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Sample records for non-rhythmic muscle activation

  1. Distinguishing rhythmic from non-rhythmic brain activity during rest in healthy neurocognitive aging.

    Science.gov (United States)

    Caplan, Jeremy B; Bottomley, Monica; Kang, Pardeep; Dixon, Roger A

    2015-05-15

    Rhythmic brain activity at low frequencies (healthy neurocognitive aging are mixed. Here we address two reasons conventional spectral analyses may have led to inconsistent results. First, spectral-power measures are compared to a baseline condition; when resting activity is the signal of interest, it is unclear what the baseline should be. Second, conventional methods do not clearly differentiate power due to rhythmic versus non-rhythmic activity. The Better OSCillation detection method (BOSC; Caplan et al., 2001; Whitten et al., 2011) avoids these problems by using the signal's own spectral characteristics as a reference to detect elevations in power lasting a few cycles. We recorded electroencephalographic (EEG) signal during rest, alternating eyes open and closed, in healthy younger (18-25 years) and older (60-74 years) participants. Topographic plots suggested the conventional and BOSC analyses measured different sources of activity, particularly at frequencies, like delta (1-4Hz), at which rhythms are sporadic; topographies were more similar in the 8-12Hz alpha band. There was little theta-band activity meeting the BOSC method's criteria, suggesting prior findings of theta power in healthy aging may reflect non-rhythmic signal. In contrast, delta oscillations were present at higher levels than theta in both age groups. In summary, applying strict and standardized criteria for rhythmicity, slow rhythms appear present in the resting brain at delta and alpha, but not theta frequencies, and appear unchanged in healthy aging.

  2. Active vs. inactive muscle (image)

    Science.gov (United States)

    ... may lose 20 to 40 percent of their muscle -- and, along with it, their strength -- as they ... have found that a major reason people lose muscle is because they stop doing everyday activities that ...

  3. A muscle model for hybrid muscle activation

    Directory of Open Access Journals (Sweden)

    Klauer Christian

    2015-09-01

    Full Text Available To develop model-based control strategies for Functional Electrical Stimulation (FES in order to support weak voluntary muscle contractions, a hybrid model for describing joint motions induced by concurrent voluntary-and FES induced muscle activation is proposed. It is based on a Hammerstein model – as commonly used in feedback controlled FES – and exemplarily applied to describe the shoulder abduction joint angle. Main component of a Hammerstein muscle model is usually a static input nonlinearity depending on the stimulation intensity. To additionally incorporate voluntary contributions, we extended the static non-linearity by a second input describing the intensity of the voluntary contribution that is estimated by electromyography (EMG measurements – even during active FES. An Artificial Neural Network (ANN is used to describe the static input non-linearity. The output of the ANN drives a second-order linear dynamical system that describes the combined muscle activation and joint angle dynamics. The tunable parameters are adapted to the individual subject by a system identification approach using previously recorded I/O-data. The model has been validated in two healthy subjects yielding RMS values for the joint angle error of 3.56° and 3.44°, respectively.

  4. smooth-muscle activity

    African Journals Online (AJOL)

    with atropine could not abolish the effect of the venom on smooth muscle. ... cholenergic factor with acetylcholine was confirmed using radioimmunoassay of ... peripheral nervous antagonists on the venom action are still uncertain. The present.

  5. Trunk extensor muscle fatigue influences trunk muscle activities.

    Science.gov (United States)

    Hoseinpoor, Tahere Seyed; Kahrizi, Sedighe; Mobini, Bahram

    2015-01-01

    Trunk muscles fatigue is one of the risk factors in workplaces and daily activities. Loads would be redistributed among active and passive tissues in a non-optimal manner in fatigue conditions. Therefore, a single tissue might be overloaded with minimal loads and as a result the risk of injury would increase. The goal of this paper was to assess the electromyographic response of trunk extensor and abdominal muscles after trunk extensor muscles fatigue induced by cyclic lifting task. This was an experimental study that twenty healthy women participated. For assessing automatic response of trunk extensor and abdominal muscles before and after the fatigue task, electromyographic activities of 6 muscles: thorasic erector spine (TES), lumbar erector spine (LES), lumbar multifidus (LMF), transverse abdominis/ internal oblique (TrA/IO), rectus abdominis (RA) and external oblique (EO) were recorded in standing position with no load and symmetric axial loads equal to 25% of their body weights. Statistical analysis showed that all the abdominal muscles activity decreased with axial loads after performing fatigue task but trunk extensor activity remained constant. Results of the current study indicated that muscle recruitment strategies changed with muscle fatigue and load bearing, therefore risks of tissue injury may increase in fatigue conditions.

  6. Complement activation promotes muscle inflammation during modified muscle use

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    Frenette, J.; Cai, B.; Tidball, J. G.

    2000-01-01

    Modified muscle use can result in muscle inflammation that is triggered by unidentified events. In the present investigation, we tested whether the activation of the complement system is a component of muscle inflammation that results from changes in muscle loading. Modified rat hindlimb muscle loading was achieved by removing weight-bearing from the hindlimbs for 10 days followed by reloading through normal ambulation. Experimental animals were injected with the recombinant, soluble complement receptor sCR1 to inhibit complement activation. Assays for complement C4 or factor B in sera showed that sCR1 produced large reductions in the capacity for activation of the complement system through both the classical and alternative pathways. Analysis of complement C4 concentration in serum in untreated animals showed that the classical pathway was activated during the first 2 hours of reloading. Analysis of factor B concentration in untreated animals showed activation of the alternative pathway at 6 hours of reloading. Administration of sCR1 significantly attenuated the invasion of neutrophils (-49%) and ED1(+) macrophages (-52%) that occurred in nontreated animals after 6 hours of reloading. The presence of sCR1 also reduced significantly the degree of edema by 22% as compared to untreated animals. Together, these data show that increased muscle loading activated the complement system which then briefly contributes to the early recruitment of inflammatory cells during modified muscle loading.

  7. Muscle activity characterization by laser Doppler Myography

    Science.gov (United States)

    Scalise, Lorenzo; Casaccia, Sara; Marchionni, Paolo; Ercoli, Ilaria; Primo Tomasini, Enrico

    2013-09-01

    Electromiography (EMG) is the gold-standard technique used for the evaluation of muscle activity. This technique is used in biomechanics, sport medicine, neurology and rehabilitation therapy and it provides the electrical activity produced by skeletal muscles. Among the parameters measured with EMG, two very important quantities are: signal amplitude and duration of muscle contraction, muscle fatigue and maximum muscle power. Recently, a new measurement procedure, named Laser Doppler Myography (LDMi), for the non contact assessment of muscle activity has been proposed to measure the vibro-mechanical behaviour of the muscle. The aim of this study is to present the LDMi technique and to evaluate its capacity to measure some characteristic features proper of the muscle. In this paper LDMi is compared with standard superficial EMG (sEMG) requiring the application of sensors on the skin of each patient. sEMG and LDMi signals have been simultaneously acquired and processed to test correlations. Three parameters has been analyzed to compare these techniques: Muscle activation timing, signal amplitude and muscle fatigue. LDMi appears to be a reliable and promising measurement technique allowing the measurements without contact with the patient skin.

  8. Muscle activation patterns in posttraumatic neck pain

    NARCIS (Netherlands)

    Nederhand, Marcus Johannes

    2003-01-01

    As an important consequence of our research, we question the relevance of the criteria of the WAD injury severity classification system. We showed that the musculoskeletal signs in WAD grade II are not characterized by muscle spasm, (i.e. increase of muscle activity), but rather by a decrease in mus

  9. Core Muscle Activation in Suspension Training Exercises.

    Science.gov (United States)

    Cugliari, Giovanni; Boccia, Gennaro

    2017-02-01

    A quantitative observational laboratory study was conducted to characterize and classify core training exercises executed in a suspension modality on the base of muscle activation. In a prospective single-group repeated measures design, seventeen active male participants performed four suspension exercises typically associated with core training (roll-out, bodysaw, pike and knee-tuck). Surface electromyographic signals were recorded from lower and upper parts of rectus abdominis, external oblique, internal oblique, lower and upper parts of erector spinae muscles using concentric bipolar electrodes. The average rectified values of electromyographic signals were normalized with respect to individual maximum voluntary isometric contraction of each muscle. Roll-out exercise showed the highest activation of rectus abdominis and oblique muscles compared to the other exercises. The rectus abdominis and external oblique reached an activation higher than 60% of the maximal voluntary contraction (or very close to that threshold, 55%) in roll-out and bodysaw exercises. Findings from this study allow the selection of suspension core training exercises on the basis of quantitative information about the activation of muscles of interest. Roll-out and bodysaw exercises can be considered as suitable for strength training of rectus abdominis and external oblique muscles.

  10. Heterogeneity of muscle activity during sedentary behavior.

    Science.gov (United States)

    Pesola, Arto J; Laukkanen, Arto; Tikkanen, Olli; Finni, Taija

    2016-11-01

    Replacing sitting by standing has been hypothesized to reduce the health risks of sitting, based on the assumption that muscles are passive during sitting and active during standing. Interventions have been more effective in overweight (OW) than in normal weight (NW) individuals, but subjects' muscle activities have not been quantified. This study compared quadriceps and hamstring muscle electromyographic (EMG) activity between 57 NW (body mass index (BMI) 22.5 ± 1.5 kg/m(2), female n = 36) and 27 OW (BMI 28.4 ± 2.9 kg/m(2), female n = 8) subjects during non-fatiguing standing (15 s, EMGstanding) and sitting (30 min). EMG amplitude was normalized to EMG measured during maximal isometric knee extension and flexion (% EMGMVC), and sitting muscle inactivity and bursts were determined using 4 thresholds (60% or 90% EMGstanding and 1% or 2% EMGMVC). Comparisons were adjusted for sex, age, knee extension strength, and the individual threshold. Standing EMG amplitude was 36% higher in OW (1.9% ± 1.5% EMGMVC) than in NW (1.4% ± 1.4% EMGMVC, P < 0.05) subjects. During sitting, muscles were inactive 89.8% ± 12.7% of the measurement time with 12.7 ± 14.2 bursts/min across all thresholds. On average, 6% more activity was recorded in NW than in OW individuals for 3 of the 4 thresholds (P < 0.05 for 60% or 90% EMGstanding and 1% EMGMVC). In conclusion, the OW group had higher muscle activity amplitude during standing but more muscle inactivity during sitting for 3/4 of the thresholds tested. Interventions should test whether the observed heterogeneity in muscle activity affects the potential to gain cardiometabolic benefits from replacing sitting with standing.

  11. Is Abdominal Muscle Activity Different from Lumbar Muscle Activity during Four-Point Kneeling?

    Directory of Open Access Journals (Sweden)

    Soraya Pirouzi

    2013-12-01

    Full Text Available Background: Stabilization exercises can improve the performance of trunk and back muscles, which are effective in the prevention and treatment of low back pain. The four-point kneeling exercise is one of the most common types of stabilization exercises. This quasi-experimental study aimed to evaluate and compare the level of activation between abdominal and lumbar muscles in the different stages of the four-point kneeling exercise. Methods: The present study was conducted on 30 healthy women between 20 and 30 years old. Muscle activity was recorded bilaterally from transversus abdominis, internal oblique, and multifidus muscles with an electromyography (EMG device during the different stages of the four-point kneeling exercise. All the collected EMG data were normalized to the percentage of maximum voluntary isometric contraction. The repeated measures ANOVA and paired t-test were used for the statistical analysis of the data. Results: A comparison between mean muscle activation in right arm extension and left leg extension showed that left internal oblique and left transverse abdominis muscles produced greater activation during left leg extension (P<0.05. The comparison of mean muscle activation between right arm extension and the bird-dog position showed that, except for the right internal oblique, all the muscles produced higher activation in the bird-dog stage (P<0.05. In comparison to the bird-dog stage, the left multifidus showed high activation during left leg extension (P<0.05. Conclusion: The results of this study showed that the activity of all the above-mentioned muscles during quadruped exercise can provide stability, coordination, and smoothness of movements.

  12. Electromyographic analysis: shoulder muscle activity revisited.

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    Heuberer, Philipp; Kranzl, Andreas; Laky, Brenda; Anderl, Werner; Wurnig, Christian

    2015-04-01

    Restoring optimal strength and biomechanics of a pathologic shoulder knowledge of activity patterns of healthy glenohumeral muscles is mandatory. Yet, data on normal shoulder muscle activity are not always conclusive. The study was undertaken (a) to evaluate muscle activity patterns in the healthy shoulder using surface and fine-wire electromyography (EMG), and (b) to assess method's suitability in the clinical setting especially regarding painfulness and practicability. Surface and fine-wire EMG was performed on 11 healthy subjects (2f/9 m, Ø age 28 years) to assess 14 muscles including rotator cuff muscles during 8 planar standardised shoulder movements (abduction, forward flexion, internal and external rotation in neutral, 45° and 90° abduction). Pain was assessed using the visual analogue scale before testing, after inserting the fine-wire electrodes, after maximal voluntary contraction, before and after exercises, and after electrode removal. The most important finding regarding EMG activity patterns in the healthy shoulder was that the subscapularis activity was found to play a major role in abduction and forward flexion. Furthermore, this study was able to show that EMG measurements, especially fine-wire EMG, is prone to high failure rates (up to 32%); however, pain was not a limiting factor. The present study (1) revealed a new insight, especially finding the subscapularis activity playing a major role in abduction and forward flexion of the healthy shoulder; and (2) motion analysis system and the use of fine-wire electrodes were prone to failure; however, pain was not a limiting factor. Basic Science, Electrodiagnostic Study.

  13. Activation of Selected Core Muscles during Pressing

    Directory of Open Access Journals (Sweden)

    Thomas W. Nesser

    2015-10-01

    Full Text Available Introduction: Unstable surface training is often used to activate core musculature during resistance training. Unfortunately, unstable surface training is risky and leads to detraining. Purpose: The purpose of this study was to determine core muscle activation during stable surface ground-based lifts. Methods: Fourteen recreational trained and former NCAA DI athletes (weight 84.2 ± 13.3 kg; height 176.0 ± 9.5 cm; age 20.9 ± 2.0 years volunteered for participation. Subjects completed two ground-based lifts: overhead press and push-press. Surface EMG was recorded from 4 muscles on the right side of the body (Rectus Abdominus (RA, External Oblique (EO, Transverse Abdominus (TA, and Erector Spinae (ES. Results: Paired sample T-tests identified significant muscle activation differences between the overhead press and the push-press included ES and EO. Average and peak EMG for ES was significantly greater in push-press (P<0.01. Anterior displacement of COP was significantly greater in push-press compared to overhead press during the eccentric phase. Conclusion: The push-press was identified as superior in core muscle activation when compared to the overhead pressing exercise. Keywords: torso, stability, weight lifting, resistance training

  14. The effects of Juchumseogi and Juchumseo Jireugi motions of taekwondo on muscle activation of paraspinal muscles.

    Science.gov (United States)

    Baek, Jongmyeng; Lee, Jaeseok; Kim, Jonghyun; Kim, Jeonghun; Han, Dongwook; Byun, Sunghak

    2015-09-01

    [Purpose] The purpose of this study is to examine the effects of Juchumseogi and Juchumseo Jireugi motions on muscle activation of the paraspinal muscles. [Subjects] The subjects of this study were 20 healthy male students who listened to an explanation of the study methods and the purpose of the experiment, and agreed to participate in the study. [Methods] Muscle activation measurements of the paraspinal muscles at C3, T7, and L3 were taken while standing still and while performing Juchumseogi and Juchumseo Jireugi movements. The Juchumseogi and Juchumseo Jireugi motions were performed 3 times, and its mean value was used for analysis. [Results] The right and left muscle activation of paraspinal muscles induced by Juchumseogi and Juchumseo Jireugi motions in C3 and T7 were significantly higher than those induced by just standing. Muscle activation of paraspinal muscles induced by Juchumseo Jireugi motions in C3, T7, and L3 were significantly higher than those induced by Juchumseogi alone. The right and left muscle activation of paraspinal muscles induced by Juchumseo Jireugi motion in C3, T7, and L3 were significantly higher than those induced by standing and Juchumseogi alone. [Conclusion] This study demonstrated that Juchumseogi and Juchumseo Jireugi motions of Taekwondo could increase muscle activation of paraspinal muscles, and Juchumseo Jireugi motions were more effective for enhancing muscle activation of paraspinal muscles.

  15. Mimicking muscle activity with electrical stimulation

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    Johnson, Lise A.; Fuglevand, Andrew J.

    2011-02-01

    Functional electrical stimulation is a rehabilitation technology that can restore some degree of motor function in individuals who have sustained a spinal cord injury or stroke. One way to identify the spatio-temporal patterns of muscle stimulation needed to elicit complex upper limb movements is to use electromyographic (EMG) activity recorded from able-bodied subjects as a template for electrical stimulation. However, this requires a transfer function to convert the recorded (or predicted) EMG signals into an appropriate pattern of electrical stimulation. Here we develop a generalized transfer function that maps EMG activity into a stimulation pattern that modulates muscle output by varying both the pulse frequency and the pulse amplitude. We show that the stimulation patterns produced by this transfer function mimic the active state measured by EMG insofar as they reproduce with good fidelity the complex patterns of joint torque and joint displacement.

  16. Is Abdominal Muscle Activity Different from Lumbar Muscle Activity during Four-Point Kneeling?

    OpenAIRE

    Soraya Pirouzi; Farahnaz Emami; Shohreh Taghizadeh; Ali Ghanbari

    2013-01-01

    Background: Stabilization exercises can improve the performance of trunk and back muscles, which are effective in the prevention and treatment of low back pain. The four-point kneeling exercise is one of the most common types of stabilization exercises. This quasi-experimental study aimed to evaluate and compare the level of activation between abdominal and lumbar muscles in the different stages of the four-point kneeling exercise. Methods: The present study was conducted on 30 healthy wom...

  17. Muscle metaboreceptor modulation of cutaneous active vasodilation

    Science.gov (United States)

    Crandall, C. G.; Stephens, D. P.; Johnson, J. M.

    1998-01-01

    PURPOSE: Isometric handgrip exercise in hyperthermia has been shown to reduce cutaneous vascular conductance (CVC) by inhibiting the cutaneous active vasodilator system. METHODS: To identify whether this response was initiated by muscle metaboreceptors, in seven subjects two 3-min bouts of isometric handgrip exercise in hyperthermia were performed, followed by 2 min of postexercise ischemia (PEI). An index of forearm skin blood flow (laser-Doppler flowmetry) was measured on the contralateral arm at an unblocked site and at a site at which adrenergic vasoconstrictor function was blocked via bretylium iontophoresis to reveal active cutaneous vasodilator function unambiguously. Sweat rate was measured via capacitance hygrometry, CVC was indexed from the ratio of skin blood flow to mean arterial pressure and was expressed as a percentage of maximal CVC at that site. In normothermia, neither isometric exercise nor PEI affected CVC (P > 0.05). RESULTS: The first bout of isometric handgrip exercise in hyperthermia reduced CVC at control sites and this reduction persisted through PEI (pre-exercise: 59.8 +/- 5.4, exercise: 49.8 +/- 4.9, PEI: 49.7 +/- 5.3% of maximum; both P vasodilator system, is primarily mediated by muscle metaboreceptors, whereas central command or muscle mechanoreceptors have less influence.

  18. Core muscle activation during dynamic upper limb exercises in women.

    Science.gov (United States)

    Tarnanen, Sami P; Siekkinen, Kirsti M; Häkkinen, Arja H; Mälkiä, Esko A; Kautiainen, Hannu J; Ylinen, Jari J

    2012-12-01

    Although several everyday functions and sporting activities demand controlled use of the abdominal and back muscles while working with the upper limbs, the activity of core muscles during dynamic upper limb exercises in the standing position has not been studied extensively. The purpose of this cross-sectional study was to examine abdominal and back muscle activity during dynamic upper limb exercises while standing and to evaluate whether dynamic exercises are appropriate for strengthening muscles. The activation of the rectus abdominis, obliquus externus abdominis, longissimus, and multifidus muscles during dynamic bilateral or unilateral shoulder exercises with or without fixation of the pelvis was measured in 20 healthy women using surface electromyography. Trunk muscle activation during isometric maximum contraction was used as a comparative reference. With bilateral shoulder extension and unilateral shoulder horizontal adduction, abdominal muscle activity was >60% of activity during reference exercises. With unilateral shoulder horizontal abduction and shoulder extension exercises, back muscle activity was >60% of the activity level reference exercise. Muscle activation levels were 35-64% lower during shoulder horizontal adduction and abduction without fixation compared with exercises with fixation. The results indicate that upper limb exercises performed in the standing position are effective for activating core muscles. Bilateral and unilateral shoulder extension and unilateral shoulder horizontal abduction and adduction with the pelvis fixed elicited the greatest activity of the core muscles.

