03-01

    Full Text Available The aim of this study was to address the question if the VO2 kinetics is further improved as the aerobic training status increases from trained to elite level athletes. Maximal oxygen uptake (VO2max, work-rate associated to VO2max (IVO2max and VO2 kinetics of moderate (Mod and maximal exercise (Max were determined in fifty- five subjects. Then, they were assigned into three groups: low (LF, intermediate (IF and high (HF aerobic fitness level. In average, the VO2max of LF, IF and HF groups were, respectively, 36.0 ± 3.1, 51.1 ± 4.5 and 68.1 ± 3.9 ml·kg·min-1 (p < 0.05 among each other. VO2 kinetics mean response time of both exercise intensities were significantly faster (p < 0.05 in HF (Mod, 27.5 ± 5.5 s; Max, 32.6 ± 8.3 s and IF (Mod, 25.0 ± 3.1 s; Max, 42.6 ± 10.4 s when compared to LF (Mod, 35.7 ± 7.9 s; Max: 57.8 ± 17.8 s. We can conclude that VO2 kinetics is improved as the fitness level is increased from low to intermediate but not further improved as the aerobic fitness level increases from intermediate to high.

  13. Transmission of reactive pulsed laser deposited VO2 films in the THz domain

    Science.gov (United States)

    Émond, Nicolas; Hendaoui, Ali; Ibrahim, Akram; Al-Naib, Ibraheem; Ozaki, Tsuneyuki; Chaker, Mohamed

    2016-08-01

    This work reports on the characteristics of the insulator-to-metal transition (IMT) of reactive pulsed laser deposited vanadium dioxide (VO2) films in the terahertz (THz) frequency range, namely the transition temperature TIMT, the amplitude contrast of the THz transmission over the IMT ΔA, the transition sharpness ΔT and the hysteresis width ΔH. XRD analysis shows the sole formation of VO2 monoclinic structure with an enhancement of (011) preferential orientation when varying the O2 pressure (PO2) during the deposition process from 2 to 25 mTorr. THz transmission measurements as a function of temperature reveal that VO2 films obtained at low PO2 exhibit low TIMT, large ΔA, and narrow ΔH. Increasing PO2 results in VO2 films with higher TIMT, smaller ΔA, broader ΔH and asymmetric hysteresis loop. The good control of the VO2 IMT features in the THz domain could be further exploited for the development of advanced smart devices, such as ultrafast switches, modulators, memories and sensors.

  14. VO 2+ ions in zinc lead borate glasses studied by EPR and optical absorption techniques

    Science.gov (United States)

    Prakash, P. Giri; Rao, J. Lakshmana

    2005-09-01

    Electron paramagnetic resonance (EPR) and optical absorption spectra of vanadyl ions in zinc lead borate (ZnO-PbO-B 2O 3) glass system have been studied. EPR spectra of all the glass samples exhibit resonance signals characteristic of VO 2+ ions. The values of spin-Hamiltonian parameters indicate that the VO 2+ ions in zinc lead borate glasses were present in octahedral sites with tetragonal compression and belong to C 4V symmetry. The spin-Hamiltonian parameters g and A are found to be independent of V 2O 5 content and temperature but changing with ZnO content. The decrease in Δ g∥/Δ g⊥ value with increase in ZnO content indicates that the symmetry around VO 2+ ions is more octahedral. The decrease in intensity of EPR signal above 10 mol% of V 2O 5 is attributed to a fall in the ratio of the number of V 4+ ions ( N4) to the number of V 5+ ions ( N5). The number of spins ( N) participating in resonance was calculated as a function of temperature for VO 2+ doped zinc lead borate glass sample and the activation energy was calculated. From the EPR data, the paramagnetic susceptibility was calculated at various temperatures and the Curie constant was evaluated from the 1/ χ- T graph. The optical absorption spectra show single absorption band due to VO 2+ ions in tetragonally distorted octahedral sites.

  15. Factors determining the time course of VO2(max) decay during bedrest: implications for VO2(max) limitation.

    Science.gov (United States)

    Capelli, C; Antonutto, G; Kenfack, M Azabji; Cautero, M; Lador, F; Moia, C; Tam, E; Ferretti, G

    2006-09-01

    The aim of this study was to characterize the time course of maximal oxygen consumption VO2(max) changes during bedrests longer than 30 days, on the hypothesis that the decrease in VO2(max) tends to asymptote. On a total of 26 subjects who participated in one of three bedrest campaigns without countermeasures, lasting 14, 42 and 90 days, respectively, VO2(max) maximal cardiac output (Qmax) and maximal systemic O2 delivery (QaO2max) were measured. After all periods of HDT, VO2max, Qmax, and QaO2max were significantly lower than before. The VO2max decreased less than qmax after the two shortest bedrests, but its per cent decay was about 10% larger than that of Qmax after 90-day bedrest. The VO2max decrease after 90-day bedrest was larger than after 42- and 14-day bedrests, where it was similar. The Qmax and QaO2max declines after 90-day bedrest was equal to those after 14- and 42-day bedrest. The average daily rates of the VO2max, Qmax, and QaO2max decay during bedrest were less if the bedrest duration were longer, with the exception of that of VO2max in the longest bedrest. The asymptotic VO2max decay demonstrates the possibility that humans could keep working effectively even after an extremely long time in microgravity. Two components in the VO2max decrease were identified, which we postulate were related to cardiovascular deconditioning and to impairment of peripheral gas exchanges due to a possible muscle function deterioration.

  16. Elite cross-country skiers do not reach their running VO2max during roller ski skating.

    Science.gov (United States)

    Losnegard, T; Hallén, J

    2014-08-01

    Cross-country skiers' VO2max is often measured during treadmill running. However, VO2max during treadmill skiing with the diagonal stride technique is higher, whereas it is lower during double poling, another classical style technique. How these values compare to VO2max during ski skating in elite cross country skiers is not known. Therefore, this study compared VO2max during treadmill uphill running and treadmill roller ski skating. Twenty-two males (21±2 years, 182±6 cm, 77±7 kg, VO2max running; 72.4±4.4 mL·kg-1·min-1) elite cross-country skiers and biathlon athletes underwent testing in both running and roller ski skating before (May) and at the end (October) of the preseason training. From May to October VO2max increased during running (3.1±4.5%, P=0.003, Effect size; ES=0.44, small) but not during roller ski skating (1.8±5.6%, P=0.13, ES=0.24, small). In May the subjects' VO2max during running was 1.7±4.7% higher compared to during roller ski skating (P=0.08, ES=0.24, small) while in October this difference was 3.0±5.0 % (PVO2max during roller ski skating than during running and this relationship does not change during the pre-season training period.

  17. Supramaximal testing to confirm attainment of VO2max in sedentary men and women.

    Science.gov (United States)

    Astorino, T A; White, A C; Dalleck, L C

    2009-04-01

    Supramaximal testing is widely used to verify VO2max attainment, yet its efficacy in sedentary subjects is unknown. The aim of the study was to test this hypothesis in men and women completing maximal cycle ergometry. Fifteen sedentary subjects (age=22.4+/-3.9 year) completed incremental exercise, and returned at least 24 h later to complete constant load exercise at 105% peak work rate (Wmax). Another group of nine sedentary men and women (age=21.8+/-5 year) completed supramaximal exercise at 115% Wmax 1-1.5 h after incremental exercise. During exercise, gas exchange data and heart rate (HR) were continuously obtained. VO2max was similar (p>0.05) between incremental and supramaximal exercise in subjects in the first (32.32+/-4.81 mL/kg/min vs. 31.80+/-5.35 mL/kg/min) and second subset (40.63+/-3.61 mL/kg/min vs. 41.66+/-5.55 mL/kg/min). Maximal HR was lower (pTest-retest reliability (r=0.81-0.89, pVO2max was high during repeated bouts of supramaximal testing. Findings support use of this protocol to confirm VO2max attainment in healthy, sedentary men and women completing incremental cycle ergometry.

  18. Epitaxial Ni/VO2 heterostructures on Si (001)

    Science.gov (United States)

    Singamaneni, Srinivasa Rao; Foley, Gabrielle; Prater, John; Narayan, Jay

    VO2 is a strongly correlated oxide, undergoes a first order metal-insulator (MIT) well above the room temperature 340K. Previous works have shown that the stress associated with structural changes across MIT, VO2 can produce significant changes in magnetic properties of over layer ferromagnetic films such as Ni. This control of the magnetic properties could be very important to many technological applications. However, the current use of r-sapphire as substrate can be restrictive in the microelectronics industry. The previous works focused their studies on polycrystalline Ni and VO2 films, which do not allow the precise controlling of the associated properties due to poor reproducibility of polycrystalline films. We have investigated the magnetic and electronic properties of Ni/VO2 films when epitaxially integrated on Si (001) by pulsed laser deposition using domain matching epitaxy paradigm. Ni was grown both in nanoscale islands and layered form. The XRD results showed that the Ni, VO2and YSZ layers were grown epitaxially in single out of plane orientations. We found that the hysteresis in resistance vs. temperature curves in VO2 thin films was retained even when it is in close proximity with the Ni layer which helped confirm that VO2 layer preserves its characteristic features, revealed the fingerprint magnetic features of Ni layer. We will present and discuss our comprehensive experimental findings.

  19. Difference in Physiological Components of VO2 Max During Incremental and Constant Exercise Protocols for the Cardiopulmonary Exercise Test.

    Science.gov (United States)

    Yamamoto, Junshiro; Harada, Tetsuya; Okada, Akinori; Maemura, Yuko; Yamamoto, Misaki; Tabira, Kazuyuki

    2014-08-01

    [Purpose] VO2 is expressed as the product of cardiac output and O2 extraction by the Fick equation. During the incremental exercise test and constant high-intensity exercise test, VO2 results in the attainment of maximal O2 uptake at exhaustion. However, the differences in the physiological components, cardiac output and muscle O2 extraction, have not been fully elucidated. We tested the hypothesis that constant exercise would result in higher O2 extraction than incremental exercise at exhaustion. [Subjects] Twenty-five subjects performed incremental exercise and constant exercise at 80% of their peak work rate. [Methods] Ventilatory, cardiovascular, and muscle oxygenation responses were measured using a gas analyzer, Finapres, and near-infrared spectroscopy, respectively. [Results] VO2 was not significantly different between the incremental exercise and constant exercise. However, cardiac output and muscle O2 saturation were significantly lower for the constant exercise than the incremental exercise at the end of exercise. [Conclusion] These findings indicate that if both tests produce a similar VO2 value, the VO2 in incremental exercise would have a higher ratio of cardiac output than constant exercise, and VO2 in constant exercise would have a higher ratio of O2 extraction than incremental exercise at the end of exercise.

  20. Estimated VO2max and its corresponding velocity predict performance of amateur runners

    Directory of Open Access Journals (Sweden)

    Bruno Ribeiro Ramalho Oliveira

    2012-03-01

    Full Text Available In recent years, there has been a substantial increase in the number of runners, with a proportional increase in their involvement in amateur street competition. Identification of the determinants of performance in this population appears necessary for optimization of time devoted to training. The objective of this study was to ascertain the association between estimated maximal oxygen uptake (VO2max, critical velocity (CV and VO2max velocity (VVO2max and athletic performance in the 3.6 km (uphill and 10 and 21.1 km (flatland events. Twelve amateur runners (nine male, mean age 36 ± 5 years underwent five tests: 1 and 5 km race on level ground, 3.6 km race with slope (≈8%, and indirect VO2max measurement. CV was determined from the linear relationship between distance and run time on the first two tests. The subjects then took part in two official 10 km and 21.1 km (half marathon races. VVO2max was calculated from the VO2max through a metabolic equation. VO2max showed the best association with running performance in the 10 and 21.1 km events. For the uphill race, VVO2max showed a better association. Overall, the variable with the highest average association was VO2max (0.91±0.07, followed by VVO2max (0.90±0.04 and VC (0.87±0.06. This study showed strong associations between physiological variables established by low-cost, user-friendly indirect methods and running performance in the 10 and 21.1 km (flatland and 3.6 km (uphill running events.

  1. Induction of cyto-protective autophagy by paramontroseite VO2 nanocrystals

    Science.gov (United States)

    Zhou, Wei; Miao, Yanyan; Zhang, Yunjiao; Liu, Liang; Lin, Jun; Yang, James Y.; Xie, Yi; Wen, Longping

    2013-04-01

    A variety of inorganic nanomaterials have been shown to induce autophagy, a cellular degradation process critical for the maintenance of cellular homeostasis. The overwhelming majority of autophagic responses elicited by nanomaterials were detrimental to cell fate and contributed to increased cell death. A widely held view is that the inorganic nanoparticles, when encapsulated and trapped by autophagosomes, may compromise the normal autophagic process due to the inability of the cells to degrade these materials and thus they manifest a detrimental effect on the well-being of a cell. Here we show that, contrary to this notion, nano-sized paramontroseite VO2 nanocrystals (P-VO2) induced cyto-protective, rather than death-promoting, autophagy in cultured HeLa cells. P-VO2 also caused up-regulation of heme oxygenase-1 (HO-1), a cellular protein with a demonstrated role in protecting cells against death under stress situations. The autophagy inhibitor 3-methyladenine significantly inhibited HO-1 up-regulation and increased the rate of cell death in cells treated with P-VO2, while the HO-1 inhibitor protoporphyrin IX zinc (II) (ZnPP) enhanced the occurrence of cell death in the P-VO2-treated cells while having no effect on the autophagic response induced by P-VO2. On the other hand, Y2O3 nanocrystals, a control nanomaterial, induced death-promoting autophagy without affecting the level of expression of HO-1, and the pro-death effect of the autophagy induced by Y2O3. Our results represent the first report on a novel nanomaterial-induced cyto-protective autophagy, probably through up-regulation of HO-1, and may point to new possibilities for exploiting nanomaterial-induced autophagy for therapeutic applications.

  2. Frequency of the VO2max plateau phenomenon in world-class cyclists.

    Science.gov (United States)

    Lucía, A; Rabadán, M; Hoyos, J; Hernández-Capilla, M; Pérez, M; San Juan, A F; Earnest, C P; Chicharro, J L

    2006-12-01

    We aimed to determine the frequency of the VO2max plateau phenomenon in top-level male professional road cyclists (n = 38; VO2max [mean +/- SD]: 73.5 +/- 5.5 ml.kg(-1).min(-1)) and in healthy, sedentary male controls (n = 37; VO2max: 42.7 +/- 5.6 ml.kg(-1).min(-1)). All subjects performed a continuous incremental cycle-ergometer test of 1-min workloads until exhaustion. Power output was increased from a starting value of 25 W (cyclists) or 20 W (controls) at the rate of 25 W.min(-1) (cyclists) or 20 W.min(-1) (controls) until volitional exhaustion. We measured gas-exchange and heart rate (HR) throughout the test. Blood concentrations of lactate (BLa) were measured at end-exercise in both groups. We defined maximal exercise exertion as the attainment of a respiratory exchange rate (RER) >or= 1.1; HR > 95 % age-predicted maximum; and BLa > 8 mmo.l(-1). The VO2max plateau phenomenon was defined as an increase in two or more consecutive 1-min mean VO2 values of less than 1.5 ml.kg(-1).min(-1). Most cyclists met our criteria for maximal exercise effort (RER > 1.1, 100 %; 95 % predicted maximal HR [HRmax], 82 %; BLa > 8 mmol.l(-1), 84 %). However, the proportion of cyclists attaining a V.O (2max) plateau was considerably lower, i.e., 47 %. The majority of controls met the criteria for maximal exercise effort (RER > 1.1, 100 %; predicted HRmax, 68 %; BLa > 8 mmol. l(-1), 73 %), but the proportion of these subjects with a VO2max plateau was only 24 % (significantly lower proportion than in cyclists [p < 0.05]). Scientists should consider 1) if typical criteria of attainment of maximal effort are sufficiently stringent, especially in elite endurance athletes; and 2) whether those humans exhibiting the VO2max plateau phenomenon are those who perform an absolute maximum effort or there are additional distinctive features associated with this phenomenon.

  3. Peak oxygen uptake in relation to total heart volume discriminates heart failure patients from healthy volunteers and athletes

    Directory of Open Access Journals (Sweden)

    Buhre Torsten

    2010-12-01

    Full Text Available Abstract Background An early sign of heart failure (HF is a decreased cardiac reserve or inability to adequately increase cardiac output during exercise. Under normal circumstances maximal cardiac output is closely related to peak oxygen uptake (VO2peak which has previously been shown to be closely related to total heart volume (THV. Thus, the aim of this study was to derive a VO2peak/THV ratio and to test the hypothesis that this ratio can be used to distinguish patients with HF from healthy volunteers and endurance athletes. Thirty-one patients with HF of different etiologies were retrospectively included and 131 control subjects (60 healthy volunteers and 71 athletes were prospectively enrolled. Peak oxygen uptake was determined by maximal exercise test and THV was determined by cardiovascular magnetic resonance. The VO2peak/THV ratio was then derived and tested. Results Peak oxygen uptake was strongly correlated to THV (r2 = 0.74, p 2 = 0.0002, p = 0.95. The VO2peak/THV ratio differed significantly between control subjects and patients, even in patients with normal ejection fraction and after normalizing for hemoglobin levels (p 2peak/THV ratio was the only independent predictor of presence of HF (p Conclusions The VO2peak/THV ratio can be used to distinguish patients with clinically diagnosed HF from healthy volunteers and athletes, even in patients with preserved systolic left ventricular function and after normalizing for hemoglobin levels.

  4. Interval training at 95% and 100% of the velocity at VO2 max: effects on aerobic physiological indexes and running performance.

    Science.gov (United States)

    Denadai, Benedito S; Ortiz, Marcelo J; Greco, Camila C; de Mello, Marco T

    2006-12-01

    The objective of this study was to analyze the effect of two different high-intensity interval training (HIT) programs on selected aerobic physiological indices and 1500 and 5000 m running performance in well-trained runners. The following tests were completed (n=17): (i) incremental treadmill test to determine maximal oxygen uptake (VO2 max), running velocity associated with VO2 max (vVO2 max), and the velocity corresponding to 3.5 mmol/L of blood lactate concentration (vOBLA); (ii) submaximal constant-intensity test to determine running economy (RE); and (iii) 1500 and 5000 m time trials on a 400 m track. Runners were then randomized into 95% vVO2 max or 100% vVO2 max groups, and undertook a 4 week training program consisting of 2 HIT sessions (performed at 95% or 100% vVO2 max, respectively) and 4 submaximal run sessions per week. Runners were retested on all parameters at the completion of the training program. The VO2 max values were not different after training for both groups. There was a significant increase in post-training vVO2 max, RE, and 1500 m running performance in the 100% vVO2 max group. The vOBLA and 5000 m running performance were significantly higher after the training period for both groups. We conclude that vOBLA and 5000 m running performance can be significantly improved in well-trained runners using a 4 week training program consisting of 2 HIT sessions (performed at 95% or 100% vVO2 max) and 4 submaximal run sessions per week. However, the improvement in vVO2 max, RE, and 1500 m running performance seems to be dependent on the HIT program at 100% vVO2 max.

  5. 基于FTO/VO2/FTO结构的VO2薄膜电压诱导相变光调制特性∗%Optical mo dulation characteristics of VO2 thin film due to electric field induced phase transition in the FTO/VO2/FTO structure

    Institute of Scientific and Technical Information of China (English)

    郝如龙; 方宝英; 王晓华; 肖寒; 李毅; 刘飞; 孙瑶; 唐佳茵; 陈培祖; 蒋蔚; 伍征义; 徐婷婷

    2015-01-01

    VO2 thin films have been studied for their semiconductor–metal reversible transition from the monoclinic to the rutile structure, where the electrical and optical properties undergo a drastic change by increasing the temperature or by applying a voltage. VO2 film is becoming a promising material for optical switch, optical storage, optical modulator, smart window, and micro-bolometer. The preparation procedures of the FTO/VO2/FTO structure in detail are as follows:First, the F-doped SnO2 conductive glass (FTO) substrates are cleaned sequentially in acetone, ethanol, and deionized water for 10 min using an ultrasonic cleaning equipment at a frequency of 20 kHz. When the FTO substrates was cleaned, they are dried with nitrogen. Second, the dried FTO substrates are placed in the chamber of a DC magnetron sputtering system equipped with a high-purity metal target of V (99.9%). After argon (99.999%) of 80 sccm flux was discharged with the current of 2 A and the voltage of 400 V for 2 min, the vanadium films are deposited on the FTO substrates. Third, the prepared vanadium films are annealed for different annealing time in an atmosphere composed of different proportions of nitrogen-oxygen. Then another layer thickness of 350 nm of FTO conductive film is deposited on the VO2 thin film by using the plasma enhanced chemical vapor deposition method. Finally, different sizes of the FTO/VO2/FTO structure are prepared by using photolithography and chemical etching processes. The effect of different annealing time and different proportions of nitrogen-oxygen atmosphere on the VO2 thin films has been studied. X-ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS) and spectrophotometer are then used to test and analyze the crystal structure, surface morphology, surface roughness, the relative content of the surface elements, and transmittance of the VO2/FTO composite films. Results show that a relatively

  6. MYOCARDIAL BLOOD-FLOW AND VO2 IN LAMBS WITH AN AORTOPULMONARY SHUNT DURING STRENUOUS EXERCISE

    NARCIS (Netherlands)

    GRATAMA, JWC; MEUZELAAR, JJ; DALINGHAUS, M; KOERS, JH; GERDING, AM; MONCHEN, MTM; TENIJENHUIS, FCAM; ZIJLSTRA, WG; KUIPERS, JRG

    To determine how much myocardial O2 consumption (VO2) would increase during an additional load on the heart in shunt as compared with control lambs, we studied 12 7-wk-old lambs with an aortopulmonary left-to-right shunt (59 +/- 3% of left ventricular output, means +/-SE) and 11 control lambs during

  7. Percent utilization of VO2 max at 5-km competition velocity does not determine time performance at 5 km among elite distance runners.

    Science.gov (United States)

    Støa, Eva Maria; Støren, Øyvind; Enoksen, Eystein; Ingjer, Frank

    2010-05-01

    The present study investigated to what extent maximum oxygen uptake (VO2 max) and fractional utilization (%VO2 max) in 5-km competition speed correlate with 5-km performance times among elite long distance runners. Eight elite long distance runners with 5-km performance times of 15.10 minutes ( +/- 32 seconds) were tested for VO2 max during an incremental protocol and for %VO2 max during an 8-minute treadmill test at the velocity representing their 5-km seasonal best performance time. There was no correlation between fractional utilization and 5-km performance. The study showed no significant difference between VO2 max obtained during an incremental VO2 max test and %VO2 max when running for 8 minutes at the runner's individual 5-km competition speed. The 5-km time was related to the runner's VO2 max even in a homogenous high-level performance group. In conclusion, the present study found no relationship between fractional utilization and 5-km performance time. Training aiming to increase %VO2 max may thus be of little or no importance in performance enhancement for competitions lasting up to approximately 20 minutes.

  8. Peak heart rate decreases with increasing severity of acute hypoxia

    DEFF Research Database (Denmark)

    Lundby, C; Araoz, M; Van Hall, Gerrit

    2001-01-01

    The purpose of the present study was to investigate the degree to which peak heart rate is reduced during exhaustive exercise in acute hypoxia. Five sea-level lowlanders performed maximal exercise at normobaric normoxia and at three different levels of hypobaric hypoxia (barometric pressures of 518......, 459, and 404 mmHg) in a hypobaric chamber and while breathing 9% O(2) in N(2). These conditions were equivalent to altitudes of 3300, 4300, 5300, and 6300 m above sea level, respectively. At 4300 m, maximal exercise was also repeated after 4 and 8 h. Peak heart rate (HR) decreased from 191 (182...

  9. Effects of optimal pacing strategies for 400-, 800-, and 1500-m races on the VO2 response.

    Science.gov (United States)

    Hanon, Christine; Thomas, Claire

    2011-06-01

    The aim of this study was to compare the evolution of oxygen uptake (VO2) in specifically trained runners during running tests based on the 400-, 800-, and 1500-m pacing strategies adopted by elite runners to optimize performance. Final velocity decreased significantly for all three distances, with the slowest velocity in the last 100 m expressed relative to the peak velocity observed in the 400 m (77%), 800 m (88%), and 1500 m (96%). Relative to the previously determined VO2max values, the respective VO 2peak corresponded to 94% (400 m) and 100% (800 and 1500 m). In the last 100 m, a decrease in VO2 was observed in all participants for the 400-m (15.6 ± 6.5%) and 800-m races (9.9 ± 6.3%), whereas a non-systematic decrease (3.6 ± 7.6%) was noted for the 1500 m. The amplitude of this decrease was correlated with the reduction in tidal volume recorded during the last 100 m of each distance (r = 0.85, P < 0.0001) and with maximal blood lactate concentrations after the three races (r = 0.55, P < 0.005). The present data demonstrate that the 800 m is similar to the 400 m in terms of decreases in velocity and VO2.

  10. Aerobic Fitness Level Typical of Elite Athletes is not Associated With Even Faster VO2 Kinetics During Cycling Exercise.

    Science.gov (United States)

    Figueira, Tiago R; Caputo, Fabrizio; Machado, Carlos E P; Denadai, Benedito S

    2008-01-01

    The aim of this study was to address the question if the VO2 kinetics is further improved as the aerobic training status increases from trained to elite level athletes. Maximal oxygen uptake (VO2max), work-rate associated to VO2max (IVO2max) and VO2 kinetics of moderate (Mod) and maximal exercise (Max) were determined in fifty- five subjects. Then, they were assigned into three groups: low (LF), intermediate (IF) and high (HF) aerobic fitness level. In average, the VO2max of LF, IF and HF groups were, respectively, 36.0 ± 3.1, 51.1 ± 4.5 and 68.1 ± 3.9 ml·kg·min(-1) (p ≤ 0.05 among each other). VO2 kinetics mean response time of both exercise intensities were significantly faster (p ≤ 0.05) in HF (Mod, 27.5 ± 5.5 s; Max, 32.6 ± 8.3 s) and IF (Mod, 25.0 ± 3.1 s; Max, 42.6 ± 10.4 s) when compared to LF (Mod, 35.7 ± 7.9 s; Max: 57.8 ± 17.8 s). We can conclude that VO2 kinetics is improved as the fitness level is increased from low to intermediate but not further improved as the aerobic fitness level increases from intermediate to high. Key pointsCurrently, it is reasonable to believe that the rate-limiting step of VO2 kinetics depends on exercise intensity.The well known physiological adaptations induced by endurance training are likely the most extreme means to overcome rate-limiting steps determining VO2 kinetics across exercise intensities.However, exercise adaptation leading individuals to the high-end of aerobic fitness level range (VO2max > 65 ml.kg.min-1) is not able to further improve VO2 kinetics during both, moderate and maximal intensity exercise.

  11. A novel inorganic precipitation-peptization method for VO2 sol and VO2 nanoparticles preparation: Synthesis, characterization and mechanism.

    Science.gov (United States)

    Li, Yao; Jiang, Peng; Xiang, Wei; Ran, Fanyong; Cao, Wenbin

    2016-01-15

    In this paper, a simple, safe and cost-saving precipitation-peptization method was proposed to prepare VO2 sol by using inorganic VOSO4-NH3⋅H2O-H2O2 reactants system in air under room temperature. In this process, VOSO4 was firstly precipitated to form VO(OH)2, then monometallic species of VO(O2)(OH)(-) were formed through the coordination between VO(OH)2 and H2O2. The rearrangement of VO(O2)(OH)(-) in a nonplanar pattern and intermolecular condensation reactions result in multinuclear species. Finally, VO2 sol is prepared through the condensation reactions between the multinuclear species. After drying the obtained sol at 40°C, VO2 xerogel exhibiting monoclinic crystal structure with the space group of C2/m was prepared. The crystal structure of VO2 nanoparticles was transferred to monoclinic crystal structure with the space group of P21/c (VO2(M)) by annealing the xerogel at 550°C. Both XRD and TEM analysis indicated that the nanoparticles possess good crystallinity with crystallite size of 34.5nm as estimated by Scherrer's method. These results suggest that the VO2 sol has been prepared successfully through the proposed simple method.

  12. Development of a hockey-specific, skate-treadmill VO2 max protocol.

    Science.gov (United States)

    Dreger, R W; Quinney, H A

    1999-12-01

    The purpose of this study was to investigate a protocol for the determination of VO2 max utilizing a motor-driven skate treadmill (ST). On separate days, 6 male hockey players completed a ST and a cycle ergometer (BK) VO2 max protocol. The results showed no significant difference between the ST and BK protocols for relative (60.4 +/- 5.09 vs. 59.0 +/- 8.31 ml.kg-1.min-1) and absolute VO2 max values (4.51 +/- 0.50 vs. 4.39 +/- 0.59 L.min-1), respectively. Significantly higher HR max was recorded during the ST protocol (202.3 +/- 4.27 vs. 200.7 +/- 4.55 b.min-1) (p < 0.05). Peak VE and VT were nonsignificant between the two conditions. However, peak f was higher for the ST protocol (63.0 +/- 7.56 vs. 60.2 +/- 7.76 breath.min-1) (p < 0.05). Although the physiological response to both protocols was similar, the ST protocol replicates a hockey stride, which may provide more applicable information for the development of training programs.

  13. Accuracy of VO2(max) prediction equations in older adults.

    Science.gov (United States)

    Peterson, Matthew J; Pieper, Carl F; Morey, Miram C

    2003-01-01

    We explored the accuracy and bias of prediction equations (ACSM and Foster) in older, deconditioned men and women. We also examined the predictors of VO2(max) to further understand which variables affect respiratory fitness in the elderly. One hundred seventy-one community dwelling, men (72.6 +/- 4.8 yr) and women (71.0 +/- 5.1 yr) screened in a clinical trial were retrospectively examined. VO2(max) was measured using a standardized protocol with gas exchange measured. Measured VO2 (max) values were compared with prediction equations via mean difference analyses, and bias was explored using Bland-Altman analyses. Regression analysis determined significant predictors of measured VO2 (max). Alpha was PVO2 (max), 21.7 +/- 4.8 and 17.3 +/- 4.0, respectively. ACSM overestimated VO2 (max) in men and women, 26.3 +/- 8.2 and 20.9 +/- 7.3, respectively. By using Bland-Altman plots, ACSM showed significant overestimation bias in more fit women (r = 0.29), whereas Foster showed no estimation bias in either gender. Significant predictors of VO2 (max) were gender, BMI, age, treadmill grade, and speed, with an equation R(2) of 0.70. A measure of current activity levels did not make it into the final model ( P= 0.0505) but is worthy of future consideration using more sensitive measures than ours. ACSM is not appropriate for use when treadmill testing older adults. We believe the Foster equation's VO2 (max) prediction accuracy is acceptable, showing no bias along a continuum of aerobic capacity.

  14. Modality determines VO2max achieved in self-paced exercise tests: validation with the Bruce protocol.

    Science.gov (United States)

    Hanson, Nicholas J; Scheadler, Cory M; Lee, Taylor L; Neuenfeldt, Noah C; Michael, Timothy J; Miller, Michael G

    2016-07-01

    The Bruce protocol is traditionally used to assess maximal cardiorespiratory fitness (VO2max), but may have limitations, such as an unknown duration and large work rate increases. The use of self-paced VO2max tests (SPVs) may be beneficial if they are able to elicit similar maximal values in a set period of time. In addition, differences in modality between SPVs have not been explored. The purpose of this study was to compare SPVs, utilizing two different modes, with the Bruce (treadmill) protocol. Thirteen healthy, recreationally active individuals (eight men, five women) volunteered and participated in three different laboratory visits with each utilizing a different VO2max testing protocol. The first visit consisted of the Bruce protocol test, and the remaining visits entailed a maximal SPV on a treadmill (TM SPV) and a cycle ergometer (CE SPV). There were no differences in VO2max values between the TM SPV and the Bruce protocol tests (55.6 ± 4.9 vs. 56.2 ± 6.8, respectively; p = .510). As expected, the CE SPV (48.3 ± 7.6) was significantly lower than the other two tests (p VO2max as the Bruce protocol and did so with less incline and in less time suggesting that there are no changes in the limits of VO2max even when the test is self-paced and perceptually regulated.

  15. Angle-independent VO2 Thin Film on Glass Fiber Cloth as a Soft-Smart-Mirror (SSM)

    Science.gov (United States)

    Cai, Nianjin; Zhang, Wang; Wang, Wanlin; Zhu, Yuchen; Zada, Imran; Gu, Jiajun; Liu, Qinglei; Su, Huilan; Guo, Cuiping; Zhang, Zhijian; Zhang, Jianzhong; Wu, Liping; Zhang, Di

    2016-11-01

    Designing materials with a negative feedback function is beneficial for achieving temperature regulation inside a greenhouse. VO2 has been studied extensively because of its low insulator-to-metal transition temperature (IMT). In this study, reflection changes during a VO2 phase transition were investigated. Glass fiber cloth was used as a substrate, as it is stable and soft. A VO2 thin film on a glass fiber cloth whose surface contained 96% V4+ and 4% V5+ was prepared using an inorganic sol-gels method. The insulator-to-metal transition temperature was decreased by 38 °C, which was observed from the reflection curve detected using an angle-resolved spectrometer. This decrease in IMT occurred mainly because of the presence of V5+, which causes destabilization of the monoclinic phase of VO2. When the greenhouse temperature was increased from 30 °C to 40 °C, the reflected intensity of VO2 on glass fiber cloth decreased by 22% for the wavelength range of 400 nm to 800 nm. In addition, the angle-independent property of the VO2 thin film was observed using an angle-resolved spectrometer. Owing to its thermo-reflective properties, the thin film can serve as a soft-smart-mirror (SSM) inside a greenhouse to stabilize the temperature, playing a negative feedback role.

  16. Submaximal treadmill test predicts VO2max in overweight children.

    Science.gov (United States)

    Nemeth, Blaise A; Carrel, Aaron L; Eickhoff, Jens; Clark, R Randall; Peterson, Susan E; Allen, David B

    2009-05-01

    To demonstrate the ability of a submaximal test to predict VO(2max) in overweight children. A total of 130 children, 11 to 14 years old, with body mass index >85 percentile for age and sex performed a submaximal walking test. VO(2max) was measured by using open circuit spirometry during a graded exercise test to volitional fatigue. An equation to predict VO(2max) was modeled by using the variables of sex, weight (kg), height (cm), heart rate (HR) after 4 minutes during the submaximal test (4minHR), HR difference (4minHR - resting HR), and submaximal treadmill speed (miles per hour [mph]) in 75% of the subjects. Validation was performed by using the remaining 25% of subjects. A total of 113 subjects achieved a maximal effort and was used in the statistical analysis. Development and validation groups were similar in all aspects. On validation, the mean square error was 241.06 with the predicted VO(2max) within 10% of the observed value in 67% of subjects. VO(2max) was accurately predicted in this cohort of overweight children by using a submaximal, treadmill-based testing protocol.

  17. Electronic structure and insulating gap in epitaxial VO2 polymorphs

    Directory of Open Access Journals (Sweden)

    Shinbuhm Lee

    2015-12-01

    Full Text Available Determining the origin of the insulating gap in the monoclinic V O2(M1 is a long-standing issue. The difficulty of this study arises from the simultaneous occurrence of structural and electronic transitions upon thermal cycling. Here, we compare the electronic structure of the M1 phase with that of single crystalline insulating V O2(A and V O2(B thin films to better understand the insulating phase of VO2. As these A and B phases do not undergo a structural transition upon thermal cycling, we comparatively study the origin of the gap opening in the insulating VO2 phases. By x-ray absorption and optical spectroscopy, we find that the shift of unoccupied t2g orbitals away from the Fermi level is a common feature, which plays an important role for the insulating behavior in VO2 polymorphs. The distinct splitting of the half-filled t2g orbital is observed only in the M1 phase, widening the bandgap up to ∼0.6 eV. Our approach of comparing all three insulating VO2 phases provides insight into a better understanding of the electronic structure and the origin of the insulating gap in VO2.

  18. Aerobic Fitness Levels and Validation of a Non-Exercise VO2max Prediction Equation for HIV-Infected Patients on HAART

    Science.gov (United States)

    Sullivan, Katherine; Shikuma, Cecilia M.; Chow, Dominic; Cornelius, Elizabeth; Romine, Rebecca K.; Lindsey, Rachel A.; Stickley, Christopher D.; Kimura, Iris F.; Hetzler, Ronald K.

    2015-01-01

    Background Non-exercise (N-EX) questionnaires have been developed to determine maximal oxygen consumption (VO2max) in healthy populations. There are limited reliable and validated N-EX questionnaires for the HIV+ population that provide estimates of habitual physical activity and not VO2max. Objectives To determine how well regression equations developed previously on healthy populations, including N-EX prediction equations for VO2max and age-predicted maximal heart rates (APMHR), worked on an HIV+ population; and to develop a specific N-EX prediction equation for VO2max and APMHR for HIV+ individuals. Methods Sixty-six HIV+ participants on stable HAART completed 4 N-EX questionnaires and performed a maximal graded exercise test. Results Sixty males and 6 females were included; mean (SD) age was 49.2 (8.2) years; CD4 count was 516.0 ± 253.0 cells·mn−3; and 92% had undetectable HIV PCR. Mean VO2max was 29.2 ± 7.6 (range, 14.4–49.4) mL·kg−1·min−1. Despite positive correlations with VO2max, previously published N-EX VO2max equations produced results significantly different than actual VO2 scores (P VO2max values, R = 0.71, when compared to achieved VO2max (P = .53). Conclusion HIV+ individuals tend to be sedentary and unfit, putting them at increased risk for the development of chronic diseases associated with a sedentary lifestyle. Based on the level of error associated with utilizing APMHR and N-EX VO2max equations with HIV+ individuals, neither should be used in this population for exercise prescription. PMID:24710921

  19. Excess VO2 during ramp exercise is positively correlated to intercostal muscles deoxyhemoglobin levels above the gas exchange threshold in young trained cyclists.

    Science.gov (United States)

    Oueslati, Ferid; Girard, Olivier; Tabka, Zouhair; Ahmaidi, Said

    2016-07-01

    We assessed respiratory muscles oxygenation responses during a ramp exercise to exhaustion and further explored their relationship with the non-linear increase of VO2 (VO2 excess) observed above the gas-exchange threshold. Ten male cyclists completed a ramp exercise to exhaustion on an electromagnetically braked cycle-ergometer with a rate of increment of 30Wmin(-1) with continuous monitoring of expired gases (breath-by-breath) and oxygenation status of intercostal muscles. Maximal inspiratory and expiratory pressure measurements were taken at rest and at exhaustion. The VO2 excess represents the difference between VO2max observed and VO2max expected using linear equation between the VO2 and the intensity before gas-exchange threshold. The deoxyhemoglobin remained unchanged until 60% of maximal aerobic power (MAP) and thereafter increased significantly by 37±18% and 40±22% at 80% and 100% of MAP, respectively. Additionally, the amplitude of deoxyhemoglobin increase between 60 and 100% of MAP positively correlated with the VO2 excess (r=0.69, p<0.05). Compared to exercise start, the oxygen tissue saturation index decreased from 80% of MAP (-4.8±3.2%, p<0.05) onwards. At exhaustion, maximal inspiratory and expiratory pressures declined by 7.8±16% and 12.6±10% (both p<0.05), respectively. In summary, our results suggest a significant contribution of respiratory muscles to the VO2 excess phenomenon.

  20. Thermochromic VO2 on Zinnwaldite Mica by pulsed laser deposition

    Science.gov (United States)

    Mathevula, L.; Ngom, B. D.; Kotsedi, L.; Sechogela, P.; Doyle, T. B.; Ghouti, M.; Maaza, M.

    2014-09-01

    VO2 thin films have been deposited by pulsed laser deposition on Zinnwaldite Mica substrates. The crystal structure, chemical composition, morphology were determined and the semiconductor/metal transition (SMT) properties of the deposited films were investigated. Without any post annealing, the films exhibit a textured nature with a VO2 (0 1 1) preferred crystallographic orientation and an elevated thermal variation of the electric resistance ratio RS/RM through the SMT at T ≈ 68 °C of the order of 104 and a narrow ∼7 °C hysteresis. In addition, the growth of the VO2 crystallites seem to be governed likely by a Volmer-Weber or Stranski-Krastanov mechanisms and certainly not a Frank-van Der Merwe process.

  1. Validity of 3 protocols for verifying VO2 max.

    Science.gov (United States)

    Kirkeberg, J M; Dalleck, L C; Kamphoff, C S; Pettitt, R W

    2011-04-01

    The verification bout has emerged as a technique for confirming 'true' VO2 max; however, validity during a single visit is unknown. We evaluated 3 different GXT durations with severe intensity verification bouts. On 3 separate days, in counterbalanced order, 12 recreational-trained men completed short (9±1 min), middle (11±1 min), and long (13±2 min) duration GXTs followed by exhaustive, sine wave verification bouts during the same visit. Intensities for verification were set at speeds equivalent to 2-stages minus end-GXT speed. No differences (pVO2 max (mL/kg/min) were observed between short (49.1), middle (48.2), and long (48.8) protocols. In addition, no differences in verification bout duration occurred between protocols (3±1 min). Validity of VO2 max was strongest for the middle duration protocol (ICC α=0.97; typical error=1 mL/kg/min; CV=2%). A small, but significantly higher HR (max) (∼1-2 bpm) was observed for the long protocol. Maximum respiratory exchange ratios were inconsistent (ICC α ranged 0.58-0.68). Our findings indicate GXT-verification bout testing during a single visit is a valid means of measuring 'true' VO2 max. The 10 min target for GXT duration was the optimum. © Georg Thieme Verlag KG Stuttgart · New York.

  2. Monitoring VO2max during fourteen weeks of endurance training using the CardioCoach.

    Science.gov (United States)

    Vehrs, Pat R; Keller, David M; George, James D; Hager, Ronald L; Fellingham, Gilbert W

    2007-02-01

    This study evaluated the validity of the desktop CardioCoach metabolic system to measure VO2max and VEmax. Sixteen subjects (mean age = 19.5 +/- 3.2 years) completed 2 maximal graded exercise tests following the same protocol before and after 7 and 14 weeks of endurance training. Subjects' VO2max and VEmax were measured by either the CardioCoach or the ParvoMedics TrueOne 2400 metabolic measurement system (TrueOne). An alpha level of significance of p test completion and the final treadmill grade of the exercise tests performed by both the CardioCoach and the TrueOne increased over the 3 testing periods, confirming an improvement in cardiorespiratory fitness resulting from the 14 weeks of training. A linear growth curve analysis indicated that there were statistically significant differences between VO2max (ml x kg(-1) x min(-1)) as measured by the TrueOne and the CardioCoach before (44.4 +/- 5.0 and 49.3 +/- 5.4) and after 7 weeks (46.0 +/- 5.2 and 48.2 +/- 5.4) of training but not after 14 weeks of training (47.8 +/- 5.6 and 48.4 +/- 5.2). Significant differences also existed in VEmax (L x min(-1)) as measured by the TrueOne and the CardioCoach before (76.8 +/- 17.7 and 71.9 +/- 13.7), after 7 weeks (81.4 +/- 16.2 and 72.8 +/- 14.1), and after 14 weeks (86.8 +/- 19.4 and 74.2 +/- 13.1) of training. Although significant growth of VO2max (0.24 ml x kg(-1) x min(-1) x wk(-1)) and VEmax (0.71 L x min(-1) x wk(-1)) was measured by the TrueOne over 14 weeks of training, the CardioCoach was unable to detect growth in VO2max (-0.02 ml x kg(-1) x min(-1) x wk(-1)) or VEmax (0.17 L x min(-1) x wk(-1)). This study indicates that the CardioCoach did not accurately measure or monitor changes in VO2max or VEmax resulting from training.

  3. Porous carbon derived from disposable shaddock peel as an excellent catalyst toward VO2+/VO2+ couple for vanadium redox battery

    Science.gov (United States)

    Liu, J.; Wang, Z. A.; Wu, X. W.; Yuan, X. H.; Hu, J. P.; Zhou, Q. M.; Liu, Z. H.; Wu, Y. P.

    2015-12-01

    Functional porous carbon (PC) derived from bio-friendly shaddock peel has been firstly explored as catalyst for vanadium redox flow battery (VRB). The prepared PC is micro-mesoporous with high BET surface area of 882.7 m2 g-1, has some surface oxygen-containing functional groups, and is doped with N and P heteroatoms. These three factors greatly favor the electrochemical reactions of VO2+/VO2+ on the PC modified glass carbon (PC-GC). Compared with the naked GC and graphite modified GC, the PC-GC presents a lower peak separation (66 mV), higher anodic current density (17.1 mA cm-2) and cathodic current density (15.0 mA cm-2). The VRB using PC modified graphite felt (GF) as positive electrode demonstrates an enhanced voltage efficiency of 82.7% at the current density of 60 mA cm-2, and a better rate performance than that from the virginal GF.

  4. Individual versus Standardized Running Protocols in the Determination of VO2max

    Directory of Open Access Journals (Sweden)

    Paula F. Sperlich, Hans-Christer Holmberg, Jennifer L. Reed, Christoph Zinner, Joachim Mester, Billy Sperlich

    2015-06-01

    Full Text Available The purpose of this study was to determine whether an individually designed incremental exercise protocol results in greater rates of oxygen uptake (VO2max than standardized testing. Fourteen well-trained, male runners performed five incremental protocols in randomized order to measure their VO2max: i an incremental test (INCS+I with pre-defined increases in speed (2 min at 8.64 km·h−1, then a rise of 1.44 km·h−1 every 30 s up to 14.4 km·h−1 and thereafter inclination (0.5° every 30 s; ii an incremental test (INCI at constant speed (14.4 km·h−1 and increasing inclination (2° every 2 min from the initial 0°; iii an incremental test (INCS at constant inclination (0° and increasing speed (0.5 km·h−1 every 30 s from the initial 12.0 km·h−1; iv a graded exercise protocol (GXP at a 1° incline with increasing speed (initially 8.64 km·h−1 + 1.44 km·h−1 every 5 min; v an individual exercise protocol (INDXP in which the runner chose the inclination and speed. VO2max was lowest (-4.2% during the GXP (p = 0.01; d = 0.06-0.61 compared to all other tests. The highest rating of perceived exertion, heart rate, ventilation and end-exercise blood lactate concentration were similar between the different protocols (p < 0.05. The time to exhaustion ranged from 7 min 18 sec (INCS to 25 min 30 sec (GXP (p = 0.01.The VO2max attained by employing an individual treadmill protocol does not differ from the values derived from various standardized incremental protocols.

  5. Identifying the active site in nitrogen-doped graphene for the VO2+/VO2(+) redox reaction.

    Science.gov (United States)

    Jin, Jutao; Fu, Xiaogang; Liu, Qiao; Liu, Yanru; Wei, Zhiyang; Niu, Kexing; Zhang, Junyan

    2013-06-25

    Nitrogen-doped graphene sheets (NGS), synthesized by annealing graphite oxide (GO) with urea at 700-1050 °C, were studied as positive electrodes in a vanadium redox flow battery. The NGS, in particular annealed at 900 °C, exhibited excellent catalytic performance in terms of electron transfer (ET) resistance (4.74 ± 0.51 and 7.27 ± 0.42 Ω for the anodic process and cathodic process, respectively) and reversibility (ΔE = 100 mV, Ipa/Ipc = 1.38 at a scan rate of 50 mV s(-1)). Detailed research confirms that not the nitrogen doping level but the nitrogen type in the graphene sheets determines the catalytic activity. Among four types of nitrogen species doped into the graphene lattice including pyridinic-N, pyrrolic-N, quaternary nitrogen, and oxidic-N, quaternary nitrogen is verified as a catalytic active center for the [VO](2+)/[VO2](+) couple reaction. A mechanism is proposed to explain the electrocatalytic performance of NGS for the [VO](2+)/[VO2](+) couple reaction. The possible formation of a N-V transitional bonding state, which facilitates the ET between the outer electrode and reactant ions, is a key step for its high catalytic activity.

  6. Why is VO2 max after altitude acclimatization still reduced despite normalization of arterial O2 content?

    Science.gov (United States)

    Calbet, J A L; Boushel, R; Radegran, G; Sondergaard, H; Wagner, P D; Saltin, B

    2003-02-01

    Acute hypoxia (AH) reduces maximal O2 consumption (VO2 max), but after acclimatization, and despite increases in both hemoglobin concentration and arterial O2 saturation that can normalize arterial O2 concentration ([O2]), VO2 max remains low. To determine why, seven lowlanders were studied at VO2 max (cycle ergometry) at sea level (SL), after 9-10 wk at 5,260 m [chronic hypoxia (CH)], and 6 mo later at SL in AH (FiO2 = 0.105) equivalent to 5,260 m. Pulmonary and leg indexes of O2 transport were measured in each condition. Both cardiac output and leg blood flow were reduced by approximately 15% in both AH and CH (P VO2 max (4.1 +/- 0.3 l/min at SL) fell to 2.2 +/- 0.1 l/min in AH (P VO2 max after acclimatization despite normalization of arterial [O2] is explained by two circulatory effects of altitude: 1) failure of cardiac output to normalize and 2) preferential redistribution of cardiac output to nonexercising tissues. Oxygen transport from blood to muscle mitochondria, on the other hand, appears unaffected by CH.

  7. Metal-insulator transition of valence-controlled VO2 thin film prepared by RF magnetron sputtering using oxygen radical

    Science.gov (United States)

    Suetsugu, Takaaki; Shimazu, Yuichi; Tsuchiya, Takashi; Kobayashi, Masaki; Minohara, Makoto; Sakai, Enju; Horiba, Koji; Kumigashira, Hiroshi; Higuchi, Tohru

    2016-06-01

    We have prepared b-axis-oriented VO2 thin films by RF magnetron sputtering using oxygen radicals as the reactive gas. The VO2 thin films consist of a mixed-valence V3+/V4+ state formed by oxygen vacancies. The V3+ ratio strongly depends on the film thickness and the oxygen partial pressure of the radical gun during deposition. The lattice constant of the b-axis increases and the metal-insulator transition (MIT) temperature decreases with decreasing V3+ ratio, although the VO2 thin films with a high V3+ ratio of 42% do not exhibit MIT. The bandwidths and spectral weights of V 3d a1g and \\text{e}\\text{g}σ bands at around the Fermi level, which correspond to the insulating phase at 300 K, are smaller in the VO2 thin films with a low V3+ ratio. These results indicate that the control of the mixed-valence V3+/V4+ state is important for the MIT of b-axis-oriented VO2 thin films.

  8. Effects of concurrent training on explosive strength and VO(2max) in prepubescent children.

    Science.gov (United States)

    Marta, C; Marinho, D A; Barbosa, T M; Izquierdo, M; Marques, M C

    2013-10-01

    The purpose of this study was to compare the effects of an 8-weeks training period of resistance training alone (GR), combined resistance and endurance training (GCON) and a control group (GC) on explosive strength and V(O2max) in a large sample of prepubescent boys and girls. 125 healthy children (58 boys, 67 girls), aged 10-11 years old (10.8±0.4 years) were assigned into 2 training groups to train twice a week for 8 weeks: GR (19 boys, 22 girls), GCON (21 boys, 24 girls) and a control group (GC: 18 boys, 21 girls; no training program). A significant but medium-sized increase from pre- to the post-training in the vertical jump (Effect size=0.22, F=34.44, ptraining group (GR and GCON) and sex factors did not significantly influence the evolution of strength variables from pre- to the post-training. The V(O2max) increased significantly only in GCON. Concurrent training is equally effective on training-induced explosive strength, and more efficient than resistance training only for V(O2max), in prepubescent boys and girls. This should be taken into consideration in order to optimize strength training school-based programs. © Georg Thieme Verlag KG Stuttgart · New York.

  9. The role of haemoglobin mass on VO(2)max following normobaric 'live high-train low' in endurance-trained athletes

    DEFF Research Database (Denmark)

    Robach, Paul; Siebenmann, Christoph; Jacobs, Robert A

    2012-01-01

    It remains unclear by which mechanism 'live high-train low' (LHTL) altitude training increases exercise performance. Haematological and skeletal muscle adaptations have both been proposed. To test the hypotheses that (i) LHTL improves maximal oxygen uptake (VO(2)max) and (ii) this improvement...... is related to hypoxia-induced increases in total haemoglobin mass (Hb(mass)) and not to improved maximal oxidative capacity of skeletal muscle, we determined VO(2)max before LHTL and after LHTL, before and after the altitude-induced increases in Hb(mass) (measured by carbon-monoxide rebreathing) had been...... to 3000 m altitude (LHTL, n=10). Four-week LHTL did not increase VO(2)max, irrespective of treatment (LHTL: 1.5%; placebo: 2.0%). Hb(mass) was slightly increased (4.6%) in 5 (of 10) LHTL subjects but this was not accompanied by a concurrent increase in VO(2)max. In the subjects demonstrating an increase...

  10. ASSESSING PEAK AEROBIC CAPACITY IN DUTCH LAW ENFORCEMENT OFFICERS

    NARCIS (Netherlands)

    Wittink, Harriet; Takken, Tim; de Groot, Janke; Reneman, Michiel; Peters, Roelof; Vanhees, Luc

    2015-01-01

    Objectives: To cross-validate the existing peak rate of oxygen consumption (VO2peak) prediction equations in Dutch law enforcement officers and to determine whether these prediction equations can be used to predict VO2peak for groups and in a single individual. A further objective was to report norm

  11. CAN WE CONFIDENTLY STUDY VO2 KINETICS IN YOUNG PEOPLE?

    Directory of Open Access Journals (Sweden)

    Samantha G. Fawkner

    2007-09-01

    Full Text Available The study of VO2 kinetics offers the potential to non-invasively examine the cardiorespiratory and metabolic response to dynamic exercise and limitations to every day physical activity. Its non-invasive nature makes it hugely attractive for use with young people, both healthy and those with disease, and yet the literature, whilst growing with respect to adults, remains confined to a cluster of studies with these special populations. It is most likely that this is partly due to the methodological difficulties involved in studying VO2 kinetics in young people which are not present, or present to a lesser degree, with adults. This article reviews these methodological issues, and explains the main procedures that might be used to overcome them

  12. VO2 Reserve vs. Heart Rate Reserve During Moderate Intensity Treadmill Exercise.

    Science.gov (United States)

    Solheim, Tanner J; Keller, Brad G; Fountaine, Charles J

    VO2 and heart rate (HR) are widely used when determining appropriate training intensities for clinical, healthy, and athletic populations. It has been shown that if the % reserve (%R) is used, rather than % of max, HR and VO2 can be used interchangeably to accurately prescribe exercise intensities. Thus, heart rate reserve (HRR) can be prescribed if VO2 reserve (VO2R) is known. Therefore, the purpose of this study was to compare VO2 R and HRR during moderate intensity exercise (50%R). Physically active college students performed a maximal treadmill test to exhaustion. During which VO2 and HR were monitored to determine max values. Upon completion of the maximal test, calculations were made to determine the % grade expected to yield approximately 50% of the subjects VO2R. Subjects then returned to complete the submaximal test (50%R) at least two days later. The %VO2R and %HRR were calculated and compared to the predicted value as well as to each other. Statistical analysis revealed that VO2 at 50%R was significantly greater than the actual VO2 achieved, p VO2 could be more accurately predicted than HR during moderate intensity exercise. The weak correlation between VO2R and HRR indicates that caution should be used when relying on a HR to determine VO2.

  13. Metal-Insulator Phase Transition in thin VO2 films: A Look from the Far Infrared Side

    DEFF Research Database (Denmark)

    Jepsen, Peter Uhd; Fischer, B. M.; Thoman, A.

    Terahertz Time-Domain Spectroscopy (THz-TDS) to investigate theoptical properties of laser-ablated VO2 films in the vicinity of the MI transition in the 0.1-2 THz frequency range. At frequencies below the phonon resonances of the material wecan obtain a clean spectroscopic signature of the carrier dynamics......Vanadium dioxide (VO2) displays a well-known metal-insulator (MI) transition at atemperature of 68oC. The MI transition in VO2 has been studied extensively by a widerange of optical, electrical, structural, and magnetic measurements. In spite of this there isstill some controversy about the nature...... of the phase transition. Mid-IR studies1 indicatethat a model based on growth of metallic domains accounts for the phase transitionwhereas other studies2 argue that a homogeneous increase of the carrier concentration isresponsible for the change in properties across the phase transition.In this study we use...

  14. Poor compensatory hyperventilation in morbidly obese women at peak exercise.

    Science.gov (United States)

    Zavorsky, Gerald S; Murias, Juan M; Kim, Do Jun; Gow, Jennifer; Christou, Nicolas V

    2007-11-15

    This study was designed to compare differences in pulmonary gas exchange at rest and at peak exercise in two groups of women: (1) physically active, non-obese women and (2) women with morbid obesity. Fourteen morbidly obese women (body mass index or BMI=49+/-7 kg/m2; peak oxygen consumption or VO2 peak=14+/-2 ml/(kg min)) and 14 physically active non-obese women (BMI=22+/-2 kg/m2; VO2 peak=50+/-6 ml/(kg min)) performed an incremental, ramped exercise test to exhaustion on a cycle ergometer. Arterial blood was sampled at rest and at peak exercise. At rest, the alveolar to arterial oxygen partial pressure difference was 3x higher in the obese women (14+/-10 mmHg) compared to non-obese women (5+/-4 mmHg). Arterial carbon dioxide pressure (PaCO2) was identical in both groups at rest (37+/-4 mmHg). Only the non-obese women showed a decrease in PaCO2 rest to peak exercise (-5+/-3 mmHg). The slope between heart rate and VO2 during exercise was higher in the morbidly obese compared to non-obese women indicating that for the same absolute increase in VO2 a larger increase in heart rate is needed, demonstrating poorer cardiac efficiency in obese women. In conclusion, morbidly obese women have poorer exercise capacity, cardiac efficiency, and compensatory hyperventilation at peak exercise, and poorer gas exchange at rest compared to physically active, non-obese women.

  15. Data of evolutionary structure change: 1CPDA-2VO2X [Confc[Archive

    Lifescience Database Archive (English)

    Full Text Available 1CPDA-2VO2X 1CPD 2VO2 A X LVHVASVEKGRSYEDFQK---VYNAIALKLREDDEYDNY...IGYGPVLVRLAWHISGTWDKHDNTGGSYGGTYRFKKEFNDPSNAGLQNGFKFLEPIHKEFPWISSGDLFSLGGVTAVQEMQGPKIPWRCGRVDTPEDTTPDNGRLPDA...GFIAEKR-------CAPLMLRLAAHSAGTFDKGTKTGGPF-GTIKHPAELAHSANNGLDIAVRLLEPLKAEFPILSYADFYQLAGVVAVEVTGGPEVPFHPGREDKP--EPPPEGRLPDA...ID> 0 1CPD A 1CPDA 1 1CPD A 1CPDA

  16. Graphene-Nanowall-Decorated Carbon Felt with Excellent Electrochemical Activity Toward VO2(+)/VO(2+) Couple for All Vanadium Redox Flow Battery.