  19. Activation and intermuscular coherence of distal arm muscles during proximal muscle contraction.

    Science.gov (United States)

    Lee, Sang Wook; Landers, Katlin; Harris-Love, Michelle L

    2014-03-01

    In the human upper extremity (UE), unintended effects of proximal muscle activation on muscles controlling the hand could be an important aspect of motor control due to the necessary coordination of distal and proximal segments during functional activities. This study aimed to elucidate the effects of concurrent activation of elbow muscles on the coordination between hand muscles performing a grip task. Eleven healthy subjects performed precision grip tasks while a constant extension or flexion moment was applied to their elbow joints, inducing a sustained submaximal contraction of elbow muscles to counter the applied torque. Activation of four hand muscles was measured during each task condition using surface electromyography (EMG). When concurrent activation of elbow muscles was induced, significant changes in the activation levels of the hand muscles were observed, with greater effects on the extrinsic finger extensor (23.2 % increase under 30 % elbow extensor activation; p = 0.003) than extrinsic finger flexor (14.2 % increase under 30 % elbow flexor activation; p = 0.130). Elbow muscle activation also induced involuntary changes in the intrinsic thumb flexor activation (44.6 % increase under 30 % elbow extensor activation; p = 0.005). EMG-EMG coherence analyses revealed that elbow muscle activation significantly reduced intermuscular coherence between distal muscle pairs, with its greatest effects on coherence in the β-band (13-25 Hz) (average of 17 % decrease under 30 % elbow flexor activation). The results of this study provide evidence for involuntary, muscle-specific interactions between distal and proximal UE muscles, which may contribute to UE motor performance in health and disease.

  20. Relative Activity of Abdominal Muscles during Commonly Prescribed Strengthening Exercises.

    Science.gov (United States)

    Willett, Gilbert M.; Hyde, Jennifer E.; Uhrlaub, Michael B.; Wendel, Cara L.; Karst, Gregory M.

    2001-01-01

    Examined the relative electromyographic (EMG) activity of upper and lower rectus abdominis (LRA) and external oblique (EOA) muscles during five abdominal strengthening exercises. Isometric and dynamic EMG data indicated that abdominal strengthening exercises activated various abdominal muscle groups. For the LRA and EOA muscle groups, there were…

  1. Compensatory muscle activation in patients with glenohumeral cuff tears

    NARCIS (Netherlands)

    Steenbrink, Franciscus

    2010-01-01

    Patients suffering tendon tears in the glenohumeral cuff muscles show activation of muscles which pull the arm downwards during arm elevation tasks. This so-called co-activation deviates from healthy controls and is triggered by pain. Goal of this thesis was to demonstrate that deviating muscle

  2. Relative activity of respiratory muscles during prescribed inspiratory muscle training in healthy people

    OpenAIRE

    Jung, Ju-hyeon; Kim, Nan-soo

    2016-01-01

    [Purpose] This study aimed to determine the effects of different intensities of inspiratory muscle training on the relative respiratory muscle activity in healthy adults. [Subjects and Methods] Thirteen healthy male volunteers were instructed to perform inspiratory muscle training (0%, 40%, 60%, and 80% maximal inspiratory pressure) on the basis of their individual intensities. The inspiratory muscle training was performed in random order of intensities. Surface electromyography data were col...

  3. Breathing modes, body positions, and suprahyoid muscle activity.

    Science.gov (United States)

    Takahashi, S; Ono, T; Ishiwata, Y; Kuroda, T

    2002-12-01

    To determine (1) how electromyographic activities of the genioglossus and geniohyoid muscles can be differentiated, and (2) whether changes in breathing modes and body positions have effects on the genioglossus and geniohyoid muscle activities. Ten normal subjects participated in the study. Electromyographic activities of both the genioglossus and geniohyoid muscles were recorded during nasal and oral breathing, while the subject was in the upright and supine positions. The electromyographic activities of the genioglossus and geniohyoid muscles were compared during jaw opening, swallowing, mandibular advancement, and tongue protrusion. The geniohyoid muscle showed greater electromyographic activity than the genioglossus muscle during maximal jaw opening. In addition, the geniohyoid muscle showed a shorter (P breathing modes and body positions, while there were no significant differences in the geniohyoid muscle activity. Electromyographic activities from the genioglossus and geniohyoid muscles are successfully differentiated. In addition, it appears that changes in the breathing mode and body position significantly affect the genioglossus muscle activity, but do not affect the geniohyoid muscle activity.

  4. Muscle activation of paraspinal muscles in different types of high heels during standing.

    Science.gov (United States)

    Han, Dongwook

    2015-01-01

    [Purpose] This study researched the effects of different types of high heels on the muscles surrounding the cervical spine, the thoracic spine, and the lumbar spine by analyzing muscle activation of the paraspinal muscles during standing while wearing high heels. The high heels were all of the same height: 8 cm. [Subjects and Methods] The 28 subjects in this experiment were females in their 20s with a foot size of 225-230 mm and a normal gait pattern. To measure the muscle activation of the paraspinal muscles, EMG electrodes were attached on the paraspinal muscles around C6, T7, and L5. The muscle activation during standing while wearing 8-cm-high wedge heels, setback heels, and French heels was then measured. The measurements were performed 3 times each, and the mean value was used for analysis. [Results] The levels of muscle activation of the paraspinal muscles induced by standing on wedge heels, setback heels, and French heels in the cervical and lumbar areas were significantly higher than those induced by standing on bare feet. But there was no significant difference according to the heel types. [Conclusion] The height of the heels presented a greater variable than the width of the heels on the muscle activation of paraspinal muscles. Therefore, wearing high heels is not recommended for those who have pain or functional problems in the cervical and/or lumbar spine.

  5. Muscle activity pattern dependent pain development and alleviation

    DEFF Research Database (Denmark)

    Sjøgaard, Gisela; Søgaard, Karen

    2014-01-01

    during physical activities at leisure and sport the motor recruitment patterns are more dynamic including regularly relatively high muscle forces - also activating type 2 muscles fibers - as well as periods of full relaxation even of the type 1 muscle fibers. Such activity is unrelated to muscle pain......Muscle activity is for decades considered to provide health benefits irrespectively of the muscle activity pattern performed and whether it is during e.g. sports, transportation, or occupational work tasks. Accordingly, the international recommendations for public health-promoting physical activity...... do not distinguish between occupational and leisure time physical activity. However, in this body of literature, attention has not been paid to the extensive documentation on occupational physical activity imposing a risk of impairment of health - in particular musculoskeletal health in terms...

  6. A 3D skeletal muscle model coupled with active contraction of muscle fibres and hyperelastic behaviour.

    Science.gov (United States)

    Tang, C Y; Zhang, G; Tsui, C P

    2009-05-11

    This paper presents a three-dimensional finite element model of skeletal muscle which was developed to simulate active and passive non-linear mechanical behaviours of the muscle during lengthening or shortening under either quasi-static or dynamic condition. Constitutive relation of the muscle was determined by using a strain energy approach, while active contraction behaviour of the muscle fibre was simulated by establishing a numerical algorithm based on the concept of the Hill's three-element muscle model. The proposed numerical algorithm could be used to predict concentric, eccentric, isometric and isotonic contraction behaviours of the muscle. The proposed numerical algorithm and constitutive model for the muscle were derived and implemented into a non-linear large deformation finite element programme ABAQUS by using user-defined material subroutines. A number of scenarios have been used to demonstrate capability of the model for simulating both quasi-static and dynamic response of the muscle. Validation of the proposed model has been performed by comparing the simulated results with the experimental ones of frog gastrocenemius muscle deformation. The effects of the fusiform muscle geometry and fibre orientation on the stress and fibre stretch distributions of frog muscle during isotonic contraction have also been investigated by using the proposed model. The predictability of the present model for dynamic response of the muscle has been demonstrated by simulating the extension of a squid tentacle during a strike to catch prey.

  7. Mean individual muscle activities and ratios of total muscle activities in a selective muscle strengthening experiment: the effects of lower limb muscle activity based on mediolateral slope angles during a one-leg stance

    Science.gov (United States)

    Lee, Sang-Yeol

    2016-01-01

    [Purpose] The purpose of this study was to provide basic data for research on selective muscle strengthening by identifying mean muscle activities and calculating muscle ratios for use in developing strengthening methods. [Subjects and Methods] Twenty-one healthy volunteers were included in this study. Muscle activity was measured during a one-leg stance under 6 conditions of slope angle: 0°, 5°, 10°, 15°, 20°, and 25°. The data used in the analysis were root mean square and % total muscle activity values. [Results] There were significant differences in the root mean square of the gluteus medius, the hamstring, and the medial gastrocnemius muscles. There were significant differences in % total muscle activity of the medial gastrocnemius. [Conclusion] Future studies aimed at developing selective muscle strengthening methods are likely to yield more effective results by using muscle activity ratios based on electromyography data. PMID:27799690

  8. Can Graduated Compressive Stockings Reduce Muscle Activity during Running?

    Science.gov (United States)

    Lucas-Cuevas, Ángel Gabriel; Priego Quesada, José Ignacio; Giménez, José Vicente; Aparicio, Inmaculada; Cortell-Tormo, Juan Manuel; Pérez-Soriano, Pedro

    2017-01-01

    Purpose: Graduated compressive stockings (GCS) have been suggested to influence performance by reducing muscle oscillations and improving muscle function and efficiency. However, no study to date has analyzed the influence of GCS on muscle activity during running. The objective of the study was to analyze the influence of GCS on the perception of…

  9. Muscle activation patterns when passively stretching spastic lower limb muscles of children with cerebral palsy.

    Science.gov (United States)

    Bar-On, Lynn; Aertbeliën, Erwin; Molenaers, Guy; Desloovere, Kaat

    2014-01-01

    The definition of spasticity as a velocity-dependent activation of the tonic stretch reflex during a stretch to a passive muscle is the most widely accepted. However, other mechanisms are also thought to contribute to pathological muscle activity and, in patients post-stroke and spinal cord injury can result in different activation patterns. In the lower-limbs of children with spastic cerebral palsy (CP) these distinct activation patterns have not yet been thoroughly explored. The aim of the study was to apply an instrumented assessment to quantify different muscle activation patterns in four lower-limb muscles of children with CP. Fifty-four children with CP were included (males/females n = 35/19; 10.8 ± 3.8 yrs; bilateral/unilateral involvement n =  32/22; Gross Motor Functional Classification Score I-IV) of whom ten were retested to evaluate intra-rater reliability. With the subject relaxed, single-joint, sagittal-plane movements of the hip, knee, and ankle were performed to stretch the lower-limb muscles at three increasing velocities. Muscle activity and joint motion were synchronously recorded using inertial sensors and electromyography (EMG) from the adductors, medial hamstrings, rectus femoris, and gastrocnemius. Muscles were visually categorised into activation patterns using average, normalized root mean square EMG (RMS-EMG) compared across increasing position zones and velocities. Based on the visual categorisation, quantitative parameters were defined using stretch-reflex thresholds and normalized RMS-EMG. These parameters were compared between muscles with different activation patterns. All patterns were dominated by high velocity-dependent muscle activation, but in more than half, low velocity-dependent activation was also observed. Muscle activation patterns were found to be both muscle- and subject-specific (pmuscles into activation patterns (pmuscles with different patterns react differently to treatment.

  10. Barnacle muscle: Ca2+, activation and mechanics.

    Science.gov (United States)

    Ashley, C C; Griffiths, P J; Lea, T J; Mulligan, I P; Palmer, R E; Simnett, S J

    1993-01-01

    In this review, aspects of the ways in which Ca2+ is transported and regulated within muscle cells have been considered, with particular reference to crustacean muscle fibres. The large size of these fibres permits easy access to the internal environment of the cell, allowing it to be altered by microinjection or microperfusion. At rest, Ca2+ is not in equilibrium across the cell membrane, it enters the cell down a steep electrochemical gradient. The free [Ca2+] at rest is maintained at a value close to 200 nM by a combination of internal buffering systems, mainly the SR, mitochondria, and the fixed and diffusible Ca(2+)-binding proteins, as well as by an energy-dependent extrusion system operating across the external cell membrane. This system relies upon the inward movement of Na+ down its own electrochemical gradient to provide the energy for the extrusion of Ca2+ ions. As a result of electrical excitation, voltage-sensitive channels for Ca2+ are activated and permit Ca2+ to enter the cell more rapidly than at rest. It has been possible to determine both the amount of Ca2+ entering by this step, and what part this externally derived Ca2+ plays in the development of force as well as in the free Ca2+ change. The latter can be determined directly by Ca(2+)-sensitive indicators introduced into the cell sarcoplasm. A combination of techniques, allowing both the total and free Ca2+ changes to be assessed during electrical excitation, has provided valuable information as to how muscle cells buffer their Ca2+ in order to regulate the extent of the change in the free Ca2+ concentration. The data indicate that the entering Ca2+ can only make a small direct contribution to the force developed by the cell. The implication here is that the major source of Ca2+ for contraction must be derived from the internal Ca2+ storage sites within the SR system, a view reinforced by caged Ca2+ methods. The ability to measure the free Ca2+ concentration changes within a single cell during

  11. The influence of experimentally induced pain on shoulder muscle activity.

    Science.gov (United States)

    Diederichsen, Louise Pyndt; Winther, Annika; Dyhre-Poulsen, Poul; Krogsgaard, Michael R; Nørregaard, Jesper

    2009-04-01

    Muscle function is altered in painful shoulder conditions. However, the influence of shoulder pain on muscle coordination of the shoulder has not been fully clarified. The aim of the present study was to examine the effect of experimentally induced shoulder pain on shoulder muscle function. Eleven healthy men (range 22-27 years), with no history of shoulder or cervical problems, were included in the study. Pain was induced by 5% hypertonic saline injections into the supraspinatus muscle or subacromially. Seated in a shoulder machine, subjects performed standardized concentric abduction (0 degrees -105 degrees) at a speed of approximately 120 degrees/s, controlled by a metronome. During abduction, electromyographic (EMG) activity was recorded by intramuscular wire electrodes inserted in two deeply located shoulder muscles and by surface-electrodes over six superficially located shoulder muscles. EMG was recorded before pain, during pain and after pain had subsided and pain intensity was continuously scored on a visual analog scale (VAS). During abduction, experimentally induced pain in the supraspinatus muscle caused a significant decrease in activity of the anterior deltoid, upper trapezius and the infraspinatus and an increase in activity of lower trapezius and latissimus dorsi muscles. Following subacromial injection a significantly increased muscle activity was seen in the lower trapezius, the serratus anterior and the latissimus dorsi muscles. In conclusion, this study shows that acute pain both subacromially and in the supraspinatus muscle modulates coordination of the shoulder muscles during voluntary movements. During painful conditions, an increased activity was detected in the antagonist (latissimus), which support the idea that localized pain affects muscle activation in a way that protects the painful structure. Further, the changes in muscle activity following subacromial pain induction tend to expand the subacromial space and thereby decrease the load

  12. The origin of activity in the biceps brachii muscle during voluntary contractions of the contralateral elbow flexor muscles

    NARCIS (Netherlands)

    Zijdewind, Inge; Butler, Jane E.; Gandevia, Simon C.; Taylor, Janet L.

    2006-01-01

    During strong voluntary contractions, activity is not restricted to the target muscles. Other muscles, including contralateral muscles, often contract. We used transcranial magnetic stimulation (TMS) to analyse the origin of these unintended contralateral contractions (termed "associated" contractio

  13. The origin of activity in the biceps brachii muscle during voluntary contractions of the contralateral elbow flexor muscles

    NARCIS (Netherlands)

    Zijdewind, Inge; Butler, Jane E.; Gandevia, Simon C.; Taylor, Janet L.

    2006-01-01

    During strong voluntary contractions, activity is not restricted to the target muscles. Other muscles, including contralateral muscles, often contract. We used transcranial magnetic stimulation (TMS) to analyse the origin of these unintended contralateral contractions (termed "associated"

  14. Effects on hamstring muscle extensibility, muscle activity, and balance of different stretching techniques.

    Science.gov (United States)

    Lim, Kyoung-Il; Nam, Hyung-Chun; Jung, Kyoung-Sim

    2014-02-01

    [Purpose] The purpose of this study was to investigate the effects of two different stretching techniques on range of motion (ROM), muscle activation, and balance. [Subjects] For the present study, 48 adults with hamstring muscle tightness were recruited and randomly divided into three groups: a static stretching group (n=16), a PNF stretching group (n=16), a control group (n=16). [Methods] Both of the stretching techniques were applied to the hamstring once. Active knee extension angle, muscle activation during maximum voluntary isometric contraction (MVC), and static balance were measured before and after the application of each stretching technique. [Results] Both the static stretching and the PNF stretching groups showed significant increases in knee extension angle compared to the control group. However, there were no significant differences in muscle activation or balance between the groups. [Conclusion] Static stretching and PNF stretching techniques improved ROM without decrease in muscle activation, but neither of them exerted statistically significant effects on balance.

  15. Effects on Hamstring Muscle Extensibility, Muscle Activity, and Balance of Different Stretching Techniques

    Science.gov (United States)

    Lim, Kyoung-Il; Nam, Hyung-Chun; Jung, Kyoung-Sim

    2014-01-01

    [Purpose] The purpose of this study was to investigate the effects of two different stretching techniques on range of motion (ROM), muscle activation, and balance. [Subjects] For the present study, 48 adults with hamstring muscle tightness were recruited and randomly divided into three groups: a static stretching group (n=16), a PNF stretching group (n=16), a control group (n=16). [Methods] Both of the stretching techniques were applied to the hamstring once. Active knee extension angle, muscle activation during maximum voluntary isometric contraction (MVC), and static balance were measured before and after the application of each stretching technique. [Results] Both the static stretching and the PNF stretching groups showed significant increases in knee extension angle compared to the control group. However, there were no significant differences in muscle activation or balance between the groups. [Conclusion] Static stretching and PNF stretching techniques improved ROM without decrease in muscle activation, but neither of them exerted statistically significant effects on balance. PMID:24648633

  16. Estrogen effect on post-exercise skeletal muscle neutrophil infiltration and calpain activity

    National Research Council Canada - National Science Library

    Tiidus P.M; Holden D; Bombardier E; Zajchowski S; Enns D; Belcastro A

    2001-01-01

    We hypothesized that estrogen administration would attenuate skeletal muscle neutrophil infiltration, indices of muscle membrane disruption, and muscle calpain activity shortly after the termination of exercise...

  17. Breakpoints in Ventilation, Cerebral and Muscle Oxygenation, and Muscle Activity During an Incremental Cycling Exercise

    Directory of Open Access Journals (Sweden)

    Sebastien eRacinais

    2014-04-01

    Full Text Available The aim of this study was to locate the breakpoints of cerebral and muscle oxygenation and muscle electrical activity during a ramp exercise in reference to the first and second ventilatory thresholds. Twenty-five cyclists completed a maximal ramp test on an electromagnetically braked cycle-ergometer with a rate of increment of 25W/min. Expired gazes (breath-by-breath, prefrontal cortex and vastus lateralis (VL oxygenation (Near-infrared spectroscopy together with electromyographic Root Mean Square activity for the VL, rectus femoris (RF and biceps femoris (BF muscles were continuously assessed. There was a non-linear increase in both cerebral deoxyhemoglobin (at 56±13% of the exercise and oxyhemoglobin (56±8% of exercise concomitantly to the first ventilatory threshold (57±6% of exercise, p>0.86, Cohen’s d0.8. We identified one threshold only for muscle parameters with a non-linear decrease in muscle oxyhemoglobin (78±9% of exercise, attenuation in muscle deoxyhemoglobin (80±8% of exercise, and increase in electromyographic activity of VL (89±5 % of exercise, RF (82±14 % of exercise and BF (85±9 % of exercise. While the thresholds in muscle oxygenation and RF electromyographic activity were contemporary to V-T2 (d0.6. Our results suggest that the metabolic and ventilatory events characterizing this latter cardiopulmonary threshold may affect both cerebral and muscle oxygenation levels, and in turn, muscle recruitment responses.

  18. Anatomical correlation of core muscle activation in different yogic postures

    Directory of Open Access Journals (Sweden)

    Mrithunjay Rathore

    2017-01-01

    Full Text Available Faulty postures due to sedentary lifestyle cause weakening of core muscles which contributes to increased incidence of musculoskeletal disorders (MSDs. Although a few research studies have quantified the core muscle activity in various yogic exercises used in rehabilitation programs, evidence correlating it to functional anatomy is scarce. Such information is important for exercise prescription when formulating treatment plans for MSDs. Therefore, the objective of this review article is to examine the literature and analyze the muscle activity produced across various yoga postures to determine which type of yoga posture elicits the highest activation for the core muscle in individuals. Literature search was performed using the following electronic databases: Cochrane Library, NCBI, PubMed, Google Scholar, EMBASE, and web of science. The search terms contained: Core muscle activation and yogic posture OR yoga and rehabilitation OR intervention AND Electromyography. Activation of specific core muscle involved asanas which depended on trunk and pelvic movements. Description of specific yogic exercise as they relate to core muscles activation is described. This information should help in planning yogic exercises that challenge the muscle groups without causing loads that may be detrimental to recovery and pain-free movement. Knowledge of activation of muscles in various yogic postures can assist health-care practitioners to make appropriate decisions for the designing of safe and effective evidence-based yoga intervention for MSDs.

  19. Trunk muscle activities during abdominal bracing: comparison among muscles and exercises.

    Science.gov (United States)

    Maeo, Sumiaki; Takahashi, Takumi; Takai, Yohei; Kanehisa, Hiroaki

    2013-01-01

    Abdominal bracing is often adopted in fitness and sports conditioning programs. However, there is little information on how muscular activities during the task differ among the muscle groups located in the trunk and from those during other trunk exercises. The present study aimed to quantify muscular activity levels during abdominal bracing with respect to muscle- and exercise-related differences. Ten healthy young adult men performed five static (abdominal bracing, abdominal hollowing, prone, side, and supine plank) and five dynamic (V- sits, curl-ups, sit-ups, and back extensions on the floor and on a bench) exercises. Surface electromyogram (EMG) activities of the rectus abdominis (RA), external oblique (EO), internal oblique (IO), and erector spinae (ES) muscles were recorded in each of the exercises. The EMG data were normalized to those obtained during maximal voluntary contraction of each muscle (% EMGmax). The % EMGmax value during abdominal bracing was significantly higher in IO (60%) than in the other muscles (RA: 18%, EO: 27%, ES: 19%). The % EMGmax values for RA, EO, and ES were significantly lower in the abdominal bracing than in some of the other exercises such as V-sits and sit-ups for RA and EO and back extensions for ES muscle. However, the % EMGmax value for IO during the abdominal bracing was significantly higher than those in most of the other exercises including dynamic ones such as curl-ups and sit-ups. These results suggest that abdominal bracing is one of the most effective techniques for inducing a higher activation in deep abdominal muscles, such as IO muscle, even compared to dynamic exercises involving trunk flexion/extension movements. Key PointsTrunk muscle activities during abdominal bracing was examined with regard to muscle- and exercise-related differences.Abdominal bracing preferentially activates internal oblique muscles even compared to dynamic exercises involving trunk flexion/extension movements.Abdominal bracing should be

  20. Trunk muscle activity with different sitting postures and pelvic inclination

    OpenAIRE

    WATANABE, MASAHIRO; Kaneoka, Koji; Wada, Yusuke; Matsui, Yasushi; Miyakawa, Shumpei

    2014-01-01

    BACKGROUND AND OBJECTIVE: Sitting posture may often place large burden on trunk muscles, while trunk muscle activities in the sitting posture have not been well clarified. In this study, a difference in trunk muscle activity between two kinds of sitting postures was evaluated, focusing on low back pain induced by posture holding.MATERIAL AND METHODS: An experiment was conducted on the subjects sitting on a stable-seat and on an unstable-seat, with the pelvis inclined forward, backward, rightw...

  1. The influence of experimentally induced pain on shoulder muscle activity

    DEFF Research Database (Denmark)

    Diederichsen, L.P.; Winther, A.; Dyhre-Poulsen, P.

    2009-01-01

    muscles. EMG was recorded before pain, during pain and after pain had subsided and pain intensity was continuously scored on a visual analog scale (VAS). During abduction, experimentally induced pain in the supraspinatus muscle caused a significant decrease in activity of the anterior deltoid, upper...... in a way that protects the painful structure. Further, the changes in muscle activity following subacromial pain induction tend to expand the subacromial space and thereby decrease the load on the painful structures Udgivelsesdato: 2009/4...

  2. Tirasemtiv amplifies skeletal muscle response to nerve activation in humans

    OpenAIRE

    Hansen,Richard; Saikali, Khalil G; Chou, Willis; Alan J Russell; Chen, Michael M.; Vijayakumar, Vipin; Stoltz, Randall R.; Baudry, Stephane; Enoka, Roger M.; Morgans, David J; Wolff, Andrew A.; Malik, Fady I

    2014-01-01

    Introduction: In this study we tested the hypothesis that tirasemtiv, a selective fast skeletal muscle troponin activator that sensitizes the sarcomere to calcium, could amplify the response of muscle to neuromuscular input in humans. Methods: Healthy men received tirasemtiv and placebo in a randomized, double-blind, 4-period, crossover design. The deep fibular nerve was stimulated transcutaneously to activate the tibialis anterior muscle and produce dorsiflexion of the foot. The force–freque...

  3. Relative activity of respiratory muscles during prescribed inspiratory muscle training in healthy people.

    Science.gov (United States)

    Jung, Ju-Hyeon; Kim, Nan-Soo

    2016-03-01

    [Purpose] This study aimed to determine the effects of different intensities of inspiratory muscle training on the relative respiratory muscle activity in healthy adults. [Subjects and Methods] Thirteen healthy male volunteers were instructed to perform inspiratory muscle training (0%, 40%, 60%, and 80% maximal inspiratory pressure) on the basis of their individual intensities. The inspiratory muscle training was performed in random order of intensities. Surface electromyography data were collected from the right-side diaphragm, external intercostal, and sternocleidomastoid, and pulmonary functions (forced expiratory volume in 1 s, forced vital capacity, and their ratio; peak expiratory flow; and maximal inspiratory pressure) were measured. [Results] Comparison of the relative activity of the diaphragm showed significant differences between the 60% and 80% maximal inspiratory pressure intensities and baseline during inspiratory muscle training. Furthermore, significant differences were found in sternocleidomastoid relative activity between the 60% and 80% maximal inspiratory pressure intensities and baseline during inspiratory muscle training. [Conclusion] During inspiratory muscle training in the clinic, the patients were assisted (verbally or through feedback) by therapists to avoid overactivation of their accessory muscles (sternocleidomastoid). This study recommends that inspiratory muscle training be performed at an accurate and appropriate intensity through the practice of proper deep breathing.

  4. MUSCLE ACTIVATION DURING LOW-INTENSITY MUSCLE CONTRACTIONS WITH VARYING LEVELS OF EXTERNAL LIMB COMPRESSION

    Directory of Open Access Journals (Sweden)

    Tomohiro Yasuda

    2008-12-01

    Full Text Available The purpose was to investigate muscle activation during low- intensity muscle contractions with various levels of external limb compression to reduce muscle perfusion/outflow. A series of unilateral elbow flexion muscle contractions (30 repetitive contractions followed by 3 sets x 15 contractions was performed at 20% of 1RM with varying levels of external compression (0 (without compression, 98, 121, and 147 mmHg external compression around the upper arm. Electromyography (EMG signals were recorded from surface electrodes placed on the biceps brachii muscle and analyzed for integrated EMG (iEMG. Maximal voluntary isometric contraction (MVC decreased similarly during the control (0 mmHg and 98 mmHg external compression bout (~18%; the decline in MVC with 121 and 147 mmHg external compression was significantly greater (~37%. Muscle activation increased progressively throughout the contraction bout with each level of external compression, but iEMG was significantly greater during 147 mmHg external compression. In conclusion, low-intensity muscle contractions performed with external compression of 147 mmHg appears to alter muscle perfusion/outflow leading to increased muscle activation without decrements in work performed during the contraction bout

  5. Agonist muscle activity and antagonist muscle co-activity levels during standardized isotonic and isokinetic knee extensions.

    Science.gov (United States)

    Remaud, Anthony; Cornu, Christophe; Guével, Arnaud

    2009-06-01

    This study aimed to analyze the effects of the contraction mode (isotonic vs. isokinetic concentric conditions), the joint angle and the investigated muscle on agonist muscle activity and antagonist muscle co-activity during standardized knee extensions. Twelve healthy adult subjects performed three sets of isotonic knee extensions at 40% of their maximal voluntary isometric torque followed by three sets of maximal isokinetic knee extensions on an isokinetic dynamometer. For each set, the mean angular velocity and the total external amount of work performed were standardized during the two contraction modes. Surface electromyographic activity of vastus lateralis (VL), vastus medialis (VM), rectus femoris (RF), semitendinosus (ST) and biceps femoris (BF) muscles was recorded. Root mean square values were then calculated for each 10 degrees between 85 degrees and 45 degrees of knee extension (0 degrees =horizontal position). Results show that agonist muscle activity and antagonist muscle co-activity levels are significantly greater in isotonic mode compared to isokinetic mode. Quadriceps activity and hamstrings co-activity are significantly lower at knee extended position in both contraction modes. Considering agonist muscles, VL reveals a specific pattern of activity compared to VM and RF; whereas considering hamstring muscles, BF shows a significantly higher co-activity than ST in both contraction modes. Results of this study confirmed our hypothesis that higher quadriceps activity is required during isotonic movements compared to isokinetic movements leading to a higher hamstrings co-activity.

  6. Muscle activation patterns when passively stretching spastic lower limb muscles of children with cerebral palsy.

    Directory of Open Access Journals (Sweden)

    Lynn Bar-On

    Full Text Available The definition of spasticity as a velocity-dependent activation of the tonic stretch reflex during a stretch to a passive muscle is the most widely accepted. However, other mechanisms are also thought to contribute to pathological muscle activity and, in patients post-stroke and spinal cord injury can result in different activation patterns. In the lower-limbs of children with spastic cerebral palsy (CP these distinct activation patterns have not yet been thoroughly explored. The aim of the study was to apply an instrumented assessment to quantify different muscle activation patterns in four lower-limb muscles of children with CP. Fifty-four children with CP were included (males/females n = 35/19; 10.8 ± 3.8 yrs; bilateral/unilateral involvement n =  32/22; Gross Motor Functional Classification Score I-IV of whom ten were retested to evaluate intra-rater reliability. With the subject relaxed, single-joint, sagittal-plane movements of the hip, knee, and ankle were performed to stretch the lower-limb muscles at three increasing velocities. Muscle activity and joint motion were synchronously recorded using inertial sensors and electromyography (EMG from the adductors, medial hamstrings, rectus femoris, and gastrocnemius. Muscles were visually categorised into activation patterns using average, normalized root mean square EMG (RMS-EMG compared across increasing position zones and velocities. Based on the visual categorisation, quantitative parameters were defined using stretch-reflex thresholds and normalized RMS-EMG. These parameters were compared between muscles with different activation patterns. All patterns were dominated by high velocity-dependent muscle activation, but in more than half, low velocity-dependent activation was also observed. Muscle activation patterns were found to be both muscle- and subject-specific (p<0.01. The intra-rater reliability of all quantitative parameters was moderate to good. Comparing RMS-EMG between

  7. Comparison between muscle activation measured by electromyography and muscle thickness measured using ultrasonography for effective muscle assessment.

    Science.gov (United States)

    Kim, Chang-Yong; Choi, Jong-Duk; Kim, Suhn-Yeop; Oh, Duck-Won; Kim, Jin-Kyung; Park, Ji-Whan

    2014-10-01

    In this study, we aimed to compare the intrarater reliability and validity of muscle thickness measured using ultrasonography (US) and muscle activity via electromyography (EMG) during manual muscle testing (MMT) of the external oblique (EO) and lumbar multifidus (MF) muscles. The study subjects were 30 healthy individuals who underwent MMT at different grades. EMG was used to measure the muscle activity in terms of ratio to maximum voluntary contraction (MVC) and root mean square (RMS) metrics. US was used to measure the raw muscle thickness, the ratio of muscle thickness at MVC, and the ratio of muscle thickness at rest. One examiner performed measurements on each subject in 3 trials. The intrarater reliabilities of the % MVC RMS and raw RMS metrics for EMG and the % MVC thickness metrics for US were excellent (ICC=0.81-0.98). There was a significant difference between all the grades measured using the % MVC thickness metric (pEMG measurement methods than with the others (r=0.51-0.61). Our findings suggest that the % MVC thickness determined by US was the most sensitive of all methods for assessing the MMT grade.

  8. Fatigue effects on tracking performance and muscle activity

    NARCIS (Netherlands)

    Huysmans, M.A.; Hoozemans, M.J.M.; Beek, A.J. van der; Looze, M.P. de; Dieën, J.H. van

    2008-01-01

    It has been suggested that fatigue affects proprioception and consequently movement accuracy, the effects of which may be counteracted by increased muscle activity. To determine the effects of fatigue on tracking performance and muscle activity in the M. extensor carpi radialis (ECR), 11 female

  9. Fatigue effects on tracking performance and muscle activity

    NARCIS (Netherlands)

    Huysmans, M.A.; Hoozemans, M.J.M.; Beek, A.J. van der; Looze, M.P. de; Dieën, J.H. van

    2008-01-01

    It has been suggested that fatigue affects proprioception and consequently movement accuracy, the effects of which may be counteracted by increased muscle activity. To determine the effects of fatigue on tracking performance and muscle activity in the M. extensor carpi radialis (ECR), 11 female part

  10. Effects of muscle activation on shear between human soleus and gastrocnemius muscles.

    Science.gov (United States)

    Finni, T; Cronin, N J; Mayfield, D; Lichtwark, G A; Cresswell, A G

    2017-01-01

    Lateral connections between muscles provide pathways for myofascial force transmission. To elucidate whether these pathways have functional roles in vivo, we examined whether activation could alter the shear between the soleus (SOL) and lateral gastrocnemius (LG) muscles. We hypothesized that selective activation of LG would decrease the stretch-induced shear between LG and SOL. Eleven volunteers underwent a series of knee joint manipulations where plantar flexion force, LG, and SOL muscle fascicle lengths and relative displacement of aponeuroses between the muscles were obtained. Data during a passive full range of motion were recorded, followed by 20° knee extension stretches in both passive conditions and with selective electrical stimulation of LG. During active stretch, plantar flexion force was 22% greater (P muscles, at least at flexed knee joint angles, which may serve to facilitate myofascial force transmission. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  11. Muscle triacylglycerol and hormone-sensitive lipase activity in untrained and trained human muscles

    DEFF Research Database (Denmark)

    Helge, Jørn Wulff; Biba, Taus O; Galbo, Henrik

    2006-01-01

    During exercise, triacylglycerol (TG) is recruited in skeletal muscles. We hypothesized that both muscle hormone-sensitive lipase (HSL) activity and TG recruitment would be higher in trained than in untrained subjects in response to prolonged exercise. Healthy male subjects (26 +/- 1 years, body ...

  12. Posture, muscle activity and muscle fatigue in prolonged VDT work at different screen height settings.

    Science.gov (United States)

    Seghers, Jan; Jochem, Arnaud; Spaepen, Arthur

    2003-06-10

    With the increasing use of video display terminals (VDTs), there is growing concern over the corresponding increase in the number of health problems reported. Although much research has focused on identifying the optimal screen height, there is to date no consensus. This study aimed to investigate the effect of prolonged (89 min) VDT work at four different screen heights on head-neck posture, muscle activity and the development of muscle fatigue. The results show that lowering screen height, starting from 15 cm above the baseline (i.e. top of the screen level with eye height while sitting), decreased the ear-eye angle, increased the viewing angle, increased the viewing angle relative to the ear-eye line, and increased the muscle activity of the neck extensor muscles. There were also some significant time effects on postural angles and muscle activity. In this study there were only rare occurrences of muscle fatigue, defined as a simultaneous increase in EMG amplitude and a shift of the EMG power spectrum to lower frequencies. Muscle activity increased significantly in some muscles and for certain screen heights.

  13. Glycerol kinase activities in muscles from vertebrates and invertebrates.

    Science.gov (United States)

    Newsholme, E A; Taylor, K

    1969-05-01

    1. Glycerol kinase (EC 2.7.1.30) activity was measured in crude extracts of skeletal muscles by a radiochemical method. The properties of the enzyme from a number of different muscles are very similar to those of the enzyme from rat liver. Glycerol kinase from locust flight muscle was inhibited competitively by l-3-glycerophosphate with a K(i) of 4.0x10(-4)m. 2. The activity of glycerol kinase was measured in a variety of muscles from vertebrates and invertebrates in an attempt to explain the large variation in the activity of this enzyme in different muscles. 3. In vertebrates glycerol kinase activities were generally higher in red muscle than in white muscle; the highest activities (approx. 0.2mumole/min./g. fresh wt.) were found in the red breast muscle of some birds (e.g. pigeon, duck, blue tit) whereas the activities in the white breast muscle of the pheasant and domestic fowl were very low (approx. 0.02mumole/min./g.). 4. On the basis of glycerol kinase activities, muscles from insects can be classified into three groups: muscles that have a low enzyme activity, i.e. muscles of all insects studied and the flight muscles of cockroaches and the tsetse fly); muscles that have an intermediate enzyme activity, i.e. 0.3-1.5mumoles/min./g. (e.g. locusts, cockchafers, moths, water-bugs); and muscles that have a high enzyme activity, i.e. >1.5mumoles/min./g. (e.g. bees, wasps, some blowflies). 5. The function of glycerol kinase in vertebrate and insect muscles that possess a low or intermediate activity is considered to be the removal of glycerol that is produced from lipolysis of triglyceride or diglyceride by the muscle. Therefore in these muscles the activity of glycerol kinase is related to the metabolism of fat, which is used to support sustained muscular activity. A possible regulatory role of glycerol kinase in the initiation of triglyceride or diglyceride lipolysis is discussed. 6. The function of glycerol kinase in the insect muscles that possess a high

  14. Hypermetabolism of skeletal muscles following sexual activity: a normal variation.

    Science.gov (United States)

    Choi, Byung Wook; Kim, Sung Hoon; Kim, Hae Won; Won, Kyoung Sook; Zeon, Seok Kil

    2010-09-01

    A 46-year-old man with early gastric cancer at the gastric antrum underwent an F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET)-computer tomography (CT) scan for staging. No definite abnormal FDG uptake of the stomach was shown. Incidentally, variable FDG uptake at the bilateral serratus muscles, abdominal muscles and muscles of both thighs (Fig. 1) was observed. He had no significant past medical history except recently diagnosed stomach cancer. On personal interview, he described having had sexual activity the night before the F-18 FDG PET/CT scan, although he was aware of needing to avoid physical activity before a PET scan. The F-18 FDG PET/CT scan was done at 2:00 p.m. Therefore, the hypermetabolism of individual skeletal muscles following sexual activity lasted over 12 h. This case illustrates the hypermetabolism of skeletal muscles following sexual activity as a normal variation.

  15. Repositioning forelimb superficialis muscles: tendon attachment and muscle activity enable active relocation of functional myofibers.

    Science.gov (United States)

    Huang, Alice H; Riordan, Timothy J; Wang, Lingyan; Eyal, Shai; Zelzer, Elazar; Brigande, John V; Schweitzer, Ronen

    2013-09-16

    The muscles that govern hand motion are composed of extrinsic muscles that reside within the forearm and intrinsic muscles that reside within the hand. We find that the extrinsic muscles of the flexor digitorum superficialis (FDS) first differentiate as intrinsic muscles within the hand and then relocate as myofibers to their final position in the arm. This remarkable translocation of differentiated myofibers across a joint is dependent on muscle contraction and muscle-tendon attachment. Interestingly, the intrinsic flexor digitorum brevis (FDB) muscles of the foot are identical to the FDS in tendon pattern and delayed developmental timing but undergo limited muscle translocation, providing strong support for evolutionary homology between the FDS and FDB muscles. We propose that the intrinsic FDB pattern represents the original tetrapod limb and that translocation of the muscles to form the FDS is a mammalian evolutionary addition.

  16. Comparison of Estimated and Measured Muscle Activity During Inclined Walking.

    Science.gov (United States)

    Alexander, Nathalie; Schwameder, Hermann

    2016-04-01

    While inclined walking is a frequent daily activity, muscle forces during this activity have rarely been examined. Musculoskeletal models are commonly used to estimate internal forces in healthy populations, but these require a priori validation. The aim of this study was to compare estimated muscle activity using a musculoskeletal model with measured EMG data during inclined walking. Ten healthy male participants walked at different inclinations of 0°, ± 6°, ± 12°, and ± 18° on a ramp equipped with 2 force plates. Kinematics, kinetics, and muscle activity of the musculus (m.) biceps femoris, m. rectus femoris, m. vastus lateralis, m. tibialis anterior, and m. gastrocnemius lateralis were recorded. Agreement between estimated and measured muscle activity was determined via correlation coefficients, mean absolute errors, and trend analysis. Correlation coefficients between estimated and measured muscle activity for approximately 69% of the conditions were above 0.7. Mean absolute errors were rather high with only approximately 38% being ≤ 30%. Trend analysis revealed similar estimated and measured muscle activities for all muscles and tasks (uphill and downhill walking), except m. tibialis anterior during uphill walking. This model can be used for further analysis in similar groups of participants.