    Science.gov (United States)

    Li, Wenyue; Zhang, Zhenyu; Tang, Yongbing; Bian, Haidong; Ng, Tsz-Wai; Zhang, Wenjun; Lee, Chun-Sing

    2016-04-01

    3D graphene-nanowall-decorated carbon felts (CF) are synthesized via an in situ microwave plasma enhanced chemical vapor deposition method and used as positive electrode for vanadium redox flow battery (VRFB). The carbon fibers in CF are successfully wrapped by vertically grown graphene nanowalls, which not only increase the electrode specific area, but also expose a high density of sharp graphene edges with good catalytic activities to the vanadium ions. As a result, the VRFB with this novel electrode shows three times higher reaction rate toward VO2(+)/VO(2+) redox couple and 11% increased energy efficiency over VRFB with an unmodified CF electrode. Moreover, this designed architecture shows excellent stability in the battery operation. After 100 charging-discharging cycles, the electrode not only shows no observable morphology change, it can also be reused in another battery and practical with the same performance. It is believed that this novel structure including the synthesis procedure will provide a new developing direction for the VRFB electrode.

  17. Evidence of O2 supply-dependent VO2 max in the exercise-trained human quadriceps.

    Science.gov (United States)

    Richardson, R S; Grassi, B; Gavin, T P; Haseler, L J; Tagore, K; Roca, J; Wagner, P D

    1999-03-01

    Maximal O2 delivery and O2 uptake (VO2) per 100 g of active muscle mass are far greater during knee extensor (KE) than during cycle exercise: 73 and 60 ml. min-1. 100 g-1 (2.4 kg of muscle) (R. S. Richardson, D. R. Knight, D. C. Poole, S. S. Kurdak, M. C. Hogan, B. Grassi, and P. D. Wagner. Am. J. Physiol. 268 (Heart Circ. Physiol. 37): H1453-H1461, 1995) and 28 and 25 ml. min-1. 100 g-1 (7.5 kg of muscle) (D. R. Knight, W. Schaffartzik, H. J. Guy, R. Predilleto, M. C. Hogan, and P. D. Wagner. J. Appl. Physiol. 75: 2586-2593, 1993), respectively. Although this is evidence of muscle O2 supply dependence in itself, it raises the following question: With such high O2 delivery in KE, are the quadriceps still O2 supply dependent at maximal exercise? To answer this question, seven trained subjects performed maximum KE exercise in hypoxia [0.12 inspired O2 fraction (FIO2)], normoxia (0.21 FIO2), and hyperoxia (1.0 FIO2) in a balanced order. The protocol (after warm-up) was a square wave to a previously determined maximum work rate followed by incremental stages to ensure that a true maximum was achieved under each condition. Direct measures of arterial and venous blood O2 concentration in combination with a thermodilution blood flow technique allowed the determination of O2 delivery and muscle VO2. Maximal O2 delivery increased with inspired O2: 1.3 +/- 0.1, 1.6 +/- 0.2, and 1.9 +/- 0.2 l/min at 0.12, 0.21, and 1.0 FIO2, respectively (P VO2 (VO2 max): 1.04 +/- 0.13, 1. 24 +/- 0.16, and 1.45 +/- 0.19 l/min at 0.12, 0.21, and 1.0 FIO2, respectively (P VO2 max, supporting our previous finding that a decrease in O2 supply will proportionately decrease muscle VO2 max. As even in the isolated quadriceps (where normoxic O2 delivery is the highest recorded in humans) an increase in O2 supply by hyperoxia allows the achievement of a greater VO2 max, we conclude that, in normoxic conditions of isolated KE exercise, KE VO2 max in trained subjects is not limited by mitochondrial

  18. Estimation of VO2 Max: A Comparative Analysis of Five Exercise Tests.

    Science.gov (United States)

    Zwiren, Linda D.; And Others

    1991-01-01

    Thirty-eight healthy females measured maximal oxygen uptake (VO2max) on the cycle ergometer and treadmill to compare five exercise tests (run, walk, step, and two tests using heart-rate response on the bicycle ergometer) in predicting VO2max. Results indicate that walk and run tests are satisfactory predictors of VO2max in 30- to 39-year-old…

  19. Effect of blood haemoglobin concentration on V(O2,max) and cardiovascular function in lowlanders acclimatised to 5260 m

    DEFF Research Database (Denmark)

    Calbet, J A L; Rådegran, G; Boushel, Robert Christopher

    2002-01-01

    +/- 5 to 185 +/- 5 g l(-1) (P delivery was reduced...... and maximal V(O(2)) was thus maintained by higher O(2) extraction. While CO increased linearly with work rate irrespective of [Hb] or inspired oxygen fraction (F(I,O(2))), both LBF and leg vascular conductance were systematically higher when [Hb] was low. Close and significant relationships were seen between...

  20. Ultrafast dynamics during the photoinduced phase transition in VO2

    Science.gov (United States)

    Wegkamp, Daniel; Stähler, Julia

    2015-12-01

    The phase transition of VO2 from a monoclinic insulator to a rutile metal, which occurs thermally at TC = 340 K, can also be driven by strong photoexcitation. The ultrafast dynamics during this photoinduced phase transition (PIPT) have attracted great scientific attention for decades, as this approach promises to answer the question of whether the insulator-to-metal (IMT) transition is caused by electronic or crystallographic processes through disentanglement of the different contributions in the time domain. We review our recent results achieved by femtosecond time-resolved photoelectron, optical, and coherent phonon spectroscopy and discuss them within the framework of a selection of latest, complementary studies of the ultrafast PIPT in VO2. We show that the population change of electrons and holes caused by photoexcitation launches a highly non-equilibrium plasma phase characterized by enhanced screening due to quasi-free carriers and followed by two branches of non-equilibrium dynamics: (i) an instantaneous (within the time resolution) collapse of the insulating gap that precedes charge carrier relaxation and significant ionic motion and (ii) an instantaneous lattice potential symmetry change that represents the onset of the crystallographic phase transition through ionic motion on longer timescales. We discuss the interconnection between these two non-thermal pathways with particular focus on the meaning of the critical fluence of the PIPT in different types of experiments. Based on this, we conclude that the PIPT threshold identified in optical experiments is most probably determined by the excitation density required to drive the lattice potential change rather than the IMT. These considerations suggest that the IMT can be driven by weaker excitation, predicting a transiently metallic, monoclinic state of VO2 that is not stabilized by the non-thermal structural transition and, thus, decays on ultrafast timescales.

  1. Comparison of a kayaking ergometer protocol with an arm crank protocol for evaluating peak oxygen consumption.

    Science.gov (United States)

    Forbes, Scott C; Chilibeck, Philip D

    2007-11-01

    The purpose of this study was to compare a kayak ergometer protocol with an arm crank protocol for determining peak oxygen consumption (V(.-)O2). On separate days in random order, 10 men and 5 women (16-24 years old) with kayaking experience completed the kayak ergometer protocol and a standardized arm crank protocol. The kayak protocol began at 70 strokes per minute and increased by 10 strokes per minute every 2 minutes until volitional fatigue. The arm crank protocol consisted of a crank rate of 70 revolutions per minute, initial loading of 35 W and subsequent increases of 35 W every 2 minutes until volitional fatigue. The results showed a significant difference (p kayak ergometer and the arm crank protocols for relative peak V(.-)O2 (47.5 +/- 3.9 ml x kg(-1) x min(-1) vs. 44.2 +/- 6.2 ml x kg(-1) x min(-1)) and absolute peak V(.-)O2 (3.38 L x min(-1) +/- 0.53 vs. 3.14 +/- 0.64 L x min(-1)). The correlation between kayak and arm crank protocol was 0.79 and 0.90, for relative and absolute V(.-)O2 peak, respectively (both p kayak ergometer may be due to the greater muscle mass involved compared to the arm crank ergometer. The kayak ergometer protocol may therefore be more specific to the sport of kayaking than an arm crank protocol.

  2. Is low VO2max/kg in obese heart failure patients indicative of cardiac dysfunction?

    Science.gov (United States)

    Hothi, S S; Tan, D K; Partridge, G; Tan, L B

    2015-04-01

    Low peak O2 consumption (VO2max/kg) has been widely used as an indirect indicator of poor cardiac fitness, and often guides management of patients with severe heart failure (HF). We hypothesized that it should be as good an indicator of cardiac dysfunction in obese and non-obese HF patients. We compared the cardiopulmonary exercise performance and non-invasive hemodynamics of 152 obese (BMI>34 kg.m(-2)) and 173 non-obese (BMI≤32) male HF patients in NYHA classes II and III, with reference to 101 healthy male controls. Their physical and cardiac functional reserves were measured during treadmill exercise testing with standard respiratory gas analyses and CO2 rebreathing to measure cardiac output non-invasively during peak exercise. Data are given as mean ± SD. Obese HF patients with BMI 40.9 ± 7.5 kg·m(-2) (age 56.1 ± 14.0 years, NYHA 2.5 ± 0.5) exercised to acceptable cardiopulmonary limits (peak RER=1.07 ± 0.12), and achieved a mean VO2max/kg of 18.6 ± 5.2 ml·kg(-1)·min(-1), significantly lower than in non-obese HF counterparts (19.9 ± 5.6 ml·kg(-1)·min(-1), P=0.02, age 55.8 ± 10.6 years, BMI 26.6 ± 3.1, NYHA 2.4 ± 0.5, peak RER=1.07 ± 0.09), with both lower than controls (38.5 ± 9.7 ml·kg(-1)·min(-1), PVO2max was higher in obese (2.31 ± 0.69 ml·min(-1)) than non-obese HF patients (1.61 ± 0.49 ml·min(-1), PVO2max/kg is not a generally reliable indicator of cardiac fitness in all patients. Instead, we found that despite having lower VO2max/kg, obese HF patients had stronger hearts capable of generating greater cardiac power than non-obese HF patients of equivalent clinical HF status. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  3. Comprehensive picture of VO2 from band theory

    KAUST Repository

    Zhu, Zhiyong

    2012-08-28

    The structural, electronic, and magnetic features of the metal-insulator transition from the tetragonal rutile (R) to the monoclinic (M1) phase of VO2 are well reproduced by band theory using the modified Becke-Johnson exchange potential. Based on this description, we identify a tendency for monoclinic charge ordering in the R phase due to electronic correlations as the origin of the phase transition. Whereas, the structural changes are crucial for the gap opening in the M1 phase, spin degeneracy in both phases is stabilized by correlation-induced delocalization of the V3d electrons.

  4. Creative MuVo2 FM 5GB

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    可存储多达2500首歌曲Creative MuVo2 FM 5GB设计轻巧简洁;尺寸只有67×665×20mm.内置了完备的FM收音/录音和语音录音功能.并设计了全新的摇杆按键,也是即插即用的大容量U盘,更具有高达98dB的信噪比,可更换式充电锂电池,

  5. Componente lento do VO2 em crianças durante exercício pesado de corrida: análise com base em diferentes modelos matemáticos Componente lento de VO2 en niños durante ejercicio arduo de carrera: análisis con base en diferentes modelos matemáticos Slow component of VO2 in children during running exercise performed at heavy intensity domain: analysis with different mathematical models

    Directory of Open Access Journals (Sweden)

    Fabiana Andrade Machado

    2006-12-01

    . Participaron del estudio 8 niños del sexo masculino (11,92 ± 0,63 años; 44,06 ± 13,01 kg; 146,63 ± 7,25 cm; y niveles de madurez sexual 1 y 2, aparentemente saludables, no entrenados, que realizaron en diferentes días: 1 Test incremental en la cinta rodante para determinar el consumo de oxígeno de pico (VO2pico y del límite de lactato (LL; y 2 Dos tests de carga constante en cinta rodante durante seis minutos a intensidad de 75%delta [75%delta = LL + 0,75 x (VO2pico - LL]. Para determinar el CL usamos: a modelo matemático de tres términos (Exp3; y b la diferencia en el VO2 entre el sexto y el tercer minuto de ejercicio (deltaVO2 6-3 min. El CL fue expresado en valores absolutos (ml/min y también como contribución porcentual de CL para el aumento de VO2 al final del ejercicio (%CL. El CL determinado por el modelo Exp3 (129,69 ± 75,71 ml/min y 8,4 ± 2,92% fue significativamente mayor al que fue obtenido por el modelo deltaVO2 6-3 min (68,69 ± 102,54 ml/min y 3,6 ± 7,34%. Por tanto, los valores de CL obtenidos en niños durante el ejercicio de carrera realizado en dominio pesado (75%delta son dependientes del modelo de análisis (Exp3 x deltaVO2 6-3 min.The purpose of this study was to identify and quantify the magnitude of the slow component of VO2 (SC in children during running exercise, performed at heavy intensity domain (75%delta, using two different mathematical models: a three-exponential model and; b deltaVO2 6-3 min. Eight healthy male children (11.92 ± 0.63 years; 44.06 ± 13.01 kg; 146.63 ± 7.25 cm; and sexual maturity levels 1 and 2, not trained, performed in different days the following tests: 1 incremental running treadmill test to determine the peak oxygen uptake (VO2peak and the lactate threshold (LT; and 2 two transitions from baseline to 75%delta [75%D = LT + 0.75 x (VO2 peak - LT] for six minutes on treadmill. The SC was deter mined by two models: a three-exponential model (Exp3; and b the VO2 difference between the sixth and the third

  6. Limitations to vasodilatory capacity and .VO2 max in trained human skeletal muscle.

    Science.gov (United States)

    Barden, Jeremy; Lawrenson, Lesley; Poole, Jennifer G; Kim, Jeannie; Wray, D Walter; Bailey, Damian M; Richardson, Russell S

    2007-05-01

    To further explore the limitations to maximal O(2) consumption (.VO(2 max)) in exercise-trained skeletal muscle, six cyclists performed graded knee-extensor exercise to maximum work rate (WR(max)) in hypoxia (12% O(2)), hyperoxia (100% O(2)), and hyperoxia + femoral arterial infusion of adenosine (ADO) at 80% WR(max). Arterial and venous blood sampling and thermodilution blood flow measurements allowed the determination of muscle O(2) delivery and O(2) consumption. At WR(max), O(2) delivery rose progressively from hypoxia (1.0 +/- 0.04 l/min) to hyperoxia (1.20 +/- 0.09 l/min) and hyperoxia + ADO (1.33 +/- 0.05 l/min). Leg .VO(2 max) varied with O(2) availability (0.81 +/- 0.05 and 0.97 +/- 0.07 l/min in hypoxia and hyperoxia, respectively) but did not improve with ADO-mediated vasodilation (0.80 +/- 0.09 l/min in hyperoxia + ADO). Although a vasodilatory reserve in the maximally working quadriceps muscle group may have been evidenced by increased leg vascular conductance after ADO infusion beyond that observed in hyperoxia (increased blood flow but no change in blood pressure), we recognize the possibility that the ADO infusion may have provoked vasodilation in nonexercising tissue of this limb. Together, these findings imply that maximally exercising skeletal muscle may maintain some vasodilatory capacity, but the lack of improvement in leg .VO(2 max) with significantly increased O(2) delivery (hyperoxia + ADO), with a degree of uncertainty as to the site of this dilation, suggests an ADO-induced mismatch between O(2) consumption and blood flow in the exercising limb.

  7. Individual versus Standardized Running Protocols in the Determination of VO2max.

    Science.gov (United States)

    Sperlich, Paula F; Holmberg, Hans-Christer; Reed, Jennifer L; Zinner, Christoph; Mester, Joachim; Sperlich, Billy

    2015-06-01

    The purpose of this study was to determine whether an individually designed incremental exercise protocol results in greater rates of oxygen uptake (VO2max) than standardized testing. Fourteen well-trained, male runners performed five incremental protocols in randomized order to measure their VO2max: i) an incremental test (INCS+I) with pre-defined increases in speed (2 min at 8.64 km·h(-1), then a rise of 1.44 km·h(-1) every 30 s up to 14.4 km·h(-1)) and thereafter inclination (0.5° every 30 s); ii) an incremental test (INCI) at constant speed (14.4 km·h(-1)) and increasing inclination (2° every 2 min from the initial 0°); iii) an incremental test (INCS) at constant inclination (0°) and increasing speed (0.5 km·h(-1) every 30 s from the initial 12.0 km·h(-1)); iv) a graded exercise protocol (GXP) at a 1° incline with increasing speed (initially 8.64 km·h(-1) + 1.44 km·h(-1) every 5 min); v) an individual exercise protocol (INDXP) in which the runner chose the inclination and speed. VO2max was lowest (-4.2%) during the GXP (p = 0.01; d = 0.06-0.61) compared to all other tests. The highest rating of perceived exertion, heart rate, ventilation and end-exercise blood lactate concentration were similar between the different protocols (p VO2max attained by employing an individual treadmill protocol does not differ from the values derived from various standardized incremental protocols. Key pointsThe mean maximum oxygen uptake during the GXP was lower than for all other tests.Differences in the maximum rate of oxygen uptake between the various protocols exhibited considerable inter-individual variation.From the current findings, it can be concluded that well trained athletes are able to perform an individually designed treadmill running protocol.

  8. Effect of hindlimb suspension on VO2 max and regional blood flow responses to exercise.

    Science.gov (United States)

    Overton, J M; Woodman, C R; Tipton, C M

    1989-02-01

    Male rodents were studied before and after undergoing one of three treatment conditions for 9 days: 1) cage control (n = 15, CON), 2) horizontal suspension (n = 15, HOZ), and 3) head-down suspension (n = 18, HDT). Testing included measurements of maximal O2 uptake (VO2 max) and select cardiovascular responses to graded treadmill exercise. VO2 max expressed on an absolute basis (ml/min) was significantly decreased after HOZ (-14.1 +/- 2.5%) and HDT (-14.3 +/- 2.0%), while being essentially unchanged in CON (-1.0 +/- 3.3%). Significant reductions in body weight were observed after both HOZ (-10.1 +/- 4.2 g) and HDT (-22.5 +/- 3.3 g), whereas CON animals exhibited a significant increase in weight (10.4 +/- 3.8 g). As a result, when VO2 max was normalized for body weight, all groups exhibited similar significant reductions of 6-7%. Although no differences in heart rate and blood pressure response to graded exercise were observed, the HDT group exhibited greater increases in mesenteric resistance at the same absolute exercise intensity. Furthermore, both suspended groups had higher iliac resistance values during exercise at similar relative exercise conditions, suggesting that muscle blood flow during treadmill running may have been reduced after suspension. In general, the decrements associated with the HOZ and HDT conditions were similar. It was concluded that reduction in exercise capacity and altered cardiovascular responses to exercise observed after 6-9 days of suspension were attributable to a combination of hypokinesia, lack of hindlimb weight bearing, or restraint, rather than to hydrostatic influences associated with HDT.

  9. Comparison of Blood Cholesterol Profiles Before and After The Measurements of Maximum Aerobic Capacity (VO2max

    Directory of Open Access Journals (Sweden)

    Ar Rasyid Shadiqin

    2013-11-01

    Full Text Available This study is aimed to compare the blood cholesterol profile, before and after the measurement of maximum aerobic capacity (VO2max in the students of Jurusan Pendidikan Olahraga dan Kesehatan (JPOK pada Fakultas Keguruan dan Ilmu Pendidikan (FKIP Universitas Lambung Mangkurat Banjarmasin.Variables in this study consist of lipid profiles, including total cholesterol, high density lipoprotein (HDL, low density lipoprotein (LDL, triglyceride (TG and Maximum Aerobic Capacity (VO2max. The concept of VO2max according to Kent(1994:268: “maximum oxygen volume consumed per minute to show total work capacity, or volume per minute relative to body weight (ml/kg.min”. Operationally, VO2max referred in this study is the maximum volume of oxygen that can be consumed per minute, as measured at progressive run (Bleep Test.The method used in this study is pre-experimental with one group pretest-posttest design. This design implies that a group of subjects are treated for a specific period and the measurements are taken both pre and post.The results: There are changes in blood cholesterol profile after the measurement of maximum oxygen capacity (VO2max, shown by significant decrease of total cholesterol variable, increased HDL, and decreased LDL. Changes in triglyceride variable showed no significant decrease despite the statistic differences. Specific HDL sub-class increasing after exercise is a constructive lipoprotein sub-class whereas LDL is destructive lipoproteins sub-class that might damage the body. Therefore, an increase in HDL and decrease in LDL found in this study appears to be advantageous and consequently might alter the risk of coronary heart disease.

  10. Indirect estimation of VO2max in athletes by ACSM’s equation: valid or not?

    Science.gov (United States)

    Koutlianos, N; Dimitros, E; Metaxas, T; Cansiz, M; Deligiannis, AS; Kouidi, E

    2013-01-01

    Aim: The purpose of this study was to assess the indirect calculation of VO2max using ACSM’s equation for Bruce protocol in athletes of different sports and to compare with the directly measured; secondly to develop regression models predicting VO2 max in athletes. Methods: Fifty five male athletes of national and international level (mean age 28.3 ± 5.6 yrs) performed graded exercise test with direct measurement of VO2 through ergospirometric device. Moreover, 3 equations were used for the indirect calculation of VO2max: a) VO2max= (0.2 · Speed) + (0.9 · Speed · Grade) + 3.5 (ACSM running equation), b) regression analysis model using enter method and c) stepwise method based on the measured data of VO2. Age, BMI, speed, grade and exercise time were used as independent variables. Results: Regression analysis using enter method yielded the equation (R=.64, standard error of estimation [SEE] = 6.11): VO2max (ml·kg-1·min-1) = 58.443 - (0.215 · age) - (0.632 · BMI) - (68.639 · grade) + (1.579 · time) while stepwise method (R = .61, SEE = 6.18) led to: VO2max (ml·kg-1·min-1) = 33.971 - (0.291 · age) + (1.481 · time). The calculated values of VO2max from these regression models did not differ significantly from the measured VO2max (p>.05). On the contrary, VO2max calculated from the ACSM’s running equation was significantly higher from the actually measured value by 14.6% (p VO2max in athletes aged 18-37 years using Bruce protocol. Only the regression models were correlated moderately with the actually measured values of VO2max. PMID:24376318

  11. Indirect estimation of VO2max in athletes by ACSM's equation: valid or not?

    Science.gov (United States)

    Koutlianos, N; Dimitros, E; Metaxas, T; Cansiz, M; Deligiannis, As; Kouidi, E

    2013-04-01

    The purpose of this study was to assess the indirect calculation of VO2max using ACSM's equation for Bruce protocol in athletes of different sports and to compare with the directly measured; secondly to develop regression models predicting VO2 max in athletes. Fifty five male athletes of national and international level (mean age 28.3 ± 5.6 yrs) performed graded exercise test with direct measurement of VO2 through ergospirometric device. Moreover, 3 equations were used for the indirect calculation of VO2max: a) VO2max= (0.2 · Speed) + (0.9 · Speed · Grade) + 3.5 (ACSM running equation), b) regression analysis model using enter method and c) stepwise method based on the measured data of VO2. Age, BMI, speed, grade and exercise time were used as independent variables. Regression analysis using enter method yielded the equation (R=.64, standard error of estimation [SEE] = 6.11): VO2max (ml·kg(-1)·min(-1)) = 58.443 - (0.215 · age) - (0.632 · BMI) - (68.639 · grade) + (1.579 · time) while stepwise method (R = .61, SEE = 6.18) led to: VO2max (ml·kg(-1)·min(-1)) = 33.971 - (0.291 · age) + (1.481 · time). The calculated values of VO2max from these regression models did not differ significantly from the measured VO2max (p>.05). On the contrary, VO2max calculated from the ACSM's running equation was significantly higher from the actually measured value by 14.6% (p VO2max in athletes aged 18-37 years using Bruce protocol. Only the regression models were correlated moderately with the actually measured values of VO2max.

  12. VO2: a novel view from band theory.

    Science.gov (United States)

    Eyert, V

    2011-07-01

    New calculations for vanadium dioxide, one of the most controversially discussed materials for decades, reveal that band theory as based on density functional theory is well capable of correctly describing the electronic and magnetic properties of the metallic as well as both the insulating M(1) and M(2) phases. Considerable progress in the understanding of the physics of VO(2) is achieved by the use of the recently developed hybrid functionals, which include part of the electron-electron interaction exactly and thereby improve on the weaknesses of semilocal exchange functionals as provided by the local density and generalized gradient approximations. Much better agreement with photoemission data as compared to previous calculations is found and a consistent description of the rutile-type early transition-metal dioxides is achieved.

  13. Erythropoietin elevates VO2,max but not voluntary wheel running in mice.

    Science.gov (United States)

    Kolb, E M; Kelly, S A; Middleton, K M; Sermsakdi, L S; Chappell, M A; Garland, T

    2010-02-01

    Voluntary activity is a complex trait, comprising both behavioral (motivation, reward) and anatomical/physiological (ability) elements. In the present study, oxygen transport was investigated as a possible limitation to further increases in running by four replicate lines of mice that have been selectively bred for high voluntary wheel running and have reached an apparent selection limit. To increase oxygen transport capacity, erythrocyte density was elevated by the administration of an erythropoietin (EPO) analogue. Mice were given two EPO injections, two days apart, at one of two dose levels (100 or 300 microg kg(-1)). Hemoglobin concentration ([Hb]), maximal aerobic capacity during forced treadmill exercise (VO2,max) and voluntary wheel running were measured. [Hb] did not differ between high runner (HR) and non-selected control (C) lines without EPO treatment. Both doses of EPO significantly (PVO2,max by approximately 5% in both the HR and C lines, with no dosexline type interaction. However, wheel running (revolutions per day) did not increase with EPO treatment in either the HR or C lines, and in fact significantly decreased at the higher dose in both line types. These results suggest that neither [Hb] per se nor VO2,max is limiting voluntary wheel running in the HR lines. Moreover, we hypothesize that the decrease in wheel running at the higher dose of EPO may reflect direct action on the reward pathway of the brain.

  14. n-VO2/p-GaN based nitride-oxide heterostructure with various thickness of VO2 layer grown by MBE

    Science.gov (United States)

    Wang, Minhuan; Bian, Jiming; Sun, Hongjun; Liu, Weifeng; Zhang, Yuzhi; Luo, Yingmin

    2016-12-01

    High quality VO2 films with precisely controlled thickness were grown on p-GaN/sapphire substrates by oxide molecular beam epitaxy (O-MBE). Results indicated that a distinct reversible semiconductor-to-metal (SMT) phase transition was observed for all the samples in the temperature dependent electrical resistance measurement, and the influence of VO2 layer thickness on the SMT properties of the as-grown n-VO2/p-GaN based nitride-oxide heterostructure was investigated. Meanwhile, the clear rectifying transport characteristics originated from the n-VO2/p-GaN interface were demonstrated before and after SMT of the VO2 over layer, which were attributed to the p-n junction behavior and Schottky contact character, respectively. Moreover, the X-ray photoelectron spectroscopy (XPS) analyses confirmed the valence state of vanadium (V) in VO2 films was principally composed of V4+ with trace amount of V5+. The design and modulation of the n-VO2/p-GaN based heterostructure devices will benefit significantly from these achievements.

  15. In situ Raman spectroscopy study of metal-enhanced hydrogenation and dehydrogenation of VO2

    Science.gov (United States)

    Wu, Hao; Fu, Qiang; Bao, Xinhe

    2016-11-01

    Vanadium dioxide (VO2) has a phase transition from insulator to metal at 340 K, and this transition can be strongly modified by hydrogenation. In this work, two dimensional (2D) VO2 sheets have been grown on Si(1 1 1) surfaces through chemical vapor deposition, and metal (Au, Pt) thin films were deposited on VO2 surfaces by sputtering. The hydrogenation and dehydrogenation of VO2 and metal-decorated VO2 structures in H2 and in air were in situ studied by Raman. We found that hydrogenation and dehydrogenation temperatures have been significantly decreased with the VO2 surface decorated by Au and Pt. The enhanced hydrogenation and dehydrogenation reactions can be attributed to catalytic dissociation of H2 and O2 molecules on metal surfaces and subsequent spillover of dissociated H and O atoms to the oxide surfaces.

  16. Monitoring changes in VO2max via the Polar FT40 in female collegiate soccer players.

    Science.gov (United States)

    Esco, Michael R; Snarr, Ronald L; Williford, Hank N

    2014-01-01

    This study was conducted to determine if the Polar FT40 could accurately track changes in maximal oxygen consumption (VO2max) in a group of female soccer players. Predicted VO2max (pVO2max) via the Polar FT40 and observed VO2max (aVO2max) from a maximal exercise test on a treadmill were determined for members of a collegiate soccer team (n = 20) before and following an 8-week endurance training protocol. Predicted (VO2max and aVO2max measures were compared at baseline and within 1 week post-training. Change values (i.e., the difference between pre to post) for each variable were also determined and compared. There was a significant difference in aVO2max (pre = 43.6 ± 2.4 ml · kg · min(-1), post = 46.2 ± 2.4 ml · kg · min(-1), P < 0.001) and pVO2max (pre = 47.3 ± 5.3 ml · kg · min(-1), post = 49.7 ± 6.2 ml · kg · min(-1), P = 0.009) following training. However, predicted values were significantly greater at each time point compared to observed values (P < 0.001 at pre and P = 0.008 at post). Furthermore, there was a weak correlation between the change in aVO2max and the change in pVO2max (r = 0.18, P = 0.45). The Polar FT40 does not appear to be a valid method for predicting changes in individual VO2max following 8 weeks of endurance training in female collegiate soccer players.

  17. The impact of decreasing cutoff values for maximal oxygen consumption (VO2max) in the decision-making process for candidates to lung cancer surgery

    Science.gov (United States)

    Gatani, Tindaro; Di Maio, Massimo; Meoli, Ilernando; La Rocca, Antonello; Martucci, Nicola; La Manna, Carmine; Stefanelli, Francesco

    2013-01-01

    Background Maximal oxygen consumption (VO2max) is considered a decisive test for risk prediction in patients with borderline cardiopulmonary reserve. Guidelines have adopted decreasing VO2max cut-off values to define operability within acceptable mortality and morbidity limits. We wanted to investigate how the adoption of decreasing VO2max cut-off-values assessment contributed to better select lung surgery candidates. Methods One hundred and nineteen consecutive surgical candidates have been prospectively analyzed as a sample population. Preoperative work-up included spirometry and transfer factor (DLco); irrespective of the spirometric values, these patients were subjected to VO2max assessment. Surgical eligibility was decided by the same surgeon throughout the series. In the postoperative period, overall mortality and the occurrence of any, major or minor complications was recorded and graded according to the Common Terminology Criteria for Adverse Events v.4.3. Results Three arbitrary cut-offs were introduced at 15, 14 and 12 mL.kg-1.min-1. Notably, 15 and 12 mL.kg-1.min-1 correlated with percentage VO2max values of 50% and 35% of predicted (PVO2max less than 35% (P=0.0017) and CTCAE >2 (P=0.0457) emerged as significant predictors of survival after surgery. Conversely on logistic regression analysis, age over 70 years (P=0.03) and pneumonectomy (P=0.001), but not VO2max cut-off values, were significant predictors of major (CTCAE >2) morbidity. Conclusions Since VO2max is increasingly used to contribute to risk prediction for the individual patient, surgeons need to be advised that the concept of a definitive, generalized cut-off value for VO2max is probably a contradiction in terms. Patient-specific VO2max values are more likely to contribute to risk assessment since they may reflect the primarily affected component among the determinants of maximal oxygen consumption. Whether patient-specific VO2max should be routinely used by surgeons to define operability for

  18. Effects of body mass on exercise efficiency and VO2 during steady-state cycling.

    Science.gov (United States)

    Berry, M J; Storsteen, J A; Woodard, C M

    1993-09-01

    Oxygen uptake (VO2) and exercise efficiency during cycle ergometer exercise are considered to be independent of body mass. To determine the validity of this assumption, 50 females ranging in body mass from 41.5-98.9 kg exercised on a cycle ergometer with no load at 60 rpm and at 25, 50, 75, and 100 W at 60 and 90 rpm. Gross VO2 and efficiency, net VO2 and efficiency, work VO2 and efficiency, and delta efficiency were computed. Gross and net VO2 were significantly and positively correlated with body mass at all work rates and pedal frequencies. Gross efficiency was significantly and negatively correlated with body mass at all work rates and pedal frequencies. Work VO2 and body mass were not significantly correlated. The correlations between work and delta efficiency and body mass were not significant. Since body mass was found to be significantly correlated with gross VO2, the following equation was developed using stepwise multiple regression to predict gross VO2: VO2 (ml.min-1) = 10.9 (work rate, W) + 8.2 (pedal rate, rpm) + 8.3 (body mass, kg) - 559.6. These data suggest that body mass should be considered when estimating the oxygen uptake during cycle ergometer exercise.

  19. Switching dynamics of single and coupled VO2-based oscillators as elements of neural networks

    Science.gov (United States)

    Velichko, Andrey; Belyaev, Maksim; Putrolaynen, Vadim; Pergament, Alexander; Perminov, Valentin

    2017-01-01

    In the present paper, we report on the switching dynamics of both single and coupled VO2-based oscillators, with resistive and capacitive coupling, and explore the capability of their application in oscillatory neural networks. Based on these results, we further select an adequate SPICE model to describe the modes of operation of coupled oscillator circuits. Physical mechanisms influencing the time of forward and reverse electrical switching, that determine the applicability limits of the proposed model, are identified. For the resistive coupling, it is shown that synchronization takes place at a certain value of the coupling resistance, though it is unstable and a synchronization failure occurs periodically. For the capacitive coupling, two synchronization modes, with weak and strong coupling, are found. The transition between these modes is accompanied by chaotic oscillations. A decrease in the width of the spectrum harmonics in the weak-coupling mode, and its increase in the strong-coupling one, is detected. The dependences of frequencies and phase differences of the coupled oscillatory circuits on the coupling capacitance are found. Examples of operation of coupled VO2 oscillators as a central pattern generator are demonstrated.

  20. A Microscopic Model for the Strongly Coupled Electron-Ion System in VO2

    Science.gov (United States)

    Lovorn, Timothy; Sarker, Sanjoy

    The metal-insulator transition (MIT) in vanadium dioxide (VO2) near 340 K is accompanied by a structural transition, suggesting strong coupling between electronic and lattice degrees of freedom. To help elucidate this relationship, we construct and analyze a microscopic model in which electrons, described by a tight-binding Hamiltonian, are dynamically coupled to Ising-like ionic degrees of freedom. A mean-field decoupling leads to an interacting two-component (pseudo) spin-1 Ising model describing the ions. An analysis of the minimal ionic model reproduces the observed M1 and M2 dimerized phases and rutile metal phase, occurring in the observed order with increasing temperature. All three transitions are first order, as observed. We further find that both dimerization and correlations play crucial roles in describing the insulating M1 phase. We discuss why dynamical coupling of electrons and ions is key to obtain a full understanding of the phenomenology of VO2, particularly in the context of the phase coexistence observed near the MIT. This research was supported by the National Science Foundation (DMR-1508680).

  1. Tuning a strain-induced orbital selective Mott transition in epitaxial VO2

    Science.gov (United States)

    Mukherjee, Shantanu; Quackenbush, N. F.; Paik, H.; Schlueter, C.; Lee, T.-L.; Schlom, D. G.; Piper, L. F. J.; Lee, Wei-Cheng

    2016-06-01

    We present evidence of strain-induced modulation of electron correlation effects and increased orbital anisotropy in the rutile phase of epitaxial VO2/TiO2 films from hard x-ray photoelectron spectroscopy and soft V L-edge x-ray absorption spectroscopy, respectively. By using the U(1) slave spin formalism, we further argue that the observed anisotropic correlation effects can be understood by a model of orbital selective Mott transition at a filling that is noninteger but close to the half filling. Because the overlaps of wave functions between d orbitals are modified by the strain, orbital-dependent renormalizations of the bandwidths and the onsite energy occur. These renormalizations generally result in different occupation numbers in different orbitals. We find that if the system has a noninteger filling number near the half filling such as for VO2, certain orbitals could reach an occupation number closer to half filling under the strain, resulting in a strong reduction in the quasiparticle weight Zα of that orbital. Our work demonstrates that such an orbital selective Mott transition, defined as the case with Zα=0 in some but not all orbitals, could be accessed by epitaxial-strain engineering of correlated electron systems.

  2. Low-temperature CVD synthesis of patterned core-shell VO2@ZnO nanotetrapods and enhanced temperature-dependent field-emission properties

    Science.gov (United States)

    Yin, Haihong; Yu, Ke; Song, Changqing; Wang, Zhiliang; Zhu, Ziqiang

    2014-09-01

    VO2 nanostructures are attractive materials because of their reversible metal-insulator transition (MIT) and wide applications in devices. When they are used as field emitters, a new type of temperature-controlled field emission device can be fabricated. Vapor transport methods used to synthesize traditional VO2 nanostructures are energy-intensive, low yield, and produce simple morphology (quasi-1D) that exhibits substrate clamping; thus they are not suitable for field emission applications. To overcome these limitations, ZnO nanotetrapods were used as templates, and patterned core-shell VO2@ZnO nanotetrapods were successfully grown on an ITO/glass substrate via a low-temperature CVD synthesis. SEM, TEM, EDX, XPS analyses and X-ray diffraction revealed that the cores and shells of these nanotetrapods were single crystal wurtzite-type ZnO and polycrystalline VO2, respectively. The VO2@ZnO nanotetrapods show strongly MIT-related FE properties, the emission current density at low temperature is significantly enhanced in comparison with pure VO2 nanostructures, and the emission current density increased by about 20 times as the ambient temperature increased from 25 to 105 °C at a fixed field of 5 V μm-1. Although the VO2@ZnO nanotetrapods show a worse FE performance at low temperatures compared with pure ZnO nanotetrapods, the FE performance was substantially improved at high temperatures, which was attributed to the MIT-related band bending near the interface and the abrupt resistance change across the MIT.

  3. Assessing peak aerobic capacity in Dutch law enforcement officers

    Directory of Open Access Journals (Sweden)

    Harriet Wittink

    2015-06-01

    Full Text Available Objectives: To cross-validate the existing peak rate of oxygen consumption (VO2peak prediction equations in Dutch law enforcement officers and to determine whether these prediction equations can be used to predict VO2peak for groups and in a single individual. A further objective was to report normative absolute and relative VO2peak values of a sample of law enforcement officers in the Netherlands. Material and Methods: The peak rate of oxygen consumption (ml×kg–1×min–1 was measured using a maximal incremental bicycle test in 1530 subjects, including 1068 male and 461 female police officers. Validity of the prediction equations for groups was assessed by comparing predicted VO2peak with measured VO2peak using paired t-tests. For individual differences limits of agreement (LoA were calculated. Equations were considered valid for individuals when the difference between measured and predicted VO2peak did not exceed ±1 metabolic equivalent (MET in 95% of individuals. Results: None of the equations met the validity criterion of 95% of individuals having ±1 MET difference or less than the measured value. Limits of agreement (LoAs were large in all predictions. At the individual level, none of the equations were valid predictors of VO2peak (ml×kg–1×min–1. Normative values for Dutch law enforcement officers were presented. Conclusions: Substantial differences between measured and predicted VO2peak (ml×kg–1×min–1 were found. Most tested equations were invalid predictors of VO2peak at group level and all were invalid at individual levels.

  4. Assessing peak aerobic capacity in Dutch law enforcement officers.

    Science.gov (United States)

    Wittink, Harriet; Takken, Tim; de Groot, Janke; Reneman, Michiel; Peters, Roelof; Vanhees, Luc

    2015-01-01

    To cross-validate the existing peak rate of oxygen consumption (VO2peak) prediction equations in Dutch law enforcement officers and to determine whether these prediction equations can be used to predict VO2peak for groups and in a single individual. A further objective was to report normative absolute and relative VO2peak values of a sample of law enforcement officers in the Netherlands. The peak rate of oxygen consumption (ml×kg-1×min-1) was measured using a maximal incremental bicycle test in 1530 subjects, including 1068 male and 461 female police officers. Validity of the prediction equations for groups was assessed by comparing predicted VO2peak with measured VO2peak using paired t-tests. For individual differences limits of agreement (LoA) were calculated. Equations were considered valid for individuals when the difference between measured and predicted VO2peak did not exceed ±1 metabolic equivalent (MET) in 95% of individuals. None of the equations met the validity criterion of 95% of individuals having ±1 MET difference or less than the measured value. Limits of agreement (LoAs) were large in all predictions. At the individual level, none of the equations were valid predictors of VO2peak (ml×kg-1×min-1). Normative values for Dutch law enforcement officers were presented. Substantial differences between measured and predicted VO2peak (ml×kg-1×min-1) were found. Most tested equations were invalid predictors of VO2peak at group level and all were invalid at individual levels. This work is available in Open Access model and licensed under a CC BY-NC 3.0 PL license.

  5. PELATIHAN LARI SIRKUIT 2 X 10 MENIT DAN PELATIHAN LARI KONTINYU 2 X 10 MENIT DAPAT MENINGKATKAN VO2 MAX TAEKWONDOIN PUTRA KABUPATEN MANGGARAI - NTT

    Directory of Open Access Journals (Sweden)

    Regina Sesilia Noy

    2014-08-01

    Full Text Available VO2 max is very important in everyday life, so as to facilitate any physicalactivity, specially for athletes in order to achieve maximum performance. In aneffort to increase VO2 max training should be carried out regularly, measured andplanned. This study aims to determine the increase in VO2 max through circuittraining run and run continuously. The sample is taekwondoin son Manggarai-NTTwith an average age of 15 years. This study is an experimental study with the studydesign used was Randomized Pre and Post Test Group desigen. With a totalsample of 7 people in each group. Samples were randomly selected. Treatmentgroup 1 (KP1 given training run circuit 2 x 10 minute and Treatment Group 2(KP2 are given continuous training run 2 x 10 minute. Training carried out for 6weeks with a frequency of four times a week starting at 17:00 to 18:00 pm locatedat Frans Sales Lega Airport Manggarai-NTT. The analysis showed an increase inVO2 max was significantly (p <0.05 against both groups fled. In both groups thecircuit run by Pulse Oxymeter and Norma Cooper an increase in VO2 max with p<0.05, as well as a continuous run either by Pulse Oxymeter and Norma Cooperwith an increase in VO2 max value of p <0.05. The results of this analysis meansthat either the training or circuit training run run continuously to improve VO2max. Based on a comparison of test data by an independent test after training inboth groups either by Pulse Oxymeter and Norma Cooper in get p values > 0.05, orthere is no significant difference. Based on these results it can be concluded thatthe run circuit training and continuous training run together can increase VO2 maxand there was no significant difference. The results of this study are expected toincrease the knowledge of coaches, teachers and taekwondoin to perform trainingon a regular basis and are also expected to do similar research that examines VO2max with different training.

  6. Reliability of treadmill measures and criteria to determine VO2max in prepubertal girls.

    Science.gov (United States)

    Figueroa-Colon, R; Hunter, G R; Mayo, M S; Aldridge, R A; Goran, M I; Weinsier, R L

    2000-04-01

    The main objective of this study was to determine the reliability of measuring treadmill exercise economy (VO2submax) and the maximal oxygen uptake (VO2max) in prepubertal girls tested twice, 6 wk apart. We also wanted to examine the percentage of young girls who were able to reach the criteria for achieving VO2max and to describe methods that would allow a high proportion of young children to achieve criteria for reaching a true VO2max. We studied 61 normal-weight, prepubertal girls with a mean (+/- SD) age 7.3+/-1.3 yr (range 4.8 to 10.3 yr). VO2submax was determined while walking for 4 min at 2.5 mph with 0% grade. VO2max was measured during a progressive, all-out, continuous treadmill test using standardized procedures and criteria. Heart rate (HR) was measured using a Polar monitor. Respiratory rate (RR), respiratory exchange ratio (RER), ventilation (V), and VO2 were measured using a Sensormedics metabolic monitor. There were no significant differences between visits I and 2 in mean HR, RR, RER, V, VO2submax (421 vs 422 mL x min(-1), respectively), and VO2max (1036 vs 1049 mL x min(-1), respectively). Intra-individual coefficients of variation (CV) between visits 1 and 2 for submaximal tests were: HR = 5.1%, RR = 12.4%, RER = 7.2%, V = 12.5%, and VO2 = 12.4%. Intra-individual CVs for the maximum tests were: HRmax = 2.1%, RRmax = 10.8%, RERmax = 5.3%, Vmax = 11.7%, and VO2max = 7.5%. A high proportion of the girls reached criteria for VO2max [RER> 1.00, HR>85% of age predicted maximum, and plateauing of VO2max] in both visits: 99% reached one of three criteria, 92% reached two of three criteria, and 70% reached all three criteria. Twenty girls [mean age 7.2+/-1.2 yr] reached at least two criteria in both visits, whereas 32 girls [mean (+/- SD) age 8.6+/-1.0 yr] reached three criteria in both visits. Exercise measurements using treadmill testing were reliable in healthy, normal-weight, prepubertal girls. Older girls when compared to the younger girls were able

  7. The Effect of Aging on Relationships between Lean Body Mass and VO2max in Rowers.

    Science.gov (United States)

    Kim, Chul-Ho; Wheatley, Courtney M; Behnia, Mehrdad; Johnson, Bruce D

    2016-01-01

    Aging is associated with a fall in maximal aerobic capacity as well as with a decline in lean body mass. The purpose of the study was to investigate the influence of aging on the relationship between aerobic capacity and lean body mass in subjects that chronically train both their upper and lower bodies. Eleven older rowers (58±5 yrs) and 11 younger rowers (27±4 yrs) participated in the study. Prior to the VO2max testing, subjects underwent a dual energy X-ray absorptiometry scan to estimate total lean body mass. Subsequently, VO2max was quantified during a maximal exercise test on a rowing ergometer as well as a semi-recumbent cycle ergometer. The test protocol included a pre-exercise stage followed by incremental exercise until VO2max was reached. The order of exercise modes was randomized and there was a wash-out period between the two tests. Oxygen uptake was obtained via a breath-by-breath metabolic cart (Vmax™ Encore, San Diego, CA). Rowing VO2max was higher than cycling VO2max in both groups (pVO2max from cycling to rowing (pVO2max for both groups (pVO2max between groups disappeared (p>0.05), however, older subjects still demonstrated a lower rowing VO2max relative to younger subjects (pVO2max obtained, however, it appears that VO2max in older subjects may be less influenced by muscle mass than in younger subjects.

  8. A longitudinal assessment of change in VO2max and maximal heart rate in master athletes.

    Science.gov (United States)

    Hawkins, S A; Marcell, T J; Victoria Jaque, S; Wiswell, R A

    2001-10-01

    The purpose of this study was to determine the longitudinal change in VO2max and HRmax in male and female master endurance runners and to compare these changes based upon gender, age, and change in training volume. Eighty-six male (53.9 +/- 1.1 yr) and 49 female (49.1 +/- 1.2 yr) master endurance runners were tested an average of 8.5 yr apart. Subjects were grouped by age at first visit, change in VO2max, and change in training volume. Measurements included body composition by hydrostatic weighing, maximal exercise testing on a treadmill, and training history by questionnaire. Data were analyzed by ANOVA and multiple regression. VO2max and HRmax declined significantly regardless of gender or age group (P VO2max by age group ranged from -1% to -4.6% per year for men and -0.5% to 2.4% per year for women. Men with the greatest loss in VO2max had the greatest loss in LBM (-2.8 +/- 0.7 kg), whereas women with the greatest loss in VO2max demonstrated the greatest change in training volume (-24.1 +/- 3.0 km.wk-1). Additionally, women with the greatest loss in VO2max (-9.6 +/- 2.6 mL.kg-1.min-1) did not replace estrogen after menopause independent of age. HRmax change did not differ by VO2max change or training volume change in either gender. In conclusion, these data suggest that VO2max declines in male and female master athletes at a rate similar to or greater than that expected in sedentary older adults. Additionally, these data suggest that maintenance of LBM and VO2max were associated in men, whereas in women, estrogen replacement and maintenance of training volume were associated with maintained VO2max.

  9. A Study of VO2 Max and Body Fat Percentage in Female Athletes

    Science.gov (United States)

    Bute, Smita S; Deshmukh, P.R

    2014-01-01

    Introduction: Aerobic capacity of athletes is an important element of success in sports achievements. It is generally considered the best indicator of cardio respiratory endurance and athletic fitness. Body fat percentage affects VO2 max and thus the cardiovascular status of the athletes. The present study was undertaken to assess the VO2 max and body fat percentage in athletes. The secondary objective of the study was to study the relationship between VO2 max and body fat percentage. Materials and Methods: Twenty five female athletes of age group 17-22years were selected for the study. VO2 max was determined by Queen’s college step test and body fat percentage by skin fold calipers. The VO2 max and body fat percentage were determined in non athletes of same age group for comparison. The statistical analysis was done by Student’s t-test and Pearson correlation test. Observation and Results: The mean VO2 max in athletic group was 39.62 ± 2.80 ml/kg/min. In non-athletic group, VO2 max was 23.54 ± 3.26 ml/kg/min. The mean body fat percentage in athletes was 24.11 ± 1.83% and in non-athletes it was 29.31 ± 3.86%.The difference in VO2 max and body fat percentage was statistically significant in our study. The VO2 max and body fat percentage in both the groups showed negative correlation by Pearson test but, was not statistically significant. Conclusion: The present study showed a statistically significant higher VO2 max in female athletes. The study showed a negative correlation between VO2 max and body fat percentage but was not statistically significant. PMID:25653935

  10. Anomalous phonon behavior: blueshift of the surface boson peak in silica glass with increasing temperature.

    Science.gov (United States)

    Steurer, W; Apfolter, A; Koch, M; Ernst, W E; Søndergård, E; Manson, J R; Holst, B

    2008-04-04

    We present helium atom scattering measurements of the boson peak at the surface of vitreous silica between 127.0 and 368.5 K. The most probable energy shows a strong temperature dependence and increases linearly with temperature in the measured range. The observed blueshift of the surface boson peak (shift rate 0.008+/-0.002 meV/K) is a factor of 4 to 10 times stronger than shift rates measured in the bulk by inelastic neutron and Raman scattering. We suggest that the anomalous shift direction of the boson peak to higher energies with increasing temperature has the same origin as the unusual temperature dependence of the bulk modulus of silica glass.

  11. Epitaxial growth of higher transition-temperature VO2 films on AlN/Si

    Directory of Open Access Journals (Sweden)

    Tetiana Slusar

    2016-02-01

    Full Text Available We report the epitaxial growth and the mechanism of a higher temperature insulator-to-metal-transition (IMT of vanadium dioxide (VO2 thin films synthesized on aluminum nitride (AlN/Si (111 substrates by a pulsed-laser-deposition method; the IMT temperature is TIMT ≈ 350 K. X-ray diffractometer and high resolution transmission electron microscope data show that the epitaxial relationship of VO2 and AlN is VO2 (010 ‖ AlN (0001 with VO2 [101] ‖   AlN   [ 2 1 ̄ 1 ̄ 0 ] zone axes, which results in a substrate-induced tensile strain along the in-plane a and c axes of the insulating monoclinic VO2. This strain stabilizes the insulating phase of VO2 and raises TIMT for 10 K higher than TIMT single crystal ≈ 340 K in a bulk VO2 single crystal. Near TIMT, a resistance change of about four orders is observed in a thick film of ∼130 nm. The VO2/AlN/Si heterostructures are promising for the development of integrated IMT-Si technology, including thermal switchers, transistors, and other applications.

  12. Removing the thermal component from heart rate provides an accurate VO2 estimation in forest work.

    Science.gov (United States)

    Dubé, Philippe-Antoine; Imbeau, Daniel; Dubeau, Denise; Lebel, Luc; Kolus, Ahmet

    2016-05-01

    Heart rate (HR) was monitored continuously in 41 forest workers performing brushcutting or tree planting work. 10-min seated rest periods were imposed during the workday to estimate the HR thermal component (ΔHRT) per Vogt et al. (1970, 1973). VO2 was measured using a portable gas analyzer during a morning submaximal step-test conducted at the work site, during a work bout over the course of the day (range: 9-74 min), and during an ensuing 10-min rest pause taken at the worksite. The VO2 estimated, from measured HR and from corrected HR (thermal component removed), were compared to VO2 measured during work and rest. Varied levels of HR thermal component (ΔHRTavg range: 0-38 bpm) originating from a wide range of ambient thermal conditions, thermal clothing insulation worn, and physical load exerted during work were observed. Using raw HR significantly overestimated measured work VO2 by 30% on average (range: 1%-64%). 74% of VO2 prediction error variance was explained by the HR thermal component. VO2 estimated from corrected HR, was not statistically different from measured VO2. Work VO2 can be estimated accurately in the presence of thermal stress using Vogt et al.'s method, which can be implemented easily by the practitioner with inexpensive instruments.

  13. Waist circumference and VO2max are associated with metabolic and hemostatic risk in premenopausal nurses

    NARCIS (Netherlands)

    Elich, H; Riese, H; De Geus, EJC

    In 21 nurses (34.4+/-3.9 yr), VO2max, physical activity, body composition and lifestyle parameters were measured to determine which of these characteristics are related to metabolic and hemostatic risk for cardiovascular disease. Physical activity was assessed with the 7-day recall interview VO2max

  14. Effect of Toe Clips During Bicycle Ergometry on VO2 max.

    Science.gov (United States)

    Moffat, Roger S.; Sparling, Phillip B.

    1985-01-01

    Eight men participated in three randomized maximal oxygen uptake tests to investigate the hypothesis that the use of toe clips on bicycle ergometers produced a higher VO2 max. No significant difference in mean VO2 max or performance time was observed. (Author/MT)

  15. Metal-insulator phase transition in a VO2 thin film observed with terahertz spectroscopy

    DEFF Research Database (Denmark)

    Jepsen, Peter Uhd; Fischer, Bernd M.; Thoman, Andreas

    2006-01-01

    We investigate the dielectric properties of a thin VO2 film in the terahertz frequency range in the vicinity of the semiconductor-metal phase transition. Phase-sensitive broadband spectroscopy in the frequency region below the phonon bands of VO2 gives insight into the conductive properties...

  16. High-intensity interval training every second week maintains VO2max in soccer players during off-season.

    Science.gov (United States)

    Slettaløkken, Gunnar; Rønnestad, Bent R

    2014-07-01

    Reduced endurance training among semiprofessional soccer players during off-season may have negative effect on game performance during the competition season. This negative effect can be prevented by adding high-intensity interval training (HIT) to normal activity. In this study, we want to compare 2 different frequencies of HIT (5 bouts of 4 minutes on 87-97% peak heart rate) session on maintenance of aerobic fitness among semiprofessional soccer players during a 6-week off-season period. Seventeen male players at second and third highest soccer division in Norway participated. The subjects were randomized into 1 HIT session every second week (HIT 0.5) or 1 HIT session per week (HIT 1). All participants performed a 20-m shuttle run test and a maximal oxygen uptake (VO2max) test on treadmill before and after the training intervention. VO2max (HIT 0.5, 63.4 ± 5.9 ml·kg-1·min-1; HIT 1, 65.6 ± 2.1 ml·kg-1·min-1) and 20-m shuttle run performance (HIT 0.5, 2335 ± 390 m, HIT 1, 2531 ± 106 m) were not different between the groups before the training intervention. VO2max was maintained after the training intervention in both HIT 0.5 and HIT 1 (64.0 ± 5.9 ml·kg-1·min-1 and 64.3 ± 1.3 ml·kg-1·min-1, respectively). There was a reduction in distance covered during the 20-m shuttle run test in HIT 1 and when groups were pooled (-7.9 ± 5.7% and -6.4 ± 7.9%, respectively, p ≤ 0.05). In conclusion, HIT 1 did not maintain VO2max better than HIT 0.5 when added to normal off-season activity. However, performance in 20-m shuttle run, which is a more soccer-specific fitness test than VO2max test, was slightly reduced when both groups was pooled.

  17. The effect of a peer on VO2 and game choice in 6-10 year old children

    Directory of Open Access Journals (Sweden)

    Lee Anne Siegmund

    2014-06-01

    Full Text Available Relative to sedentary video games (e.g., Playstation 2 (PS2, playing physically active video games (e.g., Nintendo Wii (Wii significantly increases caloric expenditure in children. Studies have demonstrated that the presence of a peer increases physical activity in children. We sought to determine if children would expend more energy and find playing Wii more motivating than PS2 when with a peer. Seventeen children (age 8.5 ± 0.4 years rested, played PS2 and Wii Sports Boxing for 10 minutes each, in two conditions: one in which the children rested/played the games alone (alone condition and another in which they played with a peer (peer condition. Oxygen consumption (VO2, and liking (visual analog scale was assessed for each 10-minute condition. After three 10-minute resting/gaming conditions, motivation was assessed using a relative reinforcing value task (RRV in which children performed computer mouse presses to gain additional access for either PS2 or Wii. VO2 was greater (p Conclusion: The presence of a peer increased VO2 during Wii play for boys but not girls. Surprisingly, the presence of a peer decreased children’s motivation to play Wii versus PS2.

  18. A new non-exercise-based Vo2max prediction equation for aerobically trained men.

    Science.gov (United States)

    Malek, Moh H; Housh, Terry J; Berger, Dale E; Coburn, Jared W; Beck, Travis W

    2005-08-01

    The purposes of the present study were to (a) modify previously published Vo(2)max equations using the constant error (CE = mean difference between actual and predicted Vo(2)max) values from Malek et al. (28); (b) cross-validate the modified equations to determine their accuracy for estimating Vo(2)max in aerobically trained men; (c) derive a new non- exercise-based equation for estimating Vo(2)max in aerobically trained men if the modified equations are not found to be accurate; and (d) cross-validate the new Vo(2)max equation using the predicted residual sum of squares (PRESS) statistic and an independent sample of aerobically trained men. One hundred and fifty-two aerobically trained men (Vo(2)max mean +/- SD = 4,154 +/- 629 ml.min(-1)) performed a maximal incremental test on a cycle ergometer to determine actual Vo(2)max. An aerobically trained man was defined as someone who had participated in continuous aerobic exercise 3 or more sessions per week for a minimum of 1 hour per session for at least the past 18 months. Nine previously published Vo(2)max equations were modified for use with aerobically trained men. The predicted Vo(2)max values from the 9 modified equations were compared to actual Vo(2)max by examining the CE, standard error of estimate (SEE), validity coefficient (r), and total error (TE). Cross-validation of the modified non-exercise-based equations on a random subsample of 50 subjects resulted in a %TE > or = 13% of the mean of actual Vo(2)max. Therefore, the following non-exercise-based Vo(2)max equation was derived from a random subsample of 112 subjects: Vo(2)max (ml.min(-1)) = 27.387(weight in kg) + 26.634(height in cm) - 27.572(age in years) + 26.161(h.wk(-1) of training) + 114.904(intensity of training using the Borg 6-20 scale) + 506.752(natural log of years of training) - 4,609.791 (R = 0.82, R(2) adjusted = 0.65, and SEE = 378 ml.min(-1)). Cross-validation of this equation on the remaining sample of 40 subjects resulted in a %TE of 10

  19. Selective growth of single phase VO2(A, B, and M polymorph thin films

    Directory of Open Access Journals (Sweden)

    Amar Srivastava

    2015-02-01

    Full Text Available We demonstrate the growth of high quality single phase films of VO2(A, B, and M on SrTiO3 substrate by controlling the vanadium arrival rate (laser frequency and oxidation of the V atoms. A phase diagram has been developed (oxygen pressure versus laser frequency for various phases of VO2 and their electronic properties are investigated. VO2(A phase is insulating VO2(B phase is semi-metallic, and VO2(M phase exhibits a metal-insulator transition, corroborated by photo-electron spectroscopic studies. The ability to control the growth of various polymorphs opens up the possibility for novel (heterostructures promising new device functionalities.

  20. Hydrothermal growth of VO2 nanoplate thermochromic films on glass with high visible transmittance

    Science.gov (United States)

    Zhang, Jiasong; Li, Jingbo; Chen, Pengwan; Rehman, Fida; Jiang, Yijie; Cao, Maosheng; Zhao, Yongjie; Jin, Haibo

    2016-06-01

    The preparation of thermochromic vanadium dioxide (VO2) films in an economical way is of interest to realizing the application of smart windows. Here, we reported a successful preparation of self-assembly VO2 nanoplate films on TiO2-buffered glass by a facile hydrothermal process. The VO2 films composed of triangle-shaped plates standing on substrates exhibit a self-generated porous structure, which favors the transmission of solar light. The porosity of films is easily controlled by changing the concentration of precursor solutions. Excellent thermochromic properties are observed with visible light transmittance as high as 70.3% and solar modulating efficiency up to 9.3% in a VO2 film with porosity of ~35.9%. This work demonstrates a promising technique to promote the commercial utilization of VO2 in smart windows.

  1. Fabrication and electrical resistivity of Mo-doped VO2 thin films coated on graphite conductive plates by a sol-gel method

    Energy Technology Data Exchange (ETDEWEB)

    Choi, W.; Jung, H.M.; Um, S. [Hanyang Univ., Seoul (Korea, Republic of). School of Mechanical Engineering

    2008-07-01

    Vanadium oxides (VO2) can be used in optical devices, thermochromic smart windows and sensors. This paper reported on a study in which vanadium pentoxide (V2O5) powder was prepared and mixed with Molybdenum Oxides (MoO3) to form Mo-doped and -undoped VO2 thin films by a sol-gel method on graphite conductive substrates. The micro-structure and chemical compositions of the Mo-doped and -undoped VO2 thin films was investigated using X-Ray diffraction and scanning electron microscopy. Changes in electrical resistivity were measured as a function of the stoichiometric compositions between vanadium and molybdenum. In this study. Mo-doped and -undoped VO2 thin films showed the typical metal to insulator transition (MIT), where temperature range could be adjusted by modifying the dopant atomic ratio. The through-plane substrate structure of the Mo-doped layer influences the electrical resistivity of the graphite substrate. As the amount of the molybdenum increases, the electrical resistivity of the graphite conductive substrate decreases in the lower temperature range below the freezing point of water. The experimental results showed that if carefully controlled, thermal dissipation of VO2 thin films can be used as a self-heating source to melt frozen water with the electrical current flowing through the graphite substrate. 3 refs., 3 figs.

  2. Time to Exhaustion at the VO2max Velocity in Swimming: A Review.

    Science.gov (United States)

    Fernandes, Ricardo J; Vilas-Boas, J Paulo

    2012-05-01

    The aim of this study was to present a review on the time to exhaustion at the minimum swimming velocity corresponding to maximal oxygen consumption (TLim-vVO2max). This parameter is critical both for the aerobic power and the lactate tolerance bioenergetical training intensity zones, being fundamental to characterize it, and to point out its main determinants. The few number of studies conducted in this topic observed that swimmers were able to maintain an exercise intensity corresponding to maximal aerobic power during 215 to 260 s (elite swimmers), 230 to 260 s (high level swimmers) and 310 to 325 s (low level swimmers), and no differences between genders were reported. TLim-vVO2max main bioenergetic and functional determinants were swimming economy and VO2 slow component (direct relationship), and vVO2max, velocity at anaerobic threshold and blood lactate production (inverse relationship); when more homogeneous groups of swimmers were analysed, the inverse correlation value between TLim-vVO2max and vVO2max was not so evident. In general, TLim-vVO2max was not related to VO2max. TLim-vVO2max seems also to be influenced by stroking parameters, with a direct relationship to stroke length and stroke index, and an inverse correlation with stroke rate. Assessing TLim-vVO2max, together with the anaerobic threshold and the biomechanical general parameters, will allow a larger spectrum of testing protocols application, helping to build more objective and efficient training programs.

  3. Potentiation increases peak twitch torque by enhancing rates of torque development and relaxation.

    Science.gov (United States)

    Froyd, Christian; Beltrami, Fernando Gabe; Jensen, Jørgen; Noakes, Timothy David

    2013-01-01

    The aim of this study was to measure the extent to which potentiation changes in response to an isometric maximal voluntary contraction. Eleven physically active subjects participated in two separate studies. Single stimulus of electrical stimulation of the femoral nerve was used to measure torque at rest in unpotentiated quadriceps muscles (study 1 and 2), and potentiated quadriceps muscles torque in a 10 min period after a 5 s isometric maximal voluntary contraction of the quadriceps muscles (study 1). Additionally, potentiated quadriceps muscles torque was measured every min after a further 10 maximal voluntary contractions repeated every min (study 2). Electrical stimulation repeated several times without previous maximal voluntary contraction showed similar peak twitch torque. Peak twitch torque 4 s after a 5 s maximal voluntary contraction increased by 45±13% (study 1) and by 56±10% (study 2), the rate of torque development by 53±13% and 82±29%, and the rate of relaxation by 50±17% and 59±22%, respectively, but potentiation was lost already two min after a 5 s maximal voluntary contraction. There was a tendency for peak twitch torque to increase for the first five repeated maximal voluntary contractions, suggesting increased potentiation with additional maximal voluntary contractions. Correlations for peak twitch torque vs the rate of torque development and for the rate of relaxation were r(2)= 0.94 and r(2)=0.97. The correlation between peak twitch torque, the rate of torque development and the rate of relaxation suggests that potentiation is due to instantaneous changes in skeletal muscle contractility and relaxation.

  4. The Effect of Training Intensity on VO2max in Young Healthy Adults: A Meta-Regression and Meta-Analysis

    OpenAIRE

    SCRIBBANS, TRISHA D.; VECSEY, STEPHAN; Hankinson, Paul B.; Foster, William S.; Brendon J Gurd

    2016-01-01

    Exercise training at a variety of intensities increases maximal oxygen uptake (VO2max), the strongest predictor of cardiovascular and all-cause mortality. The purpose of the present study was to perform a systematic review, meta-regression and meta-analysis of available literature to determine if a dose-response relationship exists between exercise intensity and training-induced increases in VO2max in young healthy adults. Twenty-eight studies involving human participants (Mean age: 23±1 yr; ...

  5. The reliability and validity of the Astrand nomogram and linear extrapolation for deriving VO2max from submaximal exercise data.

    Science.gov (United States)

    Macsween, A

    2001-09-01

    While the accepted measure of aerobic power remains the VO2max this test is extremely demanding even for athletes. There are serious practical and ethical concerns in attempting such testing in non-athletic or patient populations. An alternative method of measuring aerobic power in such populations is required. A limited body of work exists evaluating the accuracy of the Astrand-Ryhming nomogram and linear extrapolation of the heart rate/oxygen uptake plot. Issues exist in terms of both equipment employed and sample numbers. Twenty-five normal subjects (mean age 28.6, range 22-50) completed 52 trials (Bruce treadmill protocol) meeting stringent criteria for VO2max performance. Respiratory gases were measured with a portable gas analyser on a five-sec sample period. The data was analysed to allow comparison of the reliability and validity of linear extrapolations to three estimates of heart rate maximum with the Astrand nomogram prediction. Extrapolation was preferable yielding intraclass correlation co-efficients (ICC) of 0.9433 comparable to that of the observed VO2max at 0.9443 and a bias of -1.1 ml x min(-1) x kg(-1) representing a 2.19 percent underestimate. This study provides empirical evidence that extrapolation of submaximal data can be employed with confidence for both clinical monitoring and research purposes. With the use of portable equipment and submaximal testing the scope for future research in numerous populations and non-laboratory environments is considerably increased.

  6. A randomized controlled pilot study of VO2 max testing: a potential model for measuring relative in vivo efficacy of different red blood cell products.

    Science.gov (United States)

    Bennett-Guerrero, Elliott; Lockhart, Evelyn L; Bandarenko, Nicholas; Campbell, Mary L; Natoli, Michael J; Jamnik, Veronika K; Carter, Timothy R; Moon, Richard E

    2017-03-01

    Randomized trials, for example, RECESS, comparing "young" (median, 7-day) versus "middle-aged" (median, 28-day) red blood cells (RBCs), showed no difference in outcome. These data are important; however, they do not inform us about the safety and effectiveness of the oldest RBCs, which some patients receive. It may not be feasible to conduct a clinical trial randomizing patients to receive the oldest blood. Therefore, we propose strenuous exercise (VO2 max testing) as a model to study the relative efficacy to increase oxygen delivery to tissue of different RBC products, for example, extremes of storage duration. In this pilot study, eight healthy subjects had 2 units of leukoreduced RBCs collected by apheresis in AS-3 using standard methods. Subjects were randomized to receive both (2) units of their autologous RBCs at either 7 or 42 days after blood collection. VO2 max testing on a cycle ergometer was performed 2 days before (Monday) and 2 days after (Friday) the transfusion visit (Wednesday). This design avoids confounding effects on intravascular volume from the 2-unit blood transfusion. The primary outcome was the difference in VO2 max between Friday and Monday (delta VO2 max). VO2 max increased more in the 7-day RBC arm (8.7 ± 6.9% vs. 1.9 ± 6.5%, p = 0.202 for comparison between arms). Exercise duration (seconds) increased in the 7-day RBC arm (8.4 ± 1.7%) but actually decreased in the 42-day arm (-2.6 ± 3.6%, p = 0.002). This pilot study suggests that VO2 max testing has potential as a rigorous and quantitative in vivo functional assay of RBC function. Our preliminary results suggest that 42-day RBCs are inferior to 7-day RBCs at delivering oxygen to tissues. © 2016 AABB.

  7. Daily pattern of %VO2max and heart rates in normal and undernourished school children.

    Science.gov (United States)

    Spurr, G B; Reina, J C

    1990-10-01

    The pattern of usage of the VO2max, expressed as %VO2max during ordinary school days, with minute-by-minute heart rate recording, was studied in 106 boys and 83 girls, 6-16 yr of age divided into three age groups (6-8, 10-12, and 14-16 yr), living under economically deprived conditions in Colombia and classified as nutritionally normal or marginally malnourished. In a 12-h period, the 12 groups of children spent, on the average, 7-10 h at less than 30% VO2max, 1.5-4 h at 30-50% VO2max, and an accumulated time of 20-60 min above 50% VO2max. The latter occurred in short bursts rather than during sustained periods. There was a statistically significant but small decrease (approximately -3%) in the average 12 h %VO2max with age but no effects of sex or nutritional status. The overall average was about 25% VO2max in all groups. The data may suggest the existence of the regulation of physical activity to some level easily sustainable for long periods. Expressing the data as 30 min averages during 5 h of school and 5 h of free-time activity allows for the possibility of seeing group differences during shorter periods of time. This may prove useful in exercise training programs and studies of effort in the workplace.

  8. VO2 max is associated with ACE genotype in postmenopausal women.

    Science.gov (United States)

    Hagberg, J M; Ferrell, R E; McCole, S D; Wilund, K R; Moore, G E

    1998-11-01

    Relationships have frequently been found between angiotensin-converting enzyme (ACE) genotype and various pathological and physiological cardiovascular outcomes and functions. Thus we sought to determine whether ACE genotype affected maximal O2 consumption (VO2 max) and maximal exercise hemodynamics in postmenopausal women with different habitual physical activity levels. Age, body composition, and habitual physical activity levels did not differ among ACE genotype groups. However, ACE insertion/insertion (II) genotype carriers had a 6.3 ml . kg-1 . min-1 higher VO2 max (P VO2 max (P VO2 max than the DD genotype group, but the difference was not significant. ACE genotype accounted for 12% of the variation in VO2 max among women after accounting for the effect of habitual physical activity levels. The entire difference in VO2 max among ACE genotype groups was the result of differences in maximal arteriovenous O2 difference (a-vDO2). ACE genotype accounted for 17% of the variation in maximal a-vDO2 in these women. Maximal cardiac output index did not differ whatsoever among ACE genotype groups. Thus it appears that ACE genotype accounts for a significant portion of the interindividual differences in VO2 max among these women. However, this difference is the result of genotype-dependent differences in maximal a-vDO2 and not of maximal stroke volume and maximal cardiac output.

  9. Is time limit at the minimum swimming velocity of VO2 max influenced by stroking parameters?

    Science.gov (United States)

    Fernandes, Ricardo J; Marinho, Daniel A; Barbosa, Tiago M; Vilas-Boas, J Paulo

    2006-08-01

    The aim of this study was to observe the relationship between time limit at the minimum velocity that elicits maximal oxygen consumption (TLim-v VO2 max) and stroke rate, stroke length, and stroke index. 13 men and 10 women, highly trained swimmers, performed an intermittent incremental test for v VO2 max assessment and an all-out swim to estimate TLim-v VO2 max. The mean +/- SD TLim-v VO2 max, v VO2 max, stroke rate, stroke length, and stroke index values were 233.36 +/- 53.92 sec., 1.40 +/- .06 meter/sec., 35.58 +/- 2.89 cycles/min., 2.39 +/- .22 meter/cycle, and 3.36 +/- .41 meter2/(cycle x sec.), respectively. The correlation between TLim-v VO2 max and stroke rate was -.51 (p VO2 max with stroke length (r = .52, p < .01) and stroke index (r = .45, p < .05). These results seem to suggest that technical skill is a key factor in typical efforts requiring prolonged aerobic power.

  10. The influence of VO2(B nanobelts on thermal decomposition of ammonium perchlorate

    Directory of Open Access Journals (Sweden)

    Zhang Yifu

    2015-09-01

    Full Text Available The influence of vanadium dioxide VO2(B on thermal decomposition of ammonium perchlorate (AP has not been reported before. In this contribution, the effect of VO2(B nanobelts on the thermal decomposition of AP was investigated by the Thermo- Gravimetric Analysis and Differential Thermal Analysis (TG/DTA. VO2(B nanobelts were hydrothermally prepared using peroxovanadium (V complexes, ethanol and water as starting materials. The thermal decomposition temperatures of AP in the presence of I wt.%, 3 wt.% and 6 wt.% of as-obtained VO2VO2(B nanobelts had a great influence on the thermal decomposition temperature of AP Furthermore, the influence of the corresponding V2Os, which was obtained by thermal treatment of VO2(B nanobelts, on the thermal decomposition of AP was also investigated. The resufs showed that VO2(B nanobelts had a greater influence on the thermal decomposition temperature of AP than that of V2Os.

  11. The heart rate VO2 relationship of aerobic dance: a comparison of target heart rate methods.

    Science.gov (United States)

    Scharff-Olson, M; Williford, H N; Smith, F H

    1992-12-01

    The purpose of this study was to examine the relationship between heart rate (HR) and oxygen consumption (VO2) for aerobic dance exercise. Therefore, eleven females completed 20 minutes of aerobic dance with continuous monitoring of HR and VO2. These physiological responses were analyzed with correlation/regression techniques. The results showed that for aerobic dance to produce a response in excess of 50% of VO2 max, the target HR must be approximately 80% of the age-predicted HR max or greater. In contrast, previously reported data for treadmill running shows that 50% of VO2 max is achieved at approximately 65% of age-predicted HR max in females. The maximum heart rate reserve (Karvonen) method was also found to underestimate the actual VO2 of AD. With the Karvonen method, the target heart rate must approximate 65% of maximum HR reserve in order to elicit a VO2 response which is representative of 50% of VO2 max. These data support recent research which illustrates that target heart rate prescriptions derived from treadmill testing may fail to accurately place AD participants in the recommended training zone.

  12. Hamstrings to quadriceps peak torque ratios diverge between sexes with increasing isokinetic angular velocity.

    Science.gov (United States)

    Hewett, Timothy E; Myer, Gregory D; Zazulak, Bohdanna T

    2008-09-01

    Our purpose was to determine if females demonstrate decreased hamstrings to quadriceps peak torque (H/Q) ratios compared to males and if H/Q ratios increase with increased isokinetic velocity in both sexes. Maturation disproportionately increases hamstrings peak torque at high velocity in males, but not females. Therefore, we hypothesised that mature females would demonstrate decreased H/Q ratios compared to males and the difference in H/Q ratio between sexes would increase as isokinetic velocity increased. Studies that analysed the H/Q ratio with gravity corrected isokinetic strength testing reported between 1967 and 2004 were included in our review and analysis. Keywords were hamstrings/quadriceps, isokinetics, peak torque and gravity corrected. Medline and Smart databases were searched combined with cross-checked bibliographic reference lists of the publications to determine studies to be included. Twenty-two studies were included with a total of 1568 subjects (1145 male, 423 female). Males demonstrated a significant correlation between H/Q ratio and isokinetic velocity (R=0.634, pratio at the lowest angular velocity (47.8+/-2.2% at 30 degrees /s) compared to the highest velocity (81.4+/-1.1% at 360 degrees /s, pratio and isokinetic velocity (R=0.065, p=0.77) or a change in relative hamstrings strength as the speed increased (49.5+/-8.8% at 30 degrees /s; 51.0+/-5.7% at 360 degrees /s, p=0.84). Gender differences in isokinetic H/Q ratios were not observed at slower angular velocities. However, at high knee flexion/extension angular velocities, approaching those that occur during sports activities, significant gender differences were observed in the H/Q ratio. Females, unlike males, do not increase hamstrings to quadriceps torque ratios at velocities that approach those of functional activities.

  13. VO(2) based waveguide-mode plasmonic nano-gratings for optical switching.

    Science.gov (United States)

    Sharma, Yashna; Tiruveedhula, Veeranjaneya A; Muth, John F; Dhawan, Anuj

    2015-03-09

    In this paper, we present one dimensional plasmonic narrow groove nano-gratings, covered with a thin film of VO(2) (Vanadium Dioxide), as novel optical switches. These narrow groove gratings couple the incident optical radiation to plasmonic waveguide modes leading to high electromagnetic fields in the gaps between the nano-gratings. Since VO(2) changes from its semiconductor to its metallic phase on heating, on exposure to infra-red light, or on application of voltage, the optical properties of the underlying plasmonic grating also get altered during this phase transition, thereby resulting in significant switchability of the reflectance spectra. Moreover, as the phase transition in VO(2) can occur at femto-second time-scales, the VO(2)-coated plasmonic optical switch described in this paper can potentially be employed for ultrafast optical switching. We aim at maximizing this switchability, i.e., maximizing the differential reflectance (DR) between the two states (metallic and semiconductor) of this VO(2) coated nano-grating. Rigorous Coupled Wave Analysis (RCWA) reveals that the switching wavelengths - i.e., the wavelengths at which the values of the differential reflectance between VO(2) (S) and VO(2) (M) phases are maximum - can be tuned over a large spectral regime by varying the nano-grating parameters such as groove width, depth of the narrow groove, grating width, and thickness of the VO(2) layer. A comparison of the proposed ideal nano-gratings with various types of non-ideal nano-gratings - i.e., nano-gratings with non-parallel sidewalls - has also been carried out. It is found that significant switchability is also present for these non-ideal gratings that are easy to fabricate. Thus, we propose highly switchable and wide-spectra VO(2) based narrow groove nano-gratings that do not have a complex structure and can be easily fabricated.

  14. Left ventricular assist devices improve functional class without normalizing peak oxygen consumption.

    Science.gov (United States)

    Benton, Casey R; Sayer, Gabriel; Nair, Ajith P; Ashley, Kimberly; Domanski, Michael J; Henzlova, Milena J; Anyanwu, Anelechi C; Pinney, Sean P

    2015-01-01

    Heart failure patients supported with left ventricular assist devices (LVAD) enjoy improvements in functional capacity and quality of life. We reasoned that such improvements in exercise capacity should be reflected in an objective increase in peak oxygen consumption as measured by cardiopulmonary exercise testing (CPET). We performed a retrospective review of all recipients of a HeartMate II LVAD at our center from June 2009 to June 2012 who completed CPET. Thirty-seven patients completed CPET an average of 6 months after implantation. Of these, 10 patients had CPET performed before LVAD implantation. Overall, 91.4% of patients improved by at least two New York Heart Association classes, with 34.3% improving by three classes. Postimplant VO2 max was significantly less than predicted (14.7 ± 3.1 vs. 29.8 ± 6.6 ml/kg/min, p VO2 max increased significantly from 11.6 ± 5.0 to 15.4 ± 3.9 ml/kg/min (p = 0.009). VO2 max improves significantly with LVAD support but fails to normalize to predicted values, in spite of improvements in functional class. The severity of preimplantation heart failure does not associate with the degree of VO2 max improvement.

  15. Theoretical investigation of the optical and EPR parameters for VO 2+ion in some complexes

    Science.gov (United States)

    Kalfaoğlu, Emel; Karabulut, Bünyamin

    2012-04-01

    The molecular orbital coefficients and the EPR parameters of trisodium citrate dihydrate, sodium hydrogen oxalate monohydrate, potassium d-gluconate monohydrate and L-Alanine vanadyl complexes are calculated theoretically. Two d-d transition spectra and EPR parameters for the VO2+ complex are calculated theoretically by using crystal-field theory. The calculated g and A paramaters have indicated that paramagnetic center is axially symmetric. Having the relations of g∥A⊥ for VO2+ ions, it can be concluded that VO2+ ions are located in distorted octahedral sites (C4v) elongated along the z-axis and the ground state of the paramagnetic electron is dxy.

  16. Inhomogeneous electronic state near the insulator-to-metal transition in the correlated oxide VO2

    Science.gov (United States)

    Frenzel, A.; Qazilbash, M. M.; Brehm, M.; Chae, Byung-Gyu; Kim, Bong-Jun; Kim, Hyun-Tak; Balatsky, A. V.; Keilmann, F.; Basov, D. N.

    2009-09-01

    We investigate the percolative insulator-to-metal transition (IMT) in films of the correlated material vanadium dioxide (VO2) . Scattering-type scanning near-field infrared microscopy and atomic force microscopy were used to explore the relationship between the nucleation of metallic regions and the topography in insulating VO2 . We demonstrate that the IMT begins within 10 nm from grain boundaries and crevices by using mean curvature and statistical analysis. We also observe coexistence of insulating and metallic domains in a single crystalline grain that points to intrinsic inhomogeneity in VO2 due to competing electronic phases in the IMT regime.

  17. VV and VO2 defects in silicon studied with hybrid density functional theory

    KAUST Repository

    Christopoulos, Stavros Richard G

    2014-12-07

    The formation of VO (A-center), VV and VO2 defects in irradiated Czochralski-grown silicon (Si) is of technological importance. Recent theoretical studies have examined the formation and charge states of the A-center in detail. Here we use density functional theory employing hybrid functionals to analyze the formation of VV and VO2 defects. The formation energy as a function of the Fermi energy is calculated for all possible charge states. For the VV and VO2 defects double negatively charged and neutral states dominate, respectively.

  18. Influence of prior exercise on VO2 kinetics subsequent exhaustive rowing performance.

    Science.gov (United States)

    Sousa, Ana; Ribeiro, João; Sousa, Marisa; Vilas-Boas, João Paulo; Fernandes, Ricardo J

    2014-01-01

    Prior exercise has the potential to enhance subsequent performance by accelerating the oxygen uptake (VO2) kinetics. The present study investigated the effects of two different intensities of prior exercise on pulmonary VO2 kinetics and exercise time during subsequent exhaustive rowing exercise. It was hypothesized that in prior heavy, but not prior moderate exercise condition, overall VO2 kinetics would be faster and the VO2 primary amplitude would be higher, leading to longer exercise time at VO2max. Six subjects (mean ± SD; age: 22.9±4.5 yr; height: 181.2±7.1 cm and body mass: 75.5±3.4 kg) completed square-wave transitions to 100% of VO2max from three different conditions: without prior exercise, with prior moderate and heavy exercise. VO2 was measured using a telemetric portable gas analyser (K4b(2), Cosmed, Rome, Italy) and the data were modelled using either mono or double exponential fittings. The use of prior moderate exercise resulted in a faster VO2 pulmonary kinetics response (τ1 = 13.41±3.96 s), an improved performance in the time to exhaustion (238.8±50.2 s) and similar blood lactate concentrations ([La(-)]) values (11.8±1.7 mmol.L(-1)) compared to the condition without prior exercise (16.0±5.56 s, 215.3±60.1 s and 10.7±1.2 mmol.L(-1), for τ1, time sustained at VO2max and [La(-)], respectively). Performance of prior heavy exercise, although useful in accelerating the VO2 pulmonary kinetics response during a subsequent time to exhaustion exercise (τ1 = 9.18±1.60 s), resulted in a shorter time sustained at VO2max (155.5±46.0 s), while [La(-)] was similar (13.5±1.7 mmol.L(-1)) compared to the other two conditions. Although both prior moderate and heavy exercise resulted in a faster pulmonary VO2 kinetics response, only prior moderate exercise lead to improved rowing performance.

  19. The associations between peak O2 consumption and leptin in 10- to 12-year-old boys.

    Science.gov (United States)

    Cicchella, Antonio; Stefanelli, Claudio; Purge, Priit; Lätt, Evelin; Saar, Meeli; Jürimäe, Toivo

    2013-07-01

    The aim of this study was to assess the associations of circulating levels of leptin with the peak O(2) consumption (VO(2)peak ) in 10- to 12-year-old boys of different BMI selected by Cole et al. (BMJ, 320,2000,1-6): total group (n = 248), normal (n = 190), overweight (n = 34) and obese (n = 24). We hypothesized that there is a close relationship in overweight and obese subgroups of boys with relative VO(2)peak kg (-1) (ml min(-1) kg(-1)) and leptin. Most of the subjects were Tanner stage 2. Peak O(2) consumption was measured directly using an increasing incremental protocol until volitional exhaustion on an electronically braked cycle ergometer. The expired gas was sampled continuously breadth-by-breadth mode for the measurement of oxygen consumption (MetaMax, Germany). Blood samples were obtained after an overnight fast from an antecubital vein for leptin measurements. Peak O(2) consumption (l min(-1)) was higher or lower (ml min(-1) kg(-1)) in overweight and obese groups, compared with normal BMI group. Leptin was higher in overweight and obese groups, compared with normal BMI group. Peak O(2) consumption (l min(-1)) correlated significantly with leptin only in total group (n = 248, r = 0·196). Contrary, relative VO(2)peak kg (-1) correlated significantly and negatively with leptin. The relationship was highest on the total group (r = -0·674). We can conclude that leptin first of all correlated negatively with relative peak O(2) consumption. Absolute VO(2)peak correlated with leptin only in total group.

  20. Sport-specific fitness testing differentiates professional from amateur soccer players where VO2max and VO2 kinetics do not.

    Science.gov (United States)

    Wells, C M; Edwards, A M; Winter, E M; Fysh, M L; Drust, B

    2012-06-01

    The purpose of this study was to identify if sport-specific and cardiopulmonary exercise testing differentiated professional from amateur soccer players. Thirty six men comprising 18 professional (mean±s: age 23.2±2.4 years) and 18 amateur (mean±SD: age 21.1±1.6 years) soccer players participated and performed four tests on separate occasions: 1) a graded exercise test to determine VO2max; 2) four exercise transients from walking to 80%Δ for the determination of VO2 kinetics; 3) the Yo-Yo Intermittent Recovery Test level 2 (Yo-Yo IR2) and 4) a repeated sprint test (RST). The players did not differ in VO2max (professional 56.5±2.9 mL.kg-1.min-1; amateur 55.7±3.5 mL.kg-1.min-1: P=0.484) or VO2 kinetic fundamental measures (τ1 onset, professional 24.5±3.2 s; amateur 24.0±1.8 s: τ1 cessation, professional 28.7±2.8 s; amateur 29.3±3.5 s: P=0.923). However, the amateurs were outperformed in the Yo-Yo IR2 (Professional 966±153 m; Amateur 840±156 m) (P=0.034) and RST (best time, professional 6.46±0.27 s; amateur 6.84±0.24 s, P=0.012). Performance indices derived from field-based sport-specific performance tests identified significant differences between professional and amateur players (Ptests of VO2 kinetics nor VO2max differentiated between groups, suggesting laboratory tests of cardiorespiratory parameters are probably less consequential to soccer than sport-specific field-based observations.

  1. Allometric modelling of peak oxygen uptake in male soccer players of 8-18 years of age

    NARCIS (Netherlands)

    Valente-dos-Santos, Joao; Coelho-e-Silva, Manuel J.; Tavares, Oscar M.; Brito, Joao; Seabra, Andre; Rebelo, Antonio; Sherar, Lauren B.; Elferink-Gemser, Marije T.; Malina, Robert M.

    2015-01-01

    Background: Peak oxygen uptake (VO2peak) is routinely scaled as mL O-2 per kilogram body mass despite theoretical and statistical limitations of using ratios. Aim: To examine the contribution of maturity status and body size descriptors to ageassociated inter-individual variability in VO2peak and to

  2. Correlação entre as medidas direta e indireta do VO2max em atletas de futsal Correlación entre las medidas directa e indirecta del VO2max en atletas de futsal Correlation between direct and indirect VO2max measurements in indoor soccer players

    Directory of Open Access Journals (Sweden)

    Anna Myrna Jaguaribe de Lima

    2005-06-01

    de la correlación entre los tests de medida directa e indirecta del VO2max, en jugadores de futsal. Fueron analizados 13 jugadores de futsal, con edades de entre 18,6 ± 1,9 años, altura igual a 177,1 ± 3,5 cm, peso de 68,5 ± 9,5 kg, índice de masa corporal (IMC de 21,7 ± 2,3 kg/m². Para la medida directa del VO2max fué utilizado el sistema ergoespirométrico computadorizado (VO-2000, Aerosport, Medgraphics, St. Paul, Minnesota para mensura indirecta del VO2max fué realizado el test de campo de 3200m. El análisis estatístico fué elaborado a través del test t-Student para las muestras pareadas y por el coeficiente de correlación de Pearson. Los valores de VO2max obtenidos en el test de medida directa no presentaron diferencias significativas en relación a la medida indirecta (62,8 ± 10,1 vs. 58,5 ± 8,5 ml/kg/min, respectivamente. Cuando correlacionamos los valores de VO2max obtenidos en ambos tests, observamos una fuerte correlación (r = 0,72. En conclusión, los tests de medida indirecta presentaron buena aceptación para los atletas de futsal, teniendo en vista la alta correlación con los tests de medida directa, el bajo costo de su aplicación y el apercibimiento de las informaciones importantes que puedem auxiliar la prescrición de el no acompañamiento del entrenamiento.The importance of the morphofunctional qualities to greater efficiency in sports has increased the interest on the improvement on the physical fitness levels of athletes. However, not many studies on the physiological variables of indoor soccer are available in the world scientific literature. Thus, the objective of this work was to verify the existence of correlation between the direct and indirect VO2max measurement tests in indoor soccer players. Thirteen indoor soccer players with age of 18.6 ± 1.9 years, height of 177.1 ± 3.5 cm, weight of 68.5 ± 9.5 kg and body mass index (BMI of 21.7 ± 2.3 kg/m² were analyzed. For the direct VO2max measurement, the computerized

  3. High performance of solvothermally prepared VO2(B as anode for aqueous rechargeable lithium batteries

    Directory of Open Access Journals (Sweden)

    Milošević Sanja

    2015-01-01

    Full Text Available The VO2 (B was synthesized via a simple solvothermal route at 160oC in ethanol. The initial discharge capacity of VO2 (B anode, in saturated aqueous solution of LiNO3, was 177 mAh g-1 at a current rate of 50 mA g-1. After 50 cycles capacity fade was 4%, but from 20th-50th cycle no capacity drop was observed. The VO2 (B has shown very good cyclability at current rate of even 1000 mA g-1 with initial discharge capacity of 92 mAh g-1. The excellent electrochemical performance of VO2 (B was attributed to the stability of micro-nano structures to repeated intercalation /deintercalation process, very good electronic conductivity as well as the very low charge transfer resistance in the aqueous electrolyte. [Projekat Ministarstva nauke Republike Srbije, br. III45014

  4. EVALUATION AND DEVELOPMENT OF THE VO2 OF ATHLETES THAT ATTEND A SOCCER SCHOOL

    Directory of Open Access Journals (Sweden)

    Felipe Bittencourt Oliveira

    2012-11-01

    Full Text Available The goal of this study was to identify the effects from technical and physical activities on the VO2, of male athletes aged 14 to 15, participants of a soccer school, in the municipality of Rio Pardo - RS. The semi-experimental research involved 10 male adolescents. For the VO2 evaluation the 12 minute Cooper test was used. Interval-training work was applied, at which the athletes exercised 75% of their maximum speed, in 60-meter runs. After training for two months (at least two sessions a week the Cooper post-test was applied to check the improvement of the VO2. As results of this study, we can draw the conclusion that all adolescents involved in this training showed considerable improvement in their maximum VO2, especially the 15-year-old teens, who managed to obtain a much higher percentage level.

  5. Prior Knowledge of Trial Number Influences the Incidence of Plateau at VO2max

    Directory of Open Access Journals (Sweden)

    Dan Gordon

    2015-01-01

    Full Text Available The purpose of this study was to assess the VO2max plateau response at VO2max during a series of pre-determined trials. METHODS: Ten male well-trained athletes (age, 23.0 ± 3.2; height, 183.3 ± 5.5 cm; mass 77.5 ± 11.1 Kg; VO2max 66.5 ± 5.0 ml.kg-1,min-1, but who were VO2max testing naïve and with prior-knowledge of trial number completed four incremental tests to volitional exhaustion, separated by ~72-h for the determination of VO2max and gas exchange threshold. Throughout all trials VO2max was recorded on a breath-by-breath basis using a pre-calibrated metabolic cart, using a plateau criterion of Δ VO2 ≤1.5 ml.kg-1.min-1 over the final 2 consecutive 30 s sampling periods. A significant difference was observed between trial-1 and trial-4 for plateau incidence (p = 0.0285 rising from 20% in trial-1 to a 70% response rate in trial-4. Furthermore a significant difference was observed for VO2dif (difference between criterion value and Δ VO2 in trial-1, 1.02 ± 1.69 ml.kg-1.min-1 (p = 0.038, with non-significant differences observed for all other trials, despite a non-significant difference for VO2max across all trials (p > 0.05. Finally, a significant difference was observed for effort perception (RPE at volitional exhaustion between trial-1 (17.7 ± 1.3 and trial-4 (19.0 ± 1.4 (p = 0.0052. These data indicate that prior-knowledge of trial number can influence the manifestation of the VO2 plateau in a group of well-trained male athletes, thereby suggesting that a form of effort control is established in order to preserve the finite anaerobic capacity.

  6. Predicting maximal aerobic capacity (VO2max) from the critical velocity test in female collegiate rowers.

    Science.gov (United States)

    Kendall, Kristina L; Fukuda, David H; Smith, Abbie E; Cramer, Joel T; Stout, Jeffrey R

    2012-03-01

    The objective of this study was to examine the relationship between the critical velocity (CV) test and maximal oxygen consumption (VO2max) and develop a regression equation to predict VO2max based on the CV test in female collegiate rowers. Thirty-five female (mean ± SD; age, 19.38 ± 1.3 years; height, 170.27 ± 6.07 cm; body mass, 69.58 ± 0.3 1 kg) collegiate rowers performed 2 incremental VO2max tests to volitional exhaustion on a Concept II Model D rowing ergometer to determine VO2max. After a 72-hour rest period, each rower completed 4 time trials at varying distances for the determination of CV and anaerobic rowing capacity (ARC). A positive correlation was observed between CV and absolute VO2max (r = 0.775, p < 0.001) and ARC and absolute VO2max (r = 0.414, p = 0.040). Based on the significant correlation analysis, a linear regression equation was developed to predict the absolute VO2max from CV and ARC (absolute VO2max = 1.579[CV] + 0.008[ARC] - 3.838; standard error of the estimate [SEE] = 0.192 L·min(-1)). Cross validation analyses were performed using an independent sample of 10 rowers. There was no significant difference between the mean predicted VO2max (3.02 L·min(-1)) and the observed VO2max (3.10 L·min(-1)). The constant error, SEE and validity coefficient (r) were 0.076 L·min(-1), 0.144 L·min(-1), and 0.72, respectively. The total error value was 0.155 L·min(-1). The positive relationship between CV, ARC, and VO2max suggests that the CV test may be a practical alternative to measuring the maximal oxygen uptake in the absence of a metabolic cart. Additional studies are needed to validate the regression equation using a larger sample size and different populations (junior- and senior-level female rowers) and to determine the accuracy of the equation in tracking changes after a training intervention.

  7. Seasonal variations in VO2max, O2-cost, O2-deficit, and performance in elite cross-country skiers.

    Science.gov (United States)

    Losnegard, Thomas; Myklebust, Håvard; Spencer, Matt; Hallén, Jostein

    2013-07-01

    Long-term effects of training are important information for athletes, coaches, and scientists when associating changes in physiological indices with changes in performance. Therefore, this study monitored changes in aerobic and anaerobic capacities and performance in a group of elite cross-country skiers during a full sport season. Thirteen men (age, 23 ± 2 years; height, 182 ± 6 cm; body mass, 76 ± 8 kg; V2 roller ski skating VO2max, 79.3 ± 4.4 ml·kg·min or 6.0 ± 0.5 L·min) were tested during the early, middle, and late preparation phase: June (T1), August (T2), and October (T3); during the competition phase: January/February (T4); and after early precompetition phase: June (T5). O2-cost during submaximal efforts, V[Combining Dot Above]O2peak, accumulated oxygen deficit (ΣO2-deficit), and performance during a 1,000-m test were determined in the V2 ski skating technique on a roller ski treadmill. Subjects performed their training on an individual basis, and detailed training logs were categorized into different intensity zones and exercise modes. Total training volume was highest during the summer months (early preseason) and decreased toward and through the winter season, whereas the volume of high-intensity training increased (all p testing sessions for 1,000 m time, O2-cost, and ΣO2-deficit (Cohen's d effect size; ES = 0.63-1.37, moderate to large, all p < 0.05). In general, the changes occurred between T1 and T3 with minor changes in the competitive season (T3 to T4). No significant changes were found in V[Combining Dot Above]O2peak across the year (ES = 0.17, trivial). In conclusion, the training performed by elite cross-country skiers induced no significant changes in V[Combining Dot Above]O2peak but improved performance, O2-cost, and ΣO2-deficit.

  8. Patterns of Senescence in Human Cardiovascular Fitness: VO2max in Subsistence and Industrialized Populations

    Science.gov (United States)

    Pisor, Anne C.; Gurven, Michael; Blackwell, Aaron D.; Kaplan, Hillard; Yetish, Gandhi

    2014-01-01

    Objectives This study explores whether cardiovascular fitness levels and senescent decline are similar in the Tsimane of Bolivia and Canadians, as well as other subsistence and industrialized populations. Among Tsimane, we examine whether morbidity predicts lower levels and faster decline of cardiovascular fitness, or whether their lifestyle (e.g., high physical activity) promotes high levels and slow decline. Alternatively, high activity levels and morbidity might counterbalance such that Tsimane fitness levels and decline are similar to those in industrialized populations. Methods Maximal oxygen uptake (VO2max) was estimated using a step test heart rate method for 701 participants. We compared these estimates to the Canadian Health Measures Survey and previous studies in industrialized and subsistence populations. We evaluated whether health indicators and proxies for market integration were associated with VO2max levels and rate of decline for the Tsimane. Results The Tsimane have significantly higher levels of VO2max and slower rates of decline than Canadians; initial evidence suggests differences in VO2max levels between other subsistence and industrialized populations. Low hemoglobin predicts low VO2max for Tsimane women while helminth infection predicts high VO2max for Tsimane men, though results might be specific to the VO2max scaling parameter used. No variables tested interact with age to moderate decline. Conclusions The Tsimane demonstrate higher levels of cardiovascular fitness than industrialized populations, but levels similar to other subsistence populations. The high VO2max of Tsimane is consistent with their high physical activity and few indicators of cardiovascular disease, measured in previous studies. PMID:24022886

  9. Size and composition-controlled fabrication of VO2 nanocrystals by terminated cluster growth

    Energy Technology Data Exchange (ETDEWEB)

    Anders, Andre; Slack, Jonathan

    2013-05-14

    A physical vapor deposition-based route for the fabrication of VO2 nanoparticles is demonstrated, consisting of reactive sputtering and vapor condensation at elevated pressures. The oxidation of vanadium atoms is an efficient heterogeneous nucleation method, leading to high nanoparticle throughtput. Fine control of the nanoparticle size and composition is obtained. Post growth annealing leads to crystalline VO2 nanoparticles with optimum thermocromic and plasmonic properties.

  10. Resistance modulation in VO2 nanowires induced by an electric field via air-gap gates

    Science.gov (United States)

    Kanki, Teruo; Chikanari, Masashi; Wei, Tingting; Tanaka, Hidekazu; The Institute of Scientific; Industrial Research Team

    Vanadium dioxide (VO2) shows huge resistance change with metal-insulator transition (MIT) at around room temperature. Controlling of the MIT by applying an electric field is a topical ongoing research toward the realization of Mott transistor. In this study, we have successfully switched channel resistance of VO2 nano-wire channels by a pure electrostatic field effect using a side-gate-type field-effect transistor (SG-FET) viaair gap and found that single crystalline VO2 nanowires and the channels with narrower width enhance transport modulation rate. The rate of change in resistance ((R0-R)/R, where R0 and R is the resistance of VO2 channel with off state and on state gate voltage (VG) , respectively) was 0.42 % at VG = 30 V in in-plane poly-crystalline VO2 channels on Al2O3(0001) substrates, while the rate in single crystalline channels on TiO2 (001) substrates was 3.84 %, which was 9 times higher than that using the poly-crystalline channels. With reducing wire width from 3000 nm to 400 nm of VO2 on TiO2 (001) substrate, furthermore, resistance modulation ratio enhanced from 0.67 % to 3.84 %. This change can not be explained by a simple free-electron model. In this presentation, we will compare the electronic properties between in-plane polycrystalline VO2 on Al2O3 (0001) and single crystalline VO2 on TiO2 (001) substrates, and show experimental data in detail..

  11. Broadband terahertz generation using the semiconductor-metal transition in VO2

    Directory of Open Access Journals (Sweden)

    Nicholas A. Charipar

    2016-01-01

    Full Text Available We report the design, fabrication, and characterization of broadband terahertz emitters based on the semiconductor-metal transition in thin film VO2 (vanadium dioxide. With the appropriate geometry, picosecond electrical pulses are generated by illuminating 120 nm thick VO2 with 280 fs pulses from a femtosecond laser. These ultrafast electrical pulses are used to drive a simple dipole antenna, generating broadband terahertz radiation.

  12. Influence of nitrate supplementation on VO(2) kinetics and endurance of elite cyclists

    DEFF Research Database (Denmark)

    Christensen, Peter Møller; Nyberg, Michael Permin; Bangsbo, Jens

    2013-01-01

    The present study examined if an elevated nitrate intake would improve VO(2) kinetics, endurance, and repeated sprint capacity in elite endurance athletes. Ten highly trained cyclists (72¿±¿4¿mL O(2) /kg/min, mean¿±¿standard deviation) underwent testing for VO(2) kinetics (3¿×¿6¿min at 298¿±¿28¿W...

  13. Verification Testing to Confirm VO2max in Altitude-Residing, Endurance-Trained Runners.

    Science.gov (United States)

    Weatherwax, R M; Richardson, T B; Beltz, N M; Nolan, P B; Dalleck, L

    2016-06-01

    We sought to explore the utility of the verification trial to confirm individual attainment of 'true' VO2max in altitude-residing, endurance-trained runners during treadmill exercise. 24 elite endurance-trained men and women runners (age=21.5±3.3 yr, ht=174.8±9.3 cm, body mass=60.5±6.7 kg, PR 800 m 127.5±13.1 s) completed a graded exercise test (GXT) trial (VO2max=60.0±5.8 mL·kg(-1)·min(-1)), and returned 20 min after incremental exercise to complete a verification trial (VO2max=59.6±5.7 mL·kg(-1)·min(-1)) of constant load, supramaximal exercise. The incidence of 'true' VO2max confirmation using the verification trial was 24/24 (100%) with all participants revealing differences in VO2max≤3% (the technical error of our equipment) between the GXT and verification trials. These findings support use of the verification trial to confirm VO2max attainment in altitude-residing, endurance-trained runners. © Georg Thieme Verlag KG Stuttgart · New York.

  14. Association of VO2 and VCO2 rate variability with serum glucose, insulin, and glucose intolerance.

    Science.gov (United States)

    Satué-Rodríguez, Julián; Méndez, José D

    2012-08-01

    Changes in the cellular metabolism assessed by the variability of oxygen consumption (VO(2) ) and carbon dioxide production (VCO(2) ) as well as the association of serum glucose and insulin to energy spectral density (ESD) of VO(2) and VCO(2) were evaluated. Ten nonglucose intolerant and 10 glucose intolerant subjects, aged 21-70 years, were included. Glucose and insulin concentrations and VO(2) and VCO(2) records were collected every 10 min during 3 h. ESD of VO(2) and VCO(2) was estimated and associated with glucose and insulin concentrations. Statistical significance in glucose levels, insulin, and ESD of VO(2) and VCO(2) among nonglucose intolerant subjects and glucose and insulin among glucose intolerance subjects at postload glucose (PLG) state compared with basal state was found. Moreover, glucose was significantly higher in glucose intolerance subjects than nonglucose intolerant subjects for basal and PLG states. These results show an increment in ESD of VO(2) and VCO(2) at PLG state among nonglucose intolerant subjects and suggest that their measurement may be a key indicator of the variability of cellular metabolic activity and contribute to confirm disturbances in glucose metabolism.

  15. VO2 estimation using 6-axis motion sensor with sports activity classification.

    Science.gov (United States)

    Nagata, Takashi; Nakamura, Naoteru; Miyatake, Masato; Yuuki, Akira; Yomo, Hiroyuki; Kawabata, Takashi; Hara, Shinsuke

    2016-08-01

    In this paper, we focus on oxygen consumption (VO2) estimation using 6-axis motion sensor (3-axis accelerometer and 3-axis gyroscope) for people playing sports with diverse intensities. The VO2 estimated with a small motion sensor can be used to calculate the energy expenditure, however, its accuracy depends on the intensities of various types of activities. In order to achieve high accuracy over a wide range of intensities, we employ an estimation framework that first classifies activities with a simple machine-learning based classification algorithm. We prepare different coefficients of linear regression model for different types of activities, which are determined with training data obtained by experiments. The best-suited model is used for each type of activity when VO2 is estimated. The accuracy of the employed framework depends on the trade-off between the degradation due to classification errors and improvement brought by applying separate, optimum model to VO2 estimation. Taking this trade-off into account, we evaluate the accuracy of the employed estimation framework by using a set of experimental data consisting of VO2 and motion data of people with a wide range of intensities of exercises, which were measured by a VO2 meter and motion sensor, respectively. Our numerical results show that the employed framework can improve the estimation accuracy in comparison to a reference method that uses a common regression model for all types of activities.

  16. Formation energies of intrinsic point defects in monoclinic VO2 studied by first-principles calculations

    Science.gov (United States)

    Cui, Yuanyuan; Liu, Bin; Chen, Lanli; Luo, Hongjie; Gao, Yanfeng

    2016-10-01

    VO2 is an attractive candidate for intelligent windows and thermal sensors. There are challenges for developing VO2-based devices, since the properties of monoclinic VO2 are very sensitive to its intrinsic point defects. In this work, the formation energies of the intrinsic point defects in monoclinic VO2 were studied through the first-principles calculations. Vacancies, interstitials, as well as antisites at various charge states were taken into consideration, and the finite-size supercell correction scheme was adopted as the charge correction scheme. Our calculation results show that the oxygen interstitial and oxygen vacancy are the most abundant intrinsic defects in the oxygen rich and oxygen deficient condition, respectively, indicating a consistency with the experimental results. The calculation results suggest that the oxygen interstitial or oxygen vacancy is correlated with the charge localization, which can introduce holes or electrons as free carriers and subsequently narrow the band gap of monoclinic VO2. These calculations and interpretations concerning the intrinsic point defects would be helpful for developing VO2-based devices through defect modifications.

  17. Influence of lattice distortion on phase transition properties of polycrystalline VO2 thin film

    Science.gov (United States)

    Lin, Tiegui; Wang, Langping; Wang, Xiaofeng; Zhang, Yufen; Yu, Yonghao

    2016-08-01

    In this work, high power impulse magnetron sputtering was used to control the lattice distortion in polycrystalline VO2 thin film. SEM images revealed that all the VO2 thin films had crystallite sizes of below 20 nm, and similar configurations. UV-vis-near IR transmittance spectra measured at different temperatures showed that most of the as-deposited films had a typical metal-insulator transition. Four-point probe resistivity results showed that the transition temperature of the films varied from 54.5 to 32 °C. The X-ray diffraction (XRD) patterns of the as-deposited films revealed that most were polycrystalline monoclinic VO2. The XRD results also confirmed that the lattice distortions in the as-deposited films were different, and the transition temperature decreased with the difference between the interplanar spacing of the as-deposited thin film and standard rutile VO2. Furthermore, a room temperature rutile VO2 thin film was successfully synthesized when this difference was small enough. Additionally, XRD patterns measured at varied temperatures revealed that the phase transition process of the polycrystalline VO2 thin film was a coordinative deformation between grains with different orientations. The main structural change during the phase transition was a gradual shift in interplanar spacing with temperature.

  18. Soft-chemical synthesis and high-temperature electrochemical characteristics of VO2

    Institute of Scientific and Technical Information of China (English)

    ZHOU Ke-chao; CAO Du-meng; LI Zhi-you

    2006-01-01

    VO2 powder was synthesized by a new soft-chemical method using formaldehyde as a reductant. The influences of pyrolysis temperature and time on the phase and morphology of grains were investigated by using thermal gravimeter/differential thermal analysis(TG/DTA), X-ray diffraction(XRD), Fourier transform infrared(FTIR) spectroscopy and scanning electron microscope(SEM). The positive electrode discharge performances of Li-B/LiCl-KCl/VO2 thermal battery at 500 ℃ were studied. The results show that the product is mainly non-crystal when the precursor of VO2 is heated below 300 ℃. VO2(B) appears and transits into VO2(R) irreversibly as the heating temperature rises. The open-circle voltage of VO2 is 2.6 V (vs Li-B), and the initial discharge voltage of 100 mA/cm2 at 500 ℃ is 2.52 V. The specific capacities of 100 mA/cm2 and 200 mA/cm2 at cut-off voltage of 1.4 V are 449 A·s/g and 539 A·s/g, respectively.

  19. Reversible phase modulation and hydrogen storage in multivalent VO2 epitaxial thin films

    Science.gov (United States)

    Yoon, Hyojin; Choi, Minseok; Lim, Tae-Won; Kwon, Hyunah; Ihm, Kyuwook; Kim, Jong Kyu; Choi, Si-Young; Son, Junwoo

    2016-10-01

    Hydrogen, the smallest and the lightest atomic element, is reversibly incorporated into interstitial sites in vanadium dioxide (VO2), a correlated oxide with a 3d1 electronic configuration, and induces electronic phase modulation. It is widely reported that low hydrogen concentrations stabilize the metallic phase, but the understanding of hydrogen in the high doping regime is limited. Here, we demonstrate that as many as two hydrogen atoms can be incorporated into each VO2 unit cell, and that hydrogen is reversibly absorbed into, and released from, VO2 without destroying its lattice framework. This hydrogenation process allows us to elucidate electronic phase modulation of vanadium oxyhydride, demonstrating two-step insulator (VO2)-metal (HxVO2)-insulator (HVO2) phase modulation during inter-integer d-band filling. Our finding suggests the possibility of reversible and dynamic control of topotactic phase modulation in VO2 and opens up the potential application in proton-based Mottronics and novel hydrogen storage.

  20. Inverse relationship between VO2max and economy/efficiency in world-class cyclists.

    Science.gov (United States)

    Lucía, Alejandro; Hoyos, Jesus; Pérez, Margarita; Santalla, Alfredo; Chicharro, José L

    2002-12-01

    To determine the relationship that exists between VO2max and cycling economy/efficiency during intense, submaximal exercise in world-class road professional cyclists. METHODS Each of 11 male cyclists (26+/-1 yr (mean +/- SEM); VO2max: 72.0 +/- 1.8 mL x kg(-1) x min(-1)) performed: 1) a ramp test for O2max determination and 2) a constant-load test of 20-min duration at the power output eliciting 80% of subjects' VO2max during the previous ramp test (mean power output of 385 +/- 7 W). Cycling economy (CE) and gross mechanical efficiency (GE) were calculated during the constant-load tests. CE and GE averaged 85.2 +/- 2.3 W x L(-1) x min(-1) and 24.5 +/- 0.7%, respectively. An inverse, significant correlation was found between 1) VO2max (mL x kg(-0.32) x min(-1)) and both CE (r = -0.71; P = 0.01) and GE (-0.72; P = 0.01), and 2) VO2max (mL x kg(-1) x min(-1)) and both CE (r = -0.65; P = 0.03) and GE (-0.64; P = 0.03). A high CE/GE seems to compensate for a relatively low VO2max in professional cyclists.

  1. Improved VO2max and time trial performance with more high aerobic intensity interval training and reduced training volume: a case study on an elite national cyclist.

    Science.gov (United States)

    Støren, Øyvind; Bratland-Sanda, Solfrid; Haave, Marius; Helgerud, Jan

    2012-10-01

    The present study investigated to what extent more high aerobic intensity interval training (HAIT) and reduced training volume would influence maximal oxygen uptake (VO2max) and time trial (TT) performance in an elite national cyclist in the preseason period. The cyclist was tested for VO2max, cycling economy (C(c)), and TT performance on an ergometer cycle during 1 year. Training was continuously logged using heart rate monitor during the entire period. Total monthly training volume was reduced in the 2011 preseason compared with the 2010 preseason, and 2 HAIT blocks (14 sessions in 9 days and 15 sessions in 10 days) were performed as running. Between the HAIT blocks, 3 HAIT sessions per week were performed as cycling. From November 2010 to February 2011, the cyclist reduced total average monthly training volume by 18% and cycling training volume by 60%. The amount of training at 90-95% HRpeak increased by 41%. VO2max increased by 10.3% on ergometer cycle. TT performance improved by 14.9%. C(c) did not change. In conclusion, preseason reduced total training volume but increased amount of HAIT improved VO2max and TT performance without any changes in C(c). These improvements on cycling appeared despite that the HAIT blocks were performed as running. Reduced training time, and training transfer from running into improved cycling form, may be beneficial for cyclists living in cold climate areas.

  2. PROGRESSIVE MUSCLE RELAXATION INCREASE PEAK EXPIRATORY FLOW RATE ON CHRONIC OBSTRUCTIVE PULMONARY DISEASE PATIENTS

    Directory of Open Access Journals (Sweden)

    Tintin Sukartini

    2017-07-01

    Full Text Available Introduction: Limited progressive air flow in Chronic Obstructive Pulmonary Disease (COPD can caused by small airway disease (bronchiolitis obstructive and loss of elasticity of the lung (emphysema. Further it can be decreasing the quality of life in COPD patients because dyspnea and uncomfortable in activity. Progressive muscle relaxation (PMR is one of the relaxation technique that can repair pulmonary ventilation by decreasing chronic constriction of the respiratory muscles. The objective of this study was to analyze the effect of progressive muscle relaxation on raised peak expiratory flow rate (PEFR. Method: A pre-experimental one group pre-post test design was used in this study. Population was all of the COPD patients at Pulmonary Specialist Polyclinic Dr Mohamad Soewandhie Surabaya. There were 8 respondents taken by using purposive sampling. PEFR was counted by using peak flow meter every six day. Data were analyzed by using Paired t-Test with significance level  p≤0.05. Result: The result showed that PMR had significance level on increasing of PEFR (p=0.012. Discussion: It can be concluded that PMR has an effect on raise PEFR. Further studies are recommended to measure the effect of PMR on respiratory rate (RR, heart rate (HR subjective dyspnoe symptoms, forced expiration volume on the first minute (FEV1 and mid maximum flow rate (MMFR in COPD patients.

  3. A comparison of two different shuttle run tests for the estimation of VO2max.

    Science.gov (United States)

    Naughton, L M; Cooley, D; Kearney, V; Smith, S

    1996-06-01

    The aims of this experiment were twofold. The first was to determine whether there was a significant difference between two types of 20-m shuttle run test used to estimate VO2max, these being the Canadian version (CT) and the European versione (ET). The second aim was to determine which of the two tests best estimated direct VO2 measurement in our laboratory. To accomplish the first aim, 500 schoolchildren aged 12 to 16 years were randomly chosen from schools within Tasmania to undertake the two tests within seven days of each other. On the day of testing the children were assigned to one of the two tests and had no knowledge as to which test was being undertaken. Half of the children underwent the CT test first while the other half undertook the ET test first. Seven days after the first test was completed the appropriate second test was undertaken. The instructions to each child centred around the necessity to complete as many shuttles as possible staying in time with a pre-recorded signal. A relationship between the two sets of shuttle run data indicated that there was a significant correlation between the ET and CT, r = 0.834 (p test revealed that when the estimates of VO2max were compared however, there was a significant difference between the two tests (p VO2max at 34.9 +/- 0.45 ml.kg-1.min-1 whereas the CT estimated VO2max at 43.3 +/- 0.40 ml.kg-1.min-1. When this data was correlated, the co-efficient dropped to r = 0.761 which was still significant (p VO2max test (DM) which was conducted via standard open circuit spirometry using a Quinton Metabolic Cart (QMC). The highest correlation was DM:ET being r = 0.93 whereas DM:CT was r = 0.87, both being significant at p VO2max as 37.6 +/- 0.37 ml.kg-1.min-1 whereas ET underestimated DM and measured VO2max at 34.7 +/- 0.56 ml.kg-1.min-1. The CT (41.9 +/- 0.62 ml.kg-1.min-1) over estimated DM by 11.4% however, the difference here also being significant (p test or the other in the estimation of VO2max as the two

  4. Hemoglobin mass and peak oxygen uptake in untrained and trained residents of moderate altitude.

    Science.gov (United States)

    Böning, D; Rojas, J; Serrato, M; Ulloa, C; Coy, L; Mora, M; Gomez, J; Hütler, M

    2001-11-01

    Blood composition, hemoglobin mass (CO rebreathing method) and VO2peak were measured in 15 untrained (UT-Bogotá) and 14 trained males (TR-Bogotá) living at 2600 m of altitude, and in 14 untrained lowlanders (UT-Berlin). [Hb] amounted to 15.3 + 0.2(SE) g/dl in UT-Berlin, 17.4 + 0.2 g/dl in UT-Bogotá and 16.0 + 0.2 g/dl in TR-Bogotá. Hb mass was significantly higher in UT-Bogotá (13.2 + 0.4 g/kg, P < 0.01) and in TR-Bogotá (14.7 + 0.5 g/kg, P < 0.001) than in UT-Berlin (11.7 + 0.2 g/kg). In TR-Bogotá also plasma volume was expanded. Erythropoietin concentrations in UT-Bogotá and TR-Bogotá were not significantly increased. There was a positive correlation between blood volume and VO2peak for the pooled values of all subjects, if the oxygen uptake of UT-Berlin was corrected for an ascent to 2600 m. For the Hb mass - VO2peak relation two groups are indicated pointing to two types of altitude acclimatization with different Hb mass increases but similar distribution of aerobic performance capacity. We suggest that different genetic properties in a population of mixed ethnic origin might play a role.