  17. Muscle Activation during Gait in Children with Duchenne Muscular Dystrophy

    Science.gov (United States)

    Vuillerot, Carole; Tiffreau, Vincent; Peudenier, Sylviane; Cuisset, Jean-Marie; Pereon, Yann; Leboeuf, Fabien; Delporte, Ludovic; Delpierre, Yannick; Gross, Raphaël

    2016-01-01

    The aim of this prospective study was to investigate changes in muscle activity during gait in children with Duchenne muscular Dystrophy (DMD). Dynamic surface electromyography recordings (EMGs) of 16 children with DMD and pathological gait were compared with those of 15 control children. The activity of the rectus femoris (RF), vastus lateralis (VL), medial hamstrings (HS), tibialis anterior (TA) and gastrocnemius soleus (GAS) muscles was recorded and analysed quantitatively and qualitatively. The overall muscle activity in the children with DMD was significantly different from that of the control group. Percentage activation amplitudes of RF, HS and TA were greater throughout the gait cycle in the children with DMD and the timing of GAS activity differed from the control children. Significantly greater muscle coactivation was found in the children with DMD. There were no significant differences between sides. Since the motor command is normal in DMD, the hyper-activity and co-contractions likely compensate for gait instability and muscle weakness, however may have negative consequences on the muscles and may increase the energy cost of gait. Simple rehabilitative strategies such as targeted physical therapies may improve stability and thus the pattern of muscle activity. PMID:27622734

  18. How is AMPK activity regulated in skeletal muscles during exercise?

    DEFF Research Database (Denmark)

    Jørgensen, Sebastian Beck; Rose, Adam John

    2008-01-01

    discuss the influence of reactive oxygen species produced within the muscle as well as muscle glycogen and TAK1 in regulating AMPK during exercise. Currently, during intensive contraction, activation of alpha2-AMPK seems mainly to rely on AMP accumulating from ATP-hydrolysis whereas calcium signaling may...

  19. Pathophysiology of Tonic Muscle Activation During Epileptic Seizures

    DEFF Research Database (Denmark)

    Beniczky, S.; Conradsen, Isa; Wolf, P.

    2011-01-01

    , quantitative analysis of the sEMG during the epileptic seizures has received surprisingly little attention. The aim of our study was to elucidate the pathophysiology of the tonic muscle activation during seizures. SEMG was recorded from the deltoid muscles, during 58 seizures from 18 patients (9...

  20. Effect of Expiratory Resistive Loading in Expiratory Muscle Strength Training on Orbicularis Oris Muscle Activity

    Science.gov (United States)

    Yanagisawa, Yukio; Matsuo, Yoshimi; Shuntoh, Hisato; Horiuchi, Noriaki

    2014-01-01

    [Purpose] The purpose of this study was to elucidate the effect of expiratory resistive loading on orbicularis oris muscle activity. [Subjects] Subjects were 23 healthy individuals (11 males, mean age 25.5±4.3 years; 12 females, mean age 25.0±3.0 years). [Methods] Surface electromyography was performed to measure the activity of the orbicularis oris muscle during maximum lip closure and resistive loading at different expiratory pressures. Measurement was performed at 10%, 30%, 50%, and 100% of maximum expiratory pressure (MEP) for all subjects. The t-test was used to compare muscle activity between maximum lip closure and 100% MEP, and analysis of variance followed by multiple comparisons was used to compare the muscle activities observed at different expiratory pressures. [Results] No significant difference in muscle activity was observed between maximum lip closure and 100% MEP. Analysis of variance with multiple comparisons revealed significant differences among the different expiratory pressures. [Conclusion] Orbicularis oris muscle activity increased with increasing expiratory resistive loading. PMID:24648644

  1. An activation-recruitment scheme for use in muscle modeling.

    Science.gov (United States)

    Hawkins, D A; Hull, M L

    1992-12-01

    The derivation of a new activation-recruitment scheme and the results of a study designed to test its validity are presented. The activation scheme utilizes input data of processed surface EMG signals, muscle composition, muscle architecture, and experimentally determined activation coefficients. In the derivation, the relationship between muscle activation and muscle fiber recruitment was considered. In the experimental study, triceps muscle force was determined for isometric elbow extension tasks varying in intensity from 10 to 100% of a maximum voluntary contraction (MVC) using both a muscle model that incorporates the activation scheme, and inverse dynamics techniques. The forces calculated using the two methods were compared statistically. The modeled triceps force was not significantly different from the experimental results determined using inverse dynamics techniques for average activation levels greater than 25% of MVC, but was significantly different for activation levels less than 25% of MVC. These results lend support for use of the activation-recruitment scheme for moderate to large activation levels, and suggest that factors in addition to fiber recruitment play a role in force regulation at lower activation levels.

  2. Afferent contribution to locomotor muscle activity during unconstrained overground human walking: an analysis of triceps surae muscle fascicles

    DEFF Research Database (Denmark)

    Klint, Richard af; Cronin, Neil J.; Ishikawa, Masaki

    2010-01-01

    Plantar flexor series elasticity can be used to dissociate muscle fascicle and muscle tendon behaviour and, therefore, afferent feedback during human walking. We used electromyography (EMG) and high speed ultrasonography concomitantly to monitor muscle activity and muscle fascicle behaviour in ni...

  3. A method for studying jaw muscle activity during standardized jaw movements under experimental jaw muscle pain.

    Science.gov (United States)

    Sae-Lee, Daraporn; Wanigaratne, Kamal; Whittle, Terry; Peck, Christopher C; Murray, Greg M

    2006-10-30

    This paper describes a method for studying superficial and deep jaw muscle activity during standardized jaw movements under experimental jaw muscle pain. In 22 healthy adults, pain was elicited in the right masseter muscle via tonic infusion of 4.5% hypertonic saline and which resulted in scores of 30-60 mm on a 100-mm visual analogue scale. Subjects performed tasks in five sessions in a repeated measures design, i.e., control 1, test 1 (during hypertonic or isotonic saline infusion), control 2 (without infusion), test 2 (during isotonic or hypertonic saline infusion), control 3 (without infusion). During each session, subjects performed maximal clenching and standardized jaw tasks, i.e., protrusion, lateral excursion, open/close, chewing. Mandibular movement was recorded with a 6-degree-of-freedom tracking system simultaneously with electromyographic (EMG) activity from the inferior head of the lateral pterygoid muscle with fine-wire electrodes (verified by computer tomography), and from posterior temporalis, the submandibular muscle group and bilateral masseter muscles with surface electrodes. EMG root mean square values were calculated at each 0.5 mm increment of mandibular incisor movement for all tasks under each experimental session. This establishes an experimental model for testing the effects of pain on jaw muscle activity where the jaw motor system is required to perform goal-directed tasks, and therefore should extend our understanding of the effects of pain on the jaw motor system.

  4. Maximal force, voluntary activation and muscle soreness after eccentric damage to human elbow flexor muscles

    Science.gov (United States)

    Prasartwuth, O; Taylor, JL; Gandevia, SC

    2005-01-01

    Muscle damage reduces voluntary force after eccentric exercise but impaired neural drive to the muscle may also contribute. To determine whether the delayed-onset muscle soreness, which develops ∼1 day after exercise, reduces voluntary activation and to identify the possible site for any reduction, voluntary activation of elbow flexor muscles was examined with both motor cortex and motor nerve stimulation. We measured maximal voluntary isometric torque (MVC), twitch torque, muscle soreness and voluntary activation in eight subjects before, immediately after, 2 h after, 1, 2, 4 and 8 days after eccentric exercise. Motor nerve stimulation and motor cortex stimulation were used to derive twitch torques and measures of voluntary activation. Eccentric exercise immediately reduced the MVC by 38 ± 3% (mean ±s.d., n = 8). The resting twitch produced by motor nerve stimulation fell by 82 ± 6%, and the estimated resting twitch by cortical stimulation fell by 47 ± 15%. While voluntary torque recovered after 8 days, both measures of the resting twitch remained depressed. Muscle tenderness occurred 1–2 days after exercise, and pain during contractions on days 1–4, but changes in voluntary activation did not follow this time course. Voluntary activation assessed with nerve stimulation fell 19 ± 6% immediately after exercise but was not different from control values after 2 days. Voluntary activation assessed by motor cortex stimulation was unchanged by eccentric exercise. During MVCs, absolute increments in torque evoked by nerve and cortical stimulation behaved differently. Those to cortical stimulation decreased whereas those to nerve stimulation tended to increase. These findings suggest that reduced voluntary activation contributes to the early force loss after eccentric exercise, but that it is not due to muscle soreness. The impairment of voluntary activation to nerve stimulation but not motor cortical stimulation suggests that the activation deficit lies in the

  5. Force steadiness, muscle activity, and maximal muscle strength in subjects with subacromial impingement syndrome

    DEFF Research Database (Denmark)

    Bandholm, Thomas; Rasmussen, Lars; Aagaard, Per

    2006-01-01

    We investigated the effects of the subacromial impingement syndrome (SIS) on shoulder sensory-motor control and maximal shoulder muscle strength. It was hypothesized that both would be impaired due to chronic shoulder pain associated with the syndrome. Nine subjects with unilateral SIS who remained...... physically active in spite of shoulder pain and nine healthy matched controls were examined to determine isometric and isokinetic submaximal shoulder-abduction force steadiness at target forces corresponding to 20%, 27.5%, and 35% of the maximal shoulder abductor torque, and maximal shoulder muscle strength...... (MVC). Electromyographic (EMG) activity was assessed using surface and intramuscular recordings from eight shoulder muscles. Force steadiness was impaired in SIS subjects during concentric contractions at the highest target force level only, with muscle activity largely unaffected. No between...

  6. Timing of Cortico-Muscle Transmission During Active Movement.

    Science.gov (United States)

    Van Acker, Gustaf M; Luchies, Carl W; Cheney, Paul D

    2016-08-01

    Numerous studies have reported large disparities between short cortico-muscle conduction latencies and long recorded delays between cortical firing and evoked muscle activity. Using methods such as spike- and stimulus-triggered averaging of electromyographic (EMG) activity, previous studies have shown that the time delay between corticomotoneuronal (CM) cell firing and onset of facilitation of forelimb muscle activity ranges from 6.7 to 9.8 ms, depending on the muscle group tested. In contrast, numerous studies have reported delays of 60-122 ms between cortical cell firing onset and either EMG or movement onset during motor tasks. To further investigate this disparity, we simulated rapid active movement by applying frequency-modulated stimulus trains to M1 cortical sites in a rhesus macaque performing a movement task. This yielded corresponding EMG modulations, the latency of which could be measured relative to the stimulus modulations. The overall mean delay from stimulus frequency modulation to EMG modulation was 11.5 ± 5.6 ms, matching closely the conduction time through the cortico-muscle pathway (12.6 ± 2.0 ms) derived from poststimulus facilitation peaks computed at the same sites. We conclude that, during active movement, the delay between modulated M1 cortical output and its impact on muscle activity approaches the physical cortico-muscle conduction time.

  7. Influence of different control strategies on muscle activation patterns in trunk muscles.

    Science.gov (United States)

    Hansen, Laura; Anders, Christoph

    2014-12-01

    Adequate training of the trunk muscles is essential to prevent low back pain. Although sit-ups are simple to perform, the perceived high effort is the reason why training the abdominal muscles is seldom continued over a longer period of time. It is well known that the abdominal muscles are inferior to the back muscles in terms of force, but this cannot explain the extreme difference in perceived effort between trunk flexion and extension tasks. Therefore, this study was aimed at the identification of control strategy influences on the muscular stress level. Thirty-nine subjects were investigated. The performed tasks were restricted to the sagittal plane and were implemented with simulated and realized tilt angles. Subjects were investigated in an upright position with their lower bodies fixed and their upper bodies free. Posture-controlled tasks involved graded forward and backward tilting, while force-controlled tasks involved the application of force based on a virtual tilt angle. The Surface EMG (SEMG) was taken from five trunk muscles on both sides. Control strategies seemed to have no systematic influence on the SEMG amplitudes of the back muscles. In contrast, the abdominal muscles exhibited significantly higher stress levels under posture-controlled conditions without relevantly increasing antagonistic co-activation of back muscles. The abdominal muscles' relative differences ranged from an average of 20% for the external oblique abdominal muscle to approximately 40% for the rectus abdominal muscle. The perceived high effort expended during sit-ups can now be explained by the posture-controlled contractions that are required.

  8. Muscle activation sequencing of leg muscles during linear glide shot putting.

    Science.gov (United States)

    Howard, Róisín M; Conway, Richard; Harrison, Andrew J

    2017-11-01

    In the shot put, the athlete's muscles are responsible for generating the impulses to move the athlete and project the shot into the air. Information on phasic muscle activity is lacking for the glide shot put event and therefore important technical information for coaches is not currently available. This study provides an electromyography (EMG) analysis of the muscle activity of the legs during shot put. Fifteen right-handed Irish national level shot putters performed six maximum effort throws using the glide shot put technique. EMG records of eight bilateral lower limb muscles (rectus femoris, biceps femoris, medial- and lateral-gastrocnemius) were obtained during trials. Analysis using smooth EMG linear envelopes revealed patterns of muscle activity across the phases of the throw and compare men and women performers. The results showed that the preferred leg rectus femoris, the preferred leg biceps femoris and the non-preferred leg biceps femoris play important roles in the glide technique, with the total duration of high volumes of activity between 34 and 53% of the throw cycle. A comprehensive understanding of movement and muscle activation patterns for coaches could be helpful to facilitate optimal technique throughout each of the key phases of the event.

  9. Respiratory Muscle Activity During Simultaneous Stationary Cycling and Inspiratory Muscle Training.

    Science.gov (United States)

    Hellyer, Nathan J; Folsom, Ian A; Gaz, Dan V; Kakuk, Alynn C; Mack, Jessica L; Ver Mulm, Jacyln A

    2015-12-01

    Inspiratory muscle training (IMT) strengthens the muscles of respiration, improves breathing efficiency, and increases fitness. The IMT is generally performed independently of aerobic exercise; however, it is not clear whether there is added benefit of performing the IMT while simultaneously performing aerobic exercise in terms of activating and strengthening inspiratory muscles. The purpose of our study was to determine the effect of IMT on respiratory muscle electromyography (EMG) activity during stationary cycling in the upright and drops postures as compared with that when the IMT was performed alone. Diaphragm and sternocleidomastoid EMG activity was measured under different resting and cycling postures, with and without the use of the IMT at 40% maximal inspiratory pressure (n = 10; mean age 37). Cycling in an upright posture while simultaneously performing the IMT resulted in a significantly greater diaphragm EMG activity than while performing the IMT at rest in upright or drops postures (p ≤ 0.05). Cycling in drops postures while performing the IMT had a significantly greater diaphragm EMG activity than when performing the IMT at rest in either upright or drops postures (p ≤ 0.05). Sternocleidomastoid muscle activity increased with both cycling and IMT, although posture had little effect. These results support our hypothesis in that the IMT while cycling increases respiratory EMG activity to a significantly greater extent than when performing the IMT solely at rest, suggesting that the combination of IMT and cycling may provide an additive training effect.

  10. [Electromyographic (EMG) electrode impedance and EMG activity from anterior temporal muscle and masseter muscle].

    Science.gov (United States)

    Takarada, T; Alvarado Larrinaga, G; Nishida, F; Nishino, M

    1989-01-01

    The value and change with time of the impedance of surface EMG electrodes and the effects of their difference between the bipolar electrodes on the electromyographic activity from the anterior temporal muscle and the masseter muscle in six adult male subjects with normal occlusion were studied. The results were as follows: 1. In the anterior temporal muscle, if the impedance of the electrode was under 20 k omega it was stable from just after the electrode disc was applied to the skin. In the masseter muscle, if the impedance was under 30 k omega it became stable within two minutes after the electrode was applied. 2. The difference of impedance between the bipolar EMG electrodes did not correlate with EMG activity.

  11. Muscle Activity of the Gluteus Medius at Different Gait Speeds

    National Research Council Canada - National Science Library

    Lee, Su-Kyoung; Lee, Sang-Yeol; Jung, Jae-Min

    2014-01-01

    [Purpose] The present study aimed to determine the changes in the muscle activities of the gluteus medius, latissimus dorsi, and gluteus maximus at different gait speeds, to collect basic data for the study of the gluteus medius...

  12. The effects of finger extension on shoulder muscle activity

    National Research Council Canada - National Science Library

    Yi, Chae-Woo; Shin, Ju-Yong; Kim, Youn-Joung

    2015-01-01

    ...) on the activity of the shoulder muscles (proximal upper limb). [Subjects and Methods] This study involved 14 healthy male adults with no musculoskeletal disorder or pain related to the shoulders and hands...

  13. Integration core exercises elicit greater muscle activation than isolation exercises.

    Science.gov (United States)

    Gottschall, Jinger S; Mills, Jackie; Hastings, Bryce

    2013-03-01

    The American College of Sports Medicine and the United States Department of Health and Human Services advocate core training as a means to improve stability, reduce injury, and maintain mobility. There are countless exercises that target the primary core trunk muscles (abdominal and lumbar) with the aim of providing these benefits. However, it is unknown as to which exercises elicit the greatest activation thereby maximizing functional gains and peak performance. Thus, our purpose was to determine whether integration core exercises that require activation of the distal trunk muscles (deltoid and gluteal) elicit greater activation of primary trunk muscles in comparison with isolation core exercises that only require activation of the proximal trunk muscles. Twenty participants, 10 men and 10 women, completed 16 randomly assigned exercises (e.g., crunch, upper body extension, and hover variations). We measured muscle activity with surface electromyography of the anterior deltoid, rectus abdominus, external abdominal oblique, lumbar erector spinae, thoracic erector spinae, and gluteus maximus. Our results indicate that the activation of the abdominal and lumbar muscles was the greatest during the exercises that required deltoid and gluteal recruitment. In conclusion, when completing the core strength guidelines, an integrated routine that incorporates the activation of distal trunk musculature would be optimal in terms of maximizing strength, improving endurance, enhancing stability, reducing injury, and maintaining mobility.

  14. Enhanced muscle activity during lumbar extension exercise with pelvic stabilization.

    Science.gov (United States)

    Lee, Ho-Seong

    2015-12-01

    The purpose of this study was to investigate whether pelvic stabilization affects multifidus (MF) and iliocostalis lumborum (IL) muscle activities during dynamic extension exercise. Nine males (age, 25.1±6.3 yr; height, 176.6±2.4 cm; body mass, 74.9±6.7 kg) performed an isometric lumbar extension strength test and dynamic exercise in an upright seated position with or without pelvic stabilization. The electromyography and muscle strength of the MF and IL muscles were measured when the subjects performed the isometric lumbar extension strength test at the trunk angle 110°, 146°, and 182°. In addition, the trunk extensor muscle activities were measured using 50% muscle strength of maximum isometric strength during a dynamic trunk extension exercise. The MF and IL muscle activities were significantly higher at 110°, 146°, and 182° with pelvic stabilization than that without pelvic stabilization during the isometric lumbar extension strength test (Plumbar extension exercise with pelvic stabilization may be more effective for MF and IL muscle activity compared to that without pelvic stabilization.