  5. A prospective population study of resting heart rate and peak oxygen uptake (the HUNT Study, Norway.

    Directory of Open Access Journals (Sweden)

    Javaid Nauman

    Full Text Available OBJECTIVES: We assessed the prospective association of resting heart rate (RHR at baseline with peak oxygen uptake (VO(2peak 23 years later, and evaluated whether physical activity (PA could modify this association. BACKGROUND: Both RHR and VO(2peak are strong and independent predictors of cardiovascular morbidity and mortality. However, the association of RHR with VO(2peak and modifying effect of PA have not been prospectively assessed in population studies. METHODS: In 807 men and 810 women free from cardiovascular disease both at baseline (1984-86 and follow-up 23 years later, RHR was recorded at both occasions, and VO(2peak was measured by ergospirometry at follow-up. We used Generalized Linear Models to assess the association of baseline RHR with VO(2peak, and to study combined effects of RHR and self-reported PA on later VO(2peak. RESULTS: There was an inverse association of RHR at baseline with VO(2peak (p<0.01. Men and women with baseline RHR greater than 80 bpm had 4.6 mL.kg(-1.min(-1 (95% confidence interval [CI], 2.8 to 6.3 and 1.4 mL.kg(-1.min(-1 (95% CI, -0.4 to 3.1 lower VO(2peak at follow-up compared with men and women with RHR below 60 bpm at baseline. We found a linear association of change in RHR with VO(2peak (p=0.03, suggesting that a decrease in RHR over time is likely to be beneficial for cardiovascular fitness. Participants with low RHR and high PA at baseline had higher VO(2peak than inactive people with relatively high RHR. However, among participants with relatively high RHR and high PA at baseline, VO(2peak was similar to inactive people with relatively low RHR. CONCLUSION: RHR is an important predictor of VO(2peak, and serial assessments of RHR may provide useful and inexpensive information on cardiovascular fitness. The results suggest that high levels of PA may compensate for the lower VO(2peak associated with a high RHR.

  6. The effect of limited handrail support on total treadmill time and the prediction of VO2 max.

    Science.gov (United States)

    Manfre, M J; Yu, G H; Varmá, A A; Mallis, G I; Kearney, K; Karageorgis, M A

    1994-08-01

    Holding onto the front handrail during treadmill testing significantly increases total treadmill time (TT) and predicted VO2max when compared with tests without front handrail support. By limiting the amount of handrail support to the tips of two fingers of one hand, the difference in TT can be substantially reduced. In the present study, the difference in TT between tests with and without handrail support for healthy men was not significantly different. However, this was not true for healthy women and for male patients with coronary artery disease and myocardial infarction.

  7. Peak oxygen uptake in children: evaluation of an older prediction method and development of a new one.

    Science.gov (United States)

    Arngrimsson, Sigurbjorn Arni; Sveinsson, Torarinn; Jóhannsson, Erlingur

    2008-02-01

    The purpose of this study was to validate an equation that has been used to predict peak oxygen uptake (VO2peak) and, if invalid, to develop a new equation predicting VO2peak from performance on a cycle ergometer test. Forty-five 9- and 15-year-old children underwent a VO2peak test and were randomized into developmental (DEV) and cross-validation (C-V) groups. The equation under validation, which requires knowledge of resting energy expenditure (REE), underestimated VO2peak (p equation built in DEV, not using REE, was confirmed in C-V (rYY' = .98, SE = .17 L . min-1) and the slope and intercept were not different from the line of identity (p equation based on the whole sample [VO2peak = -1.5986 + 0.0115 . (maximal power output) + 0.0109 . (mass) + 0.1313 . (gender) + 0.0085 . (maximal heart rate)].

  8. A comparison of time to exhaustion at VO2 max in élite cyclists, kayak paddlers, swimmers and runners.

    Science.gov (United States)

    Billat, V; Faina, M; Sardella, F; Marini, C; Fanton, F; Lupo, S; Faccini, P; de Angelis, M; Koralsztein, J P; Dalmonte, A

    1996-02-01

    A recent study has shown the reproducibility of time to exhaustion (time limit: tlim) at the lowest velocity that elicits the maximal oxygen consumption (vVO2 max). The same study found an inverse relationship between this time to exhaustion at vVO2 max and vVO2 max among 38 élite long-distance runners (Billat et al. 1994b). The purpose of the present study was to compare the time to exhaustion at the power output (or velocity) at VO2 max for different values of VO2 max, depending on the type of exercise and not only on the aerobic capacity. The time of exhaustion at vVO2 max (tlim) has been measured among 41 élite (national level) sportsmen: 9 cyclists, 9 kayak paddlers, 9 swimmers and 14 runners using specific ergometers. Velocity or power at VO2 max (vVO2 max) was determined by continuous incremental testing. This protocol had steps of 2 min and increments of 50 W, 30 W, 0.05 m s-1 and 2 km-1 for cyclists, kayak paddlers, swimmers and runners, respectively. One week later, tlim was determined under the same conditions. After a warm-up of 10 min at 60% of their vVO2 max, subjects were concluded (in less than 45 s) to their vVO2 max and then had to sustain it as long as possible until exhaustion. Mean values of vVO2 max and tlim were respectively equal to 419 +/- 49 W (tlim = 222 +/- 91 s), 239 +/- 56 W (tlim = 376 +/- 134 s), 1.46 +/- 0.09 m s-1 (tlim = 287 +/- 160 s) and 22.4 +/- 0.8 km h-1 (tlim = 321 +/- 84 s), for cyclists, kayak paddlers, swimmers and runners. Time to exhaustion at vVO2 max was only significantly different between cycling and kayaking (ANOVA test, p < 0.05). Otherwise, VO2 max (expressed in ml min-1 kg-1) was significantly different between all sports except between cycling and running (p < 0.05). In this study, time to exhaustion at vVO2 max was also inversely related to VO2 max for the entire group of élite sportsmen (r = -0.320, p < 0.05, n = 41). The inverse relationship between VO2 max and tlim at vVO2 max has to be explained, it

  9. Effect of Sodium Phosphate Supplementation on Cycling Time Trial Performance and VO2 1 and 8 Days Post Loading

    Directory of Open Access Journals (Sweden)

    Cameron P. Brewer, Brian Dawson, Karen E. Wallman, Kym J. Guelfi

    2014-09-01

    Full Text Available This study examined the effect of 6 days of sodium phosphate (SP (50 mg·kg·FFM-1·day-1 or placebo (PL supplementation in trained cyclists on either 100 kJ (23.9 Kcal (~3-4 min or 250 kJ (59.7 Kcal (~10-12 min time trials performances both 1 and 8 days post-supplementation. Trials were performed in a counterbalanced crossover design, with a 28-day washout period between supplementation phases. No significant differences, moderate-large ES (d or likely (or greater smallest worthwhile change (SWC values were recorded for time to completion and mean power output on days 1 and 8 post-supplementation, both within and between SP and PL for either the 100 or 250 kJ (23.9 or 59.7 Kcal trials. In the 100 kJ (23.9 Kcal trial (only first minute VO2 tended to be higher in SP8 than both PL8 (d = 0.60; 88/10/2 SWC and SP1 (d = 0.47: 82/15/3 SWC, as was mean VO2 (PL8: d = 0.77; 93/6/1 SWC and SP1: d = 0.84; 90/8/3 SWC. No significant differences were found for heart rate, ratings of perceived exertion and blood lactate post-exercise within or between any trials, while serum phosphate values were not different before or after supplementation with SP or PL. In conclusion, this study showed a tendency for increased VO2 in a short duration (100 kJ/ 23.9 Kcal: ~3-4 min cycling test on day 8 after SP supplementation, but no differences in 100 or 250 kJ (23.9 or 59.7 Kcal time trials performances were observed.

  10. Reproducibility of maximum aerobic power (VO2max) among soccer players using a modified heck protocol.

    Science.gov (United States)

    Santos-Silva, Paulo Roberto; Fonseca, Alfredo José; Castro, Anita Weigand de; Greve, Júlia Maria D'Andréa; Hernandez, Arnaldo José

    2007-08-01

    To determine the degree of reproducibility of maximum oxygen consumption (VO2max) among soccer players, using a modified Heck protocol. 2 evaluations with an interval of 15 days between them were performed on 11 male soccer players. All the players were at a high performance level; they were training for an average of 10 hours per week, totaling 5 times a week. When they were evaluated, they were in the middle of the competitive season, playing 1 match per week. The soccer players were evaluated on an ergometric treadmill with velocity increments of 1.2 km.h-1 every 2 minutes and a fixed inclination of 3% during the test. VO2max was measured directly using a breath-by-breath metabolic gas analyzer. The maximum running speed and VO2max attained in the 2 tests were, respectively: (15.6 +/- 1.1 vs. 15.7 +/- 1.2 km.h-1; [P = .78]) and (54.5 +/- 3.9 vs. 55.2 +/- 4.4 ml.kg-1.min-1; [P = .88]). There was high and significant correlation of VO2max between the 2 tests with a 15-day interval between them [r = 0.97; P testing was insufficient to significantly modify the soccer players' VO2max values.

  11. Non-exercise estimation of VO2max using the International Physical Activity Questionnaire

    Science.gov (United States)

    Schembre, Susan M.; Riebe, Deborah A.

    2011-01-01

    Non-exercise equations developed from self-reported physical activity can estimate maximal oxygen uptake (VO2max) as well as submaximal exercise testing. The International Physical Activity Questionnaire (IPAQ) is the most widely used and validated self-report measure of physical activity. This study aimed to develop and test a VO2max estimation equation derived from the IPAQ-Short Form (IPAQ-S). College-aged males and females (n = 80) completed the IPAQ-S and performed a maximal exercise test. The estimation equation was created with multivariate regression in a gender-balanced subsample of participants, equally representing five levels of fitness (n = 50) and validated in the remaining participants (n = 30). The resulting equation explained 43% of the variance in measured VO2max (SEE = 5.45 ml·kg-1·min-1). Estimated VO2max for 87% of individuals fell within acceptable limits of error observed with submaximal exercise testing (20% error). The IPAQ-S can be used to successfully estimate VO2max as well as submaximal exercise tests. Development of other population-specific estimation equations is warranted. PMID:21927551

  12. The phase transition of W-doped VO2 nanoparticles synthesized by an improved thermolysis method.

    Science.gov (United States)

    Hou, Jiwei; Zhang, Jianwu; Wang, Zhongping; Zhang, Zengming; Ding, Zejun

    2013-02-01

    High-quality thermochromic monoclinic VO2(M) and series of W-doped V(1-x)W(x)O2(M) nanoparticles were successfully synthesized by an improved thermolysis method. The products were investigated using X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) technologies. The measurement of DSC revealed that the metal-insulator phase transition (MIT) of 2.0% W-doped VO2 sample occurred at 25.6 degrees C, which was much lower than the MIT of host VO2(M) nanoparticles at 67.6 degrees C. The results showed that the proportion of the transmittance of tetragonal phase reached only about 29% of that of monoclinic phase for 0.5% W-doped VO2 at the wavenumber 900 cm(-1), which indicated W-doped VO2(M) was an intelligent window and optical switch materials.

  13. Supercapacitors based on two dimensional VO2 nanosheet electrodes in organic gel electrolyte

    KAUST Repository

    Rakhi, R.B.

    2016-10-16

    VO2 is a low band-gap semiconductor with relatively high conductivity among transition metal oxides, which makes it an interesting material for supercapacitor electrode applications. The performance of VO2 as supercapacitor electrode in organic electrolytes has never been reported before. Herein, two-dimensional nanosheets of VO2 are prepared by the simultaneous solution reduction and exfoliation from bulk V2O5 powder by hydrothermal method. A specific capacitance of 405 Fg−1 is achieved for VO2 based supercapacitor in an organic electrolyte, in three electrode configuration. The symmetric capacitor based on VO2 nanosheet electrodes and the liquid organic electrolyte exhibits an energy density of 46 Wh kg−1 at a power density of 1.4 kW kg−1 at a constant current density of 1 Ag−1. Furthermore, flexible solid-state supercapacitors are fabricated using same electrode material and Alumina-silica based gel electrolyte. The solid-state device delivers a specific capacitance of 145 Fg−1 and a device capacitance of 36 Fg−1 at a discharge current density of 1 Ag−1. Series combination of three solid state capacitors is capable of lighting up a red LED for more than 1 minute.

  14. Epitaxial VO2 thin-film-based radio-frequency switches with electrical activation

    Science.gov (United States)

    Lee, Jaeseong; Lee, Daesu; Cho, Sang June; Seo, Jung-Hun; Liu, Dong; Eom, Chang-Beom; Ma, Zhenqiang

    2017-09-01

    Vanadium dioxide (VO2) is a correlated material exhibiting a sharp insulator-to-metal phase transition (IMT) caused by temperature change and/or bias voltage. We report on the demonstration of electrically triggered radio-frequency (RF) switches based on epitaxial VO2 thin films. The highly epitaxial VO2 and SnO2 template layer was grown on a (001) TiO2 substrate by pulsed laser deposition (PLD). A resistance change of the VO2 thin films of four orders of magnitude was achieved with a relatively low threshold voltage, as low as 13 V, for an IMT phase transition. VO2 RF switches also showed high-frequency responses of insertion losses of -3 dB at the on-state and return losses of -4.3 dB at the off-state over 27 GHz. Furthermore, an intrinsic cutoff frequency of 17.4 THz was estimated for the RF switches. The study on electrical IMT dynamics revealed a phase transition time of 840 ns.

  15. Steady exercise removes VO(2max) difference between mitochondrial genomic variants.

    Science.gov (United States)

    Marcuello, Ana; Martínez-Redondo, Diana; Dahmani, Yahya; Terreros, José L; Aragonés, Teresa; Casajús, José A; Echavarri, José M; Quílez, Julia; Montoya, Julio; López-Pérez, Manuel J; Díez-Sánchez, Carmen

    2009-09-01

    It has been clearly established that mitochondrial variants, among other potential factors, influence on VO(2max). With this study we sought to determine whether this genetic predisposition could be modified by steady exercise. Mitochondrial genetic variants were determined in 70 healthy controls (CON) and in 77 athletes who trained regularly (50 cyclists, aerobic training (AER), and 27 runners of 400m, anaerobic training (NoAER)). All of them were male Spanish Caucasian individuals. A maximum graded exercise test (GXT) in cycle-ergometer was performed to determine VO(2max) (mL kg(-1)min(-1)). Our results confirmed that, in CON, VO(2max) (P=0.007) was higher in Non-J than J individuals. Furthermore, we found that AER and NoAER showed, as it could be expected, higher VO(2max) than CON, but not differences between mitochondrial variants have been found. According with these findings, the influence of mitochondrial DNA (mtDNA) variants on VO(2max) has been confirmed, and a new conclusion has arisen: the steady exercise is able to remove this influence. The interest of these promising findings in muscular performance should be further explored, in particular, the understanding of potential applications in sport training and in muscle pathological syndromes.

  16. Highly integrated VO2-based tunable antenna for millimeter-wave applications

    Science.gov (United States)

    Huitema, L.; Crunteanu, A.; Wong, H.; Arnaud, E.

    2017-05-01

    We report the concept of a frequency tunable antenna device operating in the millimeter wave frequency domain. The ability of the antenna to switch between two frequency states is achieved by the monolithic integration of a metal-insulator transition material (vanadium dioxide, VO2). The VO2 material is an insulator at room temperature but can be driven in a high conductivity metallic state when it is electrically activated using a continuous (DC) voltage. The antenna design is based on a slot antenna excited by a microstrip line having a length that can be conveniently varied using a VO2-based switch. Following the high-frequency VO2 material characterization, we present its monolithic integration in the device prototype along with the comparison between the measured and the simulated performances of the agile antenna. Thus, depending on the VO2 material state, the antenna device can be conveniently switched between 33 and 37 GHz operating frequency bands presenting stable radiation patterns with 5.28 dBi and 5.41 dBi maximum gains, respectively.

  17. Concentration Dependence of VO2+ Crossover of Nafion for Vanadium Redox Flow Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Lawton, Jamie [University of Tennessee, Knoxville (UTK); Jones, Amanda [University of Tennessee, Knoxville (UTK); Zawodzinski, Thomas A [ORNL

    2013-01-01

    The VO2+ crossover, or permeability, through Nafion in a vanadium redox flow battery (VRFB) was monitored as a function of sulfuric acid concentration and VO2+ concentration. A vanadium rich solution was flowed on one side of the membrane through a flow field while symmetrically on the other side a blank or vanadium deficit solution was flowed. The blank solution was flowed through an electron paramagnetic resonance (EPR) cavity and the VO2+ concentration was determined from the intensity of the EPR signal. Concentration values were fit using a solution of Fick s law that allows for the effect of concentration change on the vanadium rich side. The fits resulted in permeability values of VO2+ ions across the membrane. Viscosity measurements of many VO2+ and H2SO4 solutions were made at 30 60 C. These viscosity values were then used to determine the effect of the viscosity of the flowing solution on the permeability of the ion. 2013 The Electrochemical Society. [DOI: 10.1149/2.004306jes] All rights reserved.

  18. VO2 Max and Back and Leg Muscle Strength Profile of Universitas Padjadjaran Swimming Team

    Directory of Open Access Journals (Sweden)

    Pitriyani Nurul Pajar

    2016-12-01

    Full Text Available Background: Cardiorespiratory endurance (VO2 max and back and leg muscle strength are a few components required to support the performance of swimming athlete during competition. The objective of this study was to determine the VO2 max and back and leg muscle strength in high category level of Universitas Padjadjaran swimming team period 2014. Methods: A descriptive study was conducted to 19 swimmers of Universitas Padjadjaran in September 2014. The variables of this study were VO2 max and back and leg muscle strength. Then, the data were categorized based on the standard of The National Sports Committee of Indonesia. Results: The data obtained showed that the VO2 max of the majority of subjects was in the very good category (6/19 subjects and the back muscle strength of the majority of subjects was in the very good category (10/19 subjects. In contrast, the leg muscle strength of majority of subjects was in the low category (11/19 subjects. Conclusions: The VO2 max and back muscle strength in high category level of the swimming team fulfilled the standard of The National Sports Committee of Indonesia.

  19. Strength training improves cycling performance, fractional utilization of VO2max and cycling economy in female cyclists.

    Science.gov (United States)

    Vikmoen, O; Ellefsen, S; Trøen, Ø; Hollan, I; Hanestadhaugen, M; Raastad, T; Rønnestad, B R

    2016-04-01

    The purpose of this study was to investigate the effect of adding heavy strength training to well-trained female cyclists' normal endurance training on cycling performance. Nineteen female cyclists were randomly assigned to 11 weeks of either normal endurance training combined with heavy strength training (E+S, n = 11) or to normal endurance training only (E, n = 8). E+S increased one repetition maximum in one-legged leg press and quadriceps muscle cross-sectional area (CSA) more than E (P < 0.05), and improved mean power output in a 40-min all-out trial, fractional utilization of VO2 max and cycling economy (P < 0.05). The proportion of type IIAX-IIX muscle fibers in m. vastus lateralis was reduced in E+S with a concomitant increase in type IIA fibers (P < 0.05). No changes occurred in E. The individual changes in performance during the 40-min all-out trial was correlated with both change in IIAX-IIX fiber proportion (r = -0.63) and change in muscle CSA (r = 0.73). In conclusion, adding heavy strength training improved cycling performance, increased fractional utilization of VO2 max , and improved cycling economy. The main mechanisms behind these improvements seemed to be increased quadriceps muscle CSA and fiber type shifts from type IIAX-IIX toward type IIA.

  20. Peak ventilatory responses during cycling and swimming in pregnant and nonpregnant women.

    Science.gov (United States)

    Spinnewijn, W E; Wallenburg, H C; Struijk, P C; Lotgering, F K

    1996-08-01

    This study was designed to determine whether pregnancy affects peak O2 uptake (VO2peak) during swimming compared with cycling. We studied 11 women at 30-34 wk gestation and 8-12 wk postpartum. We measured heart rate (HR), O2 uptake (VO2), CO2 output (VCO2), minute ventilation (VE), and lactic acid concentration. Peak HR was not significantly affected by the type of exercise or by pregnancy. VO2peak was 9% lower during swimming than during cycling but was not affected by pregnancy, with values for pregnancy cycling, pregnancy swimming, postpartum cycling, and postpartum swimming of 2.36 +/- 0.12, 2.11 +/- 0.11, 2.29 +/- 0.10, and 2.12 +/- 0.07 l/min, respectively. Peak VCO2 (VCO2peak) and peak VE were significantly lower during swimming than during cycling by 18-25%, but only VCO2peak during swimming was affected by pregnancy (-10%). Lactic acid concentrations were 12-17% lower after swimming than after cycling and 17-31% lower during pregnancy than postpartum. We conclude that perceived maximal exertion is reached at a lower percent maximal VO2 in swimming than in cycling and that the reduced energy expenditure is reflected by lower VO2peak, VCO2peak, and peak VE. Pregnancy, however, does not affect VO2peak in cycling or swimming.

  1. Development of a branching submaximal treadmill test for predicting VO2max.

    Science.gov (United States)

    Swank, A M; Serapiglia, L; Funk, D; Adams, K J; Durham, M; Berning, J M

    2001-08-01

    This study determined the reliability and validity of a branching treadmill protocol in predicting VO2max. Thirty-seven, apparently healthy individuals (19 women and 18 men); volunteered to participate. On 2 separate testing days, each subject underwent maximal exercise testing using the protocol developed. Stepwise regression analysis indicated that the percentage of age-predicted maximum heart rate (APMHR) achieved at stage 3, speed and grade at stage 3, and APMHR accounted for 89% of the variance in VO2max. The 4 predictor variables were statistically significant (p VO2max for their clients outside the laboratory environment. Furthermore, our results indicate that using the proposed regression model is reliable and has received preliminary construct validity support.

  2. Photoluminescence response of colloidal quantum dots on VO2 film across metal to insulator transition.

    Science.gov (United States)

    Kuznetsov, Sergey N; Cheremisin, Alexander B; Stefanovich, Genrikh B

    2014-01-01

    We have proposed a method to probe metal to insulator transition in VO2 measuring photoluminescence response of colloidal quantum dots deposited on the VO2 film. In addition to linear luminescence intensity decrease with temperature that is well known for quantum dots, temperature ranges with enhanced photoluminescence changes have been found during phase transition in the oxide. Corresponding temperature derived from luminescence dependence on temperature closely correlates with that from resistance measurement during heating. The supporting reflectance data point out that photoluminescence response mimics a reflectance change in VO2 across metal to insulator transition. Time-resolved photoluminescence study did not reveal any significant change of luminescence lifetime of deposited quantum dots under metal to insulator transition. It is a strong argument in favor of the proposed explanation based on the reflectance data. 71.30. + h; 73.21.La; 78.47.jd.

  3. Negative capacitance switching via VO2 band gap engineering driven by electric field

    Science.gov (United States)

    He, Xinfeng; Xu, Jing; Xu, Xiaofeng; Gu, Congcong; Chen, Fei; Wu, Binhe; Wang, Chunrui; Xing, Huaizhong; Chen, Xiaoshuang; Chu, Junhao

    2015-03-01

    We report the negative capacitance behavior of an energy band gap modulation quantum well with a sandwich VO2 layer structure. The phase transition is probed by measuring its capacitance. With the help of theoretical calculations, it shows that the negative capacitance changes of the quantum well device come from VO2 band gap by continuously tuning the temperature or voltage. Experiments reveal that as the current remains small enough, joule heating can be ignored, and the insulator-metal transition of VO2 can be induced by the electric field. Our results open up possibilities for functional devices with phase transitions induced by external electric fields other than the heating or electricity-heat transition.

  4. Field Effect and Strongly Localized Carriers in the Metal-Insulator Transition Material VO(2).

    Science.gov (United States)

    Martens, K; Jeong, J W; Aetukuri, N; Rettner, C; Shukla, N; Freeman, E; Esfahani, D N; Peeters, F M; Topuria, T; Rice, P M; Volodin, A; Douhard, B; Vandervorst, W; Samant, M G; Datta, S; Parkin, S S P

    2015-11-06

    The intrinsic field effect, the change in surface conductance with an applied transverse electric field, of prototypal strongly correlated VO(2) has remained elusive. Here we report its measurement enabled by epitaxial VO(2) and atomic layer deposited high-κ dielectrics. Oxygen migration, joule heating, and the linked field-induced phase transition are precluded. The field effect can be understood in terms of field-induced carriers with densities up to ∼5×10(13)  cm(-2) which are trongly localized, as shown by their low, thermally activated mobility (∼1×10(-3)  cm(2)/V s at 300 K). These carriers show behavior consistent with that of Holstein polarons and strongly impact the (opto)electronics of VO(2).

  5. Effects of simulated weightlessness and sympathectomy on maximum VO2 of male rats

    Science.gov (United States)

    Woodman, C. R.; Stump, C. S.; Beaulieu, S. M.; Rahman, Z.; Sebastian, L. A.

    1989-01-01

    The effects of simulated weightlessness (hind-limb suspension) and chemical sympathectomy (by repeated injections with guanethidine sulfate) on the maximum oxygen consumption (VO2 max) of female rats were investigated in rats assigned for 14 days to one of three groups: a head-down hind-limb suspension, a horizontal suspension with hind limbs weight bearing, or the caged control. The VO2 max values were assessed by having rats run on a treadmill enclosed in an airtight chamber. The hind-limb-suspended sympathectomized rats were found to exhibit shorter run times and lower mechanical efficiencies, compared to their presuspension values or the values from saline-injected suspended controls. On the other hand, the suspended sympathectomized rats did not demonstrate a decrease in the VO2 max values that was observed in saline-injected controls.

  6. Direct observation of the M2 phase with its Mott transition in a VO2 film

    Science.gov (United States)

    Kim, Hoon; Slusar, Tetiana V.; Wulferding, Dirk; Yang, Ilkyu; Cho, Jin-Cheol; Lee, Minkyung; Choi, Hee Cheul; Jeong, Yoon Hee; Kim, Hyun-Tak; Kim, Jeehoon

    2016-12-01

    In VO2, the explicit origin of the insulator-to-metal transition is still disputable between Peierls and Mott insulators. Along with the controversy, its second monoclinic (M2) phase has received considerable attention due to the presence of electron correlation in undimerized vanadium ions. However, the origin of the M2 phase is still obscure. Here, we study a granular VO2 film using conductive atomic force microscopy and Raman scattering. Upon the structural transition from monoclinic to rutile, we observe directly an intermediate state showing the coexistence of monoclinic M1 and M2 phases. The conductivity near the grain boundary in this regime is six times larger than that of the grain core, producing a donut-like landscape. Our results reveal an intra-grain percolation process, indicating that VO2 with the M2 phase is a Mott insulator.

  7. A quantitative study of the biotransformation of insulin-enhancing VO(2+) compounds.

    Science.gov (United States)

    Sanna, Daniele; Buglyó, Péter; Micera, Giovanni; Garribba, Eugenio

    2010-08-01

    Potentiometric (pH titrations) and spectroscopic (electron paramagnetic resonance) methods have been used to determine the thermodynamic stability constants of the various VO(2+) complexes formed after the interaction of four insulin-enhancing vanadium compounds, [VO(6-mepic)(2)], cis-[VO(pic)(2)(H(2)O)], [VO(acac)(2)], and [VO(dhp)(2)], where 6-mepic, pic, acac, and dhp indicate the deprotonated forms of 6-methylpicolinic acid, picolinic acid, acetylacetone, and 1,2-dimethyl-3-hydroxy-4(1H)-pyridinone, with high molecular mass [human serum apotransferrin (hTf) and human serum albumin (HSA)] and low molecular mass (lactate) components of blood serum. In particular, log beta values for the formation of (VO)hTf (13.0 +/- 0.5), (VO)(2)hTf (25.5 +/- 0.5), (VO)HSA (9.1 +/- 1.0), (VO) (2) (d) HSA (20.9 +/- 1.0), cis-VO(dhp)(2)(hTf) (25.5 +/- 0.6), cis-VO(dhp)(2)(HSA) (25.9 +/- 0.6), (VO)hTf(lact) (14.5 +/- 0.8), (VO)(2)hTf(lact)(2) (28.5 +/- 0.8), (VO)hTf(pic) (15.6 +/- 0.8), and (VO)(2)hTf(pic)(2) (30.4 +/- 0.8) were determined. The values of the stability constants were used to compare the calculated composition of ternary and quinary systems with that recently proposed by some of us through electron paramagnetic resonance and density functional theory methods (Sanna et al. in Inorg. Chem. 49:174-187, 2010) and to predict the distribution of VO(2+) ion in blood serum when one of the four insulin-enhancing vanadium compounds studied, [VO(carrier)(2)], is administered.

  8. Interaction of VO2+ ion with human serum transferrin and albumin.

    Science.gov (United States)

    Sanna, Daniele; Garribba, Eugenio; Micera, Giovanni

    2009-04-01

    The complexation of VO(2+) ion with the high molecular mass components of the blood serum, human serum transferrin (hTf) and albumin (HSA), has been re-examined using EPR spectroscopy. In the case of transferrin, the results confirm those previously obtained, showing that VO(2+) ion occupies three different binding sites, A, B(1) and B(2), distinguishable in the X-band anisotropic spectrum recorded in D(2)O. With albumin the results show that a dinuclear complex (VO)(2)(d)HSA is formed in equimolar aqueous solutions or with an excess of protein; in the presence of an excess of VO(2+), the multinuclear complex (VO)(x)(m)HSA is the prevalent species, where x=5-6 indicates the equivalents of metal ion coordinated by HSA. The structure of the dinuclear species is discussed and the donor atoms involved in the metal coordination are proposed on the basis of the measured EPR parameters. Two different binding modes of albumin can be distinguished varying the pH, with only one species being present at the physiological value. The results show that the previously named "strong" site is not the N-terminal copper binding site, and some hypothesis on the metal coordination is discussed, with the (51)V A(z) values for the proposed donor sets obtained by DFT (density functional theory) calculations. Finally, preliminary results obtained in the ternary system VO(2+)/hTf/HSA are shown in order to determine the different binding strength of the two proteins. Due to the low VO(2+) concentration used, the recording of the EPR spectra through the repeated acquisition of the weak signals is essential to obtain a good signal to noise ratio in these systems.

  9. Markers of inflammation are inversely associated with VO2 max in asymptomatic men.

    Science.gov (United States)

    Kullo, Iftikhar J; Khaleghi, Mahyar; Hensrud, Donald D

    2007-04-01

    We investigated whether markers of inflammation, including a cytokine (IL-6), acute-phase reactants [C-reactive protein (CRP) and fibrinogen], and white blood cell (WBC) count are associated with maximal O(2) consumption (Vo(2 max)) in men without coronary heart disease (CHD). In asymptomatic men (n = 172, 51 +/- 9.3 yr old), Vo(2 max) was measured during a symptom-limited graded treadmill exercise test. Physical activity level was assessed by a standardized questionnaire. IL-6 and CRP were measured by immunoassays, fibrinogen by the Clauss method, and WBC count with a Coulter counter. IL-6 and CRP were logarithmically transformed to reduce skewness. Multivariable regression was used to assess whether markers of inflammation were associated with Vo(2 max) after adjustment for age, body mass index, CHD risk factors, and lifestyle variables (physical activity level, percent body fat, and alcohol intake). Vo(2 max) was 34.5 ml.kg(-1).min(-1) (SD 6.1). Log IL-6 (r = -0.38, P max). In separate multivariable linear regression models that adjusted for age, body mass index, CHD risk factors, and lifestyle variables, log IL-6 [beta-coeff = -1.66 +/- 0.63 (SE), P = 0.010], log CRP [beta-coeff = -0.99 +/- 0.33 (SE), P = 0.003], fibrinogen [beta-coeff = -1.51 +/- 0.44 (SE), P = 0.001], and WBC count [beta-coeff = -0.52 +/- 0.30 (SE), P = 0.088] were each inversely associated with Vo(2 max). In conclusion, higher circulating levels of IL-6, CRP, and fibrinogen are independently associated with lower Vo(2 max) in asymptomatic men.

  10. Analysis of the same day of the week increases in peak electricity ...

    African Journals Online (AJOL)

    Accurate load forecasts are needed by both generators and distributors particularly during peak .... ulation growth, changing technology, economic conditions and activity, prevailing weather conditions ..... excess generating plants. Figure 10: ...

  11. The reliability of aerobic capacity (VO2max) testing in adolescent girls.

    Science.gov (United States)

    Pivarnik, J M; Dwyer, M C; Lauderdale, M A

    1996-09-01

    Despite the fact that our subjects were naive regarding the test procedures, it appears that aerobic fitness testing using an incremental treadmill protocol is extremely reliable in adolescent girls. In addition, day-to-day variability of VO2max in our subjects averaged less than 5%, which is similar to results obtained with adults (Katch, Sady, & Freedson, 1982). Finally, it was most encouraging to find that a single VO2max test trial resulted in high reliability coefficients. This finding should provide a great deal of confidence to investigators who are performing aerobic fitness tests on large numbers of subjects where multiple testing is neither practical nor cost-effective.

  12. Gas exchange threshold and VO2max testing for athletes: an update.

    Science.gov (United States)

    Pettitt, Robert W; Clark, Ida E; Ebner, Stacy M; Sedgeman, Daniel T; Murray, Steven R

    2013-02-01

    Standardized graded exercise test (GXT) protocols are ineffective for testing endurance athletes. Scientists have called for the abandonment of traditional techniques for corroborating "true" maximum oxygen uptake (VO2max), as measured during a GXT. Instead, a new technique, the verification bout subsequent to the GXT, has emerged for establishing the "true" VO2max. The addition of the verification bout reframes how the GXT should be viewed. In this article, we summarize the methods for developing custom GXT protocols, identifying threshold and interpolating power or outdoor running velocity, and implicating the verification bout.

  13. Changes in peak fat oxidation in response to different doses of endurance training

    DEFF Research Database (Denmark)

    Larsen, Mads Rosenkilde; Reichkendler, M H; Auerbach, P;

    2015-01-01

    The effect of different doses of endurance training on the capacity to oxidize fat during exercise in sedentary, overweight men and assessment of variables associated with changes in peak fat oxidation (PFO) were evaluated. Young, sedentary, overweight men were randomized to either the high......, and mitochondrial oxphos complexes II-V increased similarly in MOD and HIGH. Stepwise multiple linear regression analysis with backward elimination of individual variables correlated with changes in PFO revealed increases in cycling efficiency, FFM, and VO2 peak as the remaining associated variables. In conclusion...

  14. Controlled reactive HiPIMS—effective technique for low-temperature (300 °C) synthesis of VO2 films with semiconductor-to-metal transition

    Science.gov (United States)

    Vlček, J.; Kolenatý, D.; Houška, J.; Kozák, T.; Čerstvý, R.

    2017-09-01

    Reactive high-power impulse magnetron sputtering with a pulsed O2 flow control and to-substrate O2 injection into a high-density plasma in front of the sputtered vanadium target was used for low-temperature (300 °C) deposition of VO2 films with a pronounced semiconductor-to-metal transition onto conventional soda-lime glass substrates without any substrate bias voltage and without any interlayer. The depositions were performed using an unbalanced magnetron with a planar target of 50.8 mm diameter in argon-oxygen gas mixtures at the argon pressure of 1 Pa. The deposition-averaged target power density was close to 13 W cm-2 at a fixed duty cycle of 1% with a peak target power density up to 5 kW cm-2 during voltage pulses ranged from 40 µs to 100 µs. A high modulation of the transmittance at 2500 nm (between 51% and 8% at the film thickness of 88 nm) and the electrical resistivity (changed 350 times) at the transition temperature of 56-57 °C was achieved for the VO2 films synthesized using 50 µs voltage pulses when the crystallization of the thermochromic VO2(M1) phase was supported by the high-energy (up to 50 eV relative to ground potential) ions. Principles of this effective low-temperature deposition technique with a high application potential are presented.

  15. Effect of Different Seat Heights during an Incremental Sit-To-Stand Exercise Test on Peak Oxygen Uptake in Young, Healthy Women.

    Science.gov (United States)

    Nakamura, Keisuke; Nagasawa, Yuya; Sawaki, Shoji; Yokokawa, Yoshiharu; Ohira, Masayoshi

    2016-09-01

    'Sit-to-stand' exercise uses the repetitive motion of standing up and sitting down in a chair, a common activity of daily living. A new assessment using an incremental sit-to-stand exercise test employs an external sound to control the speed of standing-up and allows increases in work rate. The aims of the study were to examine the effect of different seat heights on peak oxygen uptake (peak VO2) during an incremental sit-to-stand exercise and to assess any difference between peak VO2 values during incremental sit-to-stand exercise compared with a cycle ergometer test. Thirteen healthy young women (age: 23.1 ± 2.6 years, height: 1.61 ± 0.06 m, body mass: 51.9 ± 7.4 kg·m(-2)) participated in four incremental sit-to-stand tests with different seat heights and cycle tests in random order. The seat heights were adjusted to 100%, 80%, 120%, and 140% of knee height distance (100%, 80%, 120%, and 140% incremental sit-to-stand exercise, respectively). The peak VO2 and completion time were measured during incremental sit-to-stand and cycle ergometer tests, and repeated-measures analysis of variance and Student's paired t-test with Holm's method were used to evaluate differences between these variables. The peak VO2 values increased by about 10-12 mL·min(-1)·kg(-1) as the seat height on the ISTS decreased over a 60% range of lower leg lengths. The peak VO2 values on the 80%, 100%, 120%, and 140% incremental sit-to-stand tests were about 11%, 25%, 40%, and 50% lower than that on the cycle ergometer test, respectively. The peak VO2 on the incremental sit-to-stand test increased as seat height decreased. These findings are useful to determine which seat height on the incremental sit-to-stand tests test is suitable for different populations.

  16. Geomorphic response of rivers to glacial retreat and increasing peak flows downstream from Mount Rainier, Washington

    Science.gov (United States)

    Czuba, J. A.; Barnas, C. R.; Magirl, C. S.; Voss, F. D.

    2010-12-01

    On Mount Rainier, Washington, the National Park Service has documented widespread aggradation of as much as 10 m since the early 20th century, of rivers draining the glaciated stratovolcano. This rapid sedimentation appears to be related to glacial retreat and also may be a function of the increased magnitude and timing of peak flows that mobilize and transport sediment. We are conducting an assessment of the Puget Lowland rivers that drain Mount Rainier, 25-100 km downstream from the park boundary, to document the geomorphic response of the downstream reaches given the widespread aggradation upstream. These downstream reaches provide critical aquatic habitat for spawning and rearing of several species of salmonids, including endangered Chinook salmon and steelhead. Fluvial sedimentation can have both deleterious and beneficial effects on aquatic habitat depending on sediment particle size, river slope and width, and river management. To date, our work shows sedimentation of as much as 2 m between 1984 and 2009 in these lowland rivers. Aggradation rates that were calculated by comparing channel change at 156 cross sections, ranged between 4.8 and 9.1 cm/yr in reaches where rivers exit the mountain front and enter the lowland. Analysis of streamflow-gaging station data from throughout the watersheds draining Mount Rainier show rapid incision and aggradation, suggesting pulses of coarse-grained bedload may be moving down the mountainous rivers as kinetic waves. Preliminary results, however, seem to indicate that the rivers in the Puget Lowland have not yet experienced significant widespread sedimentation directly related to glacial retreat. Estimating the time of arrival of mobilized alluvium is a critical need for resource managers given the potential effects of sedimentation on river flood-conveyance capacity, fish habitat, and estuarine wetlands.

  17. Effect of protocol on determination of velocity at VO2 max and on its time to exhaustion.

    Science.gov (United States)

    Billat, V L; Hill, D W; Pinoteau, J; Petit, B; Koralsztein, J P

    1996-01-01

    The velocity associated with the achievement of VO2 max during an incremental treadmill test (v VO2 max) has been reported to be an indicator of performance in middle distance running events. Previous study has shown the reproducibility of the time to exhaustion (time limit: tlim) at v VO2 max performed by well-trained males in the same condition at one week of interval (Billat et al., 1994b). It is essential in studies involving tlim at v VO2 max that the v VO2 max be precisely determined, or else the measured tlim will be meaningless. The purpose of this study was to examine the influence of the stage duration and velocity incrementation on the velocity at VO2 max and, consequently, on the two times to exhaustion (tlim) associated with the two v VO2 max generated by the two protocols. v VO2 max was determined in 15 trained male endurance athletes as the lowest speed at which VO2 max was attained in speed-incremented 0%-slope treadmill tests. For one test, increments were 1.0 km.h-1 and stages were 2 min in duration; for the other test, increments were 0.5 km.h-1 and stages were 1 min in duration. Results of paired means t-tests revealed no difference in v VO2 max obtained using the two protocols. v VO2 max was 20.7 +/- 1.0 km.h-1 with the 1.0 km.h-1 x 2 min protocol and 20.8 +/- 0.9 km.h-1 with the 0.5 km.h-1 x 1 min protocol. In addition, VO2, VCO2, VE, VE/VO2 and respiratory exchange ratio at the submaximal intensities that were common to both protocols (e.g., 17.0 km.h-1, 18.0 km.h-1, 19.0 km.h-1, 20.0 km.h-1) did not differ. Times to exhaustion at the two v VO2 max demonstrated a high degree of inter-individual variability (coefficients of variation were 35% and 45%) but did not differ (345 +/- 120 s versus 373 +/- 169 s). These results demonstrated that small changes in protocol have no significant impact on the value of v VO2 max and in consequence on tlim v VO2 max.

  18. Double dissociation: circadian off-peak times increase emotional reactivity; aging impairs emotion regulation via reappraisal.

    Science.gov (United States)

    Tucker, Adrienne M; Feuerstein, Rebecca; Mende-Siedlecki, Peter; Ochsner, Kevin N; Stern, Yaakov

    2012-10-01

    This study explored how the effectiveness of specific emotion regulation strategies might be influenced by aging and by time of day, given that in older age the circadian peak in cognitive performance is earlier in the day. We compared the benefit gained by 40 older (60-78 years; 20 women) and 40 younger (18-30 years; 20 women) adults during either on-peak or off-peak circadian times on 2 specific types of cognitive emotion regulation strategies: distraction and reappraisal. Participants rated their negative emotional responses to negative and neutral images under 3 conditions: a baseline nonregulation condition, a distraction condition involving a working memory task, and a reappraisal condition that involved reinterpreting the situation displayed using specific preselected strategies. First, as hypothesized, there was a crossover interaction such that participants in each age group reported more negative reactivity at their off-peak time of day. Second, a double dissociation was observed as circadian rhythms affected only negative reactivity-with reactivity highest at off-peak times-and aging diminished reappraisal but not distraction ability or reactivity. These findings add to growing evidence that understanding the effects of aging on emotion and emotion regulation depends on taking both time of day and type of regulatory strategy into account.

  19. The impact of increasing body mass on peak and mean plantar pressure in asymptomatic adult subjects during walking

    Directory of Open Access Journals (Sweden)

    Sara Jones

    2010-11-01

    Full Text Available Introduction: The implication of high peak plantar pressure on foot pathology in individuals both with and without diabetes has been recognized. The aim of this study was to investigate and clarify the relationship between increasing body mass and peak and mean plantar pressure in an asymptomatic adult population during walking. Methods: Thirty adults without any relevant medical history, structural foot deformities or foot posture assessed as highly pronated or supinated, and within a normal body mass index range were included in the study. An experimental, same subjects, repeated measures design was used. Peak and mean plantar pressure were evaluated with the F-Scan in-shoe plantar pressure measurement system under four different loading conditions (0, 5, 10, and 15 kg simulated with a weighted vest. Pressure data were gathered from three stances utilizing the mid-gait protocol. Results: There were statistically significant increases in peak pressure between the 10 and 15 kg load conditions compared to the control (0 kg within the heel and second to fifth metatarsal regions. The first metatarsal and hallux regions only displayed statistically significant increases in peak pressure between 15 kg and the control (0 kg. The midfoot and lesser digits regions did not display any statistically significant differences in peak pressure between any load conditions compared to the control (0 kg. The second to fifth metatarsal region displayed statistically significant increases in mean pressure in the 5, 10 and 15 kg groups compared to the control (0 kg. A statistically significant increase in peak pressure between the 15 kg and control (0 kg group was evident in all other regions. Conclusion: The relationship between increasing body mass and peak and mean plantar pressure was dependent upon the plantar region. This study provides more detail outlining the response of peak and mean pressure to different loading conditions than previously reported in the

  20. Relationship between running kinematic changes and time limit at vVO2max. DOI: http://dx.doi.org/10.5007/1980-0037.2012v14n4p428

    Directory of Open Access Journals (Sweden)

    Sebastião Iberes Lopes Melo

    2012-07-01

    Full Text Available DOI: http://dx.doi.org/10.5007/1980-0037.2012v14n4p428Exhaustive running at maximal oxygen uptake velocity (vVO2max can alter running kinematic parameters and increase energy cost along the time. The aims of the present study were to compare characteristics of ankle and knee kinematics during running at vVO2max and to verify the relationship between changes in kinematic variables and time limit (Tlim. Eleven male volunteers, recreational players of team sports, performed an incremental running test until volitional exhaustion to determine vVO2max and a constant velocity test at vVO2max. Subjects were filmed continuously from the left sagittal plane at 210 Hz for further kinematic analysis. The maximal plantar flexion during swing (p<0.01 was the only variable that increased significantly from beginning to end of the run. Increase in ankle angle at contact was the only variable related to Tlim (r=0.64; p=0.035 and explained 34% of the performance in the test. These findings suggest that the individuals under study maintained a stable running style at vVO2max and that increase in plantar flexion explained the performance in this test when it was applied in non-runners.

  1. Functional fiber mats with tunable diffuse reflectance composed of electrospun VO2/PVP composite fibers.

    Science.gov (United States)

    Li, Shaotang; Li, Yamei; Qian, Kun; Ji, Shidong; Luo, Hongjie; Gao, Yanfeng; Jin, Ping

    2014-01-01

    Thermochromic VO2 nanoparticles have been dispersed into polyvinyl pyrrolidone (PVP) fibers by electrospinning of a VO2-PVP blend solution. The structure and optical properties of the obtained composite fiber mat were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet-visible (UV-Vis) spectrophotometry, and Fourier transform infrared (FT-IR) spectroscopy. The fiber mat revealed two diffuse reflectance states in infrared spectral region at temperatures under and above the phase transition temperature of VO2 and its IR reflectance is smaller in high temperature. The difference of diffuse reflectance between the two states (ΔRdif) was obvious to be more than 25% in the wavelengths from 1.5 μm to 6 μm. The diffuse reflectance of the fiber mat could be controlled by adjusting the diameter of the fiber or the content of VO2 in the fibers and this particular optical property was explained by a multiple scattering-absorbing process.

  2. VO2sim 0.1: Using Simulation to Understand Measurement Error in Indirect Calorimetry

    Science.gov (United States)

    2015-08-01

    Calorimetry by Matthew S Tenan Approved for public release; distribution is unlimited. NOTICES Disclaimers...Simulation to Understand Measurement Error in Indirect Calorimetry by Matthew S Tenan Human Research and Engineering Directorate, ARL...VO2sim 0.1: Using Simulation to Understand Measurement Error in Indirect Calorimetry 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT

  3. Crystal Structure and Spectroscopic Properties of CsVO2SO4

    DEFF Research Database (Denmark)

    Rasmussen, Søren Birk; Boghosian, S.; Nielsen, Kurt;

    2004-01-01

    in the range 1.725(1)-1.984(2) Angstrom. The deformation of the VO6 octahedron is thus much more pronounced compared to other known oxo sulfato V(V) compounds, and the coordination polyhedron of V(V) should be regarded as a tetragonal pyramid with the vanadium atom in the center. Each VO2+ group is coordinated...

  4. Ab initio study of metal-insulator transition in VO2

    Science.gov (United States)

    Zheng, Huihuo; Wagner, Lucas K.

    2013-03-01

    The structure distortion accompanied metal-insulator transition (MIT) of vanadium dioxide (VO2) at 340K has been a matter of ongoing controversy for near four decades. It is still unclear whether the nature of this transition is due to a Peierls instability, a Mott-Hubbard transition, or other physics. Most density functional theory based methods fail to describe the nature of the electronic state in this system, further complicating theoretical description of VO2. We will report on progress in applying the first principles diffusion quantum Monte Carlo method to the electronic structure of VO2 in the metallic and insulator phases. By examining the energetic properties, one particle reduced density matrix, as well as other static correlations in the two phases of the system, we will comment on which of the two common descriptions is a closer representation of the physical reality of VO2. This work was supported by the Strategic Research Initiatives project at Illinois(HZ) and NSF DMR 12-06242 (LKW).

  5. Ultrathin Films of VO2 on r-Cut Sapphire Achieved by Postdeposition Etching.

    Science.gov (United States)

    Yamin, Tony; Wissberg, Shai; Cohen, Hagai; Cohen-Taguri, Gili; Sharoni, Amos

    2016-06-15

    The metal-insulator transition (MIT) properties of correlated oxides thin films, such as VO2, are dramatically affected by strain induced at the interface with the substrate, which usually changes with deposition thickness. For VO2 grown on r-cut sapphire, there is a minimum deposition thickness required for a significant MIT to appear, around 60 nm. We show that in these thicker films an interface layer develops, which accompanies the relaxation of film strain and enhanced electronic transition. If these interface dislocations are stable at room temperature, we conjectured, a new route opens to control thickness of VO2 films by postdeposition thinning of relaxed films, overcoming the need for thickness-dependent strain-engineered substrates. This is possible only if thinning does not alter the films' electronic properties. We find that wet etching in a dilute NaOH solution can effectively thin the VO2 films, which continue to show a significant MIT, even when etched to 10 nm, for which directly deposited films show nearly no transition. The structural and chemical composition were not modified by the etching, but the grain size and film roughness were, which modified the hysteresis width and magnitude of the MIT resistance change.

  6. VO2 Max in Variable Type Exercise Among Well-Trained Upper Body Athletes.

    Science.gov (United States)

    Seals, Douglas R.; Mullin, John P.

    1982-01-01

    The maximal oxygen consumption (VO2 max) of well-trained upper body athletes was compared to that of untrained individuals in four types of exercise: arm cranking, legs only cycling, graded treadmill running, and combined arm cranking and leg cycling. Results of the study showed that well-trained upper body athletes attained a significantly higher…

  7. Local temperature redistribution and structural transition during joule-heating-driven conductance switching in VO2.

    Science.gov (United States)

    Kumar, Suhas; Pickett, Matthew D; Strachan, John Paul; Gibson, Gary; Nishi, Yoshio; Williams, R Stanley

    2013-11-13

    Joule-heating induced conductance-switching is studied in VO2 , a Mott insulator. Complementary in situ techniques including optical characterization, blackbody microscopy, scanning transmission X-ray microscopy (STXM) and numerical simulations are used. Abrupt redistribution in local temperature is shown to occur upon conductance-switching along with a structural phase transition, at the same current.

  8. Prediction VO2max during cycle ergometry based on submaximal ventilatory indicators.

    Science.gov (United States)

    Nunes, Rodolfo Alkmim Moreira; Vale, Rodrigo Gomes de Souza; Simão, Roberto; de Salles, Belmiro Freitas; Reis, Victor Machado; Novaes, Jefferson da Silva; Miranda, Humberto; Rhea, Matthew R; Medeiros, Aldo da Cunha

    2009-09-01

    There are several equations to predict maximum oxygen consumption (VO2max) from ergometric test variables on different ergometers. However, a similar equation using ventilatory thresholds of ergospirometry in a submaximal test on a cycle ergometer is unavailable. The aim of the present study was to assess the accuracy of VO2max prediction models based on indicators of submaximal effort. Accordingly, 4,640 healthy, nonathlete women ages 20 years and older volunteered to be tested on a cycle ergometer using a maximum incremental protocol. The subjects were randomly assigned to 2 groups: group A (estimation) and group B (validation). From the independent variables of weight in kilograms, the second workload threshold (WT2), and heart rate of the second threshold (HRT2), it was possible to build a multiple linear regression model to predict maximal oxygen consumption (VO2max = 40.302 - 0.497 [Weight] - 0.001 [HRT2] + 0.239 [WT2] in mL O2/kg/min(-1); r = 0.995 and standard error of the estimate [SEE] = 0.68 mL O2/kg/min(-1)). The cross-validation method was used in group B with group A serving as the basis for building the model and the validation dataset. The results showed that, in healthy nonathlete women, it is possible to predict VO2max with a minimum of error (SEE = 1.00%) from submaximal indicators obtained in an incremental test.

  9. STUDY OF VO 2 MAX DURING PHASES OF MENSTRUATION IN YOUNG FEMALE ATHLETES

    Directory of Open Access Journals (Sweden)

    Sunitha

    2013-06-01

    Full Text Available ABSTRACT: Context: The menstrual cycle is a natural monthly event in y oung women, coordinated by the hypothalamic-pituitary ovarian axis and may influence physiological and pathological changes that occur throughout the life time of the woman. There is a cyclical change in sex hormones during the course of menstrual cycle that have the potential effects on exercise capacity and performance through numerous mechanisms, such a s substrate metabolism, cardiorespiratory function, thermoregulation, psychological factors a nd injuries. Consequently hormone level changes may theoretically lead to either improved or decrea sed performance at various times throughout the menstrual cycle. Physiological indices such as heart rate, tension, VO 2 max and aerobic power are of the main indicators of exercise performance, a potential change in these indices over the menstrual cycle will have large practical implicati ons for female athletes. VO 2 max is highly predictive of endurance performance, hence the pres ent study was done to evaluate whether there is any changes in the VO 2 max during phases of menstruation in young female athletes. Aim: The present study was done to evaluate the VO 2 max during phases of menstruation in young female athletes. Settings and Design: The present study was a cross sectional study consi sting of 30 healthy female athletes of 17-20 years of age. Materials and Methods: This study was conducted in the Department of Physiology, Adichunchanagiri inst itute of medical sciences after the institutional ethical clearance and written consent from each par ticipant. VO 2 max (maximum oxygen uptake was indirectly assessed by the Astrand nomogram met hod from submaximal exercise data obtained using Harvard step test during all the three phases of menstrual cycle. Results: The parameters were analyzed for statistical significance using St udents‘t’ test and p<0.05 was considered the level of significance. There were no significant

  10. Electrical and optical properties of VO2 thin films grown on various sapphire substrates by using RF sputtering deposition

    Science.gov (United States)

    Jung, Dae Ho; So, Hyeon Seob; Ko, Kun Hee; Park, Jun Woo; Lee, Hosun; Nguyen, Trang Thi Thu; Yoon, Seokhyun

    2016-12-01

    VO2 thin films were grown on a-, c-, m-, and r-plane sapphire and SiO2/Si substrates under identical conditions by using RF sputtering deposition from a VO2 target. The structural and the morphological properties of all VO2 films were investigated. The grain sizes of the VO2 films varied between 268 nm and 355 nm depending on the substrate's orientation. The electrical and the optical properties of all VO2 thin films were examined in detail. The metal-insulator transition temperature (TMI) varied with the substrate's orientation. The (200)/(bar 211 )-oriented VO2 films on the a-plane sapphire showed the lowest TMI of about 329.3 K (56.3 °C) while the (020)/(002)-VO2 films on the c-plane sapphire displayed the highest TMI of about 339.6 K (66.6 °C). The VO2 films showed reversible changes in the resistivity as large as 1.19 × 105 and a hysteresis of 2 K upon traversing the transition temperature. The variations observed in the TMI with respect to the substrate's orientation were due to changes in the lattice strain and the grain size distribution. Raman spectroscopy showed that metal (rutile) - insulator (monoclinic) transitions occurred via the M2 phase for VO2 films on the c-plane substrate rather than the direct M1 to rutile transition. The shifts in the phonon frequencies of the VO2 film grown on various sapphire substrates were explained in terms of the strain along the V-V atomic bond direction (cR). Our work shows a possible correlation between the transition parameters ( e.g., TMI, sharpness, and hysteresis width) and the width ( σ) of the grain size distribution. It also shows a possible correlation between the TMI and the resistivities at the insulating and the metallic phases for VO2 films grown on various sapphire substrates.

  11. Mediated proton transport through Nafion 117 membranes imbibed with varying concentrations of aqueous VOSO4 (VO2+) and NH4VO3 (VO2+) in 2 M H2SO4

    Science.gov (United States)

    Suarez, Sophia; Paterno, Domenec

    2016-11-01

    We performed an extensive study on Nafion 117 membrane imbibed with various concentrations of aqueous ammonium metavanadate (NH4VO3), and vanadyl sulfate (VOSO4), in 2 M H2SO4 over the temperature range of 20-100 °C, using 1H NMR and AC Impedance spectroscopies. The objective was to determine the effect of the tetravalent (VO2+) and pentavalent (VO2+) vanadium ions on the proton transport of Nafion 117.1H NMR chemical shift and linewidth data show greater short-range proton transport for the VO2+ imbibed membranes compared with the VO2+. However, the local environments seem to differ in that while the data for VO2+ imbibed membranes seem to follow more the trends observed for water hydrated Nafion 117, those for the VO2+ followed the trend of its aqueous bulk vanadium solvents, indicating that viscosity plays a larger role for the VO2+ imbibed membranes compared to the VO2+.

  12. Earbud-Based Sensor for the Assessment of Energy Expenditure, Heart Rate, and VO2max

    Science.gov (United States)

    LeBoeuf, Steven F.; Aumer, Michael E.; Kraus, William E.; Johnson, Johanna L.; Duscha, Brian

    2014-01-01

    Introduction/Purpose The goal of this program was to determine the feasibility of a novel noninvasive, highly miniaturized optomechanical earbud sensor for accurately estimating total energy expenditure (TEE) and maximum oxygen consumption (VO2max). The optomechanical sensor module, small enough to fit inside commercial audio earbuds, was previously developed to provide a seamless way to measure blood flow information during daily life activities. The sensor module was configured to continuously measure physiological information via photoplethysmography (PPG) and physical activity information via accelerometry. This information was digitized and sent to a microprocessor where digital signal processing (DSP) algorithms extract physiological metrics in real-time. These metrics were streamed wirelessly from the earbud to a computer. Methods In this study, 23 subjects of multiple physical habitus were divided into a training group of 14 subjects and a validation group of 9 subjects. Each subject underwent the same exercise measurement protocol consisting of treadmill-based cardiopulmonary exercise (CPX) testing to reach VO2max. Benchmark sensors included a 12-lead electrocardiography (ECG) sensor for measuring heart rate, a calibrated treadmill for measuring distance and speed, and a gas-exchange analysis instrument for measuring TEE and VO2max. The earbud sensor was the device under test (DUT). Benchmark and DUT data collected from the 14-person training dataset study were integrated into a preconceived statistical model for correlating benchmark data with earbud sensor data. Coefficients were optimized, and the optimized model was validated in the 9-person validation dataset. Results It was observed that the earbud sensor estimated TEE and VO2max with mean ± SD percent estimation errors of −0.7 ± 7.4% and −3.2 ± 7.3% respectively. Conclusion The earbud sensor can accurately estimate TEE and VO2max during CPX testing. PMID:24743110

  13. Earbud-based sensor for the assessment of energy expenditure, HR, and VO2max.

    Science.gov (United States)

    Leboeuf, Steven Francis; Aumer, Michael E; Kraus, William E; Johnson, Johanna L; Duscha, Brian

    2014-01-01

    The goal of this program was to determine the feasibility of a novel noninvasive, highly miniaturized optomechanical earbud sensor for accurately estimating total energy expenditure (TEE) and maximum oxygen consumption (VO2max). The optomechanical sensor module, small enough to fit inside commercial audio earbuds, was previously developed to provide a seamless way to measure blood flow information during daily life activities. The sensor module was configured to continuously measure physiological information via photoplethysmography and physical activity information via accelerometry. This information was digitized and sent to a microprocessor where digital signal-processing algorithms extract physiological metrics in real time. These metrics were streamed wirelessly from the earbud to a computer. In this study, 23 subjects of multiple physical habitus were divided into a training group of 14 subjects and a validation group of 9 subjects. Each subject underwent the same exercise measurement protocol consisting of treadmill-based cardiopulmonary exercise testing to reach VO2max. Benchmark sensors included a 12-lead ECG sensor for measuring HR, a calibrated treadmill for measuring distance and speed, and a gas-exchange analysis instrument for measuring TEE and VO2max. The earbud sensor was the device under test. Benchmark and device under test data collected from the 14-person training data set study were integrated into a preconceived statistical model for correlating benchmark data with earbud sensor data. Coefficients were optimized, and the optimized model was validated in the 9-person validation data set. It was observed that the earbud sensor estimated TEE and VO2max with mean ± SD percent estimation errors of -0.7 ± 7.4% and -3.2 ± 7.3%, respectively. The earbud sensor can accurately estimate TEE and VO2max during cardiopulmonary exercise testing.

  14. Influence of simulated microgravity on the VO2 max of nontrained and trained rats

    Science.gov (United States)

    Woodman, C. R.; Monnin, K. A.; Sebastian, L. A.; Tipton, C. M.

    1993-01-01

    Head-down suspension (HDS) of rats has evolved as a useful model for the simulation of a microgravity environment. Previous HDS experiments with rats have shown an impaired capacity to perform aerobic exercise as demonstrated by reductions in maximum oxygen consumption (VO2 max), treadmill run time (RT), and mechanical efficiency (ME) of treadmill running at submaximal conditions. To determine whether endurance training (TR) before HDS would modify exercise performance, male Sprague-Dawley rats were assigned to nontrained (NT) or TR groups for 6 wk and exposed to HDS or cage control (CC) conditions for 29 days. The rats were tested for VO2 max, RT, and ME before treatment and on days 7, 14, 21, and 28. In addition, water and electrolyte excretion was measured on days 1 and 21 of the experimental period. Before HDS, the TR rats had significantly higher measures of VO2 max (15%) and RT (22%) than the NT rats. On day 28, HDS was associated with significant reductions in absolute VO2 max (ml/min) in TR (-30%) and NT (-14%) rats. Relative VO2 max (ml.min-1.kg-1) was significantly reduced in TR (-15%) but not NT rats. Similar reductions in RT occurred in TR (-37%) and NT (-35%) rats by day 28. ME was reduced 22% in both TR and NT rats after 28 days of suspension. HDS elicited diuresis, natriuresis, and kaliuresis in TR rats after 21 days but not after 24 h. In contrast, HDS-NT rats exhibited no diuretic, natriuretic, or kaliuretic responses.(ABSTRACT TRUNCATED AT 250 WORDS).

  15. Bone mass in girls according to their BMI, VO2 max, hours and years of practice.

    Science.gov (United States)

    Ubago-Guisado, Esther; Martinez-Rodriguez, Alejandro; Gallardo, Leonor; Sánchez-Sánchez, Javier

    2016-11-01

    The accumulation of bone mass during puberty is related with bone health in adulthood. This accumulation is influenced by diverse factors such as body mass index (BMI), maximal oxygen uptake (VO2 max), hours of training and years of sport practice. For this reason, the objective of this study is to analyse the influence of these variables on bone mass in young female athletes. The sample is formed of 120 healthy girls with ages between 9 and 13 (11.32 ± 1.6 years old), divided into two groups depending on their BMI, VO2 max, hours of training and years of sport practice. The participants completed a series of tests to evaluate level of sexual development, body composition (fat mass, lean mass and bone mass) and physical condition. The results show higher values of total lean mass, total fat mass and percentage of body fat in the groups with higher BMI in prepubertal girls and pubertal girls (p VO2 max, in the prepubertal group, girls with lower VO2 max had higher values of total fat mass (p VO2 max also showed a higher total fat mass (p < .05). The studied variables account for a 85% and 75.4% of the variance of total bone mineral content and bone mineral density (BMD), respectively. In conclusion, the content and BMD are closely related with muscle mass and sports practice in young females. The amount of fat mass showed no association with bone mass and physical condition has an indirect relationship with bone development.

  16. A new submaximal cycle ergometer test for prediction of VO2max.

    Science.gov (United States)

    Ekblom-Bak, E; Björkman, F; Hellenius, M-L; Ekblom, B

    2014-04-01

    Maximal oxygen uptake (VO2max) is an important, independent predictor of cardiovascular health and mortality. Despite this, it is rarely measured in clinical practice. The aim of this study was to create and evaluate a submaximal cycle ergometry test based on change in heart rate (HR) between a lower standard work rate and an individually chosen higher work rate. In a mixed population (n = 143) with regard to sex (55% women), age (21-65 years), and activity status (inactive to highly active), a model included change in HR per unit change in power, sex, and age for the best estimate of VO2max. The association between estimated and observed VO2max for the mixed sample was r = 0.91, standard error of estimate = 0.302 L/min, and mean measured VO2max = 3.23 L/min. The corresponding coefficient of variation was 9.3%, a significantly improved precision compared with one of the most commonly used submaximal exercise tests, the Åstrand test, which in the present study was estimated to be 18.1%. Test-retest reliability analysis over 1 week revealed no mean difference in the estimated VO2max (-0.02 L/min, 95% confidence interval: -0.07-0.03). The new test is low-risk, easily administered, and valid for a wide capacity range, and is therefore suitable in situations as health evaluations in the general population. © 2012 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  17. Hydrothermal Synthesis of VO2 Polymorphs: Advantages, Challenges and Prospects for the Application of Energy Efficient Smart Windows.

    Science.gov (United States)

    Li, Ming; Magdassi, Shlomo; Gao, Yanfeng; Long, Yi

    2017-07-19

    Vanadium dioxide (VO2 ) is a widely studied inorganic phase change material, which has a reversible phase transition from semiconducting monoclinic to metallic rutile phase at a critical temperature of τc ≈ 68 °C. The abrupt decrease of infrared transmittance in the metallic phase makes VO2 a potential candidate for thermochromic energy efficient windows to cut down building energy consumption. However, there are three long-standing issues that hindered its application in energy efficient windows: high τc , low luminous transmittance (Tlum ), and undesirable solar modulation ability (ΔTsol ). Many approaches, including nano-thermochromism, porous films, biomimetic surface reconstruction, gridded structures, antireflective overcoatings, etc, have been proposed to tackle these issues. The first approach-nano-thermochromism-which is to integrate VO2 nanoparticles in a transparent matrix, outperforms the rest; while the thermochromic performance is determined by particle size, stoichiometry, and crystallinity. A hydrothermal method is the most common method to fabricate high-quality VO2 nanoparticles, and has its own advantages of large-scale synthesis and precise phase control of VO2 . This Review focuses on hydrothermal synthesis, physical properties of VO2 polymorphs, and their transformation to thermochromic VO2 (M), and discusses the advantages, challenges, and prospects of VO2 (M) in energy-efficient smart windows application. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Increased resolution of aromatic cross peaks using alternate {sup 13}C labeling and TROSY

    Energy Technology Data Exchange (ETDEWEB)

    Milbradt, Alexander G. [AstraZeneca Discovery Sciences, Structure and Biophysics UK (United Kingdom); Arthanari, Haribabu [Harvard Medical School, Department of Biological Chemistry and Molecular Pharmacology (United States); Takeuchi, Koh [National Institute of Advanced Industrial Science and Technology, Biomedicinal Information Research Center and Molecular Profiling Research Center for Drug Discovery (Japan); Boeszoermenyi, Andras; Hagn, Franz; Wagner, Gerhard, E-mail: gerhard-wagner@hms.harvard.edu [Harvard Medical School, Department of Biological Chemistry and Molecular Pharmacology (United States)

    2015-07-15

    For typical globular proteins, contacts involving aromatic side chains would constitute the largest number of distance constraints that could be used to define the structure of proteins and protein complexes based on NOE contacts. However, the {sup 1}H NMR signals of aromatic side chains are often heavily overlapped, which hampers extensive use of aromatic NOE cross peaks. Some of this overlap can be overcome by recording {sup 13}C-dispersed NOESY spectra. However, the resolution in the carbon dimension is rather low due to the narrow dispersion of the carbon signals, large one-bond carbon–carbon (C–C) couplings, and line broadening due to chemical shift anisotropy (CSA). Although it has been noted that the CSA of aromatic carbons could be used in TROSY experiments for enhancing resolution, this has not been used much in practice because of complications arising from large aromatic one-bond C–C couplings, and 3D or 4D carbon dispersed NOESY are typically recorded at low resolution hampering straightforward peak assignments. Here we show that the aromatic TROSY effect can optimally be used when employing alternate {sup 13}C labeling using 2-{sup 13}C glycerol, 2-{sup 13}C pyruvate, or 3-{sup 13}C pyruvate as the carbon source. With the elimination of the strong one-bond C–C coupling, the TROSY effect can easily be exploited. We show that {sup 1}H–{sup 13}C TROSY spectra of alternately {sup 13}C labeled samples can be recorded at high resolution, and we employ 3D NOESY aromatic-TROSY spectra to obtain valuable intramolecular and intermolecular cross peaks on a protein complex.

  19. Effect of Al2O3 Buffer Layers on the Properties of Sputtered VO2 Thin Films

    Science.gov (United States)

    Zhang, Dainan; Wen, Tianlong; Xiong, Ying; Qiu, Donghong; Wen, Qiye

    2017-07-01

    VO2 thin films were grown on silicon substrates using Al2O3 thin films as the buffer layers. Compared with direct deposition on silicon, VO2 thin films deposited on Al2O3 buffer layers experience a significant improvement in their microstructures and physical properties. By optimizing the growth conditions, the resistance of VO2 thin films can change by four orders of magnitude with a reduced thermal hysteresis of 4 °C at the phase transition temperature. The electrically driven phase transformation was measured in Pt/Si/Al2O3/VO2/Au heterostructures. The introduction of a buffer layer reduces the leakage current and Joule heating during electrically driven phase transitions. The C- V measurement result indicates that the phase transformation of VO2 thin films can be induced by an electrical field.

  20. A simple and low-cost combustion method to prepare monoclinic VO2 with superior thermochromic properties

    Science.gov (United States)

    Cao, Ziyi; Xiao, Xiudi; Lu, Xuanming; Zhan, Yongjun; Cheng, Haoliang; Xu, Gang

    2016-12-01

    In this approach, the VO2 nanoparticles have been successfully fabricated via combusting the low-cost precursor solution consisted of NH4VO3, C2H6O2 and C2H5OH. By the XRD, TEM and XPS analysis, it can be found that the synthetic monoclinic VO2 is single crystal and no impurity is defined. After dispersing the VO2 nanoparticles into the polymer, the solar modulation of VO2-based composite film is up to 12.5% with luminous transmission and haze around 62.2% and 0.5%, respectively. In other words, the composite films show high performance of thermochromic properties. This could open an efficient way to fabricate low-cost and large-scale VO2 (M) nanoparticles and thermochromic films.

  1. Crossvalidation of two heart rate-based equations for predicting VO2max in white and black men.

    Science.gov (United States)

    Esco, Michael R; Olson, Michele S; Williford, Henry N; Mugu, Emmanuel M; Bloomquist, Barbara E; McHugh, Aindrea N

    2012-07-01

    The purpose of this investigation was to crossvalidate 2 equations that use the ratio of maximal heart rate (HRmax) to resting HR (HRrest) for predicting maximal oxygen consumption (VO2max) in white and black men. One hundred and nine white (n = 51) and black (n = 58) men completed a maximal exercise test on a treadmill to determine VO2max. The HRrest and HRmax were used to predict VO2max via the HRindex and HRratio equations. Validity statistics were done to compare the criterion versus predicted VO2max values across the entire cohort and within each race separately. For the entire group, VO2max was significantly overestimated with the HRindex equation, but the HRratio equation yielded no significant difference compared with the criterion. In addition, there were no significant differences shown between VO2max and either HR-based prediction equation for the white subgroup. However, both equations significantly overestimated VO2max in the black group. Furthermore, large standard error of estimates (ranging from 6.92 to 7.90 ml·kg(-1)·min(-1)), total errors (ranging from 8.30 to 8.62 ml·kg(-1)·min(-1)), and limits of agreement (ranging from upper limits of 16.65 to lower limits of -18.25 ml·kg(-1)·min(-1)) were revealed when comparing the predicted to criterion VO2max for both the groups. Considering the results of this investigation, the HRratio and HRindex methods appear to crossvalidate and prove useful for estimating the mean VO2max in white men as a group but not for an age-matched group of black men. However, because of inflated values for error, caution should be exercised when using these methods to predict individual VO2max.

  2. Living and training in moderate hypoxia does not improve VO2 max more than living and training in normoxia.

    Science.gov (United States)

    Henderson, K K; Clancy, R L; Gonzalez, N C

    2001-06-01

    The objective of these experiments was to determine whether living and training in moderate hypoxia (MHx) confers an advantage on maximal normoxic exercise capacity compared with living and training in normoxia. Rats were acclimatized to and trained in MHx [inspired PO2 (PI(O2)) = 110 Torr] for 10 wk (HTH). Rats living in normoxia trained under normoxic conditions (NTN) at the same absolute work rate: 30 m/min on a 10 degrees incline, 1 h/day, 5 days/wk. At the end of training, rats exercised maximally in normoxia. Training increased maximal O2 consumption (VO2 max) in NTN and HTH above normoxic (NS) and hypoxic (HS) sedentary controls. However, VO2 max and O2 transport variables were not significantly different between NTN and HTH: VO2 max 86.6 +/- 1.5 vs. 86.8 +/- 1.1 ml x min(-1) x kg(-1); maximal cardiac output 456 +/- 7 vs. 443 +/- 12 ml x min(-1) x kg(-1); tissue blood O2 delivery (cardiac output x arterial O2 content) 95 +/- 2 vs. 96 +/- 2 ml x min(-1) x kg(-1); and O2 extraction ratio (arteriovenous O2 content difference/arterial O2 content) 0.91 +/- 0.01 vs. 0.90 +/- 0.01. Mean pulmonary arterial pressure (Ppa, mmHg) was significantly higher in HS vs. NS (P < 0.05) at rest (24.5 +/- 0.8 vs. 18.1 +/- 0.8) and during maximal exercise (32.0 +/- 0.9 vs. 23.8 +/- 0.6). Training in MHx significantly attenuated the degree of pulmonary hypertension, with Ppa being significantly lower at rest (19.3 +/- 0.8) and during maximal exercise (29.2 +/- 0.5) in HTH vs. HS. These data indicate that, despite maintaining equal absolute training intensity levels, acclimatization to and training in MHx does not confer significant advantages over normoxic training. On the other hand, the pulmonary hypertension associated with acclimatization to hypoxia is reduced with hypoxic exercise training.

  3. Effect of Sodium Phosphate Supplementation on Cycling Time Trial Performance and VO2 1 and 8 Days Post Loading.

    Science.gov (United States)

    Brewer, Cameron P; Dawson, Brian; Wallman, Karen E; Guelfi, Kym J

    2014-09-01

    This study examined the effect of 6 days of sodium phosphate (SP) (50 mg·kg·FFM(-1)·day(-1)) or placebo (PL) supplementation in trained cyclists on either 100 kJ (23.9 Kcal) (~3-4 min) or 250 kJ (59.7 Kcal) (~10-12 min) time trials performances both 1 and 8 days post-supplementation. Trials were performed in a counterbalanced crossover design, with a 28-day washout period between supplementation phases. No significant differences, moderate-large ES (d) or likely (or greater) smallest worthwhile change (SWC) values were recorded for time to completion and mean power output on days 1 and 8 post-supplementation, both within and between SP and PL for either the 100 or 250 kJ (23.9 or 59.7 Kcal) trials. In the 100 kJ (23.9 Kcal) trial (only) first minute VO2 tended to be higher in SP8 than both PL8 (d = 0.60; 88/10/2 SWC) and SP1 (d = 0.47: 82/15/3 SWC), as was mean VO2 (PL8: d = 0.77; 93/6/1 SWC and SP1: d = 0.84; 90/8/3 SWC). No significant differences were found for heart rate, ratings of perceived exertion and blood lactate post-exercise within or between any trials, while serum phosphate values were not different before or after supplementation with SP or PL. In conclusion, this study showed a tendency for increased VO2 in a short duration (100 kJ/ 23.9 Kcal: ~3-4 min) cycling test on day 8 after SP supplementation, but no differences in 100 or 250 kJ (23.9 or 59.7 Kcal) time trials performances were observed. Key PointsStudies investigating the effects of sodium phosphate loading on shorter duration (ergogenic effect may last.Loading did not improve cycling time trial (~3-4 min and 10-12 min) performance either 1 or 8 days after supplementation.Future studies should investigate the effect of sodium phosphate loading on repeated sprints and simulated cycling road race performance over extended durations (>30 min), where it may be likely to have a more beneficial effect.

  4. Mesoscopic Metal-Insulator Transition at Ferroelastic Domain Walls in VO2

    Energy Technology Data Exchange (ETDEWEB)

    Jones, Keith M [ORNL; Kalinin, Sergei V [ORNL; Kolmakov, Andrei [ORNL; Luk' yanchuk, Prof. Igor A. [University of Picardie Jules Verne, Amiens, France; Meunier, Vincent [ORNL; Proksch, Roger [Asylum Research, Santa Barbara, CA; Shelton Jr, William Allison [ORNL; Strelcov, Evgheni [Southern Illinois University; Tselev, Alexander [ORNL

    2010-01-01

    The novel phenomena induced by symmetry breaking at homointerfaces between ferroic variants in ferroelectric and ferroelastic materials have attracted recently much attention. Using variable temperature scanning microwave microscopy, we demonstrate the mesoscopic strain-induced metal-insulator phase transitions in the vicinity of ferroelastic domain walls in the semiconductive VO2 that nucleated at temperatures as much as 10-12 C below bulk transition, resulting in the formation of conductive channels in the material. Density functional theory is used to rationalize the process low activation energy. This behavior, linked to the strain inhomogeneity inherent in ferroelastic materials, can strongly affect interpretation of phase-transition studies in VO2 and similar materials with symmetry-lowering transitions, and can also be used to enable new generations of electronic devices though strain engineering of conductive and semiconductive regions.

  5. Steady State Condition in the Measurement of VO2and VCO2by Indirect Calorimetry.

    Science.gov (United States)

    Cadena, M; Sacristan, E; Infante, O; Escalante, B; Rodriguez, F

    2005-01-01

    Resting Metabolic Rate (RMR) is computed using VO2and VCO2short time 15-minute window measurement with Indirect Calorimetry (IC) instruments designed with mixing chamber. Steady state condition using a 10% variation coefficient criteria is the main objective to achieve metabolic long time prediction reliability. This study address how susceptible is the steady state VO2, VCO2measurement condition to the clino-orthostatic physiological maneuver. 30 young healthy subjects were analyzed. Only 18 passed the 10% variation coefficient inclusive criteria. They were exposed to 10 minutes clino-stage and 10 minutes orthostage. The hypothesis tests show not statistical significance (p< 0.1) in the average and variance analysis. It is concluded that the steady state is not influenced by the patient position IC test, probably because IC mixing chamber instruments are insensitive to detect a mayor physiological dynamics changes that can modify the steady state definition.

  6. Reconfigurable anisotropy and functional transformations with VO$_{2}$-based metamaterial electric circuits

    CERN Document Server

    Savo, Salvatore; Castaldi, Giuseppe; Moccia, Massimo; Galdi, Vincenzo; Ramanathan, Shriram; Sato, Yuki

    2014-01-01

    We demonstrate an innovative multifunctional artificial material that combines exotic metamaterial properties and the environmentally responsive nature of phase change media. The tunable metamaterial is designed with the aid of two interwoven coordinate-transformation equations and implemented with a network of thin film resistors and vanadium dioxide ($VO_{2}$). The strong temperature dependence of $VO_{2}$ electrical conductivity results in a relevant modification of the resistor network behavior, and we provide experimental evidence for a reconfigurable metamaterial electric circuit (MMEC) that not only mimics a continuous medium but is also capable of responding to thermal stimulation through dynamic variation of its spatial anisotropy. Upon external temperature change the overall effective functionality of the material switches between a "truncated-cloak" and "concentrator" for electric currents. Possible applications may include adaptive matching resistor networks, multifunctional electronic devices, an...

  7. Local Peltier-effect-induced reversible metal-insulator transition in VO2 nanowires

    Science.gov (United States)

    Takami, Hidefumi; Kanki, Teruo; Tanaka, Hidekazu

    2016-06-01

    We report anomalous resistance leaps and drops in VO2 nanowires with operating current density and direction, showing reversible and nonvolatile switching. This event is associated with the metal-insulator phase transition (MIT) of local nanodomains with coexistence states of metallic and insulating phases induced by thermoelectric cooling and heating effects. Because the interface of metal and insulator domains has much different Peltier coefficient, it is possible that a significant Peltier effect would be a source of the local MIT. This operation can be realized by one-dimensional domain configuration in VO2 nanowires because one straight current path through the electronic domain-interface enables theoretical control of thermoelectric effects. This result will open a new method of reversible control of electronic states in correlated electron materials.

  8. Local Peltier-effect-induced reversible metal–insulator transition in VO2 nanowires

    Directory of Open Access Journals (Sweden)

    Hidefumi Takami

    2016-06-01

    Full Text Available We report anomalous resistance leaps and drops in VO2 nanowires with operating current density and direction, showing reversible and nonvolatile switching. This event is associated with the metal–insulator phase transition (MIT of local nanodomains with coexistence states of metallic and insulating phases induced by thermoelectric cooling and heating effects. Because the interface of metal and insulator domains has much different Peltier coefficient, it is possible that a significant Peltier effect would be a source of the local MIT. This operation can be realized by one-dimensional domain configuration in VO2 nanowires because one straight current path through the electronic domain-interface enables theoretical control of thermoelectric effects. This result will open a new method of reversible control of electronic states in correlated electron materials.

  9. Resolving the VO2 controversy: Mott mechanism dominates the insulator-to-metal transition

    Science.gov (United States)

    Nájera, O.; Civelli, M.; Dobrosavljević, V.; Rozenberg, M. J.

    2017-01-01

    We consider a minimal model to investigate the metal-insulator transition in VO2. We adopt a Hubbard model with two orbitals per unit cell, which captures the competition between Mott and singlet-dimer localization. We solve the model within dynamical mean-field theory, characterizing in detail the metal-insulator transition and finding new features in the electronic states. We compare our results with available experimental data, obtaining good agreement in the relevant model parameter range. Crucially, we can account for puzzling optical conductivity data obtained within the hysteresis region, which we associate with a metallic state characterized by a split heavy quasiparticle band. Our results show that the thermal-driven insulator-to-metal transition in VO2 is compatible with a Mott electronic mechanism, providing fresh insight to a long-standing "chicken-and-egg" debate and calling for further research of "Mottronics" applications of this system.

  10. Joule Heating-Induced Metal-Insulator Transition in Epitaxial VO2/TiO2 Devices.

    Science.gov (United States)

    Li, Dasheng; Sharma, Abhishek A; Gala, Darshil K; Shukla, Nikhil; Paik, Hanjong; Datta, Suman; Schlom, Darrell G; Bain, James A; Skowronski, Marek

    2016-05-25

    DC and pulse voltage-induced metal-insulator transition (MIT) in epitaxial VO2 two terminal devices were measured at various stage temperatures. The power needed to switch the device to the ON-state decrease linearly with increasing stage temperature, which can be explained by the Joule heating effect. During transient voltage induced MIT measurement, the incubation time varied across 6 orders of magnitude. Both DC I-V characteristic and incubation times calculated from the electrothermal simulations show good agreement with measured values, indicating Joule heating effect is the cause of MIT with no evidence of electronic effects. The width of the metallic filament in the ON-state of the device was extracted and simulated within the thermal model.

  11. Reduced peak oxygen uptake and implications for cardiovascular health and quality of life in patients with schizophrenia

    Directory of Open Access Journals (Sweden)

    Heggelund Jørn

    2011-12-01

    Full Text Available Abstract Background Peak oxygen uptake (VO2peak is a strong predictor of cardiovascular disease (CVD and all-cause mortality, but is inadequately described in patients with schizophrenia. The aim of this study was to evaluate treadmill VO2peak, CVD risk factors and quality of life (QOL in patients with schizophrenia (ICD-10, F20-29. Methods 33 patients, 22 men (33.7 ± 10.4 years and 11 women (35.9 ± 11.5 years, were included. Patients VO2peak were compared with normative VO2peak in healthy individuals from the Nord-Trøndelag Health Study (HUNT. Risk factors were compared above and below the VO2peak thresholds; 44.2 and 35.1 ml·kg-1·min-1 in men and women, respectively. Results VO2peak was 37.1 ± 9.2 ml·kg-1·min-1 in men with schizophrenia; 74 ± 19% of normative healthy men (p 2peak was 35.6 ± 10.7 ml·kg-1·min-1 in women with schizophrenia; 89 ± 25% of normative healthy women (n.s.. Based on odds ratio patients were 28.3 (95% CI = 1.6-505.6 times more likely to have one or more CVD risk factors if they were below the VO2peak thresholds. VO2peak correlated with the SF-36 physical functioning (r = 0.58, general health (r = 0.53, vitality (r = 0.47, social function (r = 0.41 and physical component score (r = 0.51. Conclusion Men with schizophrenia have lower VO2peak than the general population. Patients with the lowest VO2peak have higher odds of having one or more risk factors for cardiovascular disease. VO2peak should be regarded as least as important as the conventional risk factors for CVD and evaluation of VO2peak should be incorporated in clinical practice.

  12. Synthesis of sub-10 nm VO2 nanoparticles films with plasma-treated glass slides by aqueous sol-gel method

    Science.gov (United States)

    Lan, Shi-Di; Cheng, Chih-Chia; Huang, Chi-Hsien; Chen, Jem-Kun

    2015-12-01

    This paper describes an aqueous sol-gel synthesis of thermochromic thin films consisted of vanadium dioxide nanoparticles (VNPs) on glass slides. The glass slides were treated by argon/oxygen plasma to generate dispersedly negative charge sites on the surface to attract VO2+ from a sol-gel solution. After heat treatment in a low-pressure carbon monoxide/carbon dioxide (CO/CO2) atmosphere, the VNPs could be generated in sub-10 nm of particle size on the surface. Various levels of doping were achieved by adding small quantities of a water-soluble tungsten compound to the sol; however, the particle size increased slightly with the tungsten doping levels. The change in electrical conductivity with temperature for VNP films were measured and compared to VO2 crystalline films. VNP films exhibited the lower transition temperature of the semiconductor to metal phase change; at a doping level of 4 wt% the transition temperature was measured at 32.2 ± 1.2 and 24.1 ± 1.2 °C for the VO2 and VNP films, respectively. The VNP films showed excellent visible transparency and a large change in transmittance at near-infrared (NIR) wavelengths before and after the metal-insulator phase transition (MIT). The current method is a landmark in the development of nanostructured material toward applications in energy-saving smart windows.

  13. The relation between serum leptin levels and max VO2 in male patients with type I diabetes and healthy sedentary males.

    Science.gov (United States)

    Unal, Mehmet; Unal, Durisehvar Ozer; Salman, Fatih; Baltaci, Abdulkerim Kasim; Mogulkoc, Rasim

    2004-08-01

    This study aimed at investigating leptin levels in male diabetes type I patients who were on insulin treatment and also healthy sedentary males. The study included 10 male type I diabetes patients and 17 healthy sedentary males. Leptin levels of type I diabetes patients and healthy sedentary males with body mass index (BMI) over 25 kg/m2 were evaluated separately. The relation between serum leptin, max VO2, blood lactic acid levels before and after exercise, and effort durations of participants were investigated. At the end of the tests, no difference was found between leptin levels, max VO2 values, lactic acid values before exercise, and test durations of male type I diabetes patients and healthy sedentary males (p > .05), whereas lactic acid levels after exercise were found to be lower in healthy sedentary males (p max VO2 values and test durations were higher in the group with BMI below 25 kg/m2 (p < .05). In conclusion, leptin levels of male type I diabetes patients are close to those of healthy sedentary males. The increase in leptin levels in both groups is in proportion to the BMI of individuals.

  14. Time to Exhaustion at the VO2max Velocity in Swimming: A Review

    OpenAIRE

    Fernandes, Ricardo J.; Vilas-Boas, J. Paulo

    2012-01-01

    The aim of this study was to present a review on the time to exhaustion at the minimum swimming velocity corresponding to maximal oxygen consumption (TLim-vVO2max). This parameter is critical both for the aerobic power and the lactate tolerance bioenergetical training intensity zones, being fundamental to characterize it, and to point out its main determinants. The few number of studies conducted in this topic observed that swimmers were able to maintain an exercise intensity corresponding to...

  15. Crystal Structure and Spectroscopic Characterization of K8(VO)2O(SO4)6:

    DEFF Research Database (Denmark)

    Rasmussen, Søren Birk; Rasmussen, Rikke Christina; Fehrmann, Rasmus;

    2003-01-01

    Red and yellow dichroistic crystals of a vanadium(V) compound, potassium (mu-oxo, di-mu-suifato)bis(oxodisulfato-vanadate), K-8(VO)(2)O(SO4)(6), have been obtained from the ternary catalytic model melt system K2S2O7-K2SO4-V2O5. By slow cooling of the melt from 420 to 355 degreesC, crystal growth...

  16. Attenuated Increase in Maximal Force of Rat Medial Gastrocnemius Muscle after Concurrent Peak Power and Endurance Training

    Science.gov (United States)

    Furrer, Regula; Jaspers, Richard T.; Baggerman, Hein L.; Bravenboer, Nathalie; Lips, Paul; de Haan, Arnold

    2013-01-01

    Improvement of muscle peak power and oxidative capacity are generally presumed to be mutually exclusive. However, this may not be valid by using fibre type-specific recruitment. Since rat medial gastrocnemius muscle (GM) is composed of high and low oxidative compartments which are recruited task specifically, we hypothesised that the adaptive responses to peak power training were unaffected by additional endurance training. Thirty rats were subjected to either no training (control), peak power training (PT), or both peak power and endurance training (PET), which was performed on a treadmill 5 days per week for 6 weeks. Maximal running velocity increased 13.5% throughout the training and was similar in both training groups. Only after PT, GM maximal force was 10% higher than that of the control group. In the low oxidative compartment, mRNA levels of myostatin and MuRF-1 were higher after PT as compared to those of control and PET groups, respectively. Phospho-S6 ribosomal protein levels remained unchanged, suggesting that the elevated myostatin levels after PT did not inhibit mTOR signalling. In conclusion, even by using task-specific recruitment of the compartmentalized rat GM, additional endurance training interfered with the adaptive response of peak power training and attenuated the increase in maximal force after power training. PMID:23509812

  17. Attenuated Increase in Maximal Force of Rat Medial Gastrocnemius Muscle after Concurrent Peak Power and Endurance Training

    Directory of Open Access Journals (Sweden)

    Regula Furrer

    2013-01-01

    Full Text Available Improvement of muscle peak power and oxidative capacity are generally presumed to be mutually exclusive. However, this may not be valid by using fibre type-specific recruitment. Since rat medial gastrocnemius muscle (GM is composed of high and low oxidative compartments which are recruited task specifically, we hypothesised that the adaptive responses to peak power training were unaffected by additional endurance training. Thirty rats were subjected to either no training (control, peak power training (PT, or both peak power and endurance training (PET, which was performed on a treadmill 5 days per week for 6 weeks. Maximal running velocity increased 13.5% throughout the training and was similar in both training groups. Only after PT, GM maximal force was 10% higher than that of the control group. In the low oxidative compartment, mRNA levels of myostatin and MuRF-1 were higher after PT as compared to those of control and PET groups, respectively. Phospho-S6 ribosomal protein levels remained unchanged, suggesting that the elevated myostatin levels after PT did not inhibit mTOR signalling. In conclusion, even by using task-specific recruitment of the compartmentalized rat GM, additional endurance training interfered with the adaptive response of peak power training and attenuated the increase in maximal force after power training.

  18. Characterization of pulsed laser deposition grown V2O3 converted VO2

    Science.gov (United States)

    Majid, Suhail; Shukla, D. K.; Rahman, F.; Gautam, Kamini; Sathe, V. G.; Choudhary, R. J.; Phase, D. M.

    2016-10-01

    Controllable tuning of Metal-insulator transition in VxOy thin film has been a field of extensive research. However controlled synthesis of desired Vanadium oxide phase is a challenging task. We have successfully achieved VO2 phase on Silicon substrate after post deposition annealing treatment to the PLD grown as deposited V2O3 thin films. The annealed thin film was characterized by x-ray diffraction (XRD), resistivity, Raman spectroscopy, X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) measurements. XRD confirms the crystalline nature and growth of VO2 phase in thin film. The characteristic MIT was observed from resistivity measurements and transition temperature appeared at lower value around 336 K, compared to bulk VO2. The structural transition accompanied with MIT from lower temperature monoclinic phase to higher temperature Rutile phase became evident from temperature dependent Raman measurements. Chemical state of vanadium was examined using XAS and XPS measurements which confirm the presence of +4 oxidation state of vanadium in thin film.

  19. EVALUATION AND COMPARISON OF VO2MAX ASSESSMENT MODELS IN HIGH SCHOOL STUDENTS

    Directory of Open Access Journals (Sweden)

    Lotfali Bolboli

    2013-02-01

    Full Text Available The purpose of this study was to evaluation and comparison of VO2max assessment models in students. Thirty students from high schools of Ardabil city were selected randomly and served as subjects in this study (age: 15.73±0.69 year, height: 169.46±8.1 cm, weight: 61.70±9.32 kg. Subjects were divided into two groups. In one group Rockport test was used to estimate their VO2 max and in other group Balk test was used for the same purpose. Also, the VO2max of both groups were examined by a standard treadmill test and the results were compared with the results of field tests. The one way of ANOVA and Tukey's post-hoc tests were used for data analysis (p>0/05. The results showed that there were significant differences between the results of the field tests and standard treadmill test (Bruce: 40.93±5.83 vs. Rockport: 58.71±2.73 and Balke: 52.09± 6.18. As a result of these findings it was concluded that the regression equations used in this study used is not suitable for 15-17 (yr boys and does not estimate their aerobic power correctly.

  20. Determinants of VO2 max decline with aging: an integrated perspective.

    Science.gov (United States)

    Betik, Andrew C; Hepple, Russell T

    2008-02-01

    Aging is associated with a progressive decline in the capacity for physical activity. Central to this decline is a reduction in the maximal rate of oxygen utilization, or VO2 max. This critical perspective examines the roles played by the factors that determine the rate of muscle oxygen delivery versus those that determine the utilization of oxygen by muscle as a means of probing the reasons for VO2 max decline with aging. Reductions in muscle oxygen delivery, principally due to reduced cardiac output and perhaps also a maldistribution of cardiac output, appear to play the dominant role up until late middle age. On the other hand, there is a decline in skeletal muscle oxidative capacity with aging, due in part to mitochondrial dysfunction, which appears to play a particularly important role in extreme old age (senescence) where skeletal muscle VO2 max is observed to decline by approximately 50% even under conditions of similar oxygen delivery as young adult muscle. It is noteworthy that at least the structural aspects of the capillary bed do not appear to be reduced in a manner that would compromise the capacity for muscle oxygen diffusion even in senescence.

  1. The band structure of VO2 measured by angle-resolved photoemission

    Science.gov (United States)

    Moreschini, Luca; Chang, Young Jun; Innocenti, Davide; Walter, Andrew L.; Kim, Young Su; Gaines, Geoffrey; Bostwick, Aaron; Denlinger, Jonathan; Rotenberg, Eli

    2011-03-01

    The origin of the 340K metal-insulator transition (MIT) in VO2 is still under debate. the main reason is that no direct experimental verifications of the electronic structure of VO2 exist up to this point. The quality of the available single crystals is not sufficient for ARPES measurements, so that photoemission is limited to angle-integrated mode. New opportunities are offered by oxide films, on which data of equal or even higher quality have been reported (Saeki et al., PRB 2009). WIth the in situ pulsed-laser-deposition (PLD) system available on beamline 7.0.1 at the Advanced Light Source we have grown VO2(001) films on a TiO2 substrate and measured the Fermi surface of the metallic phase. These results will permit a direct comparison with the existing band calculations and open the way to the study of the MIT as a function, e.g., of film thickness or electron doping with Cr. Work supported by U.S. DOE (DE-AC02-05CH11231 for ALS), the Max Planck Society, and the Swiss National Science Foundation (PBELP2-125484).

  2. Improvements in exercise performance with high-intensity interval training coincide with an increase in skeletal muscle mitochondrial content and function

    DEFF Research Database (Denmark)

    Jacobs, Robert Acton; Flueck, Daniela; Bonne, Thomas Christian

    2013-01-01

    to and again following training. Maximal measures of oxygen uptake ((V)O-2peak; similar to 8 P = 0.026) and cycling time to complete a set amount of work (similar to 5 P = 0.008) improved. Skeletal muscle respiratory capacities increased, most likely as a result of an expansion of skeletal muscle mitochondria...

  3. Children and adults exposed to electromagnetic fields at the ICNIRP reference levels: theoretical assessment of the induced peak temperature increase.

    Science.gov (United States)

    Bakker, J F; Paulides, M M; Neufeld, E; Christ, A; Kuster, N; van Rhoon, G C

    2011-08-07

    To avoid potentially adverse health effects of electromagnetic fields (EMF), the International Commission on Non-Ionizing Radiation Protection (ICNIRP) has defined EMF reference levels. Restrictions on induced whole-body-averaged specific absorption rate (SAR(wb)) are provided to keep the whole-body temperature increase (T(body, incr)) under 1 °C during 30 min. Additional restrictions on the peak 10 g spatial-averaged SAR (SAR(10g)) are provided to prevent excessive localized tissue heating. The objective of this study is to assess the localized peak temperature increase (T(incr, max)) in children upon exposure at the reference levels. Finite-difference time-domain modeling was used to calculate T(incr, max) in six children and two adults exposed to orthogonal plane-wave configurations. We performed a sensitivity study and Monte Carlo analysis to assess the uncertainty of the results. Considering the uncertainties in the model parameters, we found that a peak temperature increase as high as 1 °C can occur for worst-case scenarios at the ICNIRP reference levels. Since the guidelines are deduced from temperature increase, we used T(incr, max) as being a better metric to prevent excessive localized tissue heating instead of localized peak SAR. However, we note that the exposure time should also be considered in future guidelines. Hence, we advise defining limits on T(incr, max) for specified durations of exposure.

  4. Children and adults exposed to electromagnetic fields at the ICNIRP reference levels: theoretical assessment of the induced peak temperature increase

    Science.gov (United States)

    Bakker, J. F.; Paulides, M. M.; Neufeld, E.; Christ, A.; Kuster, N.; van Rhoon, G. C.

    2011-08-01

    To avoid potentially adverse health effects of electromagnetic fields (EMF), the International Commission on Non-Ionizing Radiation Protection (ICNIRP) has defined EMF reference levels. Restrictions on induced whole-body-averaged specific absorption rate (SARwb) are provided to keep the whole-body temperature increase (Tbody, incr) under 1 °C during 30 min. Additional restrictions on the peak 10 g spatial-averaged SAR (SAR10g) are provided to prevent excessive localized tissue heating. The objective of this study is to assess the localized peak temperature increase (Tincr, max) in children upon exposure at the reference levels. Finite-difference time-domain modeling was used to calculate Tincr, max in six children and two adults exposed to orthogonal plane-wave configurations. We performed a sensitivity study and Monte Carlo analysis to assess the uncertainty of the results. Considering the uncertainties in the model parameters, we found that a peak temperature increase as high as 1 °C can occur for worst-case scenarios at the ICNIRP reference levels. Since the guidelines are deduced from temperature increase, we used Tincr, max as being a better metric to prevent excessive localized tissue heating instead of localized peak SAR. However, we note that the exposure time should also be considered in future guidelines. Hence, we advise defining limits on Tincr, max for specified durations of exposure.

  5. A novel concept for increasing the peak sensitivity of LIGO by detuning the arm cavities

    CERN Document Server

    Hild, S

    2007-01-01

    We introduce a concept that uses detuned arm cavities to increase the shot noise limited sensitivity of LIGO without increasing the light power inside the arm cavities. Numerical simulations show an increased sensitivity between 125 and 400 Hz, with a maximal improvement of about 80% around 225 Hz, while the sensitivity above 400Hz is decreased. Furthermore our concept is found to give a sensitivity similar to that of a conventional RSE configuration with a Signal-Recycling mirror of moderate reflectivity. In the near future detuned arm cavities might be a beneficial alternative to RSE, due the potentially less hardware intensive implementation of the proposed concept.

  6. Estimation of peak oxygen uptake from maximal power output among 9-10 year-old children in Lhasa, Tibet

    DEFF Research Database (Denmark)

    Bianba, B; Berntsen, S; Andersen, Lars Bo

    2010-01-01

    Chinese children aged 9-10 years, living in Lhasa at 3700 meters above sea level, V.O2peak was measured directly using a portable oxygen analyzer, and predicted from maximal power output (Wmax) using a maximal cycle ergometer test. RESULTS: In multiple regression analyses with V.O2peak as dependent......AIM: The aims of the present study of Tibetan and Han Chinese children were to establish prediction equations for peak oxygen uptake (V.O2peak) using conventional power output measures, and to compare with prediction models based on data from sea level. METHODS: In 25 Tibetan children and 15 Han...... with the equations from the present study. None of the three could accurately predict the direct measured V.O2peak, and predictions differed in an unsystematic manner, including over- or underestimation and no differentiation between genders. CONCLUSION: Peak oxygen uptake could be estimated from Wmax and sex...

  7. Adjustment for gas exchange threshold enhances precision of heart rate-derived VO2 estimates during heavy exercise.

    Science.gov (United States)

    Pettitt, Robert W; Symons, J David; Taylor, Julie E; Eisenman, Patricia A; White, Andrea T

    2008-02-01

    Overestimates of oxygen uptake (VO2) are derived from the heart rate reserve-VO2 reserve (HRR-VO2R) model. We tested the hypothesis that adjusting for differences above and below gas exchange threshold (HRR-GET model) would tighten the precision of HR-derived VO2 estimates during heavy exercise. Seven men and 7 women of various VO2 max levels, on 2 separate days, cycled for 6 min at intensities equal to power at GET, 15% the difference between GET and VO2 max (15% above), and at 30% above GET. A second bout at 15% above GET (15% above (bout 2)) after 3 min of recovery was performed to assess estimates during interval training. Actual VO2 was compared with estimates derived from the HRR-VO2R and the HRR-GET. VO2 values were summed over the 6 min duration of data collection (6 min LO2) and compared with Bland-Altman plots. HRR-VO2R yielded 6 min LO2 (+/-2 SD) overestimates of 2.0 (+/-2.5), 1.9 (+/-2.7), and 1.3 (+/-3.3) for GET, 15% over, and 30% over, respectively, whereas corresponding 6 min LO2 difference values for the HRR-GET model were -0.42 (+/-1.6), -0.23 (+/-1.1), and -0.55 (+/-1.8), respectively. For 15% above (bout 2), the 6 min LO2 difference for HRR-VO2R was 1.8 (+/-2.9), whereas the difference for HRR-GET was 0.17 (+/-1.4). The 6 min LO2 values relative to the subjects' VO2 max did not vary (r=0.05 to 0.36); therefore, fitness level did not affect estimates. Sex did not affect accuracy of either estimate model (sex X estimate model interaction, p>0.95). We observed accurate estimates from the HRR-GET model during heavy exercise.

  8. Crossvalidation of two 20-m shuttle-run tests for predicting VO2max in female collegiate soccer players.

    Science.gov (United States)

    Green, Michael S; Esco, Michael R; Martin, Tyler D; Pritchett, Robert C; McHugh, Aindrea N; Williford, Henry N

    2013-06-01

    The aim of this study was twofold: (a) to compare the maximal attained speed (MAS) from the 20-m shuttle (MST) and 20-m square-shuttle (SST) tests and (b) to crossvalidate 2 equations for predicting maximal oxygen consumption (VO2max) that were previously developed from MST and SST in a group of female collegiate soccer players. Thirty-nine subjects (age: 20.1 ± 1.5 years) participated in the study. A maximal graded exercise treadmill test was used to measure VO2max. In addition, VO2max was predicted from the MAS obtained during MST ((pred)VO2maxMST) and SST ((pred)VO2maxSST) using previously developed equations. Measured VO2max for the group was 44.2 ± 3.3 ml·kg(-1)·min(-1). The MAS was 12.5 ± 0.6 km·h(-1) for MST and 13.3 ± 0.8 km·h(-1) for SST (p < 0.05). The prediction methods yielded a (pred)VO2maxMST of 49.6 ± 3.9 ml·kg(-1)·min(-1) and predVO2maxSST of 41.8 ± 3.1 ml·kg(-1)·min(-1), which were significantly different from measured VO2max (p < 0.05). The validity statistics revealed the following constant error (CE), correlation coefficient (r), standard error of estimate (SEE), and total error (TE) for (pred)VO2maxMST and (pred)VO2maxSST: CE = 5.35 ± 3.83, r = 0.45 (p < 0.05), SEE = 2.97 ml·kg(-1)·min(-1), TE = 6.39 ml·kg(-1)·min(-1); and CE = -2.43 ± 2.49, r = 0.69 (p < 0.05), SEE = 2.39 ml·kg(-1)·min(-1), TE = 3.43 ml·kg(-1)·min(-1), respectively. Residual plots indicated no proportional bias for either prediction model. The results of this study suggest that female collegiate soccer players had a higher MAS from SST compared with that from MST. In addition, SST appeared to be a more accurate predictor of VO2max than MST in the group of athletes.

  9. The Unified Parkinson’s Disease Rating Scale as a predictor of peak aerobic capacity and ambulatory function

    OpenAIRE

    Frederick M. Ivey, PhD; Leslie I. Katzel, MD, PhD; John D. Sorkin, MD, PhD; Richard F. Macko, MD; Lisa M. Shulman, MD

    2012-01-01

    The Unified Parkinson’s Disease Rating Scale (UPDRS) is a widely applied index of disease severity. Our objective was to assess the utility of UPDRS for predicting peak aerobic capacity (VO2 peak) and ambulatory function. Participants (n = 70) underwent evaluation for UPDRS (Total and Motor ratings), VO2 peak, 6-minute walk distance (6MW), and 30-foot self-selected walking speed (SSWS). Using regression, we determined the extent to which the Total and Motor UPDRS scores predicted each functio...

  10. Min-By-Min Respiratory Exchange and Oxygen Uptake Kinetics During Steady-State Exercise in Subjects of High and Low Max VO2

    Science.gov (United States)

    Weltman, Arthur; Katch, Victor

    1976-01-01

    No statistically meaningful differences in steady-state vo2 uptake for high and low max vo2 groups was indicated in this study, but a clear tendency was observed for the high max vo2 group to reach the steady-state at a faster rate. (MB)

  11. Structure and enhanced thermochromic performance of low-temperature fabricated VO2/V2O3 thin film

    Science.gov (United States)

    Sun, Guangyao; Cao, Xun; Gao, Xiang; Long, Shiwei; Liang, Mengshi; Jin, Ping

    2016-10-01

    For VO2-based smart window manufacture, it is a long-standing demand for high-quality thin films deposited at low temperature. Here, the thermochromic films of VO2 were deposited by a magnetron sputtering method at a fairly low temperature of 250 °C without subsequent annealing by embedding a V2O3 interlayer. V2O3 acts as a seed layer to lower the depositing temperature and buffer layer to epitaxial grow VO2 film. The VO2/V2O3 films display high solar modulating ability and narrow hysteresis loop. Our data can serve as a promising point for industrial production with high degree of crystallinity at a low temperature.

  12. Photoinduced insulator-to-metal transition and surface statistics of VO2 monitored by elastic light scattering.

    Science.gov (United States)

    Lysenko, Sergiy; Fernández, Felix; Rúa, Armando; Sepúlveda, Nelson; Aparicio, Joaquin

    2015-03-10

    Measurements of ultrafast light scattering within a hemisphere are performed for statistical analysis of nonequilibrium processes in VO2 epitaxial film. A Gerchberg-Saxton error reduction algorithm is applied for accurate calculation of a surface autocorrelation function from light scattering data and for partial reconstruction of a power spectral density function. Upon ultrafast photoinduced phase transition of VO2, the elastic light scattering reveals anisotropic grain-size-dependent dynamics. It was found that the transition rate depends on the optical absorption and orientation of VO2 grains with respect to polarization of the pump pulse. An observed stepwise evolution of surface autocorrelation length and transient anisotropy of the scattering field presumably originates from complex multistage transformation of VO2 lattice on a subpicosecond time scale.

  13. Suppression of metal-insulator transition in VO2 by electric field-induced oxygen vacancy formation

    National Research Council Canada - National Science Library

    Jeong, Jaewoo; Aetukuri, Nagaphani; Graf, Tanja; Schladt, Thomas D; Samant, Mahesh G; Parkin, Stuart S P

    2013-01-01

    .... We found that electrolyte gating of VO(2) leads not to electrostatically induced carriers but instead to the electric field-induced creation of oxygen vacancies, with consequent migration of oxygen from the oxide film into the ionic liquid...

  14. Fabrication of bristlegrass-like VO2 (B)-ZnO heteroarchitectures as anode materials for lithium-ion batteries

    Science.gov (United States)

    Ma, Yining; Li, Wenjing; Ji, Shidong; Zhou, Huaijuan; Li, Rong; Li, Ning; Yao, Heliang; Cao, Xun; Jin, Ping

    2017-08-01

    Three-dimensional bristlegrass-like hierarchical VO2 (B)-ZnO heteroarchitectures with ZnO nanorods grown radially on VO2 (B) nanorods were successfully fabricated via a simple two-step synthesized method. When applied as an anode material for lithium-ion batteries, the VO2 (B)-ZnO hybrid electrode exhibited high reversible capacity and excellent recyclability, which could be originated from the unique hierarchical structure of the bristlegrass. After 80 cycles, the nanocomposite still maintained a higher reversible capacity of 329.4 mA h g-1 at a current density of 50 mA g-1. Therefore, the particular architecture of VO2 (B)-ZnO nanocomposite can be a promising candidate as the anode material in lithium-ion batteries.

  15. Estimation of VO2max from the ratio between HRmax and HRrest--the Heart Rate Ratio Method.

    Science.gov (United States)

    Uth, Niels; Sørensen, Henrik; Overgaard, Kristian; Pedersen, Preben K

    2004-01-01

    The effects of training and/or ageing upon maximal oxygen uptake ( VO(2max)) and heart rate values at rest (HR(rest)) and maximal exercise (HR(max)), respectively, suggest a relationship between VO(2max) and the HR(max)-to-HR(rest) ratio which may be of use for indirect testing of VO(2max). Fick principle calculations supplemented by literature data on maximum-to-rest ratios for stroke volume and the arterio-venous O(2) difference suggest that the conversion factor between mass-specific VO(2max) (ml.min(-1).kg(-1)) and HR(max).HR(rest)(-1) is approximately 15. In the study we experimentally examined this relationship and evaluated its potential for prediction of VO(2max). VO(2max) was measured in 46 well-trained men (age 21-51 years) during a treadmill protocol. A subgroup ( n=10) demonstrated that the proportionality factor between HR(max).HR(rest)(-1) and mass-specific VO(2max) was 15.3 (0.7) ml.min(-1).kg(-1). Using this value, VO(2max) in the remaining 36 individuals could be estimated with an SEE of 0.21 l.min(-1) or 2.7 ml.min(-1).kg(-1) (approximately 4.5%). This compares favourably with other common indirect tests. When replacing measured HR(max) with an age-predicted one, SEE was 0.37 l.min(-1) and 4.7 ml.min(-1).kg(-1) (approximately 7.8%), which is still comparable with other indirect tests. We conclude that the HR(max)-to-HR(rest) ratio may provide a tool for estimation of VO(2max) in well-trained men. The applicability of the test principle in relation to other groups will have to await direct validation. VO(2max) can be estimated indirectly from the measured HR(max)-to-HR(rest) ratio with an accuracy that compares favourably with that of other common indirect tests. The results also suggest that the test may be of use for VO(2max) estimation based on resting measurements alone.

  16. VO2max estimation from a submaximal 1-mile track jog for fit college-age individuals.

    Science.gov (United States)

    George, J D; Vehrs, P R; Allsen, P E; Fellingham, G W; Fisher, A G

    1993-03-01

    The primary purpose of this study was to develop a submaximal field test for the estimation of maximal oxygen uptake (VO2max) using a 1-mile track jog. A second purpose was to determine the accuracy of the 1.5-mile run in estimating VO2max for both male and female subjects. VO2max was measured in 149 relatively fit college students (males = 88, females = 61) 18-29 yr using a treadmill protocol (mean +/- SD; VO2max = 47.7 +/- 6.3 ml.kg-1 x min-1). Multiple regression analysis (N = 54) to estimate VO2max from the submaximal, steady-state 1-mile track jog yielded the following validation (V) model (r(adi) = 0.87, SEE = 3.0 ml.kg-1 x min-1): VO2max = 100.5 + 8.344* GENDER (0 = female; 1 = male) - 0.1636* BODY MASS (kg) - 1.438* JOG TIME (min.mile-1) - 0.1928* HEART RATE (bpm). To help ensure that a submaximal level of exertion was realized for the 1-mile track jog, elapsed jog time was restricted to > or = 8.0 min for males and > or = 9.0 min for females and exercise HR to < or = 180 bpm. Cross-validation (CV) of the 1-mile track jog comparing observed and estimated VO2max (N = 52) resulted in radj = 0.84, SEE = 3.1 ml.kg-1 x min-1. Multiple regression analysis (N = 50) to estimate VO2max from the 1.5-mile run (V:N = 49, radj = 0.90, SEE = 2.8 ml.kg-1 x min-1; CV: N = 47, radj = 0.82, SEE = 3.9 ml.kg-1 x min-1), used elapsed run time, body mass, and gender as independent variables.(ABSTRACT TRUNCATED AT 250 WORDS)

  17. Antepartum cardiorespiratory fitness (CRF) quantification by estimation of maximal oxygen consumption (Vo2 max) in pregnant South Indian women.

    Science.gov (United States)

    Chakaravertty, Biswajit; Parkavi, K; Coumary, Sendhil A; Felix, A J W

    2012-04-01

    The aim of the study was to calculate the maximal oxygen consumption (Vo2max) for pregnant women of varying trimesters and to quantify the cardiorespiratory fitness (CRF)with the objective of being able to determine the exercise dose for antenatal women which can be prescribed to achieve optimal exercise benefits during various trimesters. A study group comprising 64 pregnant women with uncomplicated singleton pregnancy and control group with 77 non-pregnant women were subjected to Cooper's 12 minutes walk test. From the distance covered in 12 minutes, Vo2max was calculated. The Vo2max values were statistically analysed between the non-pregnant and pregnant and also its variability among the trimesters. Percentile tables of Vo2max were drawn and multiple comparisons were applied. Results show that the Vo2max values among non-pregnant and first trimester ranges between 18 and 22 ml/kg/minute. Trimesters II and III had a range of Vo2max values between 16-20 and 14-18 ml/kg/minute respectively. The CRF of pregnant women significantly reduced to 6%, 9% and 18% in each trimester respectively when compared with the reference table framed out of non-pregnant Vo2max values. Among the study group the reduction in Vo2max values had no statistical significance between first 2 trimesters but trimester III significantly differs from other trimesters. The exercise prescription cannot be the same for pregnant and non-pregnant women. Even among the pregnant women, III trimester needs separate exercise prescription from the other two trimesters as CRF is markedly compromised towards term.