  15. TRUNK MUSCLE ACTIVITIES DURING ABDOMINAL BRACING: COMPARISON AMONG MUSCLES AND EXERCISES

    Directory of Open Access Journals (Sweden)

    Sumiaki Maeo

    2013-09-01

    Full Text Available Abdominal bracing is often adopted in fitness and sports conditioning programs. However, there is little information on how muscular activities during the task differ among the muscle groups located in the trunk and from those during other trunk exercises. The present study aimed to quantify muscular activity levels during abdominal bracing with respect to muscle- and exercise-related differences. Ten healthy young adult men performed five static (abdominal bracing, abdominal hollowing, prone, side, and supine plank and five dynamic (V- sits, curl-ups, sit-ups, and back extensions on the floor and on a bench exercises. Surface electromyogram (EMG activities of the rectus abdominis (RA, external oblique (EO, internal oblique (IO, and erector spinae (ES muscles were recorded in each of the exercises. The EMG data were normalized to those obtained during maximal voluntary contraction of each muscle (% EMGmax. The % EMGmax value during abdominal bracing was significantly higher in IO (60% than in the other muscles (RA: 18%, EO: 27%, ES: 19%. The % EMGmax values for RA, EO, and ES were significantly lower in the abdominal bracing than in some of the other exercises such as V-sits and sit-ups for RA and EO and back extensions for ES muscle. However, the % EMGmax value for IO during the abdominal bracing was significantly higher than those in most of the other exercises including dynamic ones such as curl-ups and sit-ups. These results suggest that abdominal bracing is one of the most effective techniques for inducing a higher activation in deep abdominal muscles, such as IO muscle, even compared to dynamic exercises involving trunk flexion/extension movements

  16. The efficacy of progressive muscle relaxation in combination with spinal manipulative therapy on active trigger points of the trapezius muscle

    OpenAIRE

    2013-01-01

    M.Tech. (Chiropractic) Purpose: The trapezius muscle is thought to be the muscle most commonly associated with the presence of active myofascial trigger points (MFTP’s). Studies of the trapezius muscle clearly show that muscular activity significantly increases in response to psychological stress. Cervical spine manipulation has been proven to be highly effective in the treatment of active MFTP’s and muscular tension. Progressive muscle relaxation (PMR) therapy is frequently utilized as a ...

  17. The influence of experimentally induced pain on shoulder muscle activity

    DEFF Research Database (Denmark)

    Diederichsen, Louise Pyndt; Winther, Annika; Dyhre-Poulsen, Poul

    2009-01-01

    . EMG was recorded before pain, during pain and after pain had subsided and pain intensity was continuously scored on a visual analog scale (VAS). During abduction, experimentally induced pain in the supraspinatus muscle caused a significant decrease in activity of the anterior deltoid, upper trapezius...... the painful structure. Further, the changes in muscle activity following subacromial pain induction tend to expand the subacromial space and thereby decrease the load on the painful structures....

  18. Active and passive behaviors of soft tissues: Pelvic floor muscles

    OpenAIRE

    Areias, P.; Pato, M. P. M.

    2010-01-01

    A new active-contraction visco-elastic numerical model of the pelvic floor (skeletal) muscle is presented. Our model includes all elements that represent the muscle constitutive behavior, contraction and relaxation. In contrast with the previous models, the activation function can be null. The complete equations are shown and exactly linearized. Small verification and validation tests are performed and the pelvis is modeled using the data from the intra-abdominal pressure tests.

  19. Impaired glycogen synthase activity and mitochondrial dysfunction in skeletal muscle

    DEFF Research Database (Denmark)

    Højlund, Kurt; Beck-Nielsen, Henning

    2006-01-01

    expression analysis and proteomics have pointed to abnormalities in mitochondrial oxidative phosphorylation and cellular stress in muscle of type 2 diabetic subjects, and recent work suggests that impaired mitochondrial activity is another early defect in the pathogenesis of type 2 diabetes. This review...... will discuss the latest advances in the understanding of the molecular mechanisms underlying insulin resistance in human skeletal muscle in type 2 diabetes with focus on possible links between impaired glycogen synthase activity and mitochondrial dysfunction....

  20. Muscle atrophy reversed by growth factor activation of satellite cells in a mouse muscle atrophy model.

    Directory of Open Access Journals (Sweden)

    Simon Hauerslev

    Full Text Available Muscular dystrophies comprise a large group of inherited disorders that lead to progressive muscle wasting. We wanted to investigate if targeting satellite cells can enhance muscle regeneration and thus increase muscle mass. We treated mice with hepatocyte growth factor and leukemia inhibitory factor under three conditions: normoxia, hypoxia and during myostatin deficiency. We found that hepatocyte growth factor treatment led to activation of the Akt/mTOR/p70S6K protein synthesis pathway, up-regulation of the myognic transcription factors MyoD and myogenin, and subsequently the negative growth control factor, myostatin and atrophy markers MAFbx and MuRF1. Hypoxia-induced atrophy was partially restored by hepatocyte growth factor combined with leukemia inhibitory factor treatment. Dividing satellite cells were three-fold increased in the treatment group compared to control. Finally, we demonstrated that myostatin regulates satellite cell activation and myogenesis in vivo following treatment, consistent with previous findings in vitro. Our results suggest, not only a novel in vivo pharmacological treatment directed specifically at activating the satellite cells, but also a myostatin dependent mechanism that may contribute to the progressive muscle wasting seen in severely affected patients with muscular dystrophy and significant on-going regeneration. This treatment could potentially be applied to many conditions that feature muscle wasting to increase muscle bulk and strength.

  1. Muscle size, neuromuscular activation, and rapid force characteristics in elderly men and women

    DEFF Research Database (Denmark)

    Suetta, C; Aagaard, P; Magnusson, S P

    2007-01-01

    quadriceps muscle cross-sectional area (LCSA), contractile rate of force development (RFD, Delta force/Delta time), impulse (integral force dt), muscle activation deficit (interpolated twitch technique), maximal neuromuscular activity [electromyogram (EMG)], and antagonist muscle coactivation in elderly men...

  2. Forward Head Posture and Activation of Rectus Capitis Posterior Muscles.

    Science.gov (United States)

    Hallgren, Richard C; Pierce, Steven J; Sharma, Dhruv B; Rowan, Jacob J

    2017-01-01

    Rectus capitis posterior (RCP) muscles have physical attachments to the pain-sensitive spinal dura. Atrophy of these muscles is associated with chronic headache in some patients. The authors suspect that the significance of atrophy in the RCP muscles has been undervalued because the functional role of these muscles is not well defined. To determine whether a statistically significant change in normalized levels of electromyographic activity in RCP muscles occurs when the head is voluntarily moved from a self-selected neutral head position to a protruded head position. Fine wire, intramuscular electrodes were used to collect electromyographic data as asymptomatic participants moved their head from a neutral head position into a forward head position and back into the neutral head position. This sequence was repeated 4 times. Normalized levels of electromyographic activity were quantified using a 2-head position × 2 sides of the body repeated measures design that incorporated mixed-effects β regression models. Twenty participants were studied. Electromyographic activity collected from RCP muscles was found to increase as the head was voluntarily moved from a self-selected neutral head position (11% of maximum voluntary isometric contraction [MVIC] in RCP minor, 14% of MVIC in RCP major) into a protruded head position (35% of MVIC in RCP minor, 39% of MVIC in RCP major) (P<.001). Rectus capitis posterior muscles may contribute to segmental stabilization of the occipitoatlantal and atlantoaxial joints by helping to maintain joint congruency during movement of the head.

  3. Breast size impacts spine motion and postural muscle activation.

    Science.gov (United States)

    Schinkel-Ivy, Alison; Drake, Janessa D M

    2016-11-21

    While it is generally accepted that large breast sizes in females contribute to back pain and poor posture, the effects of breast size on spinal motion and muscle activation characteristics are poorly understood. This study examined the relationship between breast size, spine motion, and trunk muscle activation. Fifteen university-aged females, free of back pain symptoms, were tested. Breast sizes were calculated, and three-dimensional spine motion and activation from five trunk muscles bilaterally were measured during standing and trunk flexion movements. Correlations between breast size and motion and muscle activation measures were assessed. Head and trunk angles were strongly, negatively correlated to breast size during upright standing; thoracic angles were moderately, positively correlated to breast size during thoracic flexion movements. Trunk muscles showed positive, moderate-strength relationships with breast size during upright standing and some trunk movements. These findings provide a preliminary indication that increasing breast sizes are associated with altered postures and increased muscle activation in a non-clinical population, and constitute a baseline for the study of females with a full range of breast sizes. Further research is required to confirm the generalizability of these findings to other sizes, in order to inform strategies for the prevention or reduction of back pain, as well as diagnosis, treatment, and rehabilitation techniques associated with breast size and back pain.

  4. The relationship between human skeletal muscle pyruvate dehydrogenase phosphatase activity and muscle aerobic capacity.

    Science.gov (United States)

    Love, Lorenzo K; LeBlanc, Paul J; Inglis, J Greig; Bradley, Nicolette S; Choptiany, Jon; Heigenhauser, George J F; Peters, Sandra J

    2011-08-01

    Pyruvate dehydrogenase (PDH) is a mitochondrial enzyme responsible for regulating the conversion of pyruvate to acetyl-CoA for use in the tricarboxylic acid cycle. PDH is regulated through phosphorylation and inactivation by PDH kinase (PDK) and dephosphorylation and activation by PDH phosphatase (PDP). The effect of endurance training on PDK in humans has been investigated; however, to date no study has examined the effect of endurance training on PDP in humans. Therefore, the purpose of this study was to examine differences in PDP activity and PDP1 protein content in human skeletal muscle across a range of muscle aerobic capacities. This association is important as higher PDP activity and protein content will allow for increased activation of PDH, and carbohydrate oxidation. The main findings of this study were that 1) PDP activity (r(2) = 0.399, P = 0.001) and PDP1 protein expression (r(2) = 0.153, P = 0.039) were positively correlated with citrate synthase (CS) activity as a marker for muscle aerobic capacity; 2) E1α (r(2) = 0.310, P = 0.002) and PDK2 protein (r(2) = 0.229, P =0.012) are positively correlated with muscle CS activity; and 3) although it is the most abundant isoform, PDP1 protein content only explained ∼ 18% of the variance in PDP activity (r(2) = 0.184, P = 0.033). In addition, PDP1 in combination with E1α explained ∼ 38% of the variance in PDP activity (r(2) = 0.383, P = 0.005), suggesting that there may be alternative regulatory mechanisms of this enzyme other than protein content. These data suggest that with higher muscle aerobic capacity (CS activity) there is a greater capacity for carbohydrate oxidation (E1α), in concert with higher potential for PDH activation (PDP activity).

  5. Relation between muscle and brain activity during isometric contractions of the first dorsal interosseus muscle

    NARCIS (Netherlands)

    van Duinen, Hiske; Renken, Remco; Maurits, Natasha M.; Zijdewind, Inge

    2008-01-01

    We studied the relationship between muscle activity (electromyography, EMG), force, and brain activity during isometric contractions of the index finger, on a group and individual level. Ten subjects contracted their right or left index finger at 5, 15, 30, 50, and 70% of their maximal force. Subjec

  6. Muscle activity and inactivity periods during normal daily life.

    Science.gov (United States)

    Tikkanen, Olli; Haakana, Piia; Pesola, Arto J; Häkkinen, Keijo; Rantalainen, Timo; Havu, Marko; Pullinen, Teemu; Finni, Taija

    2013-01-01

    Recent findings suggest that not only the lack of physical activity, but also prolonged times of sedentary behaviour where major locomotor muscles are inactive, significantly increase the risk of chronic diseases. The purpose of this study was to provide details of quadriceps and hamstring muscle inactivity and activity during normal daily life of ordinary people. Eighty-four volunteers (44 females, 40 males, 44.1±17.3 years, 172.3±6.1 cm, 70.1±10.2 kg) were measured during normal daily life using shorts measuring muscle electromyographic (EMG) activity (recording time 11.3±2.0 hours). EMG was normalized to isometric MVC (EMG(MVC)) during knee flexion and extension, and inactivity threshold of each muscle group was defined as 90% of EMG activity during standing (2.5±1.7% of EMG(MVC)). During normal daily life the average EMG amplitude was 4.0±2.6% and average activity burst amplitude was 5.8±3.4% of EMG(MVC) (mean duration of 1.4±1.4 s) which is below the EMG level required for walking (5 km/h corresponding to EMG level of about 10% of EMG(MVC)). Using the proposed individual inactivity threshold, thigh muscles were inactive 67.5±11.9% of the total recording time and the longest inactivity periods lasted for 13.9±7.3 min (2.5-38.3 min). Women had more activity bursts and spent more time at intensities above 40% EMG(MVC) than men (p<0.05). In conclusion, during normal daily life the locomotor muscles are inactive about 7.5 hours, and only a small fraction of muscle's maximal voluntary activation capacity is used averaging only 4% of the maximal recruitment of the thigh muscles. Some daily non-exercise activities such as stair climbing produce much higher muscle activity levels than brisk walking, and replacing sitting by standing can considerably increase cumulative daily muscle activity.

  7. Muscle activity and inactivity periods during normal daily life.

    Directory of Open Access Journals (Sweden)

    Olli Tikkanen

    Full Text Available Recent findings suggest that not only the lack of physical activity, but also prolonged times of sedentary behaviour where major locomotor muscles are inactive, significantly increase the risk of chronic diseases. The purpose of this study was to provide details of quadriceps and hamstring muscle inactivity and activity during normal daily life of ordinary people. Eighty-four volunteers (44 females, 40 males, 44.1±17.3 years, 172.3±6.1 cm, 70.1±10.2 kg were measured during normal daily life using shorts measuring muscle electromyographic (EMG activity (recording time 11.3±2.0 hours. EMG was normalized to isometric MVC (EMG(MVC during knee flexion and extension, and inactivity threshold of each muscle group was defined as 90% of EMG activity during standing (2.5±1.7% of EMG(MVC. During normal daily life the average EMG amplitude was 4.0±2.6% and average activity burst amplitude was 5.8±3.4% of EMG(MVC (mean duration of 1.4±1.4 s which is below the EMG level required for walking (5 km/h corresponding to EMG level of about 10% of EMG(MVC. Using the proposed individual inactivity threshold, thigh muscles were inactive 67.5±11.9% of the total recording time and the longest inactivity periods lasted for 13.9±7.3 min (2.5-38.3 min. Women had more activity bursts and spent more time at intensities above 40% EMG(MVC than men (p<0.05. In conclusion, during normal daily life the locomotor muscles are inactive about 7.5 hours, and only a small fraction of muscle's maximal voluntary activation capacity is used averaging only 4% of the maximal recruitment of the thigh muscles. Some daily non-exercise activities such as stair climbing produce much higher muscle activity levels than brisk walking, and replacing sitting by standing can considerably increase cumulative daily muscle activity.

  8. Effects of Physical Activity and Inactivity on Muscle Fatigue

    Science.gov (United States)

    Bogdanis, Gregory C.

    2012-01-01

    The aim of this review was to examine the mechanisms by which physical activity and inactivity modify muscle fatigue. It is well known that acute or chronic increases in physical activity result in structural, metabolic, hormonal, neural, and molecular adaptations that increase the level of force or power that can be sustained by a muscle. These adaptations depend on the type, intensity, and volume of the exercise stimulus, but recent studies have highlighted the role of high intensity, short-duration exercise as a time-efficient method to achieve both anaerobic and aerobic/endurance type adaptations. The factors that determine the fatigue profile of a muscle during intense exercise include muscle fiber composition, neuromuscular characteristics, high energy metabolite stores, buffering capacity, ionic regulation, capillarization, and mitochondrial density. Muscle fiber-type transformation during exercise training is usually toward the intermediate type IIA at the expense of both type I and IIx myosin heavy-chain isoforms. High-intensity training results in increases of both glycolytic and oxidative enzymes, muscle capillarization, improved phosphocreatine resynthesis and regulation of K+, H+, and lactate ions. Decreases of the habitual activity level due to injury or sedentary lifestyle result in partial or even compete reversal of the adaptations due to previous training, manifested by reductions in fiber cross-sectional area, decreased oxidative capacity, and capillarization. Complete immobilization due to injury results in markedly decreased force output and fatigue resistance. Muscle unloading reduces electromyographic activity and causes muscle atrophy and significant decreases in capillarization and oxidative enzymes activity. The last part of the review discusses the beneficial effects of intermittent high-intensity exercise training in patients with different health conditions to demonstrate the powerful effect of exercise on health and well being. PMID

  9. Effects of physical activity and inactivity on muscle fatigue

    Directory of Open Access Journals (Sweden)

    Gregory C. Bogdanis

    2012-05-01

    Full Text Available The aim of this review was to examine the mechanisms by which physical activity and inactivity modify muscle fatigue. It is well known that acute or chronic increases in physical activity result in structural, metabolic, hormonal, neural and molecular adaptations that increase the level of force or power that can be sustained by a muscle. These adaptations depend on the type, intensity and volume of the exercise stimulus, but recent studies have highlighted the role of high intensity, short duration exercise as a time-efficient method to achieve both anaerobic and aerobic/endurance type adaptations. The factors that determine the fatigue profile of a muscle during intense exercise include muscle fibre composition, neuromuscular characteristics high energy metabolite stores, buffering capacity, ionic regulation, capillarization and mitochondrial density. Muscle fiber type transformation during exercise training is usually towards the intermediate type IIA at the expense of both type I and type IIx myosin heavy chain isoforms. High intensity training results in increases of both glycolyic and oxidative enzymes, muscle capilarization, improved phosphocreatine resynthesis and regulation of K+, H+ and lactate ions. Decreases of the habitual activity level due to injury or sedentary lifestyle result in partial or even compete reversal of the adaptations due to previous training, manifested by reductions in fibre cross-sectional area, decreased oxidative capacity and capillarization. Complete immobilization due to injury results in markedly decreased force output and fatigue resistance. Muscle unloading reduces electromyographic activity and causes muscle atrophy and significant decreases in capillarization and oxidative enzymes activity. The last part of the review discusses the beneficial effects of intermittent high intensity exercise training in patients with different health conditions to demonstrate the powerful effect exercise on health and well

  10. Muscle activity and kinematics of forefoot and rearfoot strike runners

    Directory of Open Access Journals (Sweden)

    A.N. Ahn

    2014-06-01

    Conclusion: This earlier and longer relative activation of the plantarflexors likely enhances the capacity for the passive structures of the foot and ankle to store elastic energy, and may also enhance the performance of the active muscle by increasing the storage of elastic strain energy in the cross-bridges and activated titin.

  11. Pelvic floor muscle contraction and abdominal hollowing during walking can selectively activate local trunk stabilizing muscles.

    Science.gov (United States)

    Lee, Ah Young; Baek, Seung Ok; Cho, Yun Woo; Lim, Tae Hong; Jones, Rodney; Ahn, Sang Ho

    2016-11-21

    Trunk muscle exercises are widely performed, and many studies have been performed to examine their effects on low back pains. However, the effect of trunk muscles activations during walking with pelvic floor muscle contraction (PFMC) and abdominal hollowing (AH) has not been clarified. To investigate whether walking with PFMC and AH is more effective for promoting local trunk muscle activation than walking without PFMC and AH. Twenty healthy men (28.9 ± 3.14 years, 177.2 ± 4.25 cm, 72.1 ± 6.39 kg, body mass index 22.78 ± 2.38 kg/m2) were participated in this study. Surface electrodes were attached over the multifidus (MF), lumbar erector spinae (LES), thoracic erector spinae (TES), transverse abdominus-internal oblique abdominals (TrA-IO), external oblique abdominals (EO), and rectus abdominus (RA). The amplitudes of electromyographic signals were measured during a normal walking with and without PFMC and AH. PFMC and AH while walking was found to result in significant bilateral increases in the normalized maximum voluntary contraction (MVC) of MFs and TrA-IOs (pmuscle activity to global muscle activities were increased while performing PFMC and AH during normal walking. Bilateral TrA-IO/EO activity ratios were significantly increased by PFMC and AH (pmuscles. This study suggests that PFMC and AH during normal daily walking improves activation of muscles responsible for spinal dynamic stabilization and might be useful if integrated into low back disability and pain physical rehabilitation efforts.

  12. [The characteristics of masticatory muscle activity in bruxers].

    Science.gov (United States)

    Li, Xue-ling; Lin, Xue-feng; Teng, Wei; Li, Shao-hua

    2008-12-01

    To evaluate the effects of bruxism on masticatory muscle electromyographic (EMG) activity. Twenty-four bruxers and sixteen asymptomatic control subjects were included through questionnaire and clinical examination. EMG activity was recorded by placing surface electrodes on bilateral anterior temporalis (TA), masseters (MM), anterior digastrics (DA) and sternocleidomastoid (SCM) muscles. EMG activities at rest, during maximal voluntary clenching in intercuspal position and swallowing were recorded by means of Bio PAK system. EMG activities of TA and MM at rest were significantly higher in bruxism group than in control group (PEMG activity during swallowing was no significant difference between the two groups. The asymmetry index of bilateral TA and MM in bruxism group was a little higher than the control group, but there was no significant difference between the two groups (P>0.05). Masticatory muscle dysfunction of bruxers is mainly represented as higher potential in postural position and lower potential during maximal voluntary clenching in intercuspal position of anterior temporalis and masseters.

  13. Modeling and simulation of fish swimming with active muscles.

    Science.gov (United States)

    Curatolo, Michele; Teresi, Luciano

    2016-11-21

    Our goal is to reproduce the key features of carangiform swimming by modeling muscle functioning using the notion of active distortions, thus emphasizing the kinematical role of muscle, the generation of movement, rather than the dynamical one, the production of force. This approach, already proposed to model the action of muscles in different contexts, is here tested again for the problem of developing an effective and reliable framework to model and simulate swimming. A proper undulatory movement of a fish-like body is reproduced by defining a pattern of distortions, tuned in both space and time, meant to model the muscles activation which produce the flexural motion of body fish; eventually, interactions with the surrounding water yields the desired thrust. Carangiform swimmers have a relatively inflexible anterior body section and a generally flat, flexible posterior section. Because of this configuration, undulations sent rearward along the body attain a significant amplitude only in the posterior section. We compare the performances of different swimming gaits, and we are able to find some important relations between key parameters such as frequencies, wavelength, tail amplitude, and the achieved swim velocity, or the generated thrust, which summarize the swimming performance. In particular, an interesting relation is found between the Strouhal number and the wavelength of muscles activation. We highlight the muscle function during fish locomotion describing the activation of muscles and the relation between the force production and the shortening-lengthening cycle of muscle. We found a great accordance between results and empirical relations, giving an implicit validation of our models. Copyright © 2016 Elsevier Ltd. All rights reserved.

  14. Dynamics of muscle activation during tonic-clonic seizures

    DEFF Research Database (Denmark)

    Conradsen, Isa; Moldovan, Mihai; Jennum, Poul

    2012-01-01

    The purpose of our study was to elucidate the dynamics of muscle activation during generalised tonic-clonic seizures (GTCS). We recorded surface electromyography (EMG) from the deltoid muscle during 26 GTCS from 13 patients and compared it with GTCS-like events acted by 10 control subjects. GTCS ...... is a valuable tool for monitoring the balance between pro-convulsive and anti-convulsive factors....

  15. Reflex influences on muscle spindle activity in relaxed human leg muscles.

    Science.gov (United States)

    Gandevia, S C; Miller, S; Aniss, A M; Burke, D

    1986-07-01

    The study was designed to determine whether low-threshold cutaneous and muscle afferents from the foot reflexly activate gamma-motoneurons innervating relaxed muscles of the leg. In 15 experiments multiunit recordings were made from 21 nerve fascicles innervating triceps surae or tibialis anterior. In a further nine experiments the activity of 19 identified single muscle spindle afferents was recorded, 13 from triceps surae, 5 from tibialis anterior, and 1 from extensor digitorum longus. Trains of electrical stimuli (5 stimuli, 300 Hz) were delivered to the sural nerve at the ankle (intensity, twice sensory threshold) and the posterior tibial nerve at the ankle (intensity, 1.1 times motor threshold for the small muscles of the foot). In addition, a tap on the appropriate tendon at varying times after the stimuli was used to assess the dynamic responsiveness of the afferents under study. The conditioning electrical stimuli did not change the discharge of single spindle afferents. Recordings of rectified and averaged multiunit activity also revealed no change in the overall level of background neural activity following the electrical stimuli. The afferent responses to tendon taps did not differ significantly whether or not they were preceded by stimulation of the sural or posterior tibial nerves. These results suggest that low-threshold afferents from the foot do not produce significant activation of fusimotor neurons in relaxed leg muscles, at least as judged by their ability to alter the discharge of muscle spindle afferents. As there may be no effective background activity in fusimotor neurons innervating relaxed human muscles, it is possible that these inputs from the foot could influence the fusimotor system during voluntary contractions when the fusimotor neurons have been brought to firing threshold. In one subject trains of stimuli were delivered to the posterior tibial nerve at painful levels (30 times motor threshold). They produced an acceleration of the

  16. Effect of Expiratory Resistive Loading in Expiratory Muscle Strength Training on Orbicularis Oris Muscle Activity

    OpenAIRE

    2014-01-01

    [Purpose] The purpose of this study was to elucidate the effect of expiratory resistive loading on orbicularis oris muscle activity. [Subjects] Subjects were 23 healthy individuals (11 males, mean age 25.5±4.3 years; 12 females, mean age 25.0±3.0 years). [Methods] Surface electromyography was performed to measure the activity of the orbicularis oris muscle during maximum lip closure and resistive loading at different expiratory pressures. Measurement was performed at 10%, 30%, 50%, and 100% o...

  17. The syndrome of continuous muscle fibre activity following gold therapy.

    Science.gov (United States)

    Grisold, W; Mamoli, B

    1984-01-01

    A 72-year-old man suffering from arthritis received a total dose of 500 mg sodium aurothiomalate during a period of 5 months. His clinical state then deteriorated and he had to be hospitalized. Upon admission he was bedridden, his level of consciousness was slightly impaired, he was confused and respiration was laboured. Continuous muscle activity was noted on all extremities and at first, erroneously, fasciculations were diagnosed. The EMG exhibited continuous muscle fibre activity consisting of duplets, triplets and multiplets. The discharges occurred in an irregular pattern; when various muscles were examined at the same time no synchronicity could be observed between muscle discharges. In the left m. deltoideus an increased percentage of polyphasic potentials was found, whereas mean duration of motor unit potentials was normal. Spontaneous activity remained unchanged during sleep and administration of intravenous diazepam or phenytoin. Blocking of ulnar nerve at either elbow or wrist level did not stop spontaneous activity in m. abductor digiti quinti. Ischaemia increased the amount of discharges after 7 min. Within 4 months after termination of gold therapy the patient's condition improved and he was discharged from hospital. Regular EMG follow-up after 8 months showed complete cessation of abnormal spontaneous activities. Nerve conduction velocities were normal except for markedly reduced compound action potential in peroneal nerves. Continuous muscle fibre activity as a side-effect of gold therapy is described.

  18. Baroreflex modulation of muscle sympathetic nerve activity during posthandgrip muscle ischemia in humans

    Science.gov (United States)

    Cui, J.; Wilson, T. E.; Shibasaki, M.; Hodges, N. A.; Crandall, C. G.

    2001-01-01

    To identify whether muscle metaboreceptor stimulation alters baroreflex control of muscle sympathetic nerve activity (MSNA), MSNA, beat-by-beat arterial blood pressure (Finapres), and electrocardiogram were recorded in 11 healthy subjects in the supine position. Subjects performed 2 min of isometric handgrip exercise at 40% of maximal voluntary contraction followed by 2.5 min of posthandgrip muscle ischemia. During muscle ischemia, blood pressure was lowered and then raised by intravenous bolus infusions of sodium nitroprusside and phenylephrine HCl, respectively. The slope of the relationship between MSNA and diastolic blood pressure was more negative (P ischemia (-201.9 +/- 20.4 units. beat(-1). mmHg(-1)) when compared with control conditions (-142.7 +/- 17.3 units. beat(-1). mmHg(-1)). No significant change in the slope of the relationship between heart rate and systolic blood pressure was observed. However, both curves shifted during postexercise ischemia to accommodate the elevation in blood pressure and MSNA that occurs with this condition. These data suggest that the sensitivity of baroreflex modulation of MSNA is elevated by muscle metaboreceptor stimulation, whereas the sensitivity of baroreflex of modulate heart rate is unchanged during posthandgrip muscle ischemia.

  19. Cellular mechanisms of myogenic activity in gastric smooth muscle.

    Science.gov (United States)

    Suzuki, H

    2000-06-01

    In many regions of the intestine, a thin layer of interstitial cells of Cajal (ICC) lie in the myenteric region, between the circular and longitudinal muscle layers. ICC are connected by gap junctions to surrounding ICC and also with circular and longitudinal smooth muscle cells, forming a large electrical syncytium. Damage of the ICC causes a disorder in the patterns of rhythmic activity. Isolated ICC produce a rhythmic oscillation of the membrane potential. All these observations have led to the suggestion that ICC may be the pacemaker cell responsible for intestinal activity. Gastric smooth muscles generate slow oscillatory membrane potential changes (slow waves) and spike potentials. The activity is considered to be linked to the metabolism in the cell. Three types of cells located in the gastric wall (circular and longitudinal smooth muscle cells and ICC) produce synchronized electrical responses with different shapes. The electrical responses appear to originate in ICC and then spread to the smooth muscle layers, indicating that ICC may also be the pacemaker cells responsible for gastric activity. However, isolated circular smooth muscle tissues spontaneously generate regenerative potentials, suggesting that there are at least two sites for the initiation of spontaneous activity in the stomach. Regenerative potentials persist in the presence of Ca-antagonists and are inhibited by agents which disrupt intracellular Ca(2+) homeostasis. Depolarization of the membrane elicits regenerative potentials after a long delay and the potentials have long refractory periods. This suggests that an unidentified 2nd messenger may be formed during the delay between membrane depolarization and the initiation of a regenerative potential. In gastric muscles of mutant mice which do not express inositol trisphosphate (InsP(3)) receptors, spike potentials but not slow waves are generated, suggesting the possible involvement of InsP(3) in the initiation of spontaneous activity.

  20. Fatigue-related firing of muscle nociceptors reduces voluntary activation of ipsilateral but not contralateral lower limb muscles.

    Science.gov (United States)

    Kennedy, David S; Fitzpatrick, Siobhan C; Gandevia, Simon C; Taylor, Janet L

    2015-02-15

    During fatiguing upper limb exercise, maintained firing of group III/IV muscle afferents can limit voluntary drive to muscles within the same limb. It is not known if this effect occurs in the lower limb. We investigated the effects of group III/IV muscle afferent firing from fatigued ipsilateral and contralateral extensor muscles and ipsilateral flexor muscles of the knee on voluntary activation of the knee extensors. In three experiments, we examined voluntary activation of the knee extensors by measuring changes in superimposed twitches evoked by femoral nerve stimulation. Subjects attended on 2 days for each experiment. On one day a sphygmomanometer cuff occluded blood flow of the fatigued muscles to maintain firing of group III/IV muscle afferents. After a 2-min extensor contraction (experiment 1; n = 9), mean voluntary activation was lower with than without maintained ischemia (47 ± 19% vs. 87 ± 8%, respectively; P contraction (MVC) (experiment 2; n = 8), mean voluntary activation was also lower with than without ischemia (59 ± 21% vs. 79 ± 9%; P muscle afferents reduces voluntary activation of the fatigued muscle and nonfatigued antagonist muscles in the same leg. However, group III/IV muscle afferents from the fatigued left leg had no effect on the unfatigued right leg. This suggests that any "crossover" of central fatigue in the lower limbs is not mediated by group III/IV muscle afferents.

  1. Calcineurin activation influences muscle phenotype in a muscle-specific fashion

    Directory of Open Access Journals (Sweden)

    Lees Simon J

    2004-07-01

    Full Text Available Abstract Background The calcium activated protein phosphatase 2B, also known as calcineurin, has been implicated as a cell signaling molecule involved with transduction of physiological signals (free cytosolic Ca2+ into molecular signals that influence the expression of phenotype-specific genes in skeletal muscle. In the present study we address the role of calcineurin in mediating adaptations in myosin heavy chain (MHC isoform expression and muscle mass using 3-month old wild-type (WT and transgenic mice displaying high-level expression of a constitutively active form of calcineurin (MCK-CN* mice. Results Slow muscles, e.g., soleus, were significantly larger (by ~24%, whereas fast muscles, e.g., medial gastrocnemius (MG and tibialis anterior were significantly smaller (by ~26 and ~16%, respectively in MCK-CN* mice compared to WT. The masses of mixed phenotype muscles, such as the plantaris and the extensor digitorum longus, were not significantly changed from WT. The soleus, plantaris, MG and diaphragm displayed shifts toward slower MHC isoforms, e.g., soleus from WT mice contained ~52% MHC-I, ~39% MHC-IIa, and ~9% MHC-IIx, whereas MCK-CN* mice had ~67% MHC-I, ~26% MHC-IIa, and ~7% MHC-IIx. The specific isoforms that were either up or down-regulated were muscle-specific. For instance, the proportion of MHC-IIa was decreased in the soleus and diaphragm, but increased in the plantaris and MG of MCK-CN* mice. Also, the proportion of MHC-IIx was unchanged in the soleus, decreased in the diaphragm and increased in the plantaris and MG of MCK-CN* relative to WT mice. Fast to slow shifts in fiber type proportions were evident for the plantaris, but not the soleus. Fast, but not slow, plantaris fibers of MCK-CN* mice had higher oxidative and lower glycolytic properties than WT. Conclusion These data suggest that calcineurin activation can influence muscle phenotype and that the specific influence of calcineurin activation on the phenotypic and mass

  2. Abdominal expiratory muscle activity in anesthetized vagotomized neonatal rats.

    Science.gov (United States)

    Iizuka, Makito

    2009-05-01

    The pattern of respiratory activity in abdominal muscles was studied in anesthetized, spontaneously breathing, vagotomized neonatal rats at postnatal days 0-3. Anesthesia (2.0% isoflurane, 50% O(2)) depressed breathing and resulted in hypercapnia. Under this condition, abdominal muscles showed discharge late in the expiratory phase (E2 activity) in most rats. As the depth of anesthesia decreased, the amplitude of discharges in the diaphragm and abdominal muscles increased. A small additional burst frequently occurred in abdominal muscles just after the termination of diaphragmatic inspiratory activity (E1 or postinspiratory activity). Since this E1 activity is not often observed in adult rats, the abdominal respiratory pattern likely changes during postnatal development. Anoxia-induced gasping after periodic expiratory activity without inspiratory activity, and in most rats, abdominal expiratory activity disappeared before terminal apnea. These results suggest that a biphasic abdominal motor pattern (a combination of E2 and E1 activity) is a characteristic of vagotomized neonatal rats during normal respiration.

  3. The effect of muscle length on force depression after active shortening in soleus muscle of mice.

    Science.gov (United States)

    Van Noten, Pieter; Van Leemputte, Marc

    2011-07-01

    Isometric muscle force after active shortening is reduced [force depression (FD)]. The mechanism is incompletely understood but work delivered during shortening has been suggested to be the main determinant of FD. However, whether muscle length affects the sensitivity of FD to work is unknown, although this information might add to the understanding of the phenomenon. The aim of this study is to investigate the length dependence of the FD/work ratio (Q). Therefore, isometric force production (ISO) of 10 incubated mouse soleus muscles was compared to isometric force after 0.6, 1.2, and 2.4 mm shortening (IAS) at different end lengths ranging from L(0) - 3 to L(0) + 1.8 mm in steps of 0.6 mm. FD was calculated as the force difference between an ISO and IAS contraction at the same activation time (6 s) and end length. We confirm the strong relation between FD and work at L(0) (R² = 0.92) and found that FD is length dependent with a maximum of 8.8 ± 0.3% at L(0) + 1.2 mm for 0.6 mm shortening amplitude. Q was only constant for short muscle lengths (muscle length. The observed length dependence of Q indicates that FD is not only determined by work produced during shortening but also by a length-dependent factor, possibly actin compliance, which should be incorporated in any mechanism explaining FD.

  4. Surface EMG based muscle activity analysis for aerobic cyclist.

    Science.gov (United States)

    Balasubramanian, Venkatesh; Jayaraman, Srinivasan

    2009-01-01

    In this study, we determined the muscle activity of aerobic cyclist on biceps brachii medial, trapezius medial, latissimus dorsi medial, and erector spinae muscles bilaterally during 30 min of cycling. Thirteen male volunteers were chosen and placed in two groups (with and without low back pain (LBP)). Surface electromyography (sEMG) was recorded bilaterally from selected muscle groups for 30 min of cycling for each subject. Statistical tests were performed to determine the difference in fatigue, using mean power frequency difference. LBP group showed a significantly higher fatigue (p<0.05) in left biceps brachii medial when compared to the control group. High fatigue in the back muscles in the LBP group was not found; however, when linear regression was performed for these individuals, the data showed a possibility of worsening in their condition due to 30 min of cycling.

  5. Effects of cervical traction on muscle activity.

    Science.gov (United States)

    Murphy, M J

    1991-01-01

    The effect of cervical traction on the musculature of patients with complaints of neck pain has not been thoroughly researched. Lateral neck muscles were selected for study because they receive their innervation from the lower cervical region, where traction has been documented by radiography to have its greatest mechanical effects. Six subjects with complaints of neck pain, limited range of motion, and a positive quadrant test were compared to six normal subjects. Surface electromyography (EMG) of the lateral neck musculature was recorded before, during, and after supine intermittent mechanical traction. No significant difference between groups (p > .05) was noted in EMG recordings at rest and within 10 minutes of traction. Subjective relief was noted up to 12 hours after traction in pain subjects. Cervical traction does not appear to produce immediate muscular relaxation as measured with EMG equipment. J Orthop Sports Phys Ther 1991;13(5):220-225.

  6. Molecular mechanism by which AMP-activated protein kinase activation promotes glycogen accumulation in muscle

    DEFF Research Database (Denmark)

    Hunter, Roger W; Treebak, Jonas Thue; Wojtaszewski, Jørgen

    2011-01-01

    OBJECTIVE During energy stress, AMP-activated protein kinase (AMPK) promotes glucose transport and glycolysis for ATP production, while it is thought to inhibit anabolic glycogen synthesis by suppressing the activity of glycogen synthase (GS) to maintain the energy balance in muscle. Paradoxically......, chronic activation of AMPK causes an increase in glycogen accumulation in skeletal and cardiac muscles, which in some cases is associated with cardiac dysfunction. The aim of this study was to elucidate the molecular mechanism by which AMPK activation promotes muscle glycogen accumulation. RESEARCH DESIGN...... AND METHODS We recently generated knock-in mice in which wild-type muscle GS was replaced by a mutant (Arg582Ala) that could not be activated by glucose-6-phosphate (G6P), but possessed full catalytic activity and could still be activated normally by dephosphorylation. Muscles from GS knock-in or transgenic...

  7. Muscle Atrophy Reversed by Growth Factor Activation of Satellite Cells in a Mouse Muscle Atrophy Model

    DEFF Research Database (Denmark)

    Hauerslev, Simon; Vissing, John; Krag, Thomas O

    2014-01-01

    Muscular dystrophies comprise a large group of inherited disorders that lead to progressive muscle wasting. We wanted to investigate if targeting satellite cells can enhance muscle regeneration and thus increase muscle mass. We treated mice with hepatocyte growth factor and leukemia inhibitory...... factor under three conditions: normoxia, hypoxia and during myostatin deficiency. We found that hepatocyte growth factor treatment led to activation of the Akt/mTOR/p70S6K protein synthesis pathway, up-regulation of the myognic transcription factors MyoD and myogenin, and subsequently the negative growth...... control factor, myostatin and atrophy markers MAFbx and MuRF1. Hypoxia-induced atrophy was partially restored by hepatocyte growth factor combined with leukemia inhibitory factor treatment. Dividing satellite cells were three-fold increased in the treatment group compared to control. Finally, we...

  8. Regulatory mechanisms of the phasic respiratory activity in cricothyroid muscle.

    Science.gov (United States)

    Dejonckere, P H; Lebacq, J

    1984-01-01

    Phasic respiratory activity of the cricothyroid muscle has been investigated with electromyography in 15 normal subjects, and in 19 pathological cases with well defined neurological troubles. It appears that phasic respiratory activity in the cricothyroid muscle, probably centrally generated, is under control of a complex and intricate mechanisms, in which the nervus laryngeus superior, the nervus laryngeus inferior, the vagus nerve and cross connections all together intervene. Furthermore, a peripheral modulation related somehow to the resistance of the airways is present. Despite differences between animal species, it seems that qualitatively the same contributing elements are present in animals and humans.

  9. Contributions of central command and muscle feedback to sympathetic nerve activity in contracting human skeletal muscle

    Directory of Open Access Journals (Sweden)

    Daniel eBoulton

    2016-05-01

    Full Text Available During voluntary contractions, muscle sympathetic nerve activity (MSNA to contracting muscles increases in proportion to force but the underlying mechanisms are not clear. To shed light on these mechanisms, particularly the influences of central command and muscle afferent feedback, the present study tested the hypothesis that MSNA is greater during voluntary compared with electrically-evoked contractions. Seven male subjects performed a series of 1-minute isometric dorsiflexion contractions (left leg separated by 2-minute rest periods, alternating between voluntary and electrically-evoked contractions at similar forces (5-10 % of maximum. MSNA was recorded continuously (microneurography from the left peroneal nerve and quantified from cardiac-synchronised, negative-going spikes in the neurogram. Compared with pre-contraction values, MSNA increased by 51 ± 34 % (P 0.05. MSNA analysed at 15-s intervals revealed that this effect of voluntary contraction appeared 15-30 s after contraction onset (P < 0.01, remained elevated until the end of contraction, and disappeared within 15 s after contraction. These findings suggest that central command, and not feedback from contracting muscle, is the primary mechanism responsible for the increase in MSNA to contracting muscle. The time-course of MSNA suggests that there is a longer delay in the onset of this effect compared with its cessation after contraction.