  18. Initial Weekly HRV Response is Related to the Prospective Change in VO2max in Female Soccer Players.

    Science.gov (United States)

    Esco, M R; Flatt, A A; Nakamura, F Y

    2016-06-01

    The aim of this study was to determine whether the early response in weekly measures of HRV, when derived from a smartphone application, were related to the eventual change in VO2max following an off-season training program in female soccer athletes. 9 female collegiate soccer players participated in an 11-week off-season conditioning program. In the week immediately before and after the training program, each participant performed a test on a treadmill to determine maximal oxygen consumption (VO2max). Daily measures of the log-transformed root mean square of successive R-R intervals (lnRMSSD) were performed by the participants throughout week 1 and week 3 of the conditioning program. The mean and coefficient of variation (CV) lnRMSSD values of week 1 showed small (r=- 0.13, p=0.74) and moderate (r=0.57, p=0.11), respectively, non-significant correlations to the change in VO2max at the end of the conditioning program (∆VO2max). Significant and near-perfect correlation was found between the change in the weekly mean lnRMSSD values from weeks 1 and 3 (∆lnRMSSDM) and ∆VO2max (r=0.90, p=0.002). The current results have identified that the initial change in weekly mean lnRMSSD from weeks 1 to 3 of a conditioning protocol was strongly associated with the eventual adaptation of VO2max.

  19. A novel mechanism for the oxidation reaction of VO2+ on a graphite electrode in acidic solutions

    Science.gov (United States)

    Wang, Wenjun; Fan, Xinzhuang; Liu, Jianguo; Yan, Chuanwei; Zeng, Chaoliu

    2014-09-01

    With the consideration of optimizing the performance of the all-vanadium redox flow battery (VRB), the oxidation reaction mechanism of VO2+ on a rotating graphite disk electrode has been investigated by potentiodynamic polarization in sulfuric acid solutions with various pH and vanadium concentrations. Furthermore, the reaction orders of VO2+ and H+ for the oxidation reaction of VO2+ have been calculated from the polarization results and compared with the theoretical results according to the possible reaction mechanisms available in the literature. However, a new oxidation reaction mechanism has been proposed to describe the oxidation of VO2+ at last, and the theoretic reaction orders of VO2+ and H+ based on the new mechanism are consistent with the experimental results when the electrochemical reaction is the rate-limited process. Moreover, a corresponding kinetic equation has been established for the oxidation reaction of VO2+ on a spectroscopically pure graphite electrode, and can be well used to predict the polarization behavior in V (IV) acidic solutions.

  20. Applicability of an Indirect VO2max Test: Its Association with the 400 Meters Freestyle Performance

    Directory of Open Access Journals (Sweden)

    Adalberto Veronese da Costa

    Full Text Available Abstract The aim of this study was to evaluate the VO2max using a previously validated indirect test for non-expert adult swimmers and to verify its connection with the 400 meters freestyle test. A total of 17 non-expert male swimmers (21.5 ± 3.12 years were evaluated. Body composition measurements included body weight (74 ± 9.41 kg, height (172.9 ± 5.21 cm and body fat percentage (15.2 ± 4.15 %. Two tests were conducted on different days; the 400 meters freestyle (400 MF and the Progressive Swim Test (PSwT, respectively. The participant's heart rate frequency before and after the test (BHR and AHR was analyzed, as well as the subjective perception of effort (RPE, the number of laps covered (NLP, and the time of test execution measured in minutes. Significant differences were identified in all variables (p - 0.60 was found between AHR and execution time (r > - 0.70, as well as between the VO2max estimated by the PSwT and the 400 MF performance test (r > - 0.70. The Bland-Altman Plot showed that the values discovered were within the established concordance limits of 95% (±1.96 SD. A negative correlation between a swimming test and a test that estimates the VO2max occurred, and the PSwT showed results of greater approximation of the aerobic power of non-expert swimmers. In conclusion, the PSwT is applicable for non-expert adult swimmers.

  1. Optical Switching in VO2 films by below-gap excitation

    Energy Technology Data Exchange (ETDEWEB)

    Dipartimento di Fisica, Universita?di Brescia, Italy; Universite du Quebec, INRS energie et materiaux, Varennes, Quebec; Department of Physics. Clarendon Laboratory, University of Oxford, UK; Department of Physics, University of Tokyo; Institute of Physics, University of Tsukuba, Ibaraki, Japan; Cavalleri, Andrea; Rini, Matteo; Giannetti, Claudio; Fourmaux, Sylvain; Wall, Simon; Hao, Zhao; Parmigiani, Fulvio; Fujimori, Atsushi; Onoda, Masashige; Kieffer, Jean-Claude; Schoenlein, Robert W.; Cavalleri, Andrea

    2008-03-14

    We study the photo-induced insulator-metal transition in VO2, correlating threshold and dynamic evolution with excitation wavelength. In high-quality single crystal samples, we find that switching can only be induced with photon energies above the 670-meV gap. This contrasts with the case of polycrystalline films, where formation of the metallic state can also be triggered with photon energies as low as 180 meV, well below the bandgap. Perfection of this process may be conducive to novel schemes for optical switches, limiters and detectors, operating at room temperature in the mid-IR.

  2. Marrying Step Feed with Secondary Clarifier Improvements to Significantly Increase Peak Wet Weather Treatment Capacity: An Integrated Methodology.

    Science.gov (United States)

    Daigger, Glen T; Siczka, John S; Smith, Thomas F; Frank, David A; McCorquodale, J A

    2017-08-01

      The need to increase the peak wet weather secondary treatment capacity of the City of Akron, Ohio, Water Reclamation Facility (WRF) provided the opportunity to test an integrated methodology for maximizing the peak wet weather secondary treatment capacity of activated sludge systems. An initial investigation, consisting of process modeling of the secondary treatment system and computational fluid dynamics (CFD) analysis of the existing relatively shallow secondary clarifiers (3.3 and 3.7 m sidewater depth in 30.5 m diameter units), indicated that a significant increase in capacity from 416 000 to 684 000 m3/d or more was possible by adding step feed capabilities to the existing bioreactors and upgrading the existing secondary clarifiers. One of the six treatment units at the WRF was modified, and an extensive 2-year testing program was conducted to determine the total peak wet weather secondary treatment capacity achievable. The results demonstrated that a peak wet weather secondary treatment capacity approaching 974 000 m3/d is possible as long as secondary clarifier solids and hydraulic loadings could be separately controlled using the step feed capability provided. Excellent sludge settling characteristics are routinely experienced at the City of Akron WRF, raising concerns that the identified peak wet weather secondary treatment capacity could not be maintained should sludge settling characteristics deteriorate for some reason. Computational fluid dynamics analysis indicated that the impact of the deterioration of sludge settling characteristics could be mitigated and the identified peak wet weather secondary treatment capacity maintained by further use of the step feed capability provided to further reduce secondary clarifier solids loading rates at the identified high surface overflow rates. The results also demonstrated that effluent limits not only for total suspended solids (TSS) and five-day carbonaceous biochemical oxygen demand (cBOD5) could be

  3. Variação diurna e resposta da cinética do VO2 de ciclistas durante exercício muito intenso Diurnal variation and Vo2 kinetic response of cyclists during heavy exercis e

    Directory of Open Access Journals (Sweden)

    Marcos G. Santana

    2008-06-01

    Full Text Available O objetivo do presente estudo foi avaliar a influência da hora do dia nos parâmetros da cinética do consumo de oxigênio de ciclistas durante exercício muito intenso. Nove voluntários do sexo masculino realizaram exercícios de carga constante às 08:00, 13:00 e 18:00 h, em dias diferentes. Estes exercícios foram realizados duas vezes em cada visita, com um intervalo de 1 h entre eles. A intensidade usada foi de 75%Δ (75% da diferença entre o VO2 no limiar de lactato e o VO2max. A amplitude do componente primário do VO2 (2597 ± 273 ml.min-1, 2513 ± 268 ml.min-1 e 2609 ± 370 ml.min-1, a constante de tempo do componente primário do VO2 (19.3 ± 2.5 s, 18.4 ± 3.0 s e 19.7 ± 3.9 s, o componente lento do VO2 (735 ± 81 ml.min-1, 764 ± 99 ml.min-1 e 680 ± 121 ml.min-1 e o tempo de resposta média (51.8 ± 4.2 s, 51.2 ± 4.2 s e 51.4 ± 3.4 s não apresentaram diferenças significativas entre os diferentes horários do dia (08:00, 13:00 e 18:00 h, assim como os demais parâmetros da cinética do VO2. Estes resultados sugerem que a resposta da cinética do VO2 de ciclistas durante exercício muito intenso (75%Δ não é influenciada pela hora do dia.The objective of the present study was to evaluate the influence of the time of day on the parameters of oxygen uptake kinetics of trained cyclists during high intensity exercise. Nine male volunteers repeated bouts at constant loads at 08:00, 13:00 and 18:00 h on different days. These exercise bouts were performed twice on each occasion, with an interval of 1 h between them. The load intensity used was 75%Δ (75% of the difference between the VO2 at the lactate threshold and the VO2max. The primary VO2 amplitude (2597 ± 273 ml.min-1, 2513 ± 268 ml.min-1 and 2609 ± 370 ml.min-1, the primary VO2 time constant (19.3 ± 2.5 s, 18.4 ± 3.0 s and 19.7 ± 3.9 s, the VO2 slow component (735 ± 81 ml.min-1, 764 ± 99 ml.min-1 and 680 ± 121 ml.min-1 and the mean response time (51.8 ± 4.2 s, 51

  4. THE RELATIONSHIP BETWEEN AEROBIC POWER AND REPEATED SPRINT ABILITY IN YOUNG SOCCER PLAYERS WITH DIFFERENT LEVELS OF VO2 MAX

    Directory of Open Access Journals (Sweden)

    Rostam Alizadeh

    2010-06-01

    Full Text Available In some team sports such as soccer which is interval, athletes need to prepare themselves immediatelyfor the next activity. Therefore it is very important to have enough information on characteristics of recovery phase and quick recovery to the first situation and to have the minimum speed reduction. The purpose of this study was to determine the relationship between aerobic power and repeated sprint ability (RSA or decrementindex in young soccer players in three different levels of Vo2max. Methods: For this reason 41 volunteers were divided in to three groups with different levels of Vo2max ml.kg-1.min-1 low 37.22 ± 2.3 (n= 18, age 17.1 ± 0.9 year, height 170.6 ± 0.76 cm, weight 67.1 ± 5.05 kg medium 46.46± 1.97 ml.kg-1.min-1 (n= 13, age 17.6± 0.76year, height 173.8 ± 4.84 cm, weight 65.9 ± 4.92 kg and high 55.63 ± 1.52 ml.kg-1.min-1 (n=10, age 17.4 ±0.69 year, height 177 ± 3.23 cm, weight 71.4 ± 3.94 kg. To determine Vo2max a graded exercise test until volitional exhaustion on treadmill was used, and also RAST was used to measure RSA. The lactate accumulation was measured before and after RSA protocol. Pearson's correlation was used to determine the correlation between the aerobic power and RSA. The results indicated that there are significant relationship between Vo2max anddecremental index in low Vo2max group (r= 0.86, p= 0.001, no significant relationship medium Vo2max group (r= 0.14, p= 0.63 and negative significant relationship in high Vo2max group (r= - 0.64, p= 0.04. There are no significant relationship between Lactate accumulation and decremental index in medium (r= 0.005, p= 0.98 and high Vo2max groups (r=0.27, p= 0.45. Discussion: It is possible that the recovery of inter muscular resources relates to aerobic ability, but there are other factors effective in RSA rather than Vo2max and Lactate accumulation. The current study showed a normal curved relationship between Vo2max and RSA.

  5. The influence of exercise duration at VO2 max on the off-transient pulmonary oxygen uptake phase during high intensity running activity.

    Science.gov (United States)

    Billat, V L; Hamard, L; Koralsztein, J P

    2002-12-01

    The purpose of this study was to examine the influence of time run at maximal oxygen uptake (VO2 max) on the off-transient pulmonary oxygen uptake phase after supra-lactate threshold runs. We hypothesised: 1) that among the velocities eliciting VO2 max there is a velocity threshold from which there is a slow component in the VO2-off transient, and 2) that at this velocity the longer the duration of this time at VO2 max (associated with an accumulated oxygen kinetics since VO2 can not overlap VO2 max), the longer is the off-transient phase of oxygen uptake kinetics. Nine long-distance runners performed five maximal tests on a synthetic track (400 m) while breathing through the COSMED K4b2 portable, telemetric metabolic analyser: i) an incremental test which determined VO2 max, the minimal velocity associated with VO2 max (vVO2 max) and the velocity at the lactate threshold (vLT), ii) and in a random order, four supra-lactate threshold runs performed until exhaustion at vLT + 25, 50, 75 and 100% of the difference between vLT and vVO2 max (vdelta25, vdelta50, vdelta75, vdelta100). At vdelta25, vdelta50 (= 91.0 +/- 0.9% vVO2 max) and vdelta75, an asymmetry was found between the VO2 on (double exponential) and off-transient (mono exponential) phases. Only at vdelta75 there was at positive relationship between the time run at VO2 max (%tlimtot) and the VO2 recovery time constant (Z = 1.8, P = 0.05). In conclusion, this study showed that among the velocities eliciting VO2 max, vdelta75 is the velocity at which the longer the duration of the time at VO2 max, the longer is the off-transient phase of oxygen uptake kinetics. It may be possible that at vdelta50 there is not an accumulated oxygen deficit during the plateau of VO2 at VO2 max and that the duration of the time at VO2 max during the exhaustive runs at vdelta100, could be too short to induce an accumulating oxygen deficit affecting the oxygen recovery.

  6. Exercise tolerance during VO2max testing is a multifactorial psychobiological phenomenon.

    Science.gov (United States)

    Midgley, Adrian W; Earle, Keith; McNaughton, Lars R; Siegler, Jason C; Clough, Peter; Earle, Fiona

    2017-08-21

    Fifty-nine men completed a VO2max test and a questionnaire to establish reasons for test termination, perceived exercise reserve (difference between actual test duration and the duration the individual perceived could have been achieved if continued until physical limitation), and perception of verbal encouragement. Participants gave between 1 and 11 factors as reasons for test termination, including leg fatigue, various perceptions of physical discomfort, safety concerns, and achievement of spontaneously set goals. The two most common main reasons were leg fatigue and breathing discomfort, which were predicted by pre-to-post test changes in pulmonary function (p = 0.038) and explosive leg strength (p = 0.042; R(2) = 0.40). Median (interquartile range) perceived exercise reserve, was 45 (50) s. Two-thirds of participants viewed verbal encouragement positively, whereas one-third had a neutral or negative perception. This study highlights the complexity of exercise tolerance during VO2max testing and more research should explore these novel findings.

  7. Laser-processing of VO2 thin films synthesized by polymer-assisted-deposition

    Science.gov (United States)

    Breckenfeld, Eric; Kim, Heungsoo; Gorzkowski, Edward P.; Sutto, Thomas E.; Piqué, Alberto

    2017-03-01

    We investigate a novel route for synthesis and laser-sintering of VO2 thin films via solution-based polymer-assisted-deposition (PAD). By replacing the traditional solvent for PAD (water) with propylene glycol, we are able to control the viscosity and improve the environmental stability of the precursor. The solution stability and ability to control the viscosity makes for an ideal solution to pattern simple or complex shapes via direct-write methods. We demonstrate the potential of our precursor for printing applications by combining PAD with laser induced forward transfer (LIFT). We also demonstrate large-area film synthesis on 4 in. diameter glass wafers. By varying the annealing temperature, we identify the optimal synthesis conditions, obtaining optical transmittance changes of 60% at a 2500 nm wavelength and a two-order-of-magnitude semiconductor-to-metal transition. We go on to demonstrate two routes for improved semiconductor-to-metal characteristics. The first method uses a multi-coating process to produce denser films with large particles. The second method uses a pulsed-UV-laser sintering step in films annealed at low temperatures (<450° C) to promote particle growth and improve the semiconductor-to-metal transition. By comparing the hysteresis width and semiconductor-to-metal transition magnitude in these samples, we demonstrate that both methods yield high quality VO2 with a three-order-of-magnitude transition.

  8. Determinants of maximal oxygen uptake (VO2 max) in fire fighter testing.

    Science.gov (United States)

    Vandersmissen, G J M; Verhoogen, R A J R; Van Cauwenbergh, A F M; Godderis, L

    2014-07-01

    The aim of this study was to evaluate current daily practice of aerobic capacity testing in Belgian fire fighters. The impact of personal and test-related parameters on the outcome has been evaluated. Maximal oxygen uptake (VO2 max) results of 605 male fire fighters gathered between 1999 and 2010 were analysed. The maximal cardio respiratory exercise tests were performed at 22 different centres using different types of tests (tread mill or bicycle), different exercise protocols and measuring equipment. Mean VO2 max was 43.3 (SD = 9.8) ml/kg.min. Besides waist circumference and age, the type of test, the degree of performance of the test and the test centre were statistically significant determinants of maximal oxygen uptake. Test-related parameters have to be taken into account when interpreting and comparing maximal oxygen uptake tests of fire fighters. It highlights the need for standardization of aerobic capacity testing in the medical evaluation of fire fighters. Copyright © 2014 Elsevier Ltd and The Ergonomics Society. All rights reserved.

  9. Estimation of Aerobic Capacity (VO2-max and Physical Work Capacity in Laborers

    Directory of Open Access Journals (Sweden)

    Sedeghe Hosseinabadi

    2013-06-01

    Full Text Available Introduction: Measurement of Maximum aerobic capacity (VO2-max is important in physiologically fitting the laborers to the job. This study was conducted to estimate the aerobic capacity and physical work capacity (PWC of workers of galvanize department of Semnan rolling pipe Company and also determine the relative frequency of workers whom their jobs were proportional to their physical work capacity . Methods: 50 male workers of Semnan rolling pipe company were selected randomly to participate in this cross-sectional study. Tuxworth & shahnavaz methods were applied to measure instances VO2-MAX. Independent-Sample t-test and correlation technique were used to analysis the data by SPSS software. Results: Average maximum aerobic capacity of workers was 2.88± .033 liters per minute and the average of physical work capacity was 4.76 ± 0.54 kilocalories per minute. There was a significant relationship between body mass index and aerobic capacity. The result showed that 36 percent of subjects expend more energy than their physical work capacity to perform their duties during the work time. Conclusion: According to the ILO classification, the average physical work capacity of the workers fall into a category of light energy;accordingly, on average, these workers had physical ability to performe less or lighter duties. More than one-third of these workers need to undergo job modification or to change their present job to a job with less energy consumption.

  10. Efek suplementasi kombinasi zat besi, vitamin C, dan asam folat terhadap peningkatan kadar hemoglobin dan kapasitas VO2 maks pada atlet sepak bola divisi utama dan satu nasional di Daerah Istimewa Yogyakarta

    Directory of Open Access Journals (Sweden)

    Zainal Abidin

    2006-11-01

    Full Text Available Background: Excessive endurance exercise of football players may break their blood cells and decrease the level of haemoglobin (Hb. These will influence the aerobic capacity (VO2 max and make the need for iron (Fe of an athlete more than that of common people. Objective: To know the influence of Fe, vitamin C (ascorbic acid, and  folic  acid  combined supplementation to the increase of VO2 max capacity  of  the  national  main  and  first division  club football players in Daerah Istimewa Yogyakarta. Method: The study was RCT (Randomized Controlled Trial experimental with a completely randomized design plan. The subjects were football players of Perserikatan Sepak Bola Indonesia Mataram (PSIM, Perserikatan Sepak Bola Sleman (PSS, and Perserikatan Sepak Bola Bantul (PERSIBA. They were then divided into two groups: treatment group and control group, each of them consisted of 35 players. Treatment group were given combined supplement capsules of 100 mg Fe, 100 mg vitamin C, and 2 mg folic acid three times a week for eight weeks, while the control group were given the placebo capsules. Before and after supplementation, their Hb and VO2  max were measured. However, the physical exercises were done based on the schedule, programmed by the clubs. Results: Combined supplementation of Fe, vitamin C, and folic acid could increase Hb level significantly (p=0.008, but there was no significant difference of VO2  max capacity between treatment group and control group (p=0.062. However, there was significant correlation between the increase of Hb level and VO  max capacity (r=0.712; p<0.001. Conclusion: Combined supplementation of Fe, vitamin C, and folic acid led to the increase of Hb level of main and first division clubs football players in Daerah Istimewa Yogyakarta, but could not influence their VO2 max capacity.

  11. Synthesis and supercapacitor electrode of VO2(B)/C core-shell composites with a pseudocapacitance in aqueous solution

    Science.gov (United States)

    Zhang, Yifu; Zheng, Jiqi; Hu, Tao; Tian, Fuping; Meng, Changgong

    2016-05-01

    VO2(B)/C core-shell composites were successfully prepared using commercial V2O5, glucose and water as the starting materials by a facile one-pot hydrothermal method. The composition of the products was characterized by the techniques including X-ray powder diffraction, infrared spectroscopy, Raman, energy-dispersive X-ray spectrometer and elemental analysis. The morphology of the products was observed by scanning electron microscopy and transmission electron microscopy tests. The results showed the products consisted of the crystal VO2(B) phase and the amorphous carbon phase. The amorphous carbon contained lots of organic groups, such as sbnd OH, Csbnd H, Cdbnd O and Cdbnd C, etc., which suggested that the carbon here was organic carbon. The morphology of the as-obtained VO2(B)/C composites was well-defined nanobelts, and each VO2(B) core was encapsulated into carbon. Furthermore, the electrochemical properties of VO2(B)/C core-shell composites were investigated by cyclic voltammetry and galvanostatic charge-discharge. The results showed the measured capacitance of VO2(B)/C composites was mainly based on the pseudocapacitance. VO2(B)/C composites displayed the specific capacitance of 203, 190, 182, 173, 164, and 147 F g-1 at the current density of 0.2, 0.5, 1, 5, 10 and 20 A g-1, respectively. They also showed an excellent energy density of 198.9 W h kg-1 at a power density of 504.5 W kg-1 and a rapidly reversible redox Faraday response.

  12. Ratio of total carbon dioxide produced to oxygen consumed is predictive of VO2 max during graded exercise testing

    Directory of Open Access Journals (Sweden)

    DAVID BELLAR

    2016-10-01

    Full Text Available The purpose of the present investigation was to examine the ratio between total cO2 expiration and O2 consumption to vO2max. Twenty-six male (vO2 max: 55.4± 8.3 ml O2/kg*min and thirty- five female (vO2 max: 44.1± 8.1 ml O2/kg*min recreationally active adults volunteered. The participants underwent a custom ramped treadmill protocol (gXT with expired gases monitored. Third order polynomial regression was undertaken for the vO2 and vcO2 by time (r>0.950. regression equations were integrated from 60seconds after the start of the test (to negate any initial hyperventilation until vO2 max. This area under the curve calculation was equal to the total accumulated expired cO2 and consumed O2. The ratio of total cO2 to O2 was calculated (auc ratio. Data analysis was undertaken using multiple linear regression analysis. The model included gender, rer at vO2 max and auc ratio as predictors and relative vO2 max as the outcome. The model was significant with predictor variable gender (b =0.582, p<0.001 and auc ratio (b=-0.298, p=0.019 significant in the model. Based upon these results it would appear that individuals who are more fit relying more heavily on oxidative pathways throughout the course of a GXT.

  13. CLA supplementation and aerobic exercise lower blood triacylglycerol, but have no effect on peak oxygen uptake or cardiorespiratory fatigue thresholds.

    Science.gov (United States)

    Jenkins, Nathaniel D M; Buckner, Samuel L; Cochrane, Kristen C; Bergstrom, Haley C; Goldsmith, Jacob A; Weir, Joseph P; Housh, Terry J; Cramer, Joel T

    2014-09-01

    This study examined the effects of 6 weeks of conjugated linoleic acid (CLA) supplementation and moderate aerobic exercise on peak oxygen uptake (VO2 peak), the gas exchange threshold (GET), the respiratory compensation point (RCP), and serum concentrations of cholesterol, triacylglycerol, and glucose in humans. Thirty-four untrained to moderately trained men (mean ± SD; age = 21.5 ± 2.8 years; mass = 77.2 ± 9.5 kg) completed this double-blind, placebo controlled study and were randomly assigned to either a CLA (Clarinol A-80; n = 18) or placebo (PLA; sunflower oil; n = 16) group. Prior to and following 6 weeks of aerobic training (50% VO2 peak for 30 min, twice per week) and supplementation (5.63 g of total CLA isomers [of which 2.67 g was c9, t11 and 2.67 g was t10, c12] or 7.35 g high oleic sunflower oil per day), each participant completed an incremental cycle ergometer test to exhaustion to determine their [Formula: see text] peak, GET, and RCP and fasted blood draws were performed to measure serum concentrations of cholesterol, triacylglycerol, and glucose. Serum triacylglycerol concentrations were lower (p CLA than the PLA group. For VO2 peak and glucose, there were group × time interactions (p 0.05) between the CLA and PLA groups. GET and RCP increased (p CLA and PLA groups. Overall, these data suggested that CLA and aerobic exercise may have synergistic, blood triacylglycerol lowering effects, although CLA may be ineffective for enhancing aerobic exercise performance in conjunction with a 6-week aerobic exercise training program in college-age men.

  14. Efeito da intensidade do exercício de corrida intermitente 30s:15s no tempo de manutenção no ou próximo do VO2max Effect of intensity of intermittent running exercise 30s:15s at the time maintenance at or near VO2max

    OpenAIRE

    Rafael Alves de Aguiar; Jardel Schlickmann; Tiago Turnes; Fabrizio Caputo

    2013-01-01

    O presente estudo comparou o tempo mantido acima de 90% (t90VO2max) e de 95% VO2max (t95VO2max) em três diferentes intensidades de exercício. Após a realização de um teste incremental para determinar o VO2max, oito estudantes de educação física ativos (23 ± 3 anos) executaram três sessões de exercícios intermitentes (100, 110 e 120% da velocidade do VO2max (vVO2max)) com razão esforço:recuperação de 30s:15s. O t95VO2max foi significantemente maior em 110%vVO2max (EI110%) (218,1 ± 81,6 s) quan...

  15. Increasing positive ion number densities below the peak of ion-electron pair production in Titan's ionosphere

    Energy Technology Data Exchange (ETDEWEB)

    Vigren, E.; Galand, M. [Department of Physics, Imperial College London, London SW7 2AZ (United Kingdom); Shebanits, O.; Wahlund, J.-E. [Swedish Institute of Space Physics, P.O. Box 537, SE-751 21 Uppsala (Sweden); Geppert, W. D. [Department of Physics, Stockholm University, SE-10691 Stockholm (Sweden); Lavvas, P. [Groupe de Spectrométrie Moléculaire et Atmosphérique, Université Reims Champagne-Ardenne, UMR 7331, F-51687 Reims (France); Vuitton, V. [Institut de Planétologie et d' Astrophysique de Grenoble (IPAG), UJF-Grenoble/CNRS-INSU, UMR 5274, F-38041 Grenoble (France); Yelle, R. V., E-mail: erik.vigren@irfu.se [Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721-0092 (United States)

    2014-05-01

    We combine derived ion-electron pair formation rates with Cassini Radio Plasma Wave Science Langmuir Probe measurements of electron and positive ion number densities in Titan's sunlit ionosphere. We show that positive ion number densities in Titan's sunlit ionosphere can increase toward significantly lower altitudes than the peak of ion-electron pair formation despite that the effective ion-electron recombination coefficient increases. This is explained by the increased mixing ratios of negative ions, which are formed by electron attachment to neutrals. While such a process acts as a sink for free electrons, the positive ions become longer-lived as the rate coefficients for ion-anion neutralization reactions are smaller than those for ion-electron dissociative recombination reactions.

  16. Specific Intensity for Peaking: Is Race Pace the Best Option?

    Directory of Open Access Journals (Sweden)

    Munoz

    2015-09-01

    Full Text Available Background The peaking period for endurance competition is characterized for a relative increase of the intensity of training, after a longer period of training relatively dominated by lower intensity and higher volume Objectives The present study was designed to compare physiological and 10 km performance effects of high intensity training (HIT versus race pace interval training (RP during peaking for competition in well-trained runners. Patients and Methods 13 athletes took part in the study, they were divided into two groups: HIT and RP. HIT performed short intervals at ~105% of the maximal aerobic velocity (MAV, while RP trained longer intervals at a speed of ~90% of the MAV (a speed approximating 10 km race pace. After 12 weeks of baseline training, the athletes trained for 6 weeks under one of the two peaking regimes. Subjects performed 10 km prior to and after the intervention period. The total load of training was matched between groups during the treatment phase. Subjects completed a graded treadmill running test until volitional exhaustion prior to each 10 km race. MAV was determined as the minimal velocity eliciting maximal oxygen consumption (VO2max. Results Both groups significantly improved their 10 km time (35 minutes 29 seconds ± 1 minutes 41 seconds vs 34 minutes 53 seconds ± 1 minutes 55 seconds, P 0.05. In contrast, running economy decreased significantly after HIT (210 ± 6 ml.Kg-1.km-1 vs 218 ± 9, P < 0.05. Conclusions A 6 week period of training at either 105% of MAV or 90% of MAV yielded similar performance gains in a 10km race performed at ~90% MAV. Therefore, the physiological impact of HIT training seems to be positive for VO2max but negative for running economy.

  17. Suppression of Structural Phase Transition in VO2 by Epitaxial Strain in Vicinity of Metal-insulator Transition

    Science.gov (United States)

    Yang, Mengmeng; Yang, Yuanjun; Bin Hong; Wang, Liangxin; Hu, Kai; Dong, Yongqi; Xu, Han; Huang, Haoliang; Zhao, Jiangtao; Chen, Haiping; Song, Li; Ju, Huanxin; Zhu, Junfa; Bao, Jun; Li, Xiaoguang; Gu, Yueliang; Yang, Tieying; Gao, Xingyu; Luo, Zhenlin; Gao, Chen

    2016-03-01

    Mechanism of metal-insulator transition (MIT) in strained VO2 thin films is very complicated and incompletely understood despite three scenarios with potential explanations including electronic correlation (Mott mechanism), structural transformation (Peierls theory) and collaborative Mott-Peierls transition. Herein, we have decoupled coactions of structural and electronic phase transitions across the MIT by implementing epitaxial strain on 13-nm-thick (001)-VO2 films in comparison to thicker films. The structural evolution during MIT characterized by temperature-dependent synchrotron radiation high-resolution X-ray diffraction reciprocal space mapping and Raman spectroscopy suggested that the structural phase transition in the temperature range of vicinity of the MIT is suppressed by epitaxial strain. Furthermore, temperature-dependent Ultraviolet Photoelectron Spectroscopy (UPS) revealed the changes in electron occupancy near the Fermi energy EF of V 3d orbital, implying that the electronic transition triggers the MIT in the strained films. Thus the MIT in the bi-axially strained VO2 thin films should be only driven by electronic transition without assistance of structural phase transition. Density functional theoretical calculations further confirmed that the tetragonal phase across the MIT can be both in insulating and metallic states in the strained (001)-VO2/TiO2 thin films. This work offers a better understanding of the mechanism of MIT in the strained VO2 films.

  18. Coherently Coupled ZnO and VO2 Interface studied by Photoluminescence and electrical transport across a phase transition

    Science.gov (United States)

    Srivastava, Amar; Saha, S.; Annadi, A.; Zhao, Y. L.; Gopinadhan, K.; Wang, X.; Naomi, N.; Liu, Z. Q.; Dhar, S.; Herng, T. S.; Nina, Bao; Ariando, -; Ding, Jun; Venkatesan, T.

    2012-02-01

    In this work we report a study of a coherently coupled interface consisting of a ZnO layer grown on top of an oriented VO2 layer on sapphire by photoluminescence and electrical transport measurements across the VO2 metal insulator phase transition (MIT). The photoluminescence of the ZnO layer showed a broad hysteresis induced by the phase transition of VO2 while the width of the electrical hysteresis was narrow and unaffected by the over layer. The enhanced width of the PL hysteresis was due to the formation of defects during the MIT as evidenced by a broad hysteresis in the opposite direction to that of the band edge PL in the defect luminescense. Unlike VO2 the defects in ZnO did not fully recover across the phase transition. From the defect luminescence data, oxygen interstitials were found to be the predominant defects in ZnO mediated by the strain from the VO2 phase transition. Such coherently coupled interfaces could be of use in characterizing the stability of a variety of interfaces and also for novel device application.

  19. Dual-functional sensor based on switchable plasmonic structure of VO2 nano-crystal films and Ag nanoparticles.

    Science.gov (United States)

    Yi, Mingfang; Lu, Changgui; Gong, Yan; Qi, Zhengqing; Cui, Yiping

    2014-12-01

    Utilizing the insulator-metal phase transition of vanadium dioxide (VO2) crystal films, we develop a dual-functional sensor based on the coupling between VO2 nano-crystal films and Ag nanoparticles, which can probe fluorescence or Raman signals on the same substrate and it is switchable by changing temperature. At room temperature, the VO2 crystal films is insulator phase and the fluorescence signals of probe molecules (R6G) is detectable (Raman is in "off"). At high temperature (such as 85 °C), the VO2 crystal films become metallic phase. Ag nanoparticles interact with the metal phase of VO2 crystal films to produce stronger localized electric field. The stronger electric field can excite the Raman signals of probe molecules (R6G) and the coupled structure can also emit the Raman signals out efficiently (Raman is in "on"). The switchable probe of fluorescence and Raman signals would have potential applications in active photoelectric components, such as intelligent switch and multifunctional active sensor etc.

  20. Equações para a previsão da potência aeróbia (VO2 de jovens adultos brasileiros Equations for predicting aerobic power (VO2 of young Brazilian adults

    Directory of Open Access Journals (Sweden)

    Paula Magrani

    2010-06-01

    Full Text Available FUNDAMENTO: O VO2 pode ser previsto, com base em parâmetros antropométricos e fisiológicos, para determinadas populações. OBJETIVO: Propor modelos preditivos do VO2 submáximo e máximo para jovens adultos brasileiros. MÉTODOS: Os 137 voluntários (92 homens foram submetidos ao teste progressivo de esforço máximo (GXT no ciclo ergômetro (Monark®, Br. Medidas de trocas gasosas e ventilatórias foram realizadas em circuito aberto (Aerosport® TEEM 100, EUA. Em outro grupo, 13 voluntários foram submetidos ao GXT e a um teste de onda quadrada (SWT, para avaliar a validade externa das fórmulas do ACSM, de Neder et al e do nomograma de Åstrand-Ryhming. Adotou-se o delineamento experimental de validação cruzada e o nível de significância de p BACKGROUND: VO2 may be predicted with base on anthropometric and physiological parameters for determined populations. OBJECTIVE: To propose models for submaximal and maximal VO2 prediction in young Brazilian adults. METHODS: A total of 137 volunteers (92 men underwent graded maximal exercise test (GXT in a cycle ergometer (MonarkTM, Br. Gas exchange and respiratory measurements were performed in an open circuit (AerosportTM TEEM 100, USA. In another group, 13 volunteers underwent GXT and a square wave test (SWT in order to evaluate the external validity of Neder et al's formula, ACSM's formula, and of Åstrand-Ryhming nomogram. The study design chosen was a cross-validation and the significance level was set at p < 0.05. RESULTS: For men during submaximal exercises, a mathematical model was deduced with base on workload, body mass, and age, which explained 89% of the VO2 variation, with SEE (standard error of the estimate = 0.33 l.min-1. For the maximum load in the male group, another model with the same variables explained 71% of VO2 variation, with SEE = 0.40 l.min-1. For women, 93% of VO2 variation could be explained, with SEE = 0.17 l.min-1, both in submaximal and maximal exercise, with only

  1. Modifying landing mat material properties may decrease peak contact forces but increase forefoot forces in gymnastics landings.

    Science.gov (United States)

    Mills, Chris; Yeadon, Maurice R; Pain, Matthew T G

    2010-09-01

    This study investigated how changes in the material properties of a landing mat could minimise ground reaction forces (GRF) and internal loading on a gymnast during landing. A multi-layer model of a gymnastics competition landing mat and a subject-specific seven-link wobbling mass model of a gymnast were developed to address this aim. Landing mat properties (stiffness and damping) were optimised using a Simplex algorithm to minimise GRF and internal loading. The optimisation of the landing mat parameters was characterised by minimal changes to the mat's stiffness (<0.5%) but increased damping (272%) compared to the competition landing mat. Changes to the landing mat resulted in reduced peak vertical and horizontal GRF and reduced bone bending moments in the shank and thigh compared to a matching simulation. Peak bone bending moments within the thigh and shank were reduced by 6% from 321.5 Nm to 302.5Nm and GRF by 12% from 8626 N to 7552 N when compared to a matching simulation. The reduction in these forces may help to reduce the risk of bone fracture injury associated with a single landing and reduce the risk of a chronic injury such as a stress fracture.

  2. Relative Economic Merits of Storage and Combustion Turbines for Meeting Peak Capacity Requirements under Increased Penetration of Solar Photovoltaics

    Energy Technology Data Exchange (ETDEWEB)

    Denholm, Paul [National Renewable Energy Lab. (NREL), Golden, CO (United States); Diakov, Victor [National Renewable Energy Lab. (NREL), Golden, CO (United States); Margolis, Robert [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2015-09-01

    Batteries with several hours of capacity provide an alternative to combustion turbines for meeting peak capacity requirements. Even when compared to state-of-the-art highly flexible combustion turbines, batteries can provide a greater operational value, which is reflected in a lower system-wide production cost. By shifting load and providing operating reserves, batteries can reduce the cost of operating the power system to a traditional electric utility. This added value means that, depending on battery life, batteries can have a higher cost than a combustion turbine of equal capacity and still produce a system with equal or lower overall life-cycle cost. For a utility considering investing in new capacity, the cost premium for batteries is highly sensitive to a variety of factors, including lifetime, natural gas costs, PV penetration, and grid generation mix. In addition, as PV penetration increases, the net electricity demand profile changes, which may reduce the amount of battery energy capacity needed to reliably meet peak demand.

  3. Local coexistence of VO2 phases revealed by deep data analysis

    Science.gov (United States)

    Strelcov, Evgheni; Ievlev, Anton; Belianinov, Alex; Tselev, Alexander; Kolmakov, Andrei; Kalinin, Sergei V.

    2016-07-01

    We report a synergistic approach of micro-Raman spectroscopic mapping and deep data analysis to study the distribution of crystallographic phases and ferroelastic domains in a defected Al-doped VO2 microcrystal. Bayesian linear unmixing revealed an uneven distribution of the T phase, which is stabilized by the surface defects and uneven local doping that went undetectable by other classical analysis techniques such as PCA and SIMPLISMA. This work demonstrates the impact of information recovery via statistical analysis and full mapping in spectroscopic studies of vanadium dioxide systems, which is commonly substituted by averaging or single point-probing approaches, both of which suffer from information misinterpretation due to low resolving power.

  4. Role of thermal heating on the voltage induced insulator-metal transition in VO2.

    Science.gov (United States)

    Zimmers, A; Aigouy, L; Mortier, M; Sharoni, A; Wang, Siming; West, K G; Ramirez, J G; Schuller, Ivan K

    2013-02-01

    We show that the main mechanism for the dc voltage or dc current induced insulator-metal transition in vanadium dioxide VO(2) is due to local Joule heating and not a purely electronic effect. This "tour de force" experiment was accomplished by using the fluorescence spectra of rare-earth doped micron sized particles as local temperature sensors. As the insulator-metal transition is induced by a dc voltage or dc current, the local temperature reaches the transition temperature indicating that Joule heating plays a predominant role. This has critical implications for the understanding of the dc voltage or dc current induced insulator-metal transition and has a direct impact on applications which use dc voltage or dc current to externally drive the transition.

  5. Why the Heyd-Scuseria-Ernzerhof hybrid functional description of VO2 phases is not correct

    KAUST Repository

    Grau-Crespo, Ricardo

    2012-08-06

    In contrast with recent claims that the Heyd-Scuseria-Ernzerhof (HSE) screened hybrid functional can provide a good description of the electronic and magnetic structures of VO2 phases, we show here that the HSE lowest-energy solutions for both the low-temperature monoclinic (M1) phase and the high-temperature rutile (R) phase, which are obtained upon inclusion of spin polarization, are at odds with experimental observations. For the M1 phase the ground state is (but should not be) magnetic, while the ground state of the R phase, which is also spin polarized, is not (but should be) metallic. The energy difference between the low-temperature and high-temperature phases has strong discrepancies with the experimental latent heat.

  6. [Expired gas analysis--focused on VO2 max and anaerobic threshold].

    Science.gov (United States)

    Omiya, K

    1996-07-01

    Recently, expired gas analysis(EGA) during exercise testing is broadly performed. It has been recognized that anaerobic threshold(AT) and maximal oxygen uptake(VO2 max) may be useful in identifying one's exercise tolerance. AT especially has a good correlation with endurance capacity. In the field of sports medicine, the purposes of EGA are: 1) evaluation of endurance exercise capacity. 2) decision of intensity and frequency for exercise training, and 3) prevention of overtraining syndrome. In the clinical fields, EGA is frequently performed with cardiovascular patients, for example, myocardial infarction(MI), and congestive heart failure(CHF). The purposes are: 1) decision of intensity for exercise therapy with the patients of old MI. 2) evaluation of exercise capacity with the patients' of CHF. 3) index of exercise therapy for hypertension, hyperlipidemia, and diabetes, and 4) evaluation of drug effects including vasodilators and cardiotonics.

  7. The bistability phenomenon in single and coupled oscillators based on VO2 switches

    Science.gov (United States)

    Belyaev, M. A.; Putrolaynen, V. V.; Velichko, A. A.

    2017-01-01

    New operation regimes of single and coupled oscillators in circuits based on planar VO2 switches have been studied. The phenomenon of bistability is discovered, which consists in controlled switching of self-sustained oscillations by external pulses, which is a promising basis for the creation of oscillatory memory cells and implementation of pulse coupling regimes in artificial neural networks (ANNs). The duration of switch-on and switch-off pulses is no less that 20 μs and 30 ms, respectively. It is established that the region of threshold voltages for bistable switching in coupled oscillators is much wider than in a single oscillator and the hysteresis width in the former case can reach 2 V. A regime of initiation of switching packets has been observed that models the ANN packet activity.

  8. Fast hydrogen sorption from MgH2-VO2(B) composite materials

    Science.gov (United States)

    Milošević, Sanja; Kurko, Sandra; Pasquini, Luca; Matović, Ljiljana; Vujasin, Radojka; Novaković, Nikola; Novaković, Jasmina Grbović

    2016-03-01

    The hydrogen sorption kinetics of MgH2‒VO2(B) composites synthesised by mechanical milling have been studied. The microstructural properties of composites were characterized by means of X-ray diffraction (XRD), Raman spectroscopy, Scanning electron microscopy (SEM), Particle size analysis (PSD), while sorption behaviour was followed by differential scanning calorimetry (DSC) and Sievert measurements. Results have shown that although desorption temperature reduction is moderate; there is a substantial improvement in hydrogen sorption kinetics. The complete desorption of pure MgH2 at elevated temperature takes place in more than 30 min while the composite fully desorbs in less than 2 min even at lower temperatures. It has been shown that the metastable γ-MgH2 phase and the point defects have a decisive role in desorption process only in the first sorption cycle, while the second and the subsequent sorption cycles are affected by microstructural and morphological characteristics of the composite.

  9. Achieving Peak Flow and Sediment Loading Reductions through Increased Water Storage in the Le Sueur Watershed, Minnesota: A Modeling Approach

    Science.gov (United States)

    Mitchell, N. A.; Gran, K. B.; Cho, S. J.; Dalzell, B. J.; Kumarasamy, K.

    2015-12-01

    A combination of factors including climate change, land clearing, and artificial drainage have increased many agricultural regions' stream flows and rates at which channel banks and bluffs are eroded. Increasing erosion rates within the Minnesota River Basin have contributed to higher sediment-loading rates, excess turbidity levels, and increases in sedimentation rates in Lake Pepin further downstream. Water storage sites (e.g., wetlands) have been discussed as a means to address these issues. This study uses the Soil and Water Assessment Tool (SWAT) to assess a range of water retention site (WRS) implementation scenarios in the Le Sueur watershed in south-central Minnesota, a subwatershed of the Minnesota River Basin. Sediment loading from bluffs was assessed through an empirical relationship developed from gauging data. Sites were delineated as topographic depressions with specific land uses, minimum areas (3000 m2), and high compound topographic index values. Contributing areas for the WRS were manually measured and used with different site characteristics to create 210 initial WRS scenarios. A generalized relationship between WRS area and contributing area was identified from measurements, and this relationship was used with different site characteristics (e.g., depth, hydraulic conductivity (K), and placement) to create 225 generalized WRS scenarios. Reductions in peak flow volumes and sediment-loading rates are generally maximized by placing site with high K values in the upper half of the watershed. High K values allow sites to lose more water through seepage, emptying their storages between precipitation events and preventing frequent overflowing. Reductions in peak flow volumes and sediment-loading rates also level off at high WRS extents due to the decreasing frequencies of high-magnitude events. The generalized WRS scenarios were also used to create a simplified empirical model capable of generating peak flows and sediment-loading rates from near

  10. Sputtering Deposition of Sandwich-Structured V2O5/Metal (V, W)/V2O5 Multilayers for the Preparation of High-Performance Thermally Sensitive VO2 Thin Films with Selectivity of VO2 (B) and VO2 (M) Polymorph.

    Science.gov (United States)

    Liu, Hengwu; Wan, Dongyun; Ishaq, Ahmad; Chen, Lanli; Guo, Beibei; Shi, Siqi; Luo, Hongjie; Gao, Yanfeng

    2016-03-01

    For specific application to an uncooled infrared detector, VO2 thin films should have a series of characteristics including purposefully chosen polymorphs, accurate stoichiometry, phase stabilization, a high temperature-coefficient of resistance (TCR), and suitable square-resistance. This work reports controllable preparation of high-performance VO2 films via post annealing of a sandwich-structured V2O5/metal (V, W)/V2O5 multilayer precursor, which was deposited by RF magnetron sputtering. This sandwich structure can dynamically regulate oxygen contents and doping element levels in the films, enabling us to achieve accurate regulation of stoichiometry and polymorphs. The precursor films undergo a B to M phase transition depending on the quantity of the metal layers. At the thickness of the metal layer below a limitation, the resulting film after heat treatment was VO2 (B), and above the limitation, the product was VO2 (M). The optical modulation of the VO2 (M) in the near-infrared region can be tuned from 1.2 to 39.8% (ΔT2000 nm). TCR values can range from -1.89 to -4.29%/K and the square-resistances at room temperature (R0) from 69.68 to 12.63 kΩ. The simplicity in phase regulation of the present method and the superior optical and electrical properties of the films may allow its wide applications in thermo-opto-electro sensing devices.

  11. Effect of high-intensity training versus moderate training on peak oxygen uptake and chronotropic response in heart transplant recipients

    DEFF Research Database (Denmark)

    Dall, C H; Snoer, M; Christensen, S;

    2014-01-01

    In heart transplant (HTx) recipients, there has been reluctance to recommend high-intensity interval training (HIIT) due to denervation and chronotropic impairment of the heart. We compared the effects of 12 weeks' HIIT versus continued moderate exercise (CON) on exercise capacity and chronotropic...... response in stable HTx recipients >12 months after transplantation in a randomized crossover trial. The study was completed by 16 HTx recipients (mean age 52 years, 75% males). Baseline peak oxygen uptake (VO2peak ) was 22.9 mL/kg/min. HIIT increased VO2peak by 4.9 ± 2.7 mL/min/kg (17%) and CON by 2.6 ± 2.......2 mL/kg/min (10%) (significantly higher in HIIT; p HIIT, systolic blood pressure decreased significantly (p = 0.037) with no significant change in CON (p = 0.241; between group difference p = 0.027). Peak heart rate (HRpeak ) increased significantly by 4.3 beats per minute (p = 0...

  12. Convergent Validity of the One-Mile Run and PACER VO2MAX Prediction Models in Middle School Students

    Directory of Open Access Journals (Sweden)

    Ryan D. Burns

    2014-02-01

    Full Text Available FITNESSGRAM uses an equating method to convert Progressive Aerobic Cardiovascular Endurance Run (PACER laps to One-mile run/walk (1MRW times to estimate aerobic fitness (VO2MAX in children. However, other prediction models can more directly estimate VO2MAX from PACER performance. The purpose of this study was to examine the convergent validity and relative accuracy between 1MRW and various PACER models for predicting VO2MAX in middle school students. Aerobic fitness was assessed on 134 students utilizing the 1MRW and PACER on separate testing days. Pearson correlations, Bland–Altman plots, kappa statistics, proportion of agreement, and prediction error were used to assess associations and agreement among models. Correlation coefficients were strong (r ≥ .80, p .40 and agreement > .90. The results support that PACER models contain convergent validity and strong relative accuracy with the 1MRW model.

  13. The structures of interstitial hydrogen centers in VO2 in the dilute limit from their vibrational properties and theory.

    Science.gov (United States)

    Yin, Weikai; Qin, Ying; Fowler, W Beall; Stavola, Michael; Boatner, Lynn A

    2016-10-05

    The introduction of a large concentration of H into VO2 is known to suppress the insulating phase of the metal-insulator transition that occurs upon cooling below 340 K. We have used infrared spectroscopy and complementary theory to study the properties of interstitial H and D in VO2 in the dilute limit to determine the vibrational frequencies, thermal stabilities, and equilibrium positions of isolated interstitial H and D centers. The vibrational lines of several OH and OD centers were observed to have thermal stabilities similar to that of the hydrogen that suppresses the insulating phase. Theory associates two of the four possible OH configurations for Hi in the insulating VO2 monoclinic phase with OH lines seen by experiment. Furthermore, theory predicts the energies and vibrational frequencies for configurations with Hi trapped near a substitutional impurity and suggests such defects as candidates for additional OH centers that have been observed.

  14. Prediction of VO2max from a new field test based on portable indirect calorimetry.

    Science.gov (United States)

    Flouris, Andreas D; Metsios, Giorgos S; Famisis, Konstantinos; Geladas, Nikos; Koutedakis, Yiannis

    2010-01-01

    We assessed the validity and reliability of the new 15m square shuttle run test (SST) for predicting laboratory treadmill test (TT) maximal oxygen uptake (VO(2 max)) compared to the 20 m multistage shuttle run test (MST) in 45 adult males. Thirty participants performed a TT and a SST once to develop a VO( 2max) prediction model. The remaining 15 participants performed the TT and MST once and the SST twice for cross-validation purposes. Throughout testing V O(2max) was determined via portable indirect calorimetry while blood lactate concentration was assessed at the fifth recovery minute. Comparisons of TT V O(2 max) (51.3+/-3.1 ml kg(-1)min(-1)) with SST measured (51.2+/-3.2 ml kg(-1)min(-1)) and predicted (50.9+/-3.3 ml kg(-1)min(-1)) V O(2 max) showed no differences while TT blood lactate was higher compared to SST (10.3+/-1.7 mmol vs. 9.7+/-1.7 mmol, respectively). In contrast, MST measured (53.4+/-3.5 ml kg(-1)min(-1)) and predicted (57.0+/-4.5 ml kg(-1)min(-1)) V O(2 max) and blood lactate (11.2+/-2.0 mmol) were significantly higher compared to TT. No test-retest differences were detected for SST measured and predicted V O(2 max) and blood lactate. It is concluded that the SST is a highly valid and reliable predictive test for V O(2 max). Copyright (c) 2009 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

  15. ARTICLES: Nonlinear interaction of infrared waves on a VO2 surface at a semiconductor-metal phase transition

    Science.gov (United States)

    Berger, N. K.; Zhukov, E. A.; Novokhatskiĭ, V. V.

    1984-04-01

    The use of a semiconductor-metal phase transition for wavefront reversal of laser radiation was proposed. An investigation was made of nonlinear reflection of CO2 laser radiation at a phase transition in VO2. A three-wave interaction on a VO2 surface was achieved using low-power cw and pulsed CO2 lasers. In the first case, the intensity reflection coefficient was 0.5% for a reference wave intensity of 0.9 W/cm2 and in the second case, it was 42% for a threshold reference wave energy density of 0.6-0.8 mJ/cm2.

  16. 女子アスリートにおけるトレッドミル走行または歩行によるVO_2-kineticsでの運動能力の評価

    OpenAIRE

    田中, 繁宏; 垂井, 彩未; 渡辺, 好美; 廣瀬, 由美子; 四元, 美帆; 中村, 真理子

    2007-01-01

    To evaluate the exercise performance of the time constant in the VO_2-kinetics in female athletes, we made examination of VO_2 max and the oxgen uptake kinetics (VO_2) during treadmill running (seven females) or walking (eight females). In the study of the treadmill running, the time constant of the VO_2-kinetics was significantly correlated with VO_2 max. In the study of the treadmill walking, however the time constant of the VO_2-kinetics was not significantly correlated with VO_2 max. Our ...

  17. Impact of obesity and Down syndrome on peak heart rate and aerobic capacity in youth and adults.

    Science.gov (United States)

    Wee, Sang Ouk; Pitetti, Kenneth H; Goulopoulou, Styliani; Collier, Scott R; Guerra, Myriam; Baynard, Tracy

    2014-10-24

    Individuals with Down syndrome (DS) exhibit reduced aerobic capacity with reduced peak heart rate (HRpeak). This condition is often coexistent with higher level of obesity compared to individuals without DS. The purpose of this study is to investigate the effects of obesity and Down syndrome (DS) on peak heart rate (HRpeak) and peak oxygen consumption (VO2peak) in children and adults both with and without intellectual disabilities (ID)s. VO2peak and HRpeak from individualized treadmill tests on 654 individuals were analyzed. Body mass index was used to categorize individuals' weight status using standard cut-offs. DS groups had the lowest HRpeak (167bpm±14, pObesity did not affect HRpeak among adults and children with DS. VO2peak was lower among individuals with DS (25.2mL/kg/min±6.3, pObese adults with DS had lower VO2peak (24.3mL/kg/min±6.9, p=0.001) compared to the normal weight (26.7±7.1mL/kg/min) and overweight groups (27.0mL/kg/min±6.1) with DS. Conversely, in children, obesity level did not impact VO2peak in individuals with DS. Our results suggest that DS attenuates both VO2peak and HRpeak, regardless of obesity status and age group. However, obesity was associated with lower VO2peak in all adults, but not in children with DS.

  18. Influence of work-interval intensity and duration on time spent at a high percentage of VO2max during intermittent supramaximal exercise.

    Science.gov (United States)

    Wakefield, Benjamin R; Glaister, Mark

    2009-12-01

    The purpose of this study was to examine the effect of work-interval duration (WID) and intensity on the time spent at, or above, 95% VO2max (T95 VO2max) during intermittent bouts of supramaximal exercise. Over a 5-week period, 7 physically active men with a mean (+/-SD) age, height, body mass, and VO2max of 22 +/- 5 years, 181.5 +/- 5.6 cm, 86.4 +/- 11.4 kg, and 51.5 +/- 1.5 ml.kg-1.min-1, respectively, attended 7 testing sessions. After completing a submaximal incremental test on a treadmill to identify individual oxygen uptake/running velocity relationships, subjects completed a maximal incremental test to exhaustion to VO2max and subsequently (from the aforementioned relationship) the minimum velocity required to elicit VO2max (vVO2max). In a random order, subjects then carried out 3 intermittent runs to exhaustion at both 105% and 115% vVO2max. Each test used a different WID (20 s, 25 s, or 30 s) interspersed with 20-second passive recovery periods. Results revealed no significant difference in T95 vVO2max for intermittent runs at 105% versus 115% vVO2max (p = 0.142). There was, however, a significant effect (p VO2max, with WIDs of 30 seconds enabling more time relative to WIDs of 20 seconds (p = 0.018) and 25 seconds (p = 0.009). Moreover, there was an interaction between intensity and duration such that the effect of WID was magnified at the lower exercise intensity (p = 0.046). In conclusion, despite a number of limitations, the results of this investigation suggest that exercise intensities of approximately 105% vVO2max combined with WIDs greater than 25 seconds provide the best way of optimizing T95 VO2max when using fixed 20-second stationary rest periods.

  19. Airway wall stiffening increases peak wall shear stress: a fluid-structure interaction study in rigid and compliant airways.

    Science.gov (United States)

    Xia, Guohua; Tawhai, Merryn H; Hoffman, Eric A; Lin, Ching-Long

    2010-05-01

    The airflow characteristics in a computed tomography (CT) based human airway bifurcation model with rigid and compliant walls are investigated numerically. An in-house three-dimensional (3D) fluid-structure interaction (FSI) method is applied to simulate the flow at different Reynolds numbers and airway wall stiffness. As the Reynolds number increases, the airway wall deformation increases and the secondary flow becomes more prominent. It is found that the peak wall shear stress on the rigid airway wall can be five times stronger than that on the compliant airway wall. When adding tethering forces to the model, we find that these forces, which produce larger airway deformation than without tethering, lead to more skewed velocity profiles in the lower branches and further reduced wall shear stresses via a larger airway lumen. This implies that pathologic changes in the lung such as fibrosis or remodeling of the airway wall-both of which can serve to restrain airway wall motion-have the potential to increase wall shear stress and thus can form a positive feed-back loop for the development of altered flow profiles and airway remodeling. These observations are particularly interesting as we try to understand flow and structural changes seen in, for instance, asthma, emphysema, cystic fibrosis, and interstitial lung disease.