  10. CHANGES IN QUADRICEPS MUSCLE ACTIVITY DURING SUSTAINED RECREATIONAL ALPINE SKIING

    Directory of Open Access Journals (Sweden)

    Josef Kröll

    2011-03-01

    Full Text Available During a day of skiing thousands of repeated contractions take place. Previous research on prolonged recreational alpine skiing show that physiological changes occur and hence some level of fatigue is inevitable. In the present paper the effect of prolonged skiing on the recruitment and coordination of the muscle activity was investigated. Six subjects performed 24 standardized runs. Muscle activity during the first two (PREskiing and the last two (POSTskiing runs was measured from the vastus lateralis (VL and rectus femoris (RF using EMG and quantified using wavelet and principal component analysis. The frequency content of the EMG signal shifted in seven out of eight cases significantly towards lower frequencies with highest effects observed for RF on outside leg. A significant pronounced outside leg loading occurred during POSTskiing and the timing of muscle activity peaks occurred more towards turn completion. Specific EMG frequency changes were observed at certain time points throughout the time windows and not over the whole double turn. It is suggested that general muscular fatigue, where additional specific muscle fibers have to be recruited due to the reduced power output of other fibers did not occur. The EMG frequency decrease and intensity changes for RF and VL are caused by altered timing (coordination within the turn towards a most likely more uncontrolled skiing technique. Hence, these data provide evidence to suggest recreational skiers alter their skiing technique before a potential change in muscle fiber recruitment occurs

  11. Prior history of FDI muscle contraction: different effect on MEP amplitude and muscle activity.

    Science.gov (United States)

    Talis, V L; Kazennikov, O V; Castellote, J M; Grishin, A A; Ioffe, M E

    2014-03-01

    Motor evoked potentials (MEPs) in the right first dorsal interosseous (FDI) muscle elicited by transcranial magnetic stimulation of left motor cortex were assessed in ten healthy subjects during maintenance of a fixed FDI contraction level. Subjects maintained an integrated EMG (IEMG) level with visual feedback and reproduced this level by memory afterwards in the following tasks: stationary FDI muscle contraction at the level of 40 ± 5 % of its maximum voluntary contraction (MVC; 40 % task), at the level of 20 ± 5 % MVC (20 % task), and also when 20 % MVC was preceded by either no contraction (0-20 task), by stronger muscle contraction (40-20 task) or by no contraction with a previous strong contraction (40-0-20 task). The results show that the IEMG level was within the prescribed limits when 20 and 40 % stationary tasks were executed with and without visual feedback. In 0-20, 40-20, and 40-0-20 tasks, 20 % IEMG level was precisely controlled in the presence of visual feedback, but without visual feedback the IEMG and force during 20 % IEMG maintenance were significantly higher in the 40-0-20 task than those in 0-20 and 40-20 tasks. That is, without visual feedback, there were significant variations in muscle activity due to different prehistory of contraction. In stationary tasks, MEP amplitudes in 40 % task were higher than in 20 % task. MEPs did not differ significantly during maintenance of the 20 % level in tasks with different prehistory of muscle contraction with and without visual feedback. Thus, in spite of variations in muscle background activity due to different prehistory of contraction MEPs did not vary significantly. This dissociation suggests that the voluntary maintenance of IEMG level is determined not only by cortical mechanisms, as reflected by corticospinal excitability, but also by lower levels of CNS, where afferent signals and influences from other brain structures and spinal cord are convergent.

  12. Optimization of Spinal Muscular Atrophy subject's muscle activity during gait

    Science.gov (United States)

    Umat, Gazlia; Rambely, Azmin Sham

    2014-06-01

    Spinal Muscular Atrophy (SMA) is a hereditary disease related muscle nerve disorder caused by degeneration of the anterior cells of the spinal cord. SMA is divided into four types according to the degree of seriousness. SMA patients show different gait with normal people. Therefore, this study focused on the effects of SMA patient muscle actions and the difference that exists between SMA subjects and normal subjects. Therefore, the electromyography (EMG) test will be used to track the behavior of muscle during walking and optimization methods are used to get the muscle stress that is capable of doing the work while walking. Involved objective function is non-linear function of the quadratic and cubic functions. The study concludes with a comparison of the objective function using the force that sought to use the moment of previous studies and the objective function using the data obtained from EMG. The results shows that the same muscles, peroneus longus and bisepsfemoris, were used during walking activity by SMA subjects and control subjects. Muscle stress force best solution achieved from part D in simulation carried out.

  13. A viscoplastic model for the active component in cardiac muscle.

    Science.gov (United States)

    Rubin, M B

    2016-08-01

    The HMK model (Hunter et al. in Prog Biophys Mol Biol 69:289-331, 1998) proposes mechanobiological equations for the influence of intracellular calcium concentration [Formula: see text] on the evolution of bound calcium concentration [Formula: see text] and the tropomyosin kinetics parameter z, which model processes in the active component of the tension in cardiac muscle. The inelastic response due to actin-myosin crossbridge kinetics is modeled in the HMK model with a function Q that depends on the history of the rate of total stretch of the muscle fiber. Here, an alternative model is proposed which models the active component of the muscle fiber as a viscoplastic material. In particular, an evolution equation is proposed for the elastic stretch [Formula: see text] in the active component. Specific forms of the constitutive equations are proposed and used to match experimental data. The proposed viscoplastic formulation allows for separate modeling of three processes: the high rate deactivation of crossbridges causing rapid reduction in active tension; the high but lower rate reactivation of crossbridges causing recovery of active tension; and the low rate relaxation effects characterizing the Hill model of muscles.

  14. Selective activation of neuromuscular compartments within the human trapezius muscle

    DEFF Research Database (Denmark)

    Holtermann, A; Roeleveld, K; Mork, P J

    2009-01-01

    was to investigate whether subdivisions within the human trapezius can be independently activated by voluntary command using biofeedback guidance. Bipolar electromyographical electrodes were situated on four subdivisions of the trapezius muscle. The threshold for "active" and "rest" for each subdivision was set...... to >12% and biofeedback from each of the four trapezius subdivisions, 11 of 15 subjects learned selective activation of at least one of the four anatomical subdivisions of the trapezius...

  15. Characterizing differential poststroke corticomotor drive to the dorsi- and plantarflexor muscles during resting and volitional muscle activation.

    Science.gov (United States)

    Palmer, Jacqueline A; Zarzycki, Ryan; Morton, Susanne M; Kesar, Trisha M; Binder-Macleod, Stuart A

    2017-04-01

    Imbalance of corticomotor excitability between the paretic and nonparetic limbs has been associated with the extent of upper extremity motor recovery poststroke, is greatly influenced by specific testing conditions such as the presence or absence of volitional muscle activation, and may vary across muscle groups. However, despite its clinical importance, poststroke corticomotor drive to lower extremity muscles has not been thoroughly investigated. Additionally, whereas conventional gait rehabilitation strategies for stroke survivors focus on paretic limb foot drop and dorsiflexion impairments, most contemporary literature has indicated that paretic limb propulsion and plantarflexion impairments are the most significant limiters to poststroke walking function. The purpose of this study was to compare corticomotor excitability of the dorsi- and plantarflexor muscles during resting and active conditions in individuals with good and poor poststroke walking recovery and in neurologically intact controls. We found that plantarflexor muscles showed reduced corticomotor symmetry between paretic and nonparetic limbs compared with dorsiflexor muscles in individuals with poor poststroke walking recovery during active muscle contraction but not during rest. Reduced plantarflexor corticomotor symmetry during active muscle contraction was a result of reduced corticomotor drive to the paretic muscles and enhanced corticomotor drive to the nonparetic muscles compared with the neurologically intact controls. These results demonstrate that atypical corticomotor drive exists in both the paretic and nonparetic lower limbs and implicate greater severity of corticomotor impairments to plantarflexor vs. dorsiflexor muscles during muscle activation in stroke survivors with poor walking recovery.NEW & NOTEWORTHY The present study observed that lower-limb corticomotor asymmetry resulted from both reduced paretic and enhanced nonparetic limb corticomotor excitability compared with

  16. Muscle activation patterns in patients with recurrent shoulder instability

    Science.gov (United States)

    Jaggi, Anju; Noorani, Ali; Malone, Alex; Cowan, Joseph; Lambert, Simon; Bayley, Ian

    2012-01-01

    Purpose: The aim of this study is to present muscle patterns observed with the direction of instability in a series of patients presenting with recurrent shoulder instability. Materials and Methods: A retrospective review was carried out on shoulder instability cases referred for fine wire dynamic electromyography (DEMG) studies at a specialist upper limb centre between 1981 and 2003. An experienced consultant clinical neurophysiologist performed dual needle insertion into four muscles (pectoralis major (PM), latissimus dorsi (LD), anterior deltoid (AD) and infraspinatus (IS)) in shoulders that were suspected to have increased or suppressed activation of muscles that could be contributing to the instability. Raw EMG signals were obtained while subjects performed simple uniplanar movements of the shoulder. The presence or absence of muscle activation was noted and compared to clinical diagnosis and direction of instability. Results: A total of 140 (26.6%) shoulders were referred for fine wire EMG, and 131 studies were completed. Of the shoulders tested, 122 shoulders (93%) were identified as having abnormal patterns and nine had normal patterns. PM was found to be more active in 60% of shoulders presenting with anterior instability. LD was found to be more active in 81% of shoulders with anterior instability and 80% with posterior instability. AD was found to be more active in 22% of shoulders with anterior instability and 18% with posterior instability. IS was found to be inappropriately inactive in only 3% of shoulders with anterior instability but in 25% with posterior instability. Clinical assessment identified 93% of cases suspected to have muscle patterning, but the specificity of the clinical assessment was only correct in 11% of cases. Conclusion: The DEMG results suggest that increased activation of LD may play a role in both anterior and posterior shoulder instability; increased activation of PM may play a role in anterior instability. PMID:23493512

  17. Task-dependent effects evoked by foot muscle afferents on leg muscle activity in humans.

    Science.gov (United States)

    Abbruzzese, M; Rubino, V; Schieppati, M

    1996-08-01

    The effect of low intensity electrical stimulation of the posterior tibial nerve (PTN) at the ankle on the active triceps surae (TS) muscles was studied in normal subjects, both in a prone position and while standing. PTN stimulation regularly evoked the H-reflex in the flexor digitorum brevis and, in the prone position, a short-latency facilitatory effect in the soleus muscle. During standing, the facilitatory effect was preceded by a clear-cut reduction in electromyograph (EMG) activity. The inhibition-facilitation sequence was evoked in the gastrocnemii under both conditions, on average, though individual differences were present. An EMG modulation similar to that observed under standing conditions was present also in the prone position when subjects pressed the sole of the foot against the wall. Stimulation of sural or digital nerves did not evoke similar effects. It is concluded that foot muscle afferents establish oligosynaptic connections transmitting mixed effects to the TS motoneuronal pool, and that contact with the sole of the foot plays an enabling role for the inhibitory pathway directed to the soleus muscle.

  18. Fatigue-related firing of distal muscle nociceptors reduces voluntary activation of proximal muscles of the same limb.

    Science.gov (United States)

    Kennedy, David S; McNeil, Chris J; Gandevia, Simon C; Taylor, Janet L

    2014-02-15

    With fatiguing exercise, firing of group III/IV muscle afferents reduces voluntary activation and force of the exercised muscles. These afferents can also act across agonist/antagonist pairs, reducing voluntary activation and force in nonfatigued muscles. We hypothesized that maintained firing of group III/IV muscle afferents after a fatiguing adductor pollicis (AP) contraction would decrease voluntary activation and force of AP and ipsilateral elbow flexors. In two experiments (n = 10) we examined voluntary activation of AP and elbow flexors by measuring changes in superimposed twitches evoked by ulnar nerve stimulation and transcranial magnetic stimulation of the motor cortex, respectively. Inflation of a sphygmomanometer cuff after a 2-min AP maximal voluntary contraction (MVC) blocked circulation of the hand for 2 min and maintained firing of group III/IV muscle afferents. After a 2-min AP MVC, maximal AP voluntary activation was lower with than without ischemia (56.2 ± 17.7% vs. 76.3 ± 14.6%; mean ± SD; P muscle afferents from the hand decreased voluntary drive and force of AP. Moreover, this effect decreased voluntary drive and torque of proximal unfatigued muscles, the elbow flexors. Fatigue-sensitive group III/IV muscle nociceptors act to limit voluntary drive not only to fatigued muscles but also to unfatigued muscles within the same limb.

  19. Pain-evoked trunk muscle activity changes during fatigue and DOMS

    DEFF Research Database (Denmark)

    Larsen, Lars Henrik; Hirata, Rogerio Pessoto; Graven-Nielsen, Thomas

    2017-01-01

    abdominal and back muscles. RESULTS: In DOMS, peak VAS scores were higher during bilateral control and bilateral saline-induced pain than fatigue (p ...-perturbation Delta-RMS-EMG in back muscles was higher during bilateral pain and lower during unilateral pain (p abdominal Delta-RMS-EMG was not significantly affected. CONCLUSION: Facilitated and attenuated back muscle responses to surface perturbations in bilateral and unilateral LBP, respectively......BACKGROUND: Muscle pain may reorganize trunk muscle activity but interactions with exercise-related muscle fatigue and delayed onset muscle soreness (DOMS) is to be clarified. METHODS: In 19 healthy participants, the trunk muscle activity during 20 multi-directional unpredictable surface...

  20. Assessing voluntary muscle activation with the twitch interpolation technique.

    Science.gov (United States)

    Shield, Anthony; Zhou, Shi

    2004-01-01

    The twitch interpolation technique is commonly employed to assess the completeness of skeletal muscle activation during voluntary contractions. Early applications of twitch interpolation suggested that healthy human subjects could fully activate most of the skeletal muscles to which the technique had been applied. More recently, however, highly sensitive twitch interpolation has revealed that even healthy adults routinely fail to fully activate a number of skeletal muscles despite apparently maximal effort. Unfortunately, some disagreement exists as to how the results of twitch interpolation should be employed to quantify voluntary activation. The negative linear relationship between evoked twitch force and voluntary force that has been observed by some researchers implies that voluntary activation can be quantified by scaling a single interpolated twitch to a control twitch evoked in relaxed muscle. Observations of non-linear evoked-voluntary force relationships have lead to the suggestion that the single interpolated twitch ratio can not accurately estimate voluntary activation. Instead, it has been proposed that muscle activation is better determined by extrapolating the relationship between evoked and voluntary force to provide an estimate of true maximum force. However, criticism of the single interpolated twitch ratio typically fails to take into account the reasons for the non-linearity of the evoked-voluntary force relationship. When these reasons are examined, it appears that most are even more challenging to the validity of extrapolation than they are to the linear equation. Furthermore, several factors that contribute to the observed non-linearity can be minimised or even eliminated with appropriate experimental technique. The detection of small activation deficits requires high resolution measurement of force and careful consideration of numerous experimental details such as the site of stimulation, stimulation intensity and the number of interpolated

  1. Effects of language processing on spontaneous muscle activity

    NARCIS (Netherlands)

    Stins, J.F.; Beek, P.J.

    2013-01-01

    There is evidence of the crucial involvement of the motor system in language understanding and production. We tested whether reading verbs that symbolized various actions would lead to an effector-specific modulation in subliminal muscle activity. Participants were lying in a relaxed position, and r

  2. Human masticatory muscle activity and jaw position under experimental stress.

    Science.gov (United States)

    Tsai, C-M; Chou, S-L; Gale, E N; McCall, W D

    2002-01-01

    The purpose of the present study was to determine whether stress induced a consistent pattern of increased electromyographic (EMG) activity in different masticatory muscles, and whether stress produced changes in jaw position. Thirty-five dental students at Taipei Medical College volunteered for this study. Mental arithmetic was used to create a stress condition and relaxation instruction was used to help relax the subjects. Subjects were asked to evaluate the stress they felt under each experimental condition with a visual analogue scale (VAS). Surface electrodes were used to monitor the EMG activities of the right masseter, right posterior temporalis and suprahyoid muscles. A kinesiograph was used to observe the jaw position. Data collected before mental arithmetic or relaxation monitored the baseline level. The VAS means were significantly increased during the stress condition and significantly decreased following relaxation, compared with the baseline. There was also a significant increase in EMG activity of all three muscles during mental arithmetic compared with baseline; different patterns of increased EMG activity were noticed in the three muscles under a continuous stress condition. Under stress, the incidence of tooth contact at intercuspal position was also increased.

  3. Orofacial Muscle Activity of Children Who Stutter: A Preliminary Study.

    Science.gov (United States)

    Kelly, Ellen M.; And Others

    1995-01-01

    This preliminary investigation of stuttering development and maturation of speech motor processes recorded the electromyographic activity of the orofacial muscles of nine children who stuttered. Results suggest that the emergence of tremor-like instabilities in the speech motor processes of stuttering children may coincide with aspects of general…

  4. Orofacial Muscle Activity of Children Who Stutter: A Preliminary Study.

    Science.gov (United States)

    Kelly, Ellen M.; And Others

    1995-01-01

    This preliminary investigation of stuttering development and maturation of speech motor processes recorded the electromyographic activity of the orofacial muscles of nine children who stuttered. Results suggest that the emergence of tremor-like instabilities in the speech motor processes of stuttering children may coincide with aspects of general…

  5. Muscle Activity during Unilateral Vs. Bilateral Battle Rope Exercises

    DEFF Research Database (Denmark)

    Calatayud, J.; Martin, F.; Colado, J. C.

    2015-01-01

    Calatayud, J, Martin, F, Colado, JC, Benitez, JC, Jakobsen, MD, and Andersen, LL. Muscle activity during unilateral vs. bilateral battle rope exercises. J Strength Cond Res 29(10): 2854-2859, 2015High training intensity is important for efficient strength gains. Although battle rope training is m...

  6. Mapping Muscles Activation to Force Perception during Unloading.

    Directory of Open Access Journals (Sweden)

    Simone Toma

    Full Text Available It has been largely proved that while judging a force humans mainly rely on the motor commands produced to interact with that force (i.e., sense of effort. Despite of a large bulk of previous investigations interested in understanding the contributions of the descending and ascending signals in force perception, very few attempts have been made to link a measure of neural output (i.e., EMG to the psychophysical performance. Indeed, the amount of correlation between EMG activity and perceptual decisions can be interpreted as an estimate of the contribution of central signals involved in the sensation of force. In this study we investigated this correlation by measuring the muscular activity of eight arm muscles while participants performed a quasi-isometric force detection task. Here we showed a method to quantitatively describe muscular activity ("muscle-metric function" that was directly comparable to the description of the participants' psychophysical decisions about the stimulus force. We observed that under our experimental conditions, muscle-metric absolute thresholds and the shape of the muscle-metric curves were closely related to those provided by the psychophysics. In fact a global measure of the muscles considered was able to predict approximately 60% of the perceptual decisions total variance. Moreover the inter-subjects differences in psychophysical sensitivity showed high correlation with both participants' muscles sensitivity and participants' joint torques. Overall, our findings gave insights into both the role played by the corticospinal motor commands while performing a force detection task and the influence of the gravitational muscular torque on the estimation of vertical forces.

  7. The magnetic field of gastrointestinal smooth muscle activity

    Science.gov (United States)

    Bradshaw, Alan; Ladipo, Jk; Richards, William; Wikswo, John

    1997-11-01

    The gastrointestinal (GI) tract controls the absorption and transport of ingested materials. Its function is determined largely by the electrical activity of the smooth muscle that lines the GI tract. GI electrical activity consists of an omnipresent slowly oscillating wave known as the basic electrical rhythm (BER) that modulates a higher-frequency spiking activity associated with muscle contraction. The BER has been shown to be a reliable indicator of intestinal viability, and thus, recording of smooth muscle activity may have clinical value. The BER is difficult to measure with cutaneous electrodes because layers of low-conductivity fat between the GI tract and the abdominal surface attenuate the potential. On the other hand, the magnetic field associated with GI electrical activity is mostly unaffected by intervening fat layers. We recorded the magnetic fields from GI activity in 12 volunteers using a multichannel Superconducting QUantum Interference Device (SQUID) magnetometer. Characteristics typical of gastric and intestinal BER were apparent in the data. Channels near the epigastrium recorded gastric BER, and channels in intestinal areas recorded small bowel BER. These results suggest that a single multichannel SQUID magnetometer is able to measure gastrointestinal electrical activity from multiple locations around the abdomen simultaneously.