  20. Thermochromic VO2 thin films deposited by magnetron sputtering for smart window applications

    Science.gov (United States)

    Fortier, Jean-Philippe

    "Smart" windows are a perfect innovative example of technology that reduces our energy dependence and our impact on the environment while saving on the economical point of view. With the use of vanadium dioxide (VO2), a thermochromic compound, and this, as a thin coating, it would in fact be possible to control the sun's transmission of infrared light (heat) as a function of the surrounding environment temperature. In other words, its optical behavior would allow a more effective management of heat exchanges between a living venue and the outdoor environment. However, this type of window is still in a developmental stage. First, the oxide's deposition is not simple in nature. Based on a conventional deposition technique called magnetron sputtering mainly used in the fenestration industry, several factors such as the oxygen concentration and the substrate temperature during deposition can affect the coating's thermochromic behavior, and this, by changing its composition and crystallinity. Other control parameters such as the deposition rate, the pressure in the sputtering chamber and the choice of substrate may also modify the film microstructure, thereby varying its optical and electrical properties. In addition, several issues still persist as to its commercial application. For starters, the material's structural transition, related to the change of its optical properties, only occurs around 68°C. In addition, its low transparency and natural greenish colour are not visually appealing. Then, to this day, the deposition temperature required to crystallize and form the thermochromic oxide remains an obstacle for a possible large-scale application. Ultimately, although the material's change in temperature has been shown to be advantageous in situations of varying climate, the existing corrective solutions to these issues generate a deterioration of the thermochromic behavior. With no practical expertise on the material, this project was undertaken with certain

  1. Efeito da intensidade do exercício de corrida intermitente 30s:15s no tempo de manutenção no ou próximo do VO2max Effect of intensity of intermittent running exercise 30s:15s at the time maintenance at or near VO2max

    Directory of Open Access Journals (Sweden)

    Rafael Alves de Aguiar

    2013-03-01

    Full Text Available O presente estudo comparou o tempo mantido acima de 90% (t90VO2max e de 95% VO2max (t95VO2max em três diferentes intensidades de exercício. Após a realização de um teste incremental para determinar o VO2max, oito estudantes de educação física ativos (23 ± 3 anos executaram três sessões de exercícios intermitentes (100, 110 e 120% da velocidade do VO2max (vVO2max com razão esforço:recuperação de 30s:15s. O t95VO2max foi significantemente maior em 110%vVO2max (EI110% (218,1 ± 81,6 s quando comparado a 100%vVO2max (EI100% (91,9 ± 75,2s e a 120%vVO2max (EI120% (126,3 ± 29,4 s, porém sem diferença entre EI100% e EI120%. O t90VO2max somente apresentou diferença significante entre EI110% e EI120%. Portanto, conclui-se que durante exercício intermitente com razão 30s:15s, a intensidade de 110%vVO2max apresenta-se mais adequada para manter o VO2 próximo ou no VO2max por um tempo maior.The present study compared the time maintained above 90% (t90VO2max or 95% VO2max (t95VO2max in three different exercise intensities. After performing an incremental test to determine VO2max, eight physical education active students (23 ± 3 years performed three intermittent exercise sessions (100, 110 e 120% velocity of VO2max (vVO2max with ratio effort:recovery of 30s:15s. The t95%VO2max was significantly higher at 110%vVO2max (EI110% (218.1 ± 81.6s compared to 100% vVO2max (EI100% (91.9 ± 75.2s and 120%vVO2max (EI120% (126.3 ± 29.4s, but without differences between EI100% and EI120%. The t90%vVO2max was significantly different only between EI110% and 120%. Therefore, we conclude that during intermittent exercise with ratio 30s:15s, the intensity of 110%vVO2max appears more appropriate to maintain VO2max for a longer time.

  2. Graded Exercise Testing Protocols for the Determination of VO2max: Historical Perspectives, Progress, and Future Considerations.

    Science.gov (United States)

    Beltz, Nicholas M; Gibson, Ann L; Janot, Jeffrey M; Kravitz, Len; Mermier, Christine M; Dalleck, Lance C

    2016-01-01

    Graded exercise testing (GXT) is the most widely used assessment to examine the dynamic relationship between exercise and integrated physiological systems. The information from GXT can be applied across the spectrum of sport performance, occupational safety screening, research, and clinical diagnostics. The suitability of GXT to determine a valid maximal oxygen consumption (VO2max) has been under investigation for decades. Although a set of recommended criteria exists to verify attainment of VO2max, the methods that originally established these criteria have been scrutinized. Many studies do not apply identical criteria or fail to consider individual variability in physiological responses. As an alternative to using traditional criteria, recent research efforts have been directed toward using a supramaximal verification protocol performed after a GXT to confirm attainment of VO2max. Furthermore, the emergence of self-paced protocols has provided a simple, yet reliable approach to designing and administering GXT. In order to develop a standardized GXT protocol, additional research should further examine the utility of self-paced protocols used in conjunction with verification protocols to elicit and confirm attainment of VO2max.

  3. Voltage- and current-activated metal–insulator transition in VO2-based electrical switches: a lifetime operation analysis

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    Aurelian Crunteanu, Julien Givernaud, Jonathan Leroy, David Mardivirin, Corinne Champeaux, Jean-Christophe Orlianges, Alain Catherinot and Pierre Blondy

    2010-01-01

    Full Text Available Vanadium dioxide is an intensively studied material that undergoes a temperature-induced metal–insulator phase transition accompanied by a large change in electrical resistivity. Electrical switches based on this material show promising properties in terms of speed and broadband operation. The exploration of the failure behavior and reliability of such devices is very important in view of their integration in practical electronic circuits. We performed systematic lifetime investigations of two-terminal switches based on the electrical activation of the metal–insulator transition in VO2 thin films. The devices were integrated in coplanar microwave waveguides (CPWs in series configuration. We detected the evolution of a 10 GHz microwave signal transmitted through the CPW, modulated by the activation of the VO2 switches in both voltage- and current-controlled modes. We demonstrated enhanced lifetime operation of current-controlled VO2-based switching (more than 260 million cycles without failure compared with the voltage-activated mode (breakdown at around 16 million activation cycles. The evolution of the electrical self-oscillations of a VO2-based switch induced in the current-operated mode is a subtle indicator of the material properties modification and can be used to monitor its behavior under various external stresses in sensor applications.

  4. Effects of pre-exercise alkalosis on the decrease in VO2 at the end of all-out exercise.

    Science.gov (United States)

    Thomas, Claire; Delfour-Peyrethon, Rémi; Bishop, David J; Perrey, Stéphane; Leprêtre, Pierre-Marie; Dorel, Sylvain; Hanon, Christine

    2016-01-01

    This study determined the effects of pre-exercise sodium bicarbonate ingestion (ALK) on changes in oxygen uptake (VO2) at the end of a supramaximal exercise test (SXT). Eleven well-trained cyclists completed a 70-s all-out cycling effort, in double-blind trials, after oral ingestion of either 0.3 g kg(-1) of sodium bicarbonate (NaHCO3) or 0.2 g kg(-1) body mass of calcium carbonate (PLA). Blood samples were taken to assess changes in acid-base balance before the start of the supramaximal exercise, and 0, 5 and 8 min after the exercise; ventilatory parameters were also measured at rest and during the SXT. At the end of the PLA trial, which induced mild acidosis (blood pH = 7.20), subjects presented a significant decrease in VO2 (P decrease in minute ventilation (VE) during the SXT (r = 0.70, P decrease in VO2 in eleven well-trained participants (PLA:12.5 ± 2.1 % and ALK: 4.9 ± 0.9 %, P decrease in mean power output was significantly less pronounced in ALK (P decrease between PLA and ALK trials were positively related to changes in the VE decrease (r = 0.74, P 0.05). Pre-exercise alkalosis counteracted the VO2 decrease related to mild acidosis, potentially as a result of changes in VE and in muscle acid-base status during the all-out supramaximal exercise.

  5. Temperature and electric field induced metal-insulator transition in atomic layer deposited VO2 thin films

    Science.gov (United States)

    Tadjer, Marko J.; Wheeler, Virginia D.; Downey, Brian P.; Robinson, Zachary R.; Meyer, David J.; Eddy, Charles R.; Kub, Fritz J.

    2017-10-01

    Amorphous vanadium oxide (VO2) films deposited by atomic layer deposition (ALD) were crystallized with an ex situ anneal at 660-670 °C for 1-2 h under a low oxygen pressure (10-4 to 10-5 Torr). Under these conditions the crystalline VO2 phase was maintained, while formation of the V2O5 phase was suppressed. Electrical transition from the insulator to the metallic phase was observed in the 37-60 °C range, with an ROFF/RON ratio of up to about 750 and ΔTC ≅ 7-10 °C. Lateral electric field applied across two-terminal device structures induced a reversible phase change, with a room temperature transition field of about 25 kV/cm in the VO2 sample processed with the 2 h long O2 anneal. Both the width and slope of the field induced MIT I-V hysteresis were dependent upon the VO2 crystalline quality.

  6. Hydrogen-incorporation stabilization of metallic VO2(R) phase to room temperature, displaying promising low-temperature thermoelectric effect.

    Science.gov (United States)

    Wu, Changzheng; Feng, Feng; Feng, Jun; Dai, Jun; Peng, Lele; Zhao, Jiyin; Yang, Jinlong; Si, Cheng; Wu, Ziyu; Xie, Yi

    2011-09-07

    Regulation of electron-electron correlation has been found to be a new effective way to selectively control carrier concentration, which is a crucial step toward improving thermoelectric properties. The pure electronic behavior successfully stabilized the nonambient metallic VO(2)(R) to room temperature, giving excellent thermoelectric performance among the simple oxides with wider working temperature ranges.

  7. Impact of Body Composition and Vo2 Max on the Competitive Success in Top-Level Handball Players.

    Science.gov (United States)

    Ilic, Vladimir; Ranisavljev, Igor; Stefanovic, Dorde; Ivanovic, Vuk; Mrdakovic, Vladimir

    2015-09-01

    The purpose of the study was to determine the morphological and functional characteristics of 32 Serbian national U20 handball players (age 20.43 +/- 1.16 y; training experience 8.12 +/- 1.89 y) before European championship in Switzerland (2006) and to determinate their impact on competitive performance and outstanding success achieved. The results show that wing players differ from other players in morphological characteristics. Values for body height, weight, BMI, muscle mass and fat mass were significantly lower compared to the other playing positions. Extremely low values of maximal oxygen uptake (VO2 max) were measured in all players (ranged from 2.68 to 4.66 l x min(-1)). Pivots had the highest VO2 max in absolute values (3.76 l x min(-1)), and wing players in relative terms (40.83 ml x kg(-1) x min(-1)). Handball is characterized by high intensity intermittent play, followed by a number of walking breaks and quick substitutions. This makes possible to retain high playing intensity during whole match, because players can be given rest periods whenever needed. This will result in a high intensity game that does not necessarily require high VO2 max. Competitive success in modern top-level handball might be more reliant on optimal tactical preparation than on the body composition and VO2 max of an individual athlete.

  8. Graded Exercise Testing Protocols for the Determination of VO2max: Historical Perspectives, Progress, and Future Considerations

    Directory of Open Access Journals (Sweden)

    Nicholas M. Beltz

    2016-01-01

    Full Text Available Graded exercise testing (GXT is the most widely used assessment to examine the dynamic relationship between exercise and integrated physiological systems. The information from GXT can be applied across the spectrum of sport performance, occupational safety screening, research, and clinical diagnostics. The suitability of GXT to determine a valid maximal oxygen consumption (VO2max has been under investigation for decades. Although a set of recommended criteria exists to verify attainment of VO2max, the methods that originally established these criteria have been scrutinized. Many studies do not apply identical criteria or fail to consider individual variability in physiological responses. As an alternative to using traditional criteria, recent research efforts have been directed toward using a supramaximal verification protocol performed after a GXT to confirm attainment of VO2max. Furthermore, the emergence of self-paced protocols has provided a simple, yet reliable approach to designing and administering GXT. In order to develop a standardized GXT protocol, additional research should further examine the utility of self-paced protocols used in conjunction with verification protocols to elicit and confirm attainment of VO2max.

  9. Graded Exercise Testing Protocols for the Determination of VO2max: Historical Perspectives, Progress, and Future Considerations

    Science.gov (United States)

    Gibson, Ann L.; Janot, Jeffrey M.; Kravitz, Len; Dalleck, Lance C.

    2016-01-01

    Graded exercise testing (GXT) is the most widely used assessment to examine the dynamic relationship between exercise and integrated physiological systems. The information from GXT can be applied across the spectrum of sport performance, occupational safety screening, research, and clinical diagnostics. The suitability of GXT to determine a valid maximal oxygen consumption (VO2max) has been under investigation for decades. Although a set of recommended criteria exists to verify attainment of VO2max, the methods that originally established these criteria have been scrutinized. Many studies do not apply identical criteria or fail to consider individual variability in physiological responses. As an alternative to using traditional criteria, recent research efforts have been directed toward using a supramaximal verification protocol performed after a GXT to confirm attainment of VO2max. Furthermore, the emergence of self-paced protocols has provided a simple, yet reliable approach to designing and administering GXT. In order to develop a standardized GXT protocol, additional research should further examine the utility of self-paced protocols used in conjunction with verification protocols to elicit and confirm attainment of VO2max. PMID:28116349

  10. Validade preditiva da medida e estimativas do VO2máx no desempenho de Mountain Bikers

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    Fernanda Mainardi

    2015-02-01

    Full Text Available INTRODUÇÃO: considerando o racional para a utilização das equações preditivas na estimativa do VO2máxem atletas, nenhum estudo estabeleceu sua validade para o desempenho no mountain bike cross-country(XCO.OBJETIVO: comparar diferentes estratégias de determinação do VO2máx, de forma direta ou indireta, para a predição do desempenho em uma prova real e outra simulada.MÉTODOS: 20 atletas de XCO do sexo masculino (31,6 ± 6,8 anos; 68,1 ± 6,5 kg; 175,5 ± 5,7cm; 64,9 ± 4,4 mL. kg-1.min-1, foram submetidos a três sessões experimentais. A primeira visita consistiu na estratificação de risco, avaliação antropométrica e teste progressivo máximo. Na segunda, foi realizada a prova simulada e, na terceira, foi realizada a competição de XCO.RESULTADOS: a correlação entre a prova simulada e as equações preditivas do VO2máx de forma absoluta alcançaram relação quase perfeita (r ≥ 0,9. As correlações entre a competição real e as estimativas de VO2máx relativizadas à massa corporal alcançaram resultados classificados como muito altos (r = 0,7-0,89. As associações entre a medida direta do VO2máx e a simulação apresentaram uma classificação baixa para valores relativos à massa corporal (r = 0,10, IC95%-0,35 a 0,51. Para o desempenho real, a classificação foi moderada (r = 0,48, IC95% 0,009 a 0,78.CONCLUSÃO: o presente estudo foi o primeiro a demonstrar a validade preditiva das estimativas do VO2máx para o desempenho simulado e real de MTB. Em complemento, confirmou a baixa validade preditiva da medida direta do VO2máx para o mesmo propósito.

  11. Cardiorespiratory responses and prediction of peak oxygen uptake during the shuttle walking test in healthy sedentary adult men.

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    Camila D C Neves

    Full Text Available BACKGROUND: The application of the Shuttle Walking Test (SWT to assess cardiorespiratory fitness and the intensity of this test in healthy participants has rarely been studied. This study aimed to assess and correlate the cardiorespiratory responses of the SWT with the cardiopulmonary exercise testing (CEPT and to develop a regression equation for the prediction of peak oxygen uptake (VO2 peak in healthy sedentary adult men. METHODS: In the first stage of this study, 12 participants underwent the SWT and the CEPT on a treadmill. In the second stage, 53 participants underwent the SWT twice. In both phases, the VO2 peak, respiratory exchange ratio (R, and heart rate (HR were evaluated. RESULTS: Similar results in VO2 peak (P>0.05, R peak (P>0.05 and predicted maximum HR (P>0.05 were obtained between the SWT and CEPT. Both tests showed strong and significant correlations of VO2 peak (r = 0.704, P = 0.01 and R peak (r = 0.737, P0.05 was found. CONCLUSIONS: The SWT produced maximal cardiorespiratory responses comparable to the CEPT, and the developed equation showed viability for the prediction of VO2 peak in healthy sedentary men.

  12. Cardiorespiratory Responses and Prediction of Peak Oxygen Uptake during the Shuttle Walking Test in Healthy Sedentary Adult Men

    Science.gov (United States)

    Neves, Camila D. C.; Lacerda, Ana Cristina Rodrigues; Lage, Vanessa K. S.; Lima, Liliana P.; Fonseca, Sueli F.; de Avelar, Núbia C. P.; Teixeira, Mauro M.; Mendonça, Vanessa A.

    2015-01-01

    Background The application of the Shuttle Walking Test (SWT) to assess cardiorespiratory fitness and the intensity of this test in healthy participants has rarely been studied. This study aimed to assess and correlate the cardiorespiratory responses of the SWT with the cardiopulmonary exercise testing (CEPT) and to develop a regression equation for the prediction of peak oxygen uptake (VO2 peak) in healthy sedentary adult men. Methods In the first stage of this study, 12 participants underwent the SWT and the CEPT on a treadmill. In the second stage, 53 participants underwent the SWT twice. In both phases, the VO2 peak, respiratory exchange ratio (R), and heart rate (HR) were evaluated. Results Similar results in VO2 peak (P>0.05), R peak (P>0.05) and predicted maximum HR (P>0.05) were obtained between the SWT and CEPT. Both tests showed strong and significant correlations of VO2 peak (r = 0.704, P = 0.01) and R peak (r = 0.737, P0.05) was found. Conclusions The SWT produced maximal cardiorespiratory responses comparable to the CEPT, and the developed equation showed viability for the prediction of VO2 peak in healthy sedentary men. PMID:25659094

  13. Semiconductor to Metal Transition Characteristics of VO2/NiO Epitaxial Heterostructures Integrated with Si(100)

    Science.gov (United States)

    Molaei, Roya

    The novel functionalities of Vanadium dioxide (VO2), such as, several orders of magnitude transition in resistivity and IR transmittance, provide the exciting opportunity for the development of next generation memory, sensor, and field-effect based devices. A critical issue in the development of practical devices based on metal oxides is the integration of high quality epitaxial oxide thin films with the existing silicon technology which is based on silicon (100) substrates. However, silicon is not suitable for epitaxial growth of oxides owing to its tendency to readily form an amorphous oxide layer or silicide at the film-substrate interface. The oxide films deposited directly on silicon exhibit poor crystallinity and are not suitable for device applications. To overcome this challenge, appropriate substrate templates must be developed for the growth of oxide thin films on silicon substrates. The primary objective of this dissertation was to develop an integration methodology of VO2 with Si (100) substrates so they could be used in "smart" sensor type of devices along with other multifunctional devices on the same silicon chip. This was achieved by using a NiO/c- YSZ template layer deposited in situ. It will be shown that if the deposition conditions are controlled properly. This approach was used to integrate VO 2 thin films with Si (100) substrates using pulsed laser deposition (PLD) technique. The deposition methodology of integrating VO2 thin films on silicon using various other template layers will also be discussed. Detailed epitaxial relationship of NiO/c-YSZ/Si(100) heterostructures as a template to growth of VO2 as well as were studied. We also were able to create a p-n junction within a single NiO epilayer through subsequent nanosecond laser annealing, as well as established a structure-property correlation in NiO/c-YSZ/Si(100) thin film epitaxial heterostructures with especial emphasis on the stoichiometry and crystallographic characteristics. Ni

  14. Do optimal prognostic thresholds in continuous physiological variables really exist? Analysis of origin of apparent thresholds, with systematic review for peak oxygen consumption, ejection fraction and BNP.

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    Alberto Giannoni

    Full Text Available BACKGROUND: Clinicians are sometimes advised to make decisions using thresholds in measured variables, derived from prognostic studies. OBJECTIVES: We studied why there are conflicting apparently-optimal prognostic thresholds, for example in exercise peak oxygen uptake (pVO2, ejection fraction (EF, and Brain Natriuretic Peptide (BNP in heart failure (HF. DATA SOURCES AND ELIGIBILITY CRITERIA: Studies testing pVO2, EF or BNP prognostic thresholds in heart failure, published between 1990 and 2010, listed on Pubmed. METHODS: First, we examined studies testing pVO2, EF or BNP prognostic thresholds. Second, we created repeated simulations of 1500 patients to identify whether an apparently-optimal prognostic threshold indicates step change in risk. RESULTS: 33 studies (8946 patients tested a pVO2 threshold. 18 found it prognostically significant: the actual reported threshold ranged widely (10-18 ml/kg/min but was overwhelmingly controlled by the individual study population's mean pVO2 (r = 0.86, p<0.00001. In contrast, the 15 negative publications were testing thresholds 199% further from their means (p = 0.0001. Likewise, of 35 EF studies (10220 patients, the thresholds in the 22 positive reports were strongly determined by study means (r = 0.90, p<0.0001. Similarly, in the 19 positives of 20 BNP studies (9725 patients: r = 0.86 (p<0.0001. Second, survival simulations always discovered a "most significant" threshold, even when there was definitely no step change in mortality. With linear increase in risk, the apparently-optimal threshold was always near the sample mean (r = 0.99, p<0.001. LIMITATIONS: This study cannot report the best threshold for any of these variables; instead it explains how common clinical research procedures routinely produce false thresholds. KEY FINDINGS: First, shifting (and/or disappearance of an apparently-optimal prognostic threshold is strongly determined by studies' average pVO2, EF or BNP. Second

  15. Prediction of VO2max in Children and Adolescents Using Exercise Testing and Physical Activity Questionnaire Data.

    Science.gov (United States)

    Black, Nate E; Vehrs, Pat R; Fellingham, Gilbert W; George, James D; Hager, Ron

    2016-01-01

    The purpose of this study was to evaluate the use of a treadmill walk-jog-run exercise test previously validated in adults and physical activity questionnaire data to estimate maximum oxygen consumption (VO2max) in boys (n = 62) and girls (n = 66) aged 12 to 17 years old. Data were collected from Physical Activity Rating (PA-R) and Perceived Functional Ability (PFA) questionnaires, a walk-jog-run submaximal treadmill exercise test, and a maximal graded exercise test. Regression analysis resulted in the development of 2 models to predict VO2max. Submaximal exercise test data were used to build the following model (R2 = .73; SEE = 4.59 mL + kg(- 1) + min(- 1)): VO2max (mL + kg(- 1) + min(- 1)) = 26.890+(5.877 × Gender; 0 = female; 1 = male) - (0.782 × Body Mass Index [BMI])+(0.438 × PFA Score) +(2.712 × Treadmill Speed; mph) +(0.746 × Age) +(0.449 × PA-R Score). Maximal exercise test data were used to build the following model (R2 = .83; SEE = 3.63 mL + kg(- 1) + min(- 1)): VO2max (mL + kg(- 1) + min(- 1)) = 10.716+(1.334 × Maximal Treadmill Grade) +(5.203 × Treadmill Speed; mph) +(3.494 × Gender; 0 = female; 1 = male) - (0.413 × BMI) +(0.249 × PFA). The results of this study demonstrate, for the first time, that regression equations that use both exercise data and physical activity questionnaire data can accurately predict VO2max in youth. The submaximal and maximal exercise tests that use self-selected treadmill speeds can be used to assess cardiorespiratory fitness of youth with a wide range of fitness levels.

  16. Nanoscale probing of electronic band gap and topography of VO2 thin film surfaces by scanning tunneling microscopy

    Science.gov (United States)

    Yin, W.; Wolf, S.; Ko, C.; Ramanathan, S.; Reinke, P.

    2011-01-01

    The metal-insulator transition (MIT) in vanadium dioxide in the vicinity of room temperature makes it one of the most interesting materials for novel switching device applications. It is therefore essential to have a fundamental understanding of the VO2 surface when it is incorporated into multilayer structures or nanodevices. This study focuses on the surface modification of VO2 in response to the thermal treatment during phase transition. Vacuum annealing at temperatures in the vicinity of the MIT triggers a partial reduction in the surface, and thus initiates a chemical phase transition. Scanning tunneling microscopy and spectroscopy are used to investigate the electronic properties and surface structure of the VO2 thin film on (0001) sapphire substrates. Band gap maps with a high spatial resolution and single point spectroscopy I-V curves are measured as the sample is cycled through the MIT, and thus provide a direct observation of the surface phase transition at the nanoscale. The VO2 surface exhibits a homogeneous insulating behavior with a typical band gap of ˜0.5 eV at room temperature, and the surface becomes more metallic and spatially inhomogeneous in conductivity during MIT, and wide range of surface oxides can be identified. The surface still remains partially metallic after cooling down from a long period anneal, and such irreversible surface electrical change is attributed to the loss of oxygen. The location of metallic islands after thermal cycling is strongly coupled to the topography of the film, and relaxation processes and continued modification of the spatial distribution of the metallic regions are recognized on a longer timescale. The impact of film morphology, strain, surface chemistry, and structural phase transition on the electronic characteristics of VO2 surfaces are discussed.

  17. How to Be 80 Year Old and Have a VO2max of a 35 Year Old

    Directory of Open Access Journals (Sweden)

    Trine Karlsen

    2015-01-01

    Full Text Available Background. To discuss the cardiovascular and pulmonary physiology and common risk factors of an 80-year-old man with a world record maximal oxygen uptake of 50 mL·kg−1·min−1. Methods. Case report. Results. His maximal oxygen uptake of 3.31 L·min−1, maximal heart rate of 175 beats·min−1, and maximal oxygen pulse of 19 mL·beats−1 are high. He is lean (66.6 kg and muscular (49% skeletal muscle mass. His echo parameters of mitral flow (left ventricular filling, E = 82 cm·s−1 and E/A = 1.2 were normal for 40- to 60-year-old men. Systolic and diastolic function increased adequately during exercise, with no increase in left ventricular filling pressure. He has excellent pulmonary function (FVC = 4.31 L, FEV1 = 3.41, FEV1/FVC = 0.79, and DLCO = 12.0 Si1 and normal FMD and blood volumes (5.8 L. He has a high level of daily activity (10,900 steps·day−1 and 2:51 hours·day−1 of physical activity and a lifelong history of physical activity. Conclusion. The man is in excellent cardiopulmonary fitness and is highly physically active. His cardiac and pulmonary functions are above expectations for his age, and his VO2max is comparable to that of an inactive 25-year-old and of a normal, active 35-year-old Norwegian man.

  18. Knee extensor fatigue threshold is related to whole-body VO2max.

    Science.gov (United States)

    de Ruiter, Cornelis J; Maas, Ellen A; Wesseling, Mariska G H; de Haan, Arnold

    2012-07-01

    Above a given exercise intensity, rapid muscle fatigue will occur. We explored the possibility of assessing torque threshold for peripheral fatigue during single-legged repetitive isometric knee extensor exercise. We hypothesized this fatigue threshold to be related to the general aerobic fitness level and the so-called "critical torque" (CT) established with a recently validated 5-min all-out test. Seventeen healthy men (VO(2max) = 44.7-69.6 mL·kg(-1)·min(-1)) performed six submaximal (20%-55% maximal voluntary contraction [MVC]) 5-min bouts of 60 repetitive contractions (3-s on, 2-s off). Torque was changed between bouts in steps of 5% MVC to estimate the highest intensity (fatigue threshold) at which average changes in rsEMG, EMG median power frequency, and tissue deoxygenation (near-infrared spectroscopy) of the three superficial knee extensor muscles were still test torque representing CT. Fatigue threshold (40.0% ± 8.1% MVC) was related (r(2) = 0.57, P test may be used to evaluate changes in endurance capacity of single muscle groups, without the necessity for all-out testing, which could be problematic with frail subjects.

  19. Ultrafast nano-imagining of the photoinduced phase transition dynamics in VO2

    Science.gov (United States)

    Doenges, Sven A.; Khatib, Omar; O'Callahan, Brian T.; Atkin, Joanna M.; Park, Jae Hyung; Cobden, David H.; Raschke, Markus B.

    Many quantum phase transitions in correlated matter exhibit spatial inhomogeneities with expected yet unexplored effects on the associated ultrafast dynamics. Here we demonstrate the combination of ultrafast non-degenerate pump-probe spectroscopy with scattering scanning near-field optical microscopy (s-SNOM) for ultrafast nano-imaging. In a femtosecond near-field non-degenerate near-IR (NIR) pump and mid-IR (MIR) probe experiment, we study the photoinduced insulator-to-metal (IMT) transition in nominally homogeneous VO2 micro-crystals using far-from equilibrium excitation. We observe spatial heterogeneity on 50-100 nm length scales in the fluence dependent IMT dynamics, ranging from sub-100 fs to 1 ps. With pump fluences as high as nominally 10 mJ/cm2 we can reach distinct excitation and saturation regimes. These results suggest a large sensitivity of the IMT with respect to local variations in strain, doping, or defects difficult to discern microscopically.

  20. Optical properties of correlated materials: Generalized Peierls approach and its application to VO2

    Science.gov (United States)

    Tomczak, Jan M.; Biermann, Silke

    2009-08-01

    The aim of this paper is to present a versatile scheme for the computation of optical properties of solids, with particular emphasis on realistic many-body calculations for correlated materials. Geared at the use with localized basis sets, we extend the commonly known lattice “Peierls substitution” approach to the case of multiatomic unit cells. We show in how far this generalization can be deployed as an approximation to the full Fermi-velocity matrix elements that enter the continuum description of the response of a solid to incident light. We further devise an upfolding scheme to incorporate optical transitions that involve high-energy orbitals that had been downfolded in the underlying many-body calculation of the electronic structure. As an application of the scheme, we present results on a material of longstanding interest, vanadium dioxide, VO2 . Using dynamical mean-field data of both, the metallic and the insulating phase, we calculate the corresponding optical conductivities, elucidate optical transitions and find good agreement with experimental results.

  1. Crystal structure and spectroscopic properties of Na2K6(VO)(2)(SO4)7

    DEFF Research Database (Denmark)

    Karydis, D.A.; Boghosian, S.; Nielsen, Kurt;

    2002-01-01

    Red-brown crystals of a new mixed alkali oxo sulfato vanadium(V) compound Na2K6(VO)(2)(SO4)(7), suitable for X-ray determination, have been obtained from the catalytically important binary molten salt system M2S2O7-V2O5 (M = 80% K and 20% Na). By slow cooling of a mixture with the mole fraction X...... equatorial V-O bonds in the range 1.881(6)-1.960-(6) A. The deformation of the VO6 octahedron is less pronounced compared to that of the known oxo sulfato V(V) compounds. Each VO3+ group is coordinated to five sulfate groups of which two are unidentately coordinated and three are bidentate bridging...... to neighboring VO3+ groups. The length of the S-O bonds in the S-O-V bridges of the two unidentately coordinated sulfato groups are 1.551(6) Angstrom and 1.568(6) Angstrom, respectively, which are unusually long compared to our earlier measurements of sulfate groups in other V(111), V(IV), and V(V) compounds....

  2. Predicting Thin Film Stoichiometry In V-O2 Reactive Sputtering

    Directory of Open Access Journals (Sweden)

    He Yu

    2015-06-01

    Full Text Available The electrical, optical and mechanical properties of compound oxides film depend strongly on the composition of the film, especially for vanadium oxide thin films, since the vanadium-oxygen phase diagram includes mixed valence oxides with two or more oxidation states. Therefore, it is interesting to predict the film stoichiometry in VOx films. However, it has not, to any great extent yet, been possible to predict the composition of vanadium oxides films. In this article, we present a model that enables us to predict film composition of vanadium oxides prepared by reactive sputtering. Based on this model, the fraction ratio of V, V2O3, VO2 and V2O5 in the substrate surface as a function of oxygen flow is investigated. It is concluded that the presented theoretical model for the involved reactions and composition of VOx thin film during reactive sputtering process is in qualitative agreement with the XPS results from experiment and can be used to find optimum processing conditions for deposition of films of a desired composition.DOI: http://dx.doi.org/10.5755/j01.ms.21.2.6910

  3. Structural and electrical properties of large area epitaxial VO2 films grown by electron beam evaporation

    Science.gov (United States)

    Théry, V.; Boulle, A.; Crunteanu, A.; Orlianges, J. C.; Beaumont, A.; Mayet, R.; Mennai, A.; Cosset, F.; Bessaudou, A.; Fabert, M.

    2017-02-01

    Large area (up to 4 squared inches) epitaxial VO2 films, with a uniform thickness and exhibiting an abrupt metal-insulator transition with a resistivity ratio as high as 2.85 × 10 4 , have been grown on (001)-oriented sapphire substrates by electron beam evaporation. The lattice distortions (mosaicity) and the level of strain in the films have been assessed by X-ray diffraction. It is demonstrated that the films grow in a domain-matching mode where the distortions are confined close to the interface which allows growth of high-quality materials despite the high film-substrate lattice mismatch. It is further shown that a post-deposition high-temperature oxygen annealing step is crucial to ensure the correct film stoichiometry and provide the best structural and electrical properties. Alternatively, it is possible to obtain high quality films with a RF discharge during deposition, which hence do not require the additional annealing step. Such films exhibit similar electrical properties and only slightly degraded structural properties.

  4. Evaluation of Electrocardiographic T-peak to T-end Interval in Subjects with Increased Epicardial Fat Tissue Thickness

    Directory of Open Access Journals (Sweden)

    Ozgur Kaplan

    2015-01-01

    Full Text Available AbstractBackground:The association between periatrial adiposity and atrial arrhythmias has been shown in previous studies. However, there are not enough available data on the association between epicardial fat tissue (EFT thickness and parameters of ventricular repolarization. Thus, we aimed to evaluate the association of EFT thickness with indices of ventricular repolarization by using T-peak to T-end (Tp-e interval and Tp-e/QT ratio.Methods:The present study included 50 patients whose EFT thickness ≥ 9 mm (group 1 and 40 control subjects with EFT thickness < 9 mm (group 2. Transthoracic echocardiographic examination was performed in all participants. QT parameters, Tp-e intervals and Tp-e/QT ratio were measured from the 12-lead electrocardiogram.Results:QTd (41.1 ± 2.5 vs 38.6 ± 3.2, p < 0.001 and corrected QTd (46.7 ± 4.7 vs 43.7 ± 4, p = 0.002 were significantly higher in group 1 when compared to group 2. The Tp-e interval (76.5 ± 6.3, 70.3 ± 6.8, p < 0.001, cTp-e interval (83.1 ± 4.3 vs. 76±4.9, p < 0.001, Tp-e/QT (0.20 ± 0.02 vs. 0.2 ± 0.02, p < 0.001 and Tp-e/QTc ratios (0.2 ± 0.01 vs. 0.18 ± 0.01, p < 0.001 were increased in group 1 in comparison to group 2. Significant positive correlations were found between EFT thickness and Tp-e interval (r = 0.548, p < 0.001, cTp-e interval (r = 0.259, p = 0.01, and Tp-e/QT (r = 0.662, p < 0.001 and Tp-e/QTc ratios (r = 0.560, p < 0.001.Conclusion:The present study shows that Tp-e and cTp-e interval, Tp-e/QT and Tp-e/QTc ratios were increased in subjects with increased EFT, which may suggest an increased risk of ventricular arrhythmia.

  5. Cardiorespiratory Fitness and Peak Torque Differences between Vegetarian and Omnivore Endurance Athletes: A Cross-Sectional Study

    OpenAIRE

    Lynch, Heidi M.; Wharton, Christopher M; Johnston, Carol S

    2016-01-01

    In spite of well-documented health benefits of vegetarian diets, less is known regarding the effects of these diets on athletic performance. In this cross-sectional study, we compared elite vegetarian and omnivore adult endurance athletes for maximal oxygen uptake (VO2 max) and strength. Twenty-seven vegetarian (VEG) and 43 omnivore (OMN) athletes were evaluated using VO2 max testing on the treadmill, and strength assessment using a dynamometer to determine peak torque for leg extensions. Die...

  6. A Reference Equation for Normal Standards for VO2 max: Analysis from the Fitness Registry and the Importance of Exercise National Database (FRIEND Registry).

    Science.gov (United States)

    Myers, Jonathan; Kaminsky, Leonard A; Lima, Ricardo; Chistle, Jeffrey; Ashley, Euan; Arena, Ross

    2017-04-01

    Existing normal standards for maximal oxygen uptake (VO2 max) are problematic because they tend to be population specific, lack normal distribution and portability, and are poorly represented by women. The objective of the current study was to apply the Fitness Registry and the Importance of Exercise: A National Data Base (FRIEND) Registry to improve upon previous regression formulas for normal standards for VO2 max using treadmill testing. Maximal treadmill tests were performed in 7783 healthy men and women (20-79years; maximal RER >1.0) from the FRIEND registry and a separate validation cohort of 1287 subjects. A regression equation for VO2 max was derived from the FRIEND registry and compared to the validation cohort and two commonly used equations (Wasserman and European). Age, gender, and body weight were the only significant predictors of VO2 max (multiple R=0.79, R(2)=0.62, p<0.001). The equation for predicting VO2 max was: [Formula: see text] Marked differences were observed in percentage predicted VO2 max achieved between commonly used reference equations, particularly among women, overweight and obese subjects. In the validation sample, the FRIEND equation closely paralleled measured VO2 max, with the validation group yielding a percent predicted VO2 max of 100.4% based on the FRIEND equation. An equation for age-predicted VO2 max derived from the FRIEND registry provided a lower average error between measured and predicted VO2 max than traditional equations, and thus may provide a more suitable normal standard relative to traditional equations.

  7. Physiological strain during kitchen work in relation to maximal and task-specific peak values.

    Science.gov (United States)

    Aminoff, T; Smolander, J; Korhonen, O; Louhevaara, V

    1999-04-01

    Six female and three male subjects from a hospital kitchen volunteered for the study. The subjects were working on a conveyor belt collecting and sorting dirty plates, glasses and cutlery for cleaning. In the study, a medical examination, a maximal clinical exercise test with a 12-lead electrocardiogram (ECG) and a maximal arm cranking test were performed in the laboratory. Further, each subject was studied for 30 min during a normal work shift in the kitchen. Oxygen uptake (VO2) and heart rate (HR) were continuously registered. During the work period, a rating of perceived exertion (RPE) was asked at the 5th, 15th and 30th minute. Physiological responses were measured by a portable system (K4) both in the laboratory and in the field. VO2 and HR measured in the field were proportioned to corresponding maximal values during cycling and to peak values during arm-cranking. The mean VO2 for the male and the female subjects during kitchen work was 0.65 +/- 0.16 l min-1. This corresponded to 24% of VO2max and to 41% of VO2peak during arm-cranking. The difference was significant (p < 0.001). Owing to a magnetic field at the conveyor belt, reliable HR values were obtained only from the female subjects. The mean HR during work among the female subjects was 101 beats min-1. It corresponded to 55% of HRmax and 67% of HRpeak during arm-cranking (p < 0.05). The present study shows that the relative work intensity is markedly higher when it is expressed relative to the corresponding muscle group's VO2peak instead of the VO2max. Similar difference was also seen in the HR response. More task-specific testing of physical capacity may provide improved evaluation of physical strain in a job.

  8. High prevalence of false-positive plateau phenomena during VO2max testing in adolescents.

    Science.gov (United States)

    Beltrami, Fernando G; Wong, Del P; Noakes, Timothy D

    2014-09-01

    It is believed that a plateau in oxygen consumption (VO2) at the end of an incremental exercise test identifies the upper limits of cardiovascular capacity. We investigated how different criteria influence the frequency with which the "plateau phenomenon" is detected and the prevalence at which "false" plateau phenomena occurs during sub-maximal exercise. Cross-sectional. Six different criteria with 3 different sampling intervals each were used to identify the "plateau phenomenon" from a single data set comprising 63 incremental exercise tests along with secondary criteria based on target heart rate (HR) and respiratory exchange ratio (RER). A single criterion from the original 18 (HALF) was also used to detect the incidence of any plateau phenomena during each test. The plateau phenomenon was detected in 16-82% of the tests depending on the criteria used, mostly as a result of the different sampling intervals. HALF identified 103 "plateau phenomena" but 73 (70.9%) of these occurred during sub-maximal exercise and so were "false". "False" plateaus were verified by at least one secondary criterion in 27% of cases. Participants reached the HR and RER targets after 83.6 ± 11.7% and 81.9 ± 18.1% of total test duration, respectively. The wide range in the percentage of plateau phenomena detected by different criteria plus the high rate (71%) of "false" plateau during sub-maximal exercise could indicate that this phenomenon is a calculation artifact rather than an indicator of true physiological events. Secondary criteria can be reached early in exercise and often identify "false" plateau phenomena as "true". Copyright © 2013 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

  9. Effects of acute inhalation of albuterol on submaximal and maximal VO2 and blood lactate.

    Science.gov (United States)

    Fleck, S J; Lucia, A; Storms, W W; Wallach, J M; Vint, P F; Zimmerman, S D

    1993-07-01

    The acute effects of inhaled albuterol, a selective beta-2 adrenergic agonist, on measures of endurance cycling performance and pulmonary function were assessed in 21 competitive road cyclists. A 5 step methacholine challenge revealed all cyclists to be non-asthmatic. Albuterol (A) total dose 360 micrograms or a saline placebo (P) was administered by inhaler, in 4 metered doses of 90 micrograms each, 15 minutes before cycle ergometry exercise. Heart rate, whole blood lactate, perceived exertion and VO2 were determined at the submaximal workloads of 150, 200, 225, 250, 275, 300 watts and at max. Pulmonary function tests determining forced vital capacity, forced expiratory volume during the first second of expiration, forced mid-expiratory flow and maximal voluntary ventilation were performed prior to and 10 minutes after inhalation; and 5, 10 and 15 minutes after termination of the exercise protocol. Heart rate was significantly greater during the A compared to the P treatment at 200 (150.8 +/- 2.5 vs 146.7 +/- 2.8 beats per minute), 225 (159.7 +/- 2.4 vs 154.6 +/- 2.7 beats per minute) and 250 watts (166.9 +/- 2.4 vs 164.4 +/- 2.6 beats per minute). Whole blood lactate was significantly greater during the A compared to the P treatment at 275 watts (4.7 +/- 0.3 vs 4.2 +/- 0.4 mmol.l-1). No other significant differences were found between the 2 treatments at any time point. These data indicate that the acute effect of albuterol inhalation at twice the recommended dosage has no positive effect on endurance performance measures or pulmonary function in athletes who are not asthmatic.

  10. Cardiac rehabilitation increases physical capacity but not mental health after heart valve surgery

    DEFF Research Database (Denmark)

    Sibilitz, Kirstine L.; Berg, Selina K.; Rasmussen, Trine B.

    2016-01-01

    -educational consultations (intervention) versus usual care without structured physical exercise or psycho-educational consultations (control). Primary outcome was physical capacity measured by VO2 peak and secondary outcome was self-reported mental health measured by Short Form-36. Results: 76% were men, mean age 62 years.......40) or the exploratory physical and mental outcomes. Cardiac rehabilitation increased the occurrence of self-reported non-serious adverse events (11/72 vs 3/75, p=0.02). Conclusions: Cardiac rehabilitation after heart valve surgery significantly improves VO2 peak at 4 months but has no effect on mental health and other......, with aortic (62%), mitral (36%) or tricuspid/pulmonary valve surgery (2%). Cardiac rehabilitation compared with control had a beneficial effect on VO2 peak at 4 months (24.8 mL/kg/min vs 22.5 mL/kg/min, p=0.045) but did not affect Short Form-36 Mental Component Scale at 6 months (53.7 vs 55.2 points, p=0...

  11. Effects of exercise mode on the peak oxygen uptake and blood lactate response in boys aged 11-12 years

    Directory of Open Access Journals (Sweden)

    Fabiana Andrade Machado

    2006-09-01

    Full Text Available The objective of this study was to analyze the effects of exercise mode (running x cycling on the indexesrelated to aerobic fitness (VO2peak and blood lactate response to exercise in children. Participated of this study 20 active boys apparently healthy (age = 11.48 + 0.41 yr.; body mass = 41.38 + 10.45 kg; stature = 147.45 + 6.56 cm, with sexual maturational level 1 and 2 (pubic hair, which performed two incremental tests, with stages of 3 minutes until voluntary exhaustion, in treadmill (TR and cycle ergometer (CE, to the determination of peak oxygen uptake (VO2peak and lactate threshold (LT. The VO2peak was determined through the higher value obtained at intervals of 15 seconds. The LT was determined as the exercise intensity where the first and sustained increase of blood lactate above rest level occurred. The VO2peak (45.16 + 5.98 x 42.93 + 7.51 ml/kg/min, maximal heart rate (196.5 + 6.98 x 187.3 + 9.27 bpm, VO2 at LL (31.82 + 10.09 x 25.19 + 7.36 ml/kg/min and HR at LL (150.5 + 17.75 x 131.3 + 12.98 bpm were significantly higher in TR than CE, respectively. Thus, similar to adults, boys of 11 to 12 years present higher aerobic indexes (submaximal and maximal in running than cycling, which can haveimportant implications for healthy professionals that utilize exercise for the healthy promotion, rehabilitation and experimental designs. RESUMO O objetivo deste estudo foi analisar os efeitos do modo de exercício (corrida x ciclismo sobre os índices relacionados com a aptidão aeróbia (VO2pico e resposta de lactato ao exercício em crianças. Participaram doestudo 20 meninos, aparentemente saudáveis e ativos (idade = 11,48 + 0,41 anos; massa corporal = 41,38 + 10,45 kg; estatura = 147,45 + 6,56 cm, com níveis de maturação sexual 1 e 2 (pilosidade pubiana, que realizaram dois testes incrementais, com estágios de 3 minutos até a exaustão voluntária, em esteira rolante (ER e bicicleta ergométrica (BE, para a determinação do pico do

  12. Dynamically tracking the joule heating effect on the voltage induced metal-insulator transition in VO2 crystal film

    Directory of Open Access Journals (Sweden)

    G. M. Liao

    2016-04-01

    Full Text Available Insulator to metal phase transitions driven by external electric field are one of the hottest topics in correlated oxide study. While this electric triggered phenomena always mixes the electric field switching effect and joule thermal effect together, which are difficult to clarify the intrinsic mechanism. In this paper, we investigate the dynamical process of voltage-triggered metal-insulator transition (MIT in a VO2 crystal film and observe the temperature dependence of the threshold voltages and switching delay times, which can be explained quite well based on a straightforward joule thermal model. By conducting the voltage controlled infrared transmittance measurement, the delayed infrared transmission change is also observed, further confirming the homogeneous switching process for a large-size film. All of these results show strong evidences that joule thermal effect plays a dominated role in electric-field-induced switching of VO2 crystal.

  13. Dynamically tracking the joule heating effect on the voltage induced metal-insulator transition in VO2 crystal film

    Science.gov (United States)

    Liao, G. M.; Chen, S.; Fan, L. L.; Chen, Y. L.; Wang, X. Q.; Ren, H.; Zhang, Z. M.; Zou, C. W.

    2016-04-01

    Insulator to metal phase transitions driven by external electric field are one of the hottest topics in correlated oxide study. While this electric triggered phenomena always mixes the electric field switching effect and joule thermal effect together, which are difficult to clarify the intrinsic mechanism. In this paper, we investigate the dynamical process of voltage-triggered metal-insulator transition (MIT) in a VO2 crystal film and observe the temperature dependence of the threshold voltages and switching delay times, which can be explained quite well based on a straightforward joule thermal model. By conducting the voltage controlled infrared transmittance measurement, the delayed infrared transmission change is also observed, further confirming the homogeneous switching process for a large-size film. All of these results show strong evidences that joule thermal effect plays a dominated role in electric-field-induced switching of VO2 crystal.

  14. Optical and electrical studies of possible VO2 thin film nanostructures grown using laser ablated V2O5

    Science.gov (United States)

    Zinzuvadiya, Sushant; Joshi, U. S.

    2017-05-01

    The metal insulator transition (MIT) has been a focus of study for many years to researchers as the results are expected to help its future device applications in electronics. VO2 in its pure crystalline phase exhibit reversible MIT at about 68 °C, making it promising for memory based devices. Due to the multivalent nature of vanadium, synthesis of stoichiometric VO2 is a challenge. In this communication, we report the results of electrical and surface structural studies of Vanadium Oxide thin film nanostructures. The films were prepared using Pulsed Laser Deposition (PLD) Technique on quartz substrates. XRD revealed single orthorhombic phase. A smooth surface topography showing 58 nm average grain size with highly mono-dispersed grain distribution as studied by Atomic Force Microscopy (AFM). The temperatures dependant resistance measurements exhibited a clear and reversible MIT near 280° C. The band-gap was estimated to be 3.5 eV using the UV-Vis. spectroscopy.

  15. Specificity of VO2MAX and the ventilatory threshold in free swimming and cycle ergometry: comparison between triathletes and swimmers.

    Science.gov (United States)

    Roels, B; Schmitt, L; Libicz, S; Bentley, D; Richalet, J-P; Millet, G

    2005-12-01

    To compare maximal heart rate (HRmax), maximal oxygen consumption (VO2MAX), and the ventilatory threshold (VT; %VO2MAX) during cycle ergometry and free swimming between swimmers and triathletes. Nine swimmers and ten triathletes completed an incremental swimming and cycling test to exhaustion. Whole body metabolic responses were determined in each test. The swimmers exhibited a significantly higher VO2MAX in swimming than in cycling (58.4 (5.6) v 51.3 (5.1) ml/kg/min), whereas the opposite was found in the triathletes (53.0 (6.7) v 68.2 (6.8) ml/kg/min). HRmax was significantly different in the maximal cycling and swimming tests for the triathletes (188.6 (7.5) v 174.8 (9.0) beats/min). In the maximal swimming test, HRmax was significantly higher in the swimmers than in the triathletes (174.8 (9.0) v 184.6 (9.7) beats/min). No significant differences were found for VT measured in swimming and cycling in the triathletes and swimmers. This study confirms that the exercise testing mode affects the VO2MAX value, and that swimmers have very specific training adaptations even compared with triathletes. This may be a function of acute physiological responses combined with the specialist training status of the different athletes influencing maximal cardiac output or oxygen extraction. In contrast, the different training regimens do not seem to influence the VT, as this variable did not differ between the two testing modes in either group.

  16. Relationship between velocity reached at VO2(max) and time-trial performances in elite Australian Rules footballers.

    Science.gov (United States)

    Lorenzen, Christian; Williams, Morgan D; Turk, Paul S; Meehan, Daniel L; Kolsky, Daniel J Cicioni

    2009-09-01

    Running velocity reached at maximal oxygen uptake (vVO2(max)) can be a useful measure to prescribe training intensity for aerobic conditioning. Obtaining it in the laboratory is often not practical, and average velocities from time trials are an attractive alternative. To date, the efficacies of such practices for team sport players are unknown. This study aimed to assess the relationship between vVO2(max) obtained in the laboratory against two time-trial estimates (1500 m and 3200 m). During the early preseason, elite Australian Rules football players (n = 23, 22.7 +/- 3.4 y, 187.7 +/- 8.2 cm, 75.5 +/- 9.2 kg) participated in a laboratory test on a motorized treadmill and two outdoor time trials. Based on average velocity the 1500-m time-trial performance (5.01 +/- 0.23 m x s(-1)) overestimated (0.36 m x s(-1), d = 1.75), whereas the 3200-m time trial (4.47 +/- 0.23 m x s(-1)) underestimated (0.17 m x s(-1), d = 0.83) the laboratory vVO2(max) (4.64 +/- 0.18 m x s(-1)). Despite these differences, both 1500-m and 3200-m time-trial performances correlated with the laboratory measure (r = -0.791; r = -0.793 respectively). Both subsequent linear regressions were of good fit and predicted the laboratory measure within +/- 0.12 m x s(-1). Estimates of vVO2(max) should not be used interchangeably, nor should they replace the laboratory measure. When laboratory testing is not accessible for team sports players, prescription of training intensity may be more accurately estimated from linear regression based on either 1500-m or 3200-m time-trial performance than from the corresponding average velocity.

  17. EPR and optical studies of VO2+ doped potassium succinate-succinic acid single crystal - Substitutional incorporation

    Science.gov (United States)

    Juliet sheela, K.; Radha Krishnan, S.; Shanmugam, V. M.; Subramanian, P.

    2017-03-01

    EPR and optical absorption studies of VO2+ doped potassium succinate-succinic acid (KSSA) single crystal has been examined at room temperature. EPR spectrum shows that well resolved hyperfine lines. The angular variation of the EPR spectra has shown that two different VO2+ complexes are located in different chemical environments. Among the number of sites, two sites have been followed and reported here. From the EPR analysis, spin Hamiltonian parameters g and A tensors and their directional cosines are evaluated. Both the sites experience rhombic crystal field symmetry around the impurity ion. The VO2+ ion entering the site location of potassium ion has coordination of eight oxygen atoms in a distorted dodecahedral arrangement. The Optical absorption spectrum studied at room temperature shows bands corresponding to C4v symmetry. The crystal field parameter and tetragonal field parameters are calculated. From the Optical and EPR data various molecular orbital coefficients are evaluated and the nature of bonding in the crystal is discussed.

  18. Mesoscopic structural phase progression in photo-excited VO2 revealed by time-resolved x-ray diffraction microscopy

    Science.gov (United States)

    Zhu, Yi; Cai, Zhonghou; Chen, Pice; Zhang, Qingteng; Highland, Matthew J.; Jung, Il Woong; Walko, Donald A.; Dufresne, Eric M.; Jeong, Jaewoo; Samant, Mahesh G.; Parkin, Stuart S. P.; Freeland, John W.; Evans, Paul G.; Wen, Haidan

    2016-02-01

    Dynamical phase separation during a solid-solid phase transition poses a challenge for understanding the fundamental processes in correlated materials. Critical information underlying a phase transition, such as localized phase competition, is difficult to reveal by measurements that are spatially averaged over many phase separated regions. The ability to simultaneously track the spatial and temporal evolution of such systems is essential to understanding mesoscopic processes during a phase transition. Using state-of-the-art time-resolved hard x-ray diffraction microscopy, we directly visualize the structural phase progression in a VO2 film upon photoexcitation. Following a homogenous in-plane optical excitation, the phase transformation is initiated at discrete sites and completed by the growth of one lattice structure into the other, instead of a simultaneous isotropic lattice symmetry change. The time-dependent x-ray diffraction spatial maps show that the in-plane phase progression in laser-superheated VO2 is via a displacive lattice transformation as a result of relaxation from an excited monoclinic phase into a rutile phase. The speed of the phase front progression is quantitatively measured, and is faster than the process driven by in-plane thermal diffusion but slower than the sound speed in VO2. The direct visualization of localized structural changes in the time domain opens a new avenue to study mesoscopic processes in driven systems.

  19. Tracking the insulator-to-metal phase transition in VO2 with few-femtosecond extreme UV transient absorption spectroscopy.

    Science.gov (United States)

    Jager, Marieke F; Ott, Christian; Kraus, Peter M; Kaplan, Christopher J; Pouse, Winston; Marvel, Robert E; Haglund, Richard F; Neumark, Daniel M; Leone, Stephen R

    2017-09-05

    Coulomb correlations can manifest in exotic properties in solids, but how these properties can be accessed and ultimately manipulated in real time is not well understood. The insulator-to-metal phase transition in vanadium dioxide (VO2) is a canonical example of such correlations. Here, few-femtosecond extreme UV transient absorption spectroscopy (FXTAS) at the vanadium M2,3 edge is used to track the insulator-to-metal phase transition in VO2 This technique allows observation of the bulk material in real time, follows the photoexcitation process in both the insulating and metallic phases, probes the subsequent relaxation in the metallic phase, and measures the phase-transition dynamics in the insulating phase. An understanding of the VO2 absorption spectrum in the extreme UV is developed using atomic cluster model calculations, revealing V(3+)/d(2) character of the vanadium center. We find that the insulator-to-metal phase transition occurs on a timescale of 26 ± 6 fs and leaves the system in a long-lived excited state of the metallic phase, driven by a change in orbital occupation. Potential interpretations based on electronic screening effects and lattice dynamics are discussed. A Mott-Hubbard-type mechanism is favored, as the observed timescales and d(2) nature of the vanadium metal centers are inconsistent with a Peierls driving force. The findings provide a combined experimental and theoretical roadmap for using time-resolved extreme UV spectroscopy to investigate nonequilibrium dynamics in strongly correlated materials.

  20. Can common exercise indices determine peak exercise oxygen consumption and anaerobic threshold during stress testing in patients with chronic congestive heart failure?

    Science.gov (United States)

    Chandrashekhar, Y; Anand, I S

    1993-01-01

    Maximal oxygen consumption (VO2 max) is one of the most important predictors of prognosis in chronic heart failure and is now used to define degree of heart failure. While most centres can routinely do treadmill exercise testing (TMT), VO2 max measurements are not widely available. We, therefore, analysed the ability to predict VO2 max from common TMT variables: Peak exercise heart rate, exercise time, and METS achieved in 26 patients with chronic congestive heart failure (NYHA II-III, ejection fraction 43 +/- 2%) in whom exercise VO2 studies were simultaneously done by breath to breath expiratory gas analysis using a metabolic cart. METS achieved during exercise and exercise time correlated reasonably well although not perfectly (r = 0.78 & 0.73 respectively, tail critical value +/-0.41). Resting ejection fraction did not correlate at all (r = 0.0004). The regression equation (2.7) (METS) + 5.8 defined VO2 max with SE of 0.47. Although in unvariate analysis, exercise time, METS achieved & peak heart rate predicted VO2 max, only METS achieved was predictive in step wise regression. None of the parameters predicted the anaerobic threshold accurately although there was a modest relation between AT and peak exercise VO2. We conclude that most exercise variables do not accurately predict VO2 max in patients with chronic congestive heart failure. METS achieved is the best predictor and the VO2 max can be predicted using a regression equation. Anaerobic threshold cannot be predicted without tests involving expiratory gas analysis.

  1. Preparation, Characterization and Thermo-Chromic Properties of EVA/VO2 Laminate Films for Smart Window Applications and Energy Efficiency in Building

    Directory of Open Access Journals (Sweden)

    Onruthai Srirodpai

    2017-01-01

    Full Text Available Thermochromic films based on vanadium dioxide (VO2/ethylene vinyl acetate copolymer (EVA composite were developed. The monoclinic VO2 particles was firstly prepared via hydrothermal and calcination processes. The effects of hydrothermal time and tungsten doping agent on crystal structure and morphology of the calcined metal oxides were reported. After that, 1 wt % of the prepared VO2 powder was mixed with EVA compound, using two different mixing processes. It was found that mechanical properties of the EVA/VO2 films prepared by the melt process were superior to those of which prepared by the solution process. On the other hand, percentage visible light transmittance of the solution casted EVA/VO2 film was greater than that of the melt processed composite film. This was related to the different gel content of EVA rubber and state of dispersion and distribution of VO2 within the polymer matrix phase. Thermochromic behaviors and heat reflectance of the EVA/VO2 film were also verified. In overall, this study demonstrated that it was possible to develop a thermochromic film using the polymer composite approach. In this regard, the mixing condition was found to be one of the most important factors affecting morphology and thermo-mechanical properties of the films.

  2. Coherent control of optical absorption and the energy transfer pathway of an infrared quantum dot hybridized with a VO2 nanoparticle

    Science.gov (United States)

    Hatef, Ali; Zamani, Naser; Johnston, William

    2017-04-01

    We systematically investigate the optical response of a semiconductor quantum dot (QD) hybridized with a vanadium dioxide nanoparticle (VO2NP) in the infrared (IR) region. The VO2NP features a semiconductor to metal phase change characteristic below and above a critical temperature that leads to an abrupt change in the particle’s optical properties. This feature means that the QD-VO2NP hybrid system can support the coherent coupling of exciton-polaritons and exciton-plasmon polaritons in the semiconductor and metal phases of the VO2NP, respectively. In our calculations, the VO2NP phase transition is modelled with a filling fraction (f), representing the fraction of the VO2NP in the metallic phase. The phase transition is driven by the hybrid system’s interaction with a continuous wave (CW) IR laser field. In this paper, we show how control over the filling fraction results in the enhancement or suppression of the QD’s linear absorption. These variations in the QD absorption is due to dramatic changes in the effective local field experienced by the QD and the non-radiative energy transfer from the QD to the VO2NP. The presented results have the potential to be applied to the design of thermal sensors at the nanoscale.

  3. Applications of VO2 in adaptive infrared stealth technology%二氧化钒在红外自适应隐身技术中的应用

    Institute of Scientific and Technical Information of China (English)

    刘东青; 程海峰; 郑文伟; 张朝阳

    2012-01-01

    二氧化钒(VO2)是一种热致可逆相变氧化物,在约68℃时发生由半导体态向金属态的一级位移型相变,同时伴随着显著的电学、磁学、光学特性的变化,且相变温度可通过掺杂调节.制备了二氧化钒粉体和薄膜材料,分别研究了两种材料的热致红外发射率变化特性;采用热像仪拍摄了二氧化钒涂层和薄膜不同温度的红外热图,探讨了其在隐身技术中的应用.结果表明:二氧化钒涂层和薄膜在相变前后具有主动控制自身辐射强度的特性,在红外自适应隐身技术中具有一定的应用前景.%Thermochromic vanadium dioxide (VO2) exhibits a semi-conduction to metallic phase transition at about 68℃, involving strong variations in electrical, magnetic and optical properties. Besides, the phase transition temperature of VO2 can be changed by doping. Thin films and powder of VO2 were prepared respectively, and their infrared thermochromic properties were also studied. Thermal images of VO2 thin films and VO2 coatings under different temperatures were derived by infrared camera, and the applications of VO2 in infared stealth technology were discussed. The results show that VO2 thin films and VO2 coatings can control their infrared radiant intensity actively, and have great application prospects in the field of adaptive infrared stealth technology.

  4. Efeito da intensidade do exercício de corrida intermitente 30s:15s no tempo de manutenção no ou próximo do VO2max

    OpenAIRE

    Aguiar,Rafael Alves de; Schlickmann, Jardel; Turnes, Tiago; Caputo, Fabrizio [UNESP

    2013-01-01

    O presente estudo comparou o tempo mantido acima de 90% (t90VO2max) e de 95% VO2max (t95VO2max) em três diferentes intensidades de exercício. Após a realização de um teste incremental para determinar o VO2max, oito estudantes de educação física ativos (23 ± 3 anos) executaram três sessões de exercícios intermitentes (100, 110 e 120% da velocidade do VO2max (vVO2max)) com razão esforço:recuperação de 30s:15s. O t95VO2max foi significantemente maior em 110%vVO2max (EI110%) (218,1 ± 81,6 s) quan...

  5. Aerobic power and peak power of elite America's Cup sailors.

    Science.gov (United States)

    Neville, Vernon; Pain, Matthew T G; Folland, Jonathan P

    2009-05-01

    Big-boat yacht racing is one of the only able bodied sporting activities where standing arm-cranking ('grinding') is the primary physical activity. However, the physiological capabilities of elite sailors for standing arm-cranking have been largely unreported. The purpose of the study was to assess aerobic parameters, VO(2peak) and onset of blood lactate (OBLA), and anaerobic performance, torque-crank velocity and power-crank velocity relationships and therefore peak power (P (max)) and optimum crank-velocity (omega(opt)), of America's Cup sailors during standing arm-cranking. Thirty-three elite professional sailors performed a step test to exhaustion, and a subset of ten grinders performed maximal 7 s isokinetic sprints at different crank velocities, using a standing arm-crank ergometer. VO(2peak) was 4.7 +/- 0.5 L/min (range 3.6-5.5 L/min) at a power output of 332 +/- 44 W (range 235-425 W). OBLA occurred at a power output of 202 +/- 31 W (61% of W(max)) and VO(2) of 3.3 +/- 0.4 L/min (71% of VO(2peak)). The torque-crank velocity relationship was linear for all participants (r = 0.9 +/- 0.1). P (max) was 1,420 +/- 37 W (range 1,192-1,617 W), and omega(opt) was 125 +/- 6 rpm. These data are among the highest upper-body anaerobic and aerobic power values reported. The unique nature of these athletes, with their high fat-free mass and specific selection and training for standing arm cranking, likely accounts for the high values. The influence of crank velocity on peak power implies that power production during on-board 'grinding' may be optimised through the use of appropriate gear-ratios and the development of efficient gear change mechanisms.

  6. Substrate-induced microstructure effects on the dynamics of the photo-induced Metal-insulator transition in VO$_2$ thin films

    CERN Document Server

    Radue, E; Kittiwatanakul, S; Lu, J; Wolf, S A; Rossi, E; Lukaszew, R A; Novikova, I

    2014-01-01

    We investigate the differences in the dynamics of the ultrafast photo-induced metal-insulator transition (MIT) of two VO$_2$ thin films deposited on different substrates, TiO$_2$ and Al$_2$O$_3$, and in particular the temperature dependence of the threshold laser fluence values required to induce various MIT stages in a wide range of sample temperatures (150 K - 320 K). We identified that, although the general pattern of MIT evolution was similar for the two samples, there were several differences. Most notably, the threshold values of laser fluence required to reach the transition to a fully metallic phase in the VO$_2$ film on the TiO$_2$ substrate were nearly constant in the range of temperatures considered, whereas the VO$_2$/Al$_2$O$_3$ sample showed clear temperature dependence. Our analysis qualitatively connects such behavior to the structural differences in the two VO$_2$ films.

  7. The Unified Parkinson's Disease Rating Scale as a predictor of peak aerobic capacity and ambulatory function.

    Science.gov (United States)

    Ivey, Frederick M; Katzel, Leslie I; Sorkin, John D; Macko, Richard F; Shulman, Lisa M

    2012-01-01

    The Unified Parkinson's Disease Rating Scale (UPDRS) is a widely applied index of disease severity. Our objective was to assess the utility of UPDRS for predicting peak aerobic capacity (VO2 peak) and ambulatory function. Participants (n = 70) underwent evaluation for UPDRS (Total and Motor ratings), VO2 peak, 6-minute walk distance (6MW), and 30-foot self-selected walking speed (SSWS). Using regression, we determined the extent to which the Total and Motor UPDRS scores predicted each functional capacity measure after adjusting for age and sex. We also tested whether adding the Hoehn and Yahr scale (H-Y) to the model changed predictive power of the UPDRS. Adjusted for age and sex, both the Total UPDRS and Motor UPDRS subscale failed to predict VO2 peak. The Total UPDRS did weakly predict 6MW and SSWS (both p UPDRS subscale did not predict these ambulatory function tests. After adding H-Y to the model, Total UPDRS was no longer an independent predictor of 6MW but remained a predictor of SSWS. We conclude that Total and Motor UPDRS rating scales do not predict VO2 peak, but that a weak relationship exists between Total UPDRS and measures of ambulatory function.

  8. Concurrent validity of the non-exercise based VO2max prediction equation using percentage body fat as a variable in asian Indian adults

    Science.gov (United States)

    2012-01-01

    Background Aerobic capacity (VO2max) is highly dependent upon body composition of an individual and body composition varies with ethnicity. The purpose of this study was to check the concurrent validity of the non-exercise prediction equation developed by Jackson and colleagues (1990) using percentage body fat as a variable in Asian Indian adults. Methods One hundred twenty college-aged participants (60 male, 60 female, mean age 22.02 ± 2.29 yrs) successfully completed a maximal graded exercise test (GXT) on a motorized treadmill to assess VO2max. VO2max was then estimated by the non-exercise prediction equation developed by Jackson and colleagues (1990) using percentage body fat. Percentage body fat was calculated by three different models (Sandhu et al’s fat mass equation, Durnin-womersley’s 4 site percentage body fat and Jackson & Pollock’s 4 site percentage body fat) and was used in the above equation. The results of VO2max obtained using “gold standard” treadmill methods were then compared with the three results of VO2max obtained by Jackson et al’s equation (using three different models to calculate percentage body fat) and it was determined which equation is best suited to determine percentage body fat and in turn VO2 max for Indian population. Results Jackson et al’s prediction equation overpredicts VO2max in Asian Indian subjects who have a lower VO2max (33.41 ± 14.39 ml/kg/min) than those reported in other age matched populations. percentage body fats calculated by the three equations were significantly different and the correlation coefficient (r) between VO2max calculated by Jackson and colleagues (1990) using Sandhu et al’s equation for percentage body fat with VO2 max calculated using treadmill (gold standard) (r = .817) was found slightly more significantly correlated than the other two equations and was not statistically different from the measured value. Conclusions This study proves that VO2max equation using

  9. Oxidative stress-mediated selective antimicrobial ability of nano-VO2 against Gram-positive bacteria for environmental and biomedical applications

    Science.gov (United States)

    Li, Jinhua; Zhou, Huaijuan; Wang, Jiaxing; Wang, Donghui; Shen, Ruxiang; Zhang, Xianlong; Jin, Ping; Liu, Xuanyong

    2016-06-01

    Vanadium dioxide (VO2) is a unique thermochromic material as a result of its semiconductor-metal transition, holding great promise for energy-saving intelligent windows. Herein, pure nano-VO2 from discrete nanoparticles to continuous films were successfully deposited on quartz glass by controlling the sputtering parameters. It was demonstrated that, for Gram-positive S. aureus and S. epidermidis, the nano-VO2 could effectively disrupt bacteria morphology and membrane integrity, and eventually cause death. By contrast, the nano-VO2 did not exhibit significant toxicity towards Gram-negative E. coli and P. aeruginosa. To our knowledge, this is the first report on a selective antimicrobial effect of nano-VO2 materials on Gram-positive bacteria. Based on the experimental results, a plausible mechanism was proposed for the antimicrobial selectivity, which might originate from the different sensitivity of Gram-positive and Gram-negative bacteria to intracellular reactive oxygen species (ROS) level. Elevated intracellular ROS levels exceed the threshold that bacteria can self-regulate to maintain cellular redox homeostasis and thus cause oxidative stress, which can be alleviated by the intervention of glutathione (GSH) antioxidant. In addition, nano-VO2 did not produce significant cytotoxicity (hemolysis) against human erythrocytes within 12 h. Meanwhile, potential cytotoxicity against HIBEpiC revealed a time- and dose-dependent behavior that might be controlled and balanced by careful design. The findings in the present work may contribute to understanding the antimicrobial behavior of nano-VO2, and to expanding the new applications of VO2-based nanomaterials in environmental and biomedical fields.

  10. Exercise increases endostatin in circulation of healthy volunteers

    Directory of Open Access Journals (Sweden)

    Makey Ian

    2004-01-01

    Full Text Available Abstract Background Physical inactivity increases the risk of atherosclerosis. However, the molecular mechanisms of this relation are poorly understood. A recent report indicates that endostatin, an endogenous angiostatic factor, inhibits the progression of atherosclerosis, and suggests that reducing intimal and atherosclerotic plaque tissue neovascularization can inhibit the progression atherosclerosis in animal models. We hypothesize that exercise can elevate the circulatory endostatin level. Hence, exercise can protect against one of the mechanisms of atherosclerosis. Results We examined treadmill exercise tests in healthy volunteers to determine the effect of exercise on plasma levels of endostatin and other angiogenic regulators. Oxygen consumption (VO2 was calculated. Plasma levels of endostatin, vascular endothelial growth factor (VEGF, and basic fibroblast growth factor (bFGF were determined using ELISA. The total peak VO2 (L in 7 male subjects was 29.5 ± 17.8 over a 4–10 minute interval of exercise. Basal plasma levels of endostatin (immediately before exercise were 20.3 ± 3.2 pg/ml, the plasma levels increased to 29.3 ± 4.2, 35.2 ± 1.8, and 27.1 ± 2.2 ng/ml, at 0.5, 2, and 6 h, respectively, after exercise. There was a strong linear correlation between increased plasma levels of endostatin (% and the total peak VO2 (L related to exercise (R2 = 0.9388; P Conclusions The results suggest that circulating endostatin can be significantly increased by exercise in proportion to the peak oxygen consumption under physiological conditions in healthy volunteers. These findings may provide new insights into the molecular links between physical inactivity and the risk of angiogenesis dependent diseases such as atherosclerosis.

  11. Increasing the medium-term clinical benefits of hospital-based cardiac rehabilitation by physical activity telemonitoring in coronary artery disease patients.

    Science.gov (United States)

    Frederix, Ines; Van Driessche, Niels; Hansen, Dominique; Berger, Jan; Bonne, Kim; Alders, Toon; Dendale, Paul

    2015-02-01

    The purpose of this study was to evaluate the effect of a physical activity telemonitoring program on daily physical activity level, oxygen uptake capacity (VO(2peak)), and cardiovascular risk profile in coronary artery disease (CAD) patients who completed phase II cardiac rehabilitation (CR). Eighty CAD patients who completed phase II CR were randomly assigned to an additional telemonitoring intervention or standard CR. The patients in the intervention group (n = 40) wore a motion sensor continuously for 18 weeks. Each week these patients received a step count goal, with the aim to gradually increase the patients' physical activity level. In the control group (n = 40), the patients wore an unreadable motion sensor for seven days for measurement purposes only (at start of follow-up, and after six and 18 weeks). At start of follow-up and after 18 weeks blood lipid profile, glycemic control, waist circumference and body mass index was assessed. VO(2peak) was assessed at start of follow-up, and after six and 18 weeks. Re-hospitalisation rate was followed during this timeframe. In the intervention group, VO(2peak) increased significantly during follow-up (P = 0.001), in the control group it did not (P = 0.273). A significant correlation was found between daily aerobic step count and improvement in VO(2peak) (P = 0.030, r = 0.47). Kaplan-Meier curve analysis showed a trend towards fewer re-hospitalisations for patients in the telemonitoring group (P = 0.09). The study showed that, to maintain exercise tolerance and lower re-hospitalisation rate after hospital-based CR in CAD patients, a physical activity telemonitoring program might be an effective intervention. © The European Society of Cardiology 2013 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

  12. High-performance thermal sensitive W-doped VO2(B) thin film and its identification by first-principles calculations

    Science.gov (United States)

    Wan, Dongyun; Xiong, Ping; Chen, Lanli; Shi, Siqi; Ishaq, Ahmad; Luo, Hongjie; Gao, Yanfeng

    2017-03-01

    VO2(B) is currently a preferred phase structure for the application as bolometer material, which, however, suffers from low temperature-coefficient-of-resistance (TCR) values and large resistances. Here we present the combined experimental and first-principles calculations study on both doped and undoped VO2(B) thin films enabling us to attain high TCR (-3.9%/k) and suitable square-resistance (32.7 kΩ) by controlled W doping employing the widely used magnetron sputtering technique. The TCR value is 50% larger than reported ones at the similar resistance. The underlying microscopic mechanism for the performance improvement was studied and results indicated that the introduction of extra electrons and the variation in the band structure resulting from the incorporation of W6+ ions in the VO2(B) crystal lattice contribute to the enhancement of the electronic conductivity. Moreover, the special two-dimensional octahedral structure of monoclinic (C2/m) B-phase VO2 favors the strain control with W-doping for achieving a large TCR, which overcomes the analogous predicament between the high conductivity and large TCR generated by dopants in the M-phase VO2. The present findings provides a facile and simple pathway for the design and fabrication of high performance W-doped VO2(B) thin films rendering superior optical and electrical properties for its wide applications in thermo-opto-electro sensing devices.

  13. Comparison of the IPAQ-A and actigraph in relation to VO2max among European adolescents: the HELENA study.

    Science.gov (United States)

    Ottevaere, Charlene; Huybrechts, Inge; De Bourdeaudhuij, Ilse; Sjöström, Michael; Ruiz, Jonatan R; Ortega, Francisco B; Hagströmer, Maria; Widhalm, Kurt; Molnár, Dénes; Moreno, Luis A; Beghin, Laurent; Kafatos, Anthony; Polito, Angela; Manios, Yannis; Mártinez-Gómez, David; De Henauw, Stefaan

    2011-07-01

    The purpose was to compare data obtained from a modified, long, self-administered version of the International Physical Activity Questionnaire (IPAQ-A) with objective data obtained in parallel from Actigraph accelerometers, and VO(2)max in adolescents. The study comprised a total of 2018 adolescents (46% male) from ten European cities participating in the HELENA (Healthy Lifestyle in Europe by Nutrition in Adolescence) study. Physical activity was assessed over seven consecutive days by accelerometry and expressed as min/day of moderate, vigorous, and moderate to vigorous (MVPA) physical activity (PA). PA was also assessed with the IPAQ-A. VO(2)max was estimated from a 20-m shuttle run test. Poor to fair correlations between the two methodologies were found for the whole study sample and when stratified by age and gender (r(s) = 0.08-0.26, p < 0.01). On average, the self-reported time spent in moderate PA was higher compared to the time measured with the accelerometer, while the differences between both instruments were less clear for vigorous intensity. Adolescents reporting high levels of PA (3rd tertile IPAQ-A) also showed higher levels of PA (accelerometers) in all the study variables (moderate, vigorous and MVPA), compared to adolescents reporting low PA (1st tertile IPAQ-A) (all p < 0.001). Both methods were moderately correlated with estimated VO(2)max. Within the HELENA-study, the IPAQ-A showed the modest comparability with the accelerometer data for assessing PA in each intensity level and was the highest for vigorous intensity. Both instruments are able to detect the adolescents with the highest cardio respiratory fitness, which are the most active adolescents. Crown Copyright © 2011. Published by Elsevier Ltd. All rights reserved.

  14. Desenvolvimento de equações para estimativa do VO2PICO pelo teste de 9 minutos

    Directory of Open Access Journals (Sweden)

    Ana Carolina Paludo

    2014-06-01

    Full Text Available OBJETIVO: Desenvolver e validar modelos matemáticos para predição do VO2pico em crianças e adolescentes, por meio da utilização do teste de campo de corrida/caminhada de 9 minutos. MÉTODOS: Foram avaliados 211 escolares, de sete a 12 anos de idade, de ambos os sexos, regularmente matriculados em duas escolas do Município de Londrina - PR, sendo 141 escolares separados para amostra de desenvolvimento e 70 para validação das equações desenvolvidas. As medidas avaliadas foram: massa corporal, estatura, espessuras de dobras cutâneas (tricipital e subescapular, além da maturação biológica. Os testes de corrida/caminha de 9 minutos foram realizados em pista de atletismo e a análise direta do VO2pico (mL/kg/min realizada em laboratório, com analisador de gás portátil, através um teste incremental em esteira rolante. O desenvolvimento das equações foi realizado através da análise de regressão linear pelo método stepwise e a validação foi realizada pelos testes matemáticos específicos levando em consideração uma significância de 5% para todas as análises. RESULTADOS: A equação geral para a amostra total foi VO2pico= 24,506+16,672 (maturação, 0=pré e 1=púbere e pós - 0,346 (Σ DC + 5,187 (sexo, 0=F e 1=M + 0,009 (distância com um r=0,742 e EPE=9,149 mL/kg/min e sua validação apresentou r=0,570, CCI= 0,68, limites de concordância de -1,4 mL/kg/min, EPE=8,39 mL/kg/min e CV= 21,94%. CONCLUSÃO: Conclui-se que a equação generalizada desenvolvida fornece uma estimativa válida do VO2pico em crianças e adolescentes de sete a 12 anos de idade.

  15. Silver Vanadium Phosphorous Oxide, Ag(2)VO(2)PO(4): Chimie Douce Preparation and Resulting Lithium Cell Electrochemistry.

    Science.gov (United States)

    Kim, Young Jin; Marschilok, Amy C; Takeuchi, Kenneth J; Takeuchi, Esther S

    2011-08-15

    Recently, we have shown silver vanadium phosphorous oxide (Ag(2)VO(2)PO(4), SVPO) to be a promising cathode material for lithium based batteries. Whereas the first reported preparation of SVPO employed an elevated pressure, hydrothermal approach, we report herein a novel ambient pressure synthesis method to prepare SVPO, where our chimie douce preparation is readily scalable and provides material with a smaller, more consistent particle size and higher surface area relative to SVPO prepared via the hydrothermal method. Lithium electrochemical cells utilizing SVPO cathodes made by our new process show improved power capability under constant current and pulse conditions over cells containing cathode from SVPO prepared via the hydrothermal method.

  16. Nonlinear interaction of infrared waves on a VO2 surface at a semiconductor-metal phase transition

    Science.gov (United States)

    Berger, N. K.; Zhukov, E. A.; Novokhatskii, V. V.

    1984-04-01

    Nonlinear interactions (including wavefront reversal) of light from CW or pulsed 10.6-micron CO2 lasers at the semiconductor-metal phase transition in a VO2 film are investigated experimentally. The results are presented in graphs and characterized in detail. The intensity reflection coefficients of the three-wave interactions are found to be 0.5 percent for a CW reference wave of intensity 900 mW/sq cm and 42 percent for a pulsed reference wave of threshold density 600-800 microjoule/sq cm.

  17. A acurácia da determinação do VO2max e do limiar anaeróbio La exactitud en la determinacion del VO2máx y del umbral anaerobico Accuracy of VO2max and anaerobic threshold determination

    Directory of Open Access Journals (Sweden)

    Paulo Cesar N Granja Filho

    2005-06-01

    Full Text Available São raros estudos que tratam da acurácia de parâmetros de trocas gasosas durante o esforço, com a população brasileira. OBJETIVO: Determinar a confiabilidade do consumo máximo de oxigênio (VO2max e do limiar anaeróbio (LAn, assim como, a objetividade do segundo (LAn em adultos jovens saudáveis. MÉTODOS: Foram aplicados dois testes de esforço máximo, a partir dos quais dois observadores independentes determinaram o LAn através do método de inspeção visual. Os dados foram tratados por meio da análise de regressão, coeficiente de correlação intraclasse (CCI, ANOVA com dois fatores com teste post hoc de Tukey e teste t pareado para alfa Son raros los estudios que tratan de la exactitud de los parámetros de cambios gaseosos durante el esfuerzo con la población brasileña. OBJETIVO: Determinar la confiabilidad del consumo máximo de oxigeno (VO2max y del umbral anaeróbico (LAn, así como la objetividad del segundo, (LAn en adultos jovenes saludables. MÉTODOS: Fueron aplicados dos tests de esfuerzo máximo, a partir de los cuales dos observadores independientes determinaron el LAn a través del método de inspección visual. Los datos fueron tratados por medio del análisis de regresión, coeficiente de relación intraclase (CCI, ANOVA com dos factores con test post hoc de Tukey y el test t apareado para alfa Studies on the accuracy of the gas exchange and ventilation parameters during exertion involving the Brazilian population are scarce in literature. OBEJCTIVE: To determine the reliability of the maximal oxygen intake (VO2max and anaerobic threshold (AnT, as well as the objectivity of the AnT determination in Brazilian healthy youth adults. METHODS: Two tests of maximal exertion were applied. Two independent observers applied the visual inspection method for the AnT determination. The data were compared by means of the regression analysis, intraclass correlation coefficient (ICC, two-way ANOVA and the paired t-test for an

  18. 快速热处理对磁控溅射VO2薄膜光电特性的影响%Influence of Rapid Thermal Process Conditions on Electrical and Optical Properties of VO2 Thin Film

    Institute of Scientific and Technical Information of China (English)

    后顺保; 胡明; 吕志军; 梁继然; 陈涛

    2012-01-01

    采用反应磁控溅射法制备二氧化钒( VO2)薄膜,并对其进行快速热处理(RTP).主要研究500℃快速热处理10、15、20 s工艺条件下VO2薄膜结晶状况和光电性能的变化.在20℃~80℃温区内,应用四探针薄膜电阻测试方法和太赫兹时域频谱技术(THz-TDS)测量了各样品的电学相变特性和光学相变特性.结果表明,经过快速热处理的样品电学相变幅度均达到了2个数量级以上;THz波的透射率在半导体-金属相变前后的最大变化达到了57.9%.同时发现,热处理500℃,10 s时VO2的电学和光学相变幅度相对要大,当热处理时间达到15s左右时薄膜的相变幅度变化不再明显.快速热处理时间的长短对热致相变温度点的影响较小,但热致电学相变和光学相变的相变温度点不同:光学相变的温度为60℃左右,电学相变温度则在56℃附近.%Vanadium dioxide (VO2) samples are deposited by reactive magnetron sputter. And then a series of rapid thermal process (RTP) conditions: 500 ℃ /10 s、500℃ /15 s and 500 ℃ /20 s are employed to treat the samples. In the temperature cycle 20 ℃ ~ 80 ℃ . Electrical and optical properties of VO2 thin film are measured by four-probe meter and terahertz time-domain spectroscopy (THz-TDS) technology, respectively. It is observed that the electrical phase transition can reach up to more than two orders of magnitude and maximal change of the THz transmission is 57.9% before and after semiconductor-metal phase transition. Moreover, both electrical and optical phase transition amplitudes of sample treated by 500 XL /10 s are larger than the other two samples. In fact, the transition amplitude does not change any more when the RTP time reaches about 15 s. The phase transition temperature is almost the same among the different samples. But the electrical phase transitions temperature is lower than the optical transitions temperature. Electrical transition temperature is about 56

  19. Very short (15s-15s) interval-training around the critical velocity allows middle-aged runners to maintain VO2 max for 14 minutes.

    Science.gov (United States)

    Billat, V L; Slawinksi, J; Bocquet, V; Chassaing, P; Demarle, A; Koralsztein, J P

    2001-04-01

    The purpose of this study was to compare the effectiveness of three very short interval training sessions (15-15 s of hard and easier runs) run at an average velocity equal to the critical velocity to elicit VO2 max for more than 10 minutes. We hypothesized that the interval with the smallest amplitude (defined as the ratio between the difference in velocity between the hard and the easy run divided by the average velocity and multiplied by 100) would be the most efficient to elicit VO2 max for the longer time. The subjects were middle-aged runners (52 +/- 5 yr, VO2 max of 52.1 +/- 6 mL x min(-1) x kg(-1), vVO2 max of 15.9 +/- 1.8 km x h(-1), critical velocity of 85.6 +/- 1.2% vVO2 max) who were used to long slow distance-training rather than interval training. They performed three interval-training (IT) sessions on a synthetic track (400 m) whilst breathing through the COSMED K4b2 portable metabolic analyser. These three IT sessions were: A) 90-80% vVO2 max (for hard bouts and active recovery periods, respectively), the amplitude= (90-80/85) 100=11%, B) 100-70% vVO2 max amplitude=35%, and C) 60 x 110% vVO2 max amplitude = 59%. Interval training A and B allowed the athlete to spend twice the time at VO2 max (14 min vs. 7 min) compared to interval training C. Moreover, at the end of interval training A and B the runners had a lower blood lactate than after the procedure C (9 vs. 11 mmol x l(-1)). In conclusion, short interval-training of 15s-15s at 90-80 and 100-70% of vVO2 max proved to be the most efficient in stimulating the oxygen consumption to its highest level in healthy middle-aged long-distance runners used to doing only long slow distance-training.

  20. Direct correlation of structural and electrical properties of electron-doped individual VO2 nanowires on devised TEM grids

    Science.gov (United States)

    Jo, Y.-R.; Kim, M.-W.; Kim, B.-J.

    2016-10-01

    Nano-scale VO2 wires with controlled parameters such as electron-doping have attracted intense interest due to their capability of suppressing the temperature of the metal-insulator transition (MIT). However, because their diameters are smaller than the spatial resolutions of the conventional measuring equipment, the ability to perform a thorough examination of the wires has been hindered. Here, we report the fabrication of a transmission electron microscopy (TEM) grid with an optimum design of Si3N4 windows on which the photolithography for individual electron-doped VO2 nanowire devices can be safely accomplished, allowing the cross-examination of the structural and electrical properties. TEM dark-field imaging was used to quantitatively investigate the fractions of rutile and M1 phases, and their lattice alignments were observed using high-resolution TEM (HRTEM) with small area diffraction. Moreover, electron energy loss spectroscopy (EELS) revealed that the rutile domain would be created by the strain induced by oxygen vacancies. Importantly, we successfully tuned the transition temperature by changing the rutile fraction while maintaining a high level of resistivity change. The resistivity at room temperature linearly decreased with the rutile fraction, following a simple model. Furthermore, the T dependence of the threshold voltage can be attributed to the Joule heating, exhibiting an identical thermal dependence, irrespective of the rutile fraction.

  1. Phase coexistence and pressure-temperature phase evolution of VO2(A ) nanorods near the semiconductor-semiconductor transition

    Science.gov (United States)

    Samanta, Sudeshna; Li, Quanjun; Cheng, Benyuan; Huang, Yanwei; Pei, Cuiying; Wang, Qinglin; Ma, Yanzhang; Wang, Lin

    2017-01-01

    A comprehensive understanding of the physical origins of the phase transition behaviors of transition metal oxides is still complex due to the interplay among competing interactions of comparable strengths tuning their nature. Widespread interest in such phase transitions has motivated explorations of nanocrystalline vanadium dioxide (VO2) in various forms and a long-running debate persists over the roles played by electron-electron correlation with lattice distortion. External stimuli like pressure and temperature have strong effects on the appearance, stability, and spacial distribution of the high-resistive (HR) and low-resistive (LR) phases accompanying their structural modification. Our comprehensive experiments establish the pressure-induced and thermally driven evolution of phase coexistence in VO2(A ) nanorods. Our experimental evidence supports coexisting HR and LR phases, where compression suppressed coexistence at ˜7 GPa, followed by a semiconductor-semiconductor transition at around ˜10 GPa with the absence of pressure-induced metallization. X-ray diffraction revealed lattice distortion with local microscopic strain inhomogeneity in the nanorods, without any discontinuity in the pressure-volume data. We further investigated the vibrational modes and relaxations of the samples related to their thermal expansions. We also found that the pressure-dependent hierarchy of microstructural densification contributed significantly to the resulting transport properties.

  2. Efeitos do estado e especificidade do treinamento aeróbio na relação %VO2max versus %FCmax durante o ciclismo Effects of the state and specificity of aerobic training on the %VO2max versus %HRmax ratio during cycling

    Directory of Open Access Journals (Sweden)

    Fabrizio Caputo

    2005-01-01

    Full Text Available OBJETIVO: Determinar os efeitos do estado e especificidade de treinamento aeróbio na relação entre o percentual do consumo máximo de oxigênio (%VO2max e o percentual da frequência cardíaca máxima (%FCmax durante o exercício incremental realizado no cicloergômetro. MÉTODOS: Sete corredores, 9 ciclistas, 11 triatletas e 12 sedentários, todos do sexo masculino e aparentemente saudáveis, foram submetidos a um teste incremental até a exaustão no cicloergômetro. Regressões lineares entre %VO2max e %FCmax foram determinadas para cada indivíduo. Com base nessas regressões, foram calculados %FCmax correspondentes a determinados %VO2max (50, 60, 70, 80 e 90% de cada participante. RESULTADOS: Não foram encontradas diferenças significantes entre todos os grupos nos %FCmax para cada um dos %VO2max avaliados. Analisando-se os voluntários como um único grupo, as médias dos %FCmax correspondentes a 50, 60, 70, 80 e 90% %VO2max foram 67, 73, 80, 87, e 93%, respectivamente. CONCLUSÃO: Nos grupos analisados, a relação entre o %VO2max e %FCmax durante o exercício incremental no ciclismo não é dependente do estado e especificidade do treinamento aeróbio.OBJECTIVE: To determine the effects of the status and specificity of exercise training in the ratio between maximum oxygen consumption (%VO2max and the percentage of maximal heart rate (%HRmax during incremental exercise on a cycle ergometer. METHODS: Seven runners, 9 cyclists, 11 triathletes, and 12 sedentary individuals, all male and apparently healthy, underwent exhaustive incremental exercise on cycle ergometers. Linear regressions between %VO2max x %HRmax were determined for each individual. Based on these regressions, %HRmax was assessed corresponding to a determined %VO2max (50, 60, 70, 80, and 90% from each participant. RESULTS: Significant differences were not found between the groups in %HRmax for each of the %VO2max assessed. Analyzing the volunteers as a single group, the

  3. Influência do estado nutricional e do VO2max nos níveis de adiponectina em homens acima de 35 anos Influencia del Estado Nutricional y del VO2max en los Niveles de Adiponectina en Hombres que superan los 35 Años Influence of nutritional status and VO2max on adiponectin levels in men older than 35 years

    Directory of Open Access Journals (Sweden)

    Eduardo Camillo Martinez

    2011-06-01

    Full Text Available FUNDAMENTO: A adiponectina é considerada importante fator na patogênese das doenças cardiovasculares e metabólicas, por suas propriedades antiaterogênicas e antiinflamatórias. Poucos estudos, entretanto, sugerem a existência de relação direta entre os níveis de adiponectina e os níveis de condicionamento cardiorrespiratório e atividade física. OBJETIVO: Verificar a influência do estado nutricional e do condicionamento cardiorrespiratório nos níveis plasmáticos de adiponectina em homens adultos. MÉTODOS: Foram avaliados 250 sujeitos, homens, todos militares da ativa do Exército Brasileiro (42,6 ± 4,8 anos. Foram mensurados os níveis plasmáticos de adiponectina, massa corporal, estatura, circunferência da cintura (CC, percentual de gordura por pesagem hidrostática e VO2max por ergoespirometria. Um questionário foi utilizado para obter as características do treinamento físico realizado pelos sujeitos. RESULTADOS: Na amostra, 121 (48% sujeitos apresentaram sobrepeso e 36 (14% eram obesos. Ainda, 66 sujeitos (27% apresentaram percentual de gordura maior que 25% e 26.7% apresentaram CC > 94 cm. Sujeitos com sobrepeso e obesidade apresentaram valores significativamente menores de adiponectina em relação aqueles com estado nutricional normal. Sujeitos no mais alto tercil de VO2max apresentaram níveis de adiponectina mais altos que os demais. Os níveis de adiponectina estiveram positivamente correlacionados com o tempo total de treinamento físico semanal e com o VO2max e inversamente correlacionados com os valores de massa corporal, IMC e CC. A correlação dos níveis de adiponectina e do VO2max não permaneceu significante após controlada pelo IMC e CC. CONCLUSÃO: Sujeitos com melhor condicionamento cardiorrespiratório e com estado nutricional normal parecem apresentar níveis mais saudáveis de adiponectina.FUNDAMENTO: La adiponectina es considerada un importante factor en la patogénesis de las enfermedades

  4. 补服乳清蛋白对人体最大吸氧量的影响%Effects of supplementation Whey-protein On VO2max

    Institute of Scientific and Technical Information of China (English)

    任秀红; 张翔; 杨多多

    2012-01-01

    This study examined the effects of whey-protein, or placebo on VO2max, researched effects of intaking whey protein on aerobic exercise power as well. Method: twelve healthy males who major in PE participated in this research study. Single-blind design was employed, participants performed three times increasing the load continuous on anaerobic power cycling which lasted for 3 minutes followed by consumption of 7g whey-protein, 14g whey-protein or placebo 30 minutes before exercise. Results: There was significantly different between supplementation 7g whey-protein and placebo(p〈.05), similarly there was very significantly different between intaklng 7g whey-protein and 14g whey-protein(p〈.01).Conclusion: supplementation different mount of whey-protein has different effects on VO2max, Maybe supplementation whey-protein will effect the power of aerobic exercise.%目的:研究补服不同量的乳清蛋白对人体最大吸氧量的变化,探讨补服乳清蛋白对人体有氧运动能力的影响。方法:采用单盲实验法,体育系12名健康男性大学生作为被试,每次(共3次)补服不同的补剂,然后在无氧功率自行车上进行3个连续三分钟的递增负荷运动,作自身对照。结果:补服7g和14g乳清蛋白与安慰剂相比最大吸氧量水平都有不同程度的变化,补服7g乳清蛋白与安慰剂相比差异性显著,p〈0.05,补服14g乳清蛋白与安慰剂相比差异性非常显著p〈0.01。结论:(1)补服不同量的乳清蛋白都不同程度影响人体的最大吸氧量水平;(2)说明乳清蛋白的补服对人体有氧运动能力有一定影响。

  5. The effect of acute L-Carnitine supplementation on the blood lactate, glucose, VO2max and power in trained men: a brief report

    Directory of Open Access Journals (Sweden)

    Arazi H

    2013-04-01

    Full Text Available Background: Probably L-Carnitine can induce increasing of Pyruvate dehydrogenase activity, decreasing of lactic acid production and performance improvements due to the reinforcement of long chain fatty acid oxidation and stabilize of Coenzyme A (CoASH to free Coenzyme A (COA. Based on this, the aim of this study was to investigate the effect of acute L-Carnitine supplementation on blood lactate, glucose, VO2max and anaerobic power in trained men.Methods: Sixteen trained men (aged 19-23 volunteers from University of Guilan, facul-ty of Physical Education and Sport Sciences participated as subjects in this investiga-tion. Subjects divided to aerobic (A and anaerobic (An group randomly. In a double blind design, subjects participated in two separated tests by one week. Subjects ingested 3 grams of L-Carnitine supplementation or placebo (maltodextrin 90 minute before aerobic and anaerobic exercise. For aerobic activity used shuttle run 20 meter and for anaerobic activity used RAST test. Blood samples were collected 5 minute prior at rest and 4 minute post tests. Participants were asked in the morning to obtain fasting blood samples and perform tests. A t-test was used to detect differences between supplementa-tion and placebo groups in each exercise.Results: L-Carnitine group ((A 141.25±20.62 and (An 145.38±55.47 significantly had lower lactate concentration than placebo ((A 151.00±20.85 and (An 152.50±28.59 after tests (P≤0.05. L-Carnitine group ((A 136.00±19.74 and (An 115.50±13.64 had significa-ntly higher blood glucose compared to placebo ((A 121.62±15.65 and (An 110.12±12.63 too (P≤0.05. Also, VO2max, mean and maximum anaerobic power in L-Carnitine group were significantly more than ones in placebo (P<0.05.Conclusion: These findings indicate that acute oral supplementation of L-Carnitine can induce fatigue decreasing and improvement of aerobic and anaerobic performance.

  6. Polymorphism of NaVO2F2: a P2₁/c superstructure with pseudosymmetry of P2₁/m in the subcell.

    Science.gov (United States)

    Yu, Zi-Qun; Wang, Jing-Quan; Huang, Ya-Xi; Botis, Sanda M; Pan, Yuanming; Mi, Jin-Xiao

    2015-06-01

    The ADDSYM routine in the program PLATON [Spek (2015). Acta Cryst. C71, 9-18] has helped researchers to avoid structures of (metal-)organic compounds being reported in an unnecessarily low symmetry space group. However, determination of the correct space group may get more complicated in cases of pseudosymmetric inorganic compounds. One example is NaVO2F2, which was reported [Crosnier-Lopez et al. (1994). Eur. J. Solid State Inorg. Chem. 31, 957-965] in the acentric space group P2₁ based on properties but flagged by ADDSYM as (pseudo)centrosymmetric P2₁/m within default distance tolerances. Herein a systematic investigation reveals that NaVO2F2 exists in at least four polymorphs: P2₁, (I), P2₁/m, (II), P2₁/c, (III), and one or more low-temperature ones. The new centrosymmetric modification, (III), with the space group P2₁/c has a similar atomic packing geometry to phase (I), except for having a doubled c axis. The double-cell of phase (III) arises from atomic shifts from the glide plane c at (x, ¼, z). With increasing temperature, the number of observed reflections decreases. The odd l reflections gradually become weaker and, correspondingly, all atoms shift towards the glide plane, resulting in a gradual second-order transformation of (III) into high-temperature phase (II) (P2₁/m) at below 493 K. At least one first-order enantiotropic phase transition was observed below 139 K from both the single-crystal X-ray diffraction and the differential scanning calorimetry analyses. Periodic first-principles calculations within density functional theory show that both P2₁/c superstructure (III) and P2₁ substructure (I) are more stable than P2₁/m structure (II), and that P2₁/c superstructure (III) is more stable that P2₁ substructure (I).

  7. Maintained peak leg and pulmonary VO2 despite substantial reduction in muscle mitochondrial capacity

    DEFF Research Database (Denmark)

    Boushel, Robert; Gnaiger, E.; Larsen, F. J.;

    2015-01-01

    We recently reported the circulatory and muscle oxidative capacities of the arm after prolonged low-intensity skiing in the arctic (Boushel et al., 2014). In the present study, leg VO2 was measured by the Fick method during leg cycling while muscle mitochondrial capacity was examined on a biopsy...... of the vastus lateralis in healthy volunteers (7 male, 2 female) before and after 42 days of skiing at 60% HR max. Peak pulmonary VO2 (3.52 ± 0.18 L.min-1 pre vs 3.52 ± 0.19 post) and VO2 across the leg (2.8 ± 0.4L.min-1 pre vs 3.0 ± 0.2 post) were unchanged after the ski journey. Peak leg O2 delivery (3.6 ± 0...

  8. Effect of Endurance Training on the Determinants of Peak Exercise Oxygen Consumption in Elderly Patients with Stable Compensated Heart Failure and Preserved Ejection Fraction

    Science.gov (United States)

    Haykowsky, Mark J.; Brubaker, Peter H.; Stewart, Kathryn P.; Morgan, Timothy M.; Eggebeen, Joel; Kitzman, Dalane W.

    2012-01-01

    Objective Evaluate the mechanism(s) for improved exercise capacity after endurance exercise training (ET) in elderly patients with heart failure and preserved ejection fraction (HFPEF). Background: Exercise intolerance, measured objectively by reduced peak oxygen consumption (VO2), is the primary chronic symptom in HFPEF and is improved by ET. However, the mechanism(s) are unknown. Methods Forty stable, compensated HFPEF outpatients (mean age 69 ± 6 yrs) were examined at baseline and after 4 months of ET (n=22) or attention control (n=18). VO2 and its determinants were assessed during rest and peak upright cycle exercise. Results Following ET, peak VO2 was higher than controls (16.3 ± 2.6 vs. 13.1 ± 3.4 ml/kg/min; p=0.002). This was associated with higher peak heart rate (139 ± 16 vs. 131 ± 20 beats/min; p=0.03), but no difference in peak end-diastolic volume (77 ± 18 vs. 77 ± 17 ml; p=0.51), stroke volume (48 ± 9 vs. 46 ± 9 ml; p=0.83), or cardiac output (6.6 ± 1.3 vs. 5.9 ± 1.5 L/min; p=0.32). However, estimated peak arterial-venous oxygen difference (A-VO2 Diff) was significantly higher in ET (19.8 ± 4.0 vs. 17.3 ± 3.7 ml/dl; p=0.03). The effect of ET on cardiac output was responsible for elderly stable compensated HFPEF patients, peak A-VO2 Diff was higher following ET and was the primary contributor to improved peak VO2. This suggests that peripheral mechanisms (improved microvascular and/or skeletal muscle function) contribute to the improved exercise capacity after ET in HFPEF. PMID:22766338

  9. Effect of blood haemoglobin concentration on V(O2,max) and cardiovascular function in lowlanders acclimatised to 5260 m

    DEFF Research Database (Denmark)

    Calbet, J A L; Rådegran, G; Boushel, Robert Christopher

    2002-01-01

    The principal aim of this investigation was to determine the influence of blood haemoglobin concentration ([Hb]) on maximal exercise capacity and maximal O(2) consumption (V(O(2),max)) in healthy subjects acclimatised to high altitude. Secondarily, we examined the effects of [Hb] on the regulation...... of cardiac output (CO), blood pressure and muscular blood flow (LBF) during exercise. Eight Danish lowlanders (three females and five males; 24 +/- 0.6 years, mean +/- S.E.M.) performed submaximal and maximal exercise on a cycle ergometer after 9 weeks at an altitude of 5260 m (Mt Chacaltaya, Bolivia......). This was done first with the high [Hb] resulting from acclimatisation and again 2-4 days later, 1 h after isovolaemic haemodilution with Dextran 70 to near sea level [Hb]. After measurements at maximal exercise while breathing air at each [Hb], subjects were switched to hyperoxia (55 % O(2) in N(2...

  10. EPR and UV/VIS spectroscopic investigations of VO2+ complexes and compounds formed in alkali pyrosulfates

    DEFF Research Database (Denmark)

    Rasmussen, Søren Birk; Eriksen, Kim Michael; Fehrmann, Rasmus

    2002-01-01

    fraction of the sample occupied by the cation. This indicates that spin-spin relaxation effects are the major contribution to line broadening. Combining information from UV/VIS and EPR spectra shows that the VO2+ unit in the molten salt solvent exhibits electronic properties close to aqueous solutions of V(IV).......The catalytically important molten salt-gas system M2S2O7-M2SO4-V2O5/SO2(g) (M = Na. K, Rb, Cs) has been investigated by X- and Q-band EPR spectroscopy. In order to obtain information about the V(IV) complex formation in the melts, samples rather dilute in V2O5 were quenched from the molten state...

  11. Reversible switching between pressure-induced amorphization and thermal-driven recrystallization in VO2(B) nanosheets.

    Science.gov (United States)

    Wang, Yonggang; Zhu, Jinlong; Yang, Wenge; Wen, Ting; Pravica, Michael; Liu, Zhenxian; Hou, Mingqiang; Fei, Yingwei; Kang, Lei; Lin, Zheshuai; Jin, Changqing; Zhao, Yusheng

    2016-07-18

    Pressure-induced amorphization (PIA) and thermal-driven recrystallization have been observed in many crystalline materials. However, controllable switching between PIA and a metastable phase has not been described yet, due to the challenge to establish feasible switching methods to control the pressure and temperature precisely. Here, we demonstrate a reversible switching between PIA and thermally-driven recrystallization of VO2(B) nanosheets. Comprehensive in situ experiments are performed to establish the precise conditions of the reversible phase transformations, which are normally hindered but occur with stimuli beyond the energy barrier. Spectral evidence and theoretical calculations reveal the pressure-structure relationship and the role of flexible VOx polyhedra in the structural switching process. Anomalous resistivity evolution and the participation of spin in the reversible phase transition are observed for the first time. Our findings have significant implications for the design of phase switching devices and the exploration of hidden amorphous materials.

  12. Visualization of one-dimensional diffusion and spontaneous segregation of hydrogen in single crystals of VO2.

    Science.gov (United States)

    Kasırga, T Serkan; Coy, Jim M; Park, Jae H; Cobden, David H

    2016-08-26

    Hydrogen intercalation in solids is common, complicated, and very difficult to monitor. In a new approach to the problem, we have studied the profile of hydrogen diffusion in single-crystal nanobeams and plates of VO2, exploiting the fact that hydrogen doping in this material leads to visible darkening near room temperature connected with the metal-insulator transition at 65 °C. We observe hydrogen diffusion along the rutile c-axis but not perpendicular to it, making this a highly one-dimensional diffusion system. We obtain an activated diffusion coefficient, [Formula: see text] applicable in metallic phase. In addition, we observe dramatic supercooling of the hydrogen-induced metallic phase and spontaneous segregation of the hydrogen into stripes implying that the diffusion process is highly nonlinear, even in the absence of defects. Similar complications may occur in hydrogen motion in other materials but are not revealed by conventional measurement techniques.

  13. Joule-heat-driven high-efficiency electronic-phase switching in freestanding VO2/TiO2 nanowires

    Science.gov (United States)

    Higuchi, Yoshiyuki; Kanki, Teruo; Tanaka, Hidekazu

    2017-03-01

    In this study, we demonstrated that an insulator-to-metal transition is driven by a low electric power using freestanding structures with two different sizes. The critical power (P C) required to induce the insulator-to-metal transition was measured with clamped and freestanding nanowires. The required P C for 400-nm-wide freestanding nanowires was 483 nW at a temperature 2 K lower than the temperature of the insulator-to-metal transition. This P C value is approximately 1 order of magnitude smaller than that for freestanding microwires with a width of 1 µm. The thermal dissipation model explains the changes in P C. These results provide guidelines for achieving significant reductions in P C in two-terminal VO2 phase-switching devices.

  14. Evidence for a structurally-driveninsulator-to-metal transitionin VO2: A view from the ultrafast timescale

    Energy Technology Data Exchange (ETDEWEB)

    Cavalleri, A.; Dekorsy, Th.; Chong, H.H.W.; Kieffer, J.C.; Schoenlein, R.W .

    2004-06-29

    We apply ultrafast spectroscopy to establish a time-domainhierarchy between structural and electronic effects in a stronglycorrelated electron system. We discuss the case of the model system VO2,a prototypical nonmagnetic compound that exhibits cell doubling, chargelocalization, and a metal-insulator transition below 340 K. We initiatethe formation of the metallic phase by prompt hole photo-doping into thevalence band ofthe low-T insulator. The insulator-to-metal transition is,however, delayed with respect to hole injection,exhibiting a bottlenecktime scale, associated with the phonon connecting the twocrystallographic phases. This structural bottleneck is observed despitefaster depletion of the d bands and is indicative of important bandlikecharacter for this controversial insulator.

  15. Evidence for a structurally-driven insulator-to-metal transition in VO2 : A view from the ultrafast timescale

    Science.gov (United States)

    Cavalleri, A.; Dekorsy, Th.; Chong, H. H. W.; Kieffer, J. C.; Schoenlein, R. W.

    2004-10-01

    We apply ultrafast spectroscopy to establish a time-domain hierarchy between structural and electronic effects in a strongly correlated electron system. We discuss the case of the model system VO2 , a prototypical nonmagnetic compound that exhibits cell doubling, charge localization, and a metal-insulator transition below 340 K. We initiate the formation of the metallic phase by prompt hole photo-doping into the valence band of the low- T insulator. The insulator-to-metal transition is, however, delayed with respect to hole injection, exhibiting a bottleneck time scale, associated with the phonon connecting the two crystallographic phases. This structural bottleneck is observed despite faster depletion of the d bands and is indicative of important bandlike character for this controversial insulator.

  16. Reversible switching between pressure-induced amorphization and thermal-driven recrystallization in VO2(B) nanosheets

    Science.gov (United States)

    Wang, Yonggang; Zhu, Jinlong; Yang, Wenge; Wen, Ting; Pravica, Michael; Liu, Zhenxian; Hou, Mingqiang; Fei, Yingwei; Kang, Lei; Lin, Zheshuai; Jin, Changqing; Zhao, Yusheng

    2016-07-01

    Pressure-induced amorphization (PIA) and thermal-driven recrystallization have been observed in many crystalline materials. However, controllable switching between PIA and a metastable phase has not been described yet, due to the challenge to establish feasible switching methods to control the pressure and temperature precisely. Here, we demonstrate a reversible switching between PIA and thermally-driven recrystallization of VO2(B) nanosheets. Comprehensive in situ experiments are performed to establish the precise conditions of the reversible phase transformations, which are normally hindered but occur with stimuli beyond the energy barrier. Spectral evidence and theoretical calculations reveal the pressure-structure relationship and the role of flexible VOx polyhedra in the structural switching process. Anomalous resistivity evolution and the participation of spin in the reversible phase transition are observed for the first time. Our findings have significant implications for the design of phase switching devices and the exploration of hidden amorphous materials.

  17. Role of microstructures on the M1-M2 phase transition in epitaxial VO2 thin films

    Science.gov (United States)

    Ji, Yanda; Zhang, Yin; Gao, Min; Yuan, Zhen; Xia, Yudong; Jin, Changqing; Tao, Bowan; Chen, Chonglin; Jia, Quanxi; Lin, Yuan

    2014-05-01

    Vanadium dioxide (VO2) with its unique sharp resistivity change at the metal-insulator transition (MIT) has been extensively considered for the near-future terahertz/infrared devices and energy harvesting systems. Controlling the epitaxial quality and microstructures of vanadium dioxide thin films and understanding the metal-insulator transition behaviors are therefore critical to novel device development. The metal-insulator transition behaviors of the epitaxial vanadium dioxide thin films deposited on Al2O3 (0001) substrates were systematically studied by characterizing the temperature dependency of both Raman spectrum and Fourier transform infrared spectroscopy. Our findings on the correlation between the nucleation dynamics of intermediate monoclinic (M2) phase with microstructures will open a new avenue for the design and integration of advanced heterostructures with controllable multifunctionalities for sensing and imaging system applications.

  18. Escala de VO2pico em adolescentes obesos e não-Obesos por diferentes métodos

    OpenAIRE

    2009-01-01

    FUNDAMENTO: O consumo de oxigênio de pico (VO2pico) pode ser definido como a maior taxa de consumo de oxigênio durante exercício exaustivo ou máximo. A avaliação da aptidão aeróbica pode ser expressa como relativa à massa corporal, mas esse procedimento pode não remover completamente as diferenças quando indivíduos pesados são avaliados. Assim, o procedimento com escala alométrica é uma estratégia atraente para comparar indivíduos com grandes diferenças em massa corporal. OBJETIVO: Investigar...

  19. Dual-Phase Transformation: Spontaneous Self-Template Surface-Patterning Strategy for Ultra-transparent VO2 Solar Modulating Coatings.

    Science.gov (United States)

    Liu, Minsu; Su, Bin; Kaneti, Yusuf V; Chen, Zhang; Tang, Yue; Yuan, Yuan; Gao, Yanfeng; Jiang, Lei; Jiang, Xuchuan; Yu, Aibing

    2017-01-24

    Dual-phase transformation has been developed as a template-free surface patterning technique in this study. Ordered VO2 honeycomb structures with a complex hierarchy have been fabricated via this method, and the microstructures of the obtained VO2(M) coatings are tunable by tailoring the pertinent variables. The VO2(M) honeycomb-structured coatings have excellent visible light transmittance at 700 nm (Tvis) up to 95.4% with decent solar modulating ability (ΔTsol) of 5.5%, creating the potential as ultratransparent smart solar modulating coatings. Its excellent performance has been confirmed by a proof-of-principle demonstration. The dual-phase transformation technique has dramatically simplified the conventional colloidal lithography technique as a scalable surface patterning technique for achieving high-performance metal oxide coatings with diverse applications, such as catalysis, sensing, optics, electronics, and superwettable materials.

  20. Pemberian minuman kombinasi maltodekstrin dan vitamin C terhadap mood negatif dan VO2 maks atlet sepak bola

    Directory of Open Access Journals (Sweden)

    Yuni Afriani

    2017-04-01

    Full Text Available Background: Stress during the match can influence the change of mood and performance of athletes. Physical exercise can improve the ability of physiologically and psychologically, but lead to fatigue, dehydration and hypoglycemia. Maltodextrin has a lower osmolarity to improve emotional and performance. Vitamin C as a cofactor of neurotransmitters can support the performance of athletes. Objective: This study aimed to determine the effectiveness of a combination drinks of maltodextrin and vitamin C on mood and the correlation with VO2 max of football athletes. Method: This research is a quasi experimental with same subject design. The subjects were 14 University state of Yogyakarta football athlete. Subjects received a drink of 15% maltodextrin and 250 mg of vitamin C in 300 ml given 30 minutes before and 5 minutes after the performance test using yo-yo intermittent test continued by physical exercise. Measurement of mood would be done in 3 times; before cardiorespiratory test, 5 minutes after physical exercise, and 15 minutes after drink. Results: There are significant changes after consuming a combination of maltodextrin and vitamin C on the confusion (p0.05. There are significant changes after consuming plain water on fatigue and tension (p0.05. There are no significant differences in every components of mood between two treatments. There is a correlation between anger and confusion with cardiorespiratory after consuming a combination of maltodextrin and vitamin C. Conclusion: Maltodextrin and vitamin C has the potential effect to improve the mood condition and have a correlation with VO2 Max improvement in football athletes.

  1. [Pre-operative screening tests for lung cancer using the analysis of expired gas with exercise testing--principally VO2 max/m2].

    Science.gov (United States)

    Nagamatsu, Y; Ono, H; Hiraki, H; Matsuo, T; Mitsuoka, M; Takamori, S; Hayashi, A; Yamana, H; Hayashida, R; Kakegawa, T

    1994-10-01

    The analysis of expired gas with exercise testing was conducted preoperatively with lung cancer patients in order to examine the relationship between maximum oxygen consumption (VO2 max) and postoperative complications, determining the cut-off of VO2 max/m2. The usefulness of the test as a preoperative screening test for both pulmonary ventilation and circulation was evaluated in comparison to pulmonary ventilation tests with spirometry and pulmonary circulation tests with Swan-Ganz catheter. Preoperative VO2 max/m2 was calculated from VO2 max in 111 patients with lung cancer who underwent lobectomy of more than one lobe. Also preoperatively conducted were pulmonary ventilation tests by spirometry and pulmonary circulation tests using the Swan-Ganz catheter to measure VC, %VC, FEV1.0, FEV1.0%, mean pulmonary arterial pressure (PPA) and cardiac output coefficient (C.I.). Form theses measurements, VC/m2, FEV1.0/m2 and total pulmonary vascular resistance (TPVR) were calculated. After the cut-off values of VO2 max/m2 were set tentatively at three stages, 600, 650 and 700 ml/min/m2 based on the incidence of postoperative complications, the 111 patients were divided into two groups in each cut-off value; one with VO2 max/m2 greater than the cut-off value and the other less than the cut-off value. Comparison of measurements obtained by spirometry between the two groups disclosed significant differences (p < 0.001) in VC/m2, %VC and FEV1.0/m2 in all cut-off values. Similarly, comparison of measurements obtained using the Swan-Ganz catheter between the two groups yielded significant differences (p < 0.05 to p < 0.01) in PPA and TPVR in all cut-off values.(ABSTRACT TRUNCATED AT 250 WORDS)

  2. Estimation of peak oxygen uptake from maximal power output among 9-10 year-old children in Lhasa, Tibet

    DEFF Research Database (Denmark)

    Bianba, B; Berntsen, S; Andersen, Lars Bo;

    2010-01-01

    in a progressive cycle ergometer test among children living at 3700 meters in Tibet. The estimate of V.O2peak is probably more valid using the present equations than prediction models based on data from sea level. The equations used for the prediction are: BianbaeqT: (l·min-1) = 0.5419 + (0.0096· Wmax) - (0...... Chinese children aged 9-10 years, living in Lhasa at 3700 meters above sea level, V.O2peak was measured directly using a portable oxygen analyzer, and predicted from maximal power output (Wmax) using a maximal cycle ergometer test. RESULTS: In multiple regression analyses with V.O2peak as dependent......AIM: The aims of the present study of Tibetan and Han Chinese children were to establish prediction equations for peak oxygen uptake (V.O2peak) using conventional power output measures, and to compare with prediction models based on data from sea level. METHODS: In 25 Tibetan children and 15 Han...

  3. Electric field-induced transport modulation in VO2 FETs with high-k oxide/organic parylene-C hybrid gate dielectric

    Science.gov (United States)

    Wei, Tingting; Kanki, Teruo; Fujiwara, Kohei; Chikanari, Masashi; Tanaka, Hidekazu

    2016-02-01

    We report on the observation of reversible and immediate resistance switching by high-k oxide Ta2O5/organic parylene-C hybrid dielectric-gated VO2 thin films. Resistance change ratios at various temperatures in the insulating regime were demonstrated to occur in the vicinity of phase transition temperature. We also found an asymmetric hole-electron carrier modulation related to the suppression of phase transition temperature. The results in this research provide a possibility for clarifying the origin of metal-insulator transition in VO2 through the electrostatic field-induced transport modulation.

  4. Evaluation of Maximal Oxygen Uptake (V02max) and Submaximal Estimates of VO2max Before, During and After Long Duration ISS Missions

    Science.gov (United States)

    Moore, Alan; Evetts, Sim