  8. Exercise-induced AMPK activity in skeletal muscle

    DEFF Research Database (Denmark)

    Friedrichsen, Martin; Mortensen, Brynjulf; Pehmøller, Christian

    2013-01-01

    The energy/fuel sensor 5'-AMP-activated protein kinase (AMPK) is viewed as a master regulator of cellular energy balance due to its many roles in glucose, lipid, and protein metabolism. In this review we focus on the regulation of AMPK activity in skeletal muscle and its involvement in glucose me...... metabolism, including glucose transport and glycogen synthesis. In addition, we discuss the plausible interplay between AMPK and insulin signaling regulating these processes.......The energy/fuel sensor 5'-AMP-activated protein kinase (AMPK) is viewed as a master regulator of cellular energy balance due to its many roles in glucose, lipid, and protein metabolism. In this review we focus on the regulation of AMPK activity in skeletal muscle and its involvement in glucose...

  9. Genetically enhancing mitochondrial antioxidant activity improves muscle function in aging.

    Science.gov (United States)

    Umanskaya, Alisa; Santulli, Gaetano; Xie, Wenjun; Andersson, Daniel C; Reiken, Steven R; Marks, Andrew R

    2014-10-21

    Age-related skeletal muscle dysfunction is a leading cause of morbidity that affects up to half the population aged 80 or greater. Here we tested the effects of increased mitochondrial antioxidant activity on age-dependent skeletal muscle dysfunction using transgenic mice with targeted overexpression of the human catalase gene to mitochondria (MCat mice). Aged MCat mice exhibited improved voluntary exercise, increased skeletal muscle specific force and tetanic Ca(2+) transients, decreased intracellular Ca(2+) leak and increased sarcoplasmic reticulum (SR) Ca(2+) load compared with age-matched wild type (WT) littermates. Furthermore, ryanodine receptor 1 (the sarcoplasmic reticulum Ca(2+) release channel required for skeletal muscle contraction; RyR1) from aged MCat mice was less oxidized, depleted of the channel stabilizing subunit, calstabin1, and displayed increased single channel open probability (Po). Overall, these data indicate a direct role for mitochondrial free radicals in promoting the pathological intracellular Ca(2+) leak that underlies age-dependent loss of skeletal muscle function. This study harbors implications for the development of novel therapeutic strategies, including mitochondria-targeted antioxidants for treatment of mitochondrial myopathies and other healthspan-limiting disorders.

  10. Chest wall and trunk muscle activity during inspiratory loading.

    Science.gov (United States)

    Cala, S J; Edyvean, J; Engel, L A

    1992-12-01

    We measured the electromyographic (EMG) activity in four chest wall and trunk (CWT) muscles, the erector spinae, latissimus dorsi, pectoralis major, and trapezius, together with the parasternal, in four normal subjects during graded inspiratory efforts against an occlusion in both upright and seated postures. We also measured CWT EMGs in six seated subjects during inspiratory resistive loading at high and low tidal volumes [1,280 +/- 80 (SE) and 920 +/- 60 ml, respectively]. With one exception, CWT EMG increased as a function of inspiratory pressure generated (Pmus) at all lung volumes in both postures, with no systematic difference in recruitment between CWT and parasternal muscles as a function of Pmus. At any given lung volume there was no consistent difference in CWT EMG at a given Pmus between the two postures (P > 0.09). However, at a given Pmus during both graded inspiratory efforts and inspiratory resistive loading, EMGs of all muscles increased with lung volume, with greater volume dependence in the upright posture (P < 0.02). The results suggest that during inspiratory efforts, CWT muscles contribute to the generation of inspiratory pressure. The CWT muscles may act as fixators opposing deflationary forces transmitted to the vertebral column by rib cage articulations, a function that may be less effective at high lung volumes if the direction of the muscular insertions is altered disadvantageously.

  11. Non-crossbridge stiffness in active muscle fibres.

    Science.gov (United States)

    Colombini, Barbara; Nocella, Marta; Bagni, Maria Angela

    2016-01-01

    Stretching of an activated skeletal muscle induces a transient tension increase followed by a period during which the tension remains elevated well above the isometric level at an almost constant value. This excess of tension in response to stretching has been called 'static tension' and attributed to an increase in fibre stiffness above the resting value, named 'static stiffness'. This observation was originally made, by our group, in frog intact muscle fibres and has been confirmed more recently, by us, in mammalian intact fibres. Following stimulation, fibre stiffness starts to increase during the latent period well before crossbridge force generation and it is present throughout the whole contraction in both single twitches and tetani. Static stiffness is dependent on sarcomere length in a different way from crossbridge force and is independent of stretching amplitude and velocity. Static stiffness follows a time course which is distinct from that of active force and very similar to the myoplasmic calcium concentration time course. We therefore hypothesize that static stiffness is due to a calcium-dependent stiffening of a non-crossbridge sarcomere structure, such as the titin filament. According to this hypothesis, titin, in addition to its well-recognized role in determining the muscle passive tension, could have a role during muscle activity.

  12. The Assessment Methods of Laryngeal Muscle Activity in Muscle Tension Dysphonia: A Review

    OpenAIRE

    Seyyedeh Maryam Khoddami; Noureddin Nakhostin Ansari; Farzad Izadi; Saeed Talebian Moghadam

    2013-01-01

    The purpose of this paper is to review the methods used for the assessment of muscular tension dysphonia (MTD). The MTD is a functional voice disorder associated with abnormal laryngeal muscle activity. Various assessment methods are available in the literature to evaluate the laryngeal hyperfunction. The case history, laryngoscopy, and palpation are clinical methods for the assessment of patients with MTD. Radiography and surface electromyography (EMG) are objective methods to provide physio...

  13. Afferent contribution to locomotor muscle activity during unconstrained overground human walking: an analysis of triceps surae muscle fascicles.

    Science.gov (United States)

    af Klint, R; Cronin, N J; Ishikawa, M; Sinkjaer, T; Grey, M J

    2010-03-01

    Plantar flexor series elasticity can be used to dissociate muscle-fascicle and muscle-tendon behavior and thus afferent feedback during human walking. We used electromyography (EMG) and high-speed ultrasonography concomitantly to monitor muscle activity and muscle fascicle behavior in 19 healthy volunteers as they walked across a platform. On random trials, the platform was dropped (8 cm, 0.9 g acceleration) or held at a small inclination (up to +/-3 degrees in the parasagittal plane) with respect to level ground. Dropping the platform in the mid and late phases of stance produced a depression in the soleus muscle activity with an onset latency of about 50 ms. The reduction in ground reaction force also unloaded the plantar flexor muscles. The soleus muscle fascicles shortened with a minimum delay of 14 ms. Small variations in platform inclination produced significant changes in triceps surae muscle activity; EMG increased when stepping on an inclined surface and decreased when stepping on a declined surface. This sensory modulation of the locomotor output was concomitant with changes in triceps surae muscle fascicle and gastrocnemius tendon length. Assuming that afferent activity correlates to these mechanical changes, our results indicate that within-step sensory feedback from the plantar flexor muscles automatically adjusts muscle activity to compensate for small ground irregularities. The delayed onset of muscle fascicle movement after dropping the platform indicates that at least the initial part of the soleus depression is more likely mediated by a decrease in force feedback than length-sensitive feedback, indicating that force feedback contributes to the locomotor activity in human walking.

  14. Structural dynamics of troponin during activation of skeletal muscle

    Science.gov (United States)

    Fusi, Luca; Brunello, Elisabetta; Sevrieva, Ivanka R.; Sun, Yin-Biao; Irving, Malcolm

    2014-01-01

    Time-resolved changes in the conformation of troponin in the thin filaments of skeletal muscle were followed during activation in situ by photolysis of caged calcium using bifunctional fluorescent probes in the regulatory and the coiled-coil (IT arm) domains of troponin. Three sequential steps in the activation mechanism were identified. The fastest step (1,100 s−1) matches the rate of Ca2+ binding to the regulatory domain but also dominates the motion of the IT arm. The second step (120 s−1) coincides with the azimuthal motion of tropomyosin around the thin filament. The third step (15 s−1) was shown by three independent approaches to track myosin head binding to the thin filament, but is absent in the regulatory head. The results lead to a four-state structural kinetic model that describes the molecular mechanism of muscle activation in the thin filament–myosin head complex under physiological conditions. PMID:24616505

  15. Variation in masticatory muscle activity during subsequent, submaximal clenching efforts.

    Science.gov (United States)

    Lobbezoo, F; Huddleston Slater, J J R

    2002-06-01

    In previous studies to the relative contribution of the jaw closing muscles to the maintenance of submaximal clenching levels, a considerable variation in the electromyography (EMG) activities of these muscles during subsequent efforts was found. In this study, it was examined to what extent this variation could be explained by coincidental variations in mandibular positioning. From seven healthy individuals, a total of 90 EMG sweeps was recorded: three conditions (intercuspal position and two types of stabilization appliances) x three clenching levels (10, 30 and 50% of maximum voluntary contraction level) x 10 repetitions. Mandibular position was monitored with a six degrees of freedom opto-electronic jaw movement recording system. Variations in mandibular positioning during subsequent, submaximal clenching efforts explained up to 25% of the variance in the indices that quantify the relative contribution of the jaw closing muscles to the total clenching effort (P=0.000; ANOVA). Only a weak dependency of positioning upon clenching condition was found whereas during higher clenching levels, the positioning effect tended to be smaller than during lower levels. In conclusion small, coincidental variations in mandibular positioning during subsequent clenching efforts partly explain the variance in EMG activity of jaw closing muscles, especially at lower clenching levels.

  16. Role of intracortical inhibition in selective hand muscle activation.

    Science.gov (United States)

    Stinear, Cathy M; Byblow, Winston D

    2003-04-01

    Previous studies have shown that intracortical inhibition (ICI) plays an important role in shaping the output from primary motor cortex (M1). This study explored the muscle specificity and temporal modulation of ICI during the performance of a phasic index finger flexion task. Fifteen subjects were asked to rest their dominant hand on a computer mouse and depress the mouse button using their index finger in time with a 1-Hz auditory metronome, while keeping the rest of their hand as relaxed as possible. Responses to single- and paired-pulse transcranial magnetic stimulation were recorded from the first dorsal interosseous (FDI) and abductor pollicis brevis (APB) muscles while subjects were at rest and during "on" and "off" phases of the task. For FDI during the on phase, motor evoked potential (MEP) amplitude and pretrigger EMG increased and ICI decreased, as expected. This pattern of modulation was also observed for APB in seven subjects. The remaining eight subjects demonstrated a decrease in MEP amplitude and increase in ICI for APB during the on phase. This was associated with significantly less APB activation during the on phase. These findings suggest that an increase in ICI and decrease in corticospinal excitability can prevent unwanted muscle activation in a muscle-specific, temporally modulated manner.

  17. Activity of upper limb muscles during human walking.

    Science.gov (United States)

    Kuhtz-Buschbeck, Johann P; Jing, Bo

    2012-04-01

    The EMG activity of upper limb muscles during human gait has rarely been studied previously. It was examined in 20 normal volunteers in four conditions: walking on a treadmill (1) with unrestrained natural arm swing (Normal), (2) while volitionally holding the arms still (Held), (3) with the arms immobilized (Bound), and (4) with the arms swinging in phase with the ipsilateral legs, i.e. opposite-to-normal phasing (Anti-Normal). Normal arm swing involved weak rhythmical lengthening and shortening contractions of arm and shoulder muscles. Phasic muscle activity was needed to keep the unrestricted arms still during walking (Held), indicating a passive component of arm swing. An active component, possibly programmed centrally, existed as well, because some EMG signals persisted when the arms were immobilized during walking (Bound). Anti-Normal gait involved stronger EMG activity than Normal walking and was uneconomical. The present results indicate that normal arm swing has both passive and active components. Copyright © 2011 Elsevier Ltd. All rights reserved.

  18. Craniofacial pain and jaw-muscle activity during sleep.

    Science.gov (United States)

    Yachida, W; Castrillon, E E; Baad-Hansen, L; Jensen, R; Arima, T; Tomonaga, A; Ohata, N; Svensson, P

    2012-06-01

    This study compared the jaw-muscle electromyographic (EMG) activity during sleep in patients with craniofacial pain (n = 63) or no painful conditions (n = 52) and between patients with tension-type headache (TTH: n = 30) and healthy control individuals (n = 30). All participants used a portable single-channel EMG device (Medotech A/S) for four nights. There was no significant difference in EMG activity between craniofacial pain (24.5 ± 17.9 events/hr) and no painful conditions (19.7 ± 14.5), or between TTH (20.8 ± 15.0) and healthy control individuals (15.2 ± 11.6, p >.050). There were positive correlations between EMG activity and number of painful muscles (r = 0.188; p = 0.044), characteristic pain intensity (r = 0.187; p = 0.046), McGill Pain Questionnaire (r = 0.251; p = 0.008), and depression scores (r = 0.291; p = 0.002). Patients with painful conditions had significantly higher night-to-night variability compared with pain-free individuals (p craniofacial pain conditions and pain-free individuals in terms of jaw-muscle EMG activity recorded with a single-channel EMG device during sleep. However, some associations may exist between the level of EMG activity and various parameters of craniofacial pain. Longitudinal studies are warranted to further explore the relationship between sleep bruxism and craniofacial pain.

  19. Systematic review of core muscle activity during physical fitness exercises.

    Science.gov (United States)

    Martuscello, Jason M; Nuzzo, James L; Ashley, Candi D; Campbell, Bill I; Orriola, John J; Mayer, John M

    2013-06-01

    A consensus has not been reached among strength and conditioning specialists regarding what physical fitness exercises are most effective to stimulate activity of the core muscles. Thus, the purpose of this article was to systematically review the literature on the electromyographic (EMG) activity of 3 core muscles (lumbar multifidus, transverse abdominis, quadratus lumborum) during physical fitness exercises in healthy adults. CINAHL, Cochrane Central Register of Controlled Trials, EMBASE, PubMed, SPORTdiscus, and Web of Science databases were searched for relevant articles using a search strategy designed by the investigators. Seventeen studies enrolling 252 participants met the review's inclusion/exclusion criteria. Physical fitness exercises were partitioned into 5 major types: traditional core, core stability, ball/device, free weight, and noncore free weight. Strength of evidence was assessed and summarized for comparisons among exercise types. The major findings of this review with moderate levels of evidence indicate that lumbar multifidus EMG activity is greater during free weight exercises compared with ball/device exercises and is similar during core stability and ball/device exercises. Transverse abdominis EMG activity is similar during core stability and ball/device exercises. No studies were uncovered for quadratus lumborum EMG activity during physical fitness exercises. The available evidence suggests that strength and conditioning specialists should focus on implementing multijoint free weight exercises, rather than core-specific exercises, to adequately train the core muscles in their athletes and clients.

  20. Lower Extremity Muscle Activity During a Women's Overhand Lacrosse Shot

    Directory of Open Access Journals (Sweden)

    Millard Brianna M.

    2014-07-01

    Full Text Available The purpose of this study was to describe lower extremity muscle activity during the lacrosse shot. Participants (n=5 females, age 22±2 years, body height 162.6±15.2 cm, body mass 63.7±23.6 kg were free from injury and had at least one year of lacrosse experience. The lead leg was instrumented with electromyography (EMG leads to measure muscle activity of the rectus femoris (RF, biceps femoris (BF, tibialis anterior (TA, and medial gastrocnemius (GA. Participants completed five trials of a warm-up speed shot (Slow and a game speed shot (Fast. Video analysis was used to identify the discrete events defining specific movement phases. Full-wave rectified data were averaged per muscle per phase (Crank Back Minor, Crank Back Major, Stick Acceleration, Stick Deceleration. Average EMG per muscle was analyzed using a 4 (Phase x 2 (Speed ANOVA. BF was greater during Fast vs. Slow for all phases (p0.05. RF and GA were each influenced by the interaction of Phase and Speed (p<0.05 with GA being greater during Fast vs. Slow shots during all phases and RF greater during Crank Back Minor and Major as well as Stick Deceleration (p<0.05 but only tended to be greater during Stick Acceleration (p=0.076 for Fast vs. Slow. The greater muscle activity (BF, RF, GA during Fast vs. Slow shots may have been related to a faster approach speed and/or need to create a stiff lower extremity to allow for faster upper extremity movements.

  1. Increased neck muscle activity and impaired balance among females with whiplash-related chronic neck pain

    DEFF Research Database (Denmark)

    Juul-Kristensen, Birgit; Clausen, Brian; Ris Hansen, Inge

    2013-01-01

    To investigate neck muscle activity and postural control in patients with whiplash-associated disorder compared with healthy controls.......To investigate neck muscle activity and postural control in patients with whiplash-associated disorder compared with healthy controls....

  2. Influence of gravity compensation on muscle activity during reach and retrieval in healthy elderly.

    NARCIS (Netherlands)

    Prange, Grada Berendina; Kallenberg, L.A.C.; Jannink, M.J.A.; Stienen, Arno; van der Kooij, Herman; IJzerman, Maarten Joost; Hermens, Hermanus J.

    2007-01-01

    INTRODUCTION: Arm support like gravity compensation may improve arm movements during stroke rehabilitation. It is unknown how gravity compensation affects muscle activation patterns during reach and retrieval movements. Since muscle activity during reach is represented by a component varying with

  3. Eccentric activation and muscle damage: biomechanical and physiological considerations during downhill running.

    Science.gov (United States)

    Eston, R G; Mickleborough, J; Baltzopoulos, V

    1995-01-01

    An eccentric muscle activation is the controlled lengthening of the muscle under tension. Functionally, most leg muscles work eccentrically for some part of a normal gait cycle, to support the weight of the body against gravity and to absorb shock. During downhill running the role of eccentric work of the 'anti-gravity' muscles--knee extensors, muscles of the anterior and posterior tibial compartments and hip extensors--is accentuated. The purpose of this paper is to review the relationship between eccentric muscle activation and muscle damage, particularly as it relates to running, and specifically, downhill running. PMID:7551767

  4. Methods for demonstration of enzyme activity in muscle fibres at the muscle/bone interface in demineralized tissue

    DEFF Research Database (Denmark)

    Kirkeby, S; Vilmann, H

    1981-01-01

    A method for demonstration of activity for ATPase and various oxidative enzymes (succinic dehydrogenase, alpha-glycerophosphate dehydrogenase, and lactic dehydrogenase) in muscle/bone sections of fixed and demineralized tissue has been developed. It was found that it is possible to preserve...... with the aid of a mapping of presence of phosphomonoesterases on bone surfaces, the method may be used to study possible biochemical interactions between bone and muscle tissue at the muscle/bone interface....

  5. Purinergic effects on Na,K-ATPase activity differ in rat and human skeletal muscle

    DEFF Research Database (Denmark)

    Juel, Carsten; Nordsborg, Nikolai Baastrup; Bangsbo, Jens

    2014-01-01

    P2Y receptor activation may link the effect of purines to increased maximal in vitro activity of the Na,K-ATPase in rat muscle. The hypothesis that a similar mechanism is present in human skeletal muscle was investigated with membranes from rat and human skeletal muscle.......P2Y receptor activation may link the effect of purines to increased maximal in vitro activity of the Na,K-ATPase in rat muscle. The hypothesis that a similar mechanism is present in human skeletal muscle was investigated with membranes from rat and human skeletal muscle....

  6. Does the habitual mastication side impact jaw muscle activity?

    Science.gov (United States)

    Turcio, Karina Helga Leal; Zuim, Paulo Renato Junqueira; Guiotti, Aimée Maria; Dos Santos, Daniela Micheline; Goiato, Marcelo Coelho; Brandini, Daniela Atili

    2016-07-01

    To compare electrical activity in the anterior temporal and masseter muscles on the habitual (HMS) and non-habitual mastication side (NHMS), during mastication and in the mandibular postural position. In addition, the increase in electrical activity during mastication was assessed for the HMS and NHMS, analysing both working (WSM) and non-working side during mastication (NWSM). A total of 28 healthy women (18-32 years) participated in the study. They were submitted to Kazazoglu's test to identify the HMS. Bioresearch 'Bio EMG' software and bipolar surface electrodes were used in the exams. The exams were conducted in the postural position and during the unilateral mastication of raisins, on both the HMS and NHMS. The working and non-working side on HMS and NHMS were assessed separately. The obtained data were then statistically analysed with SPSS 20.0, using the Paired Samples Test at a significance level of 95%. The differences in the average EMG values between HMS and NHMS were not statistically significant in the postural position (Temporal p=0.2; Masseter p=0.4) or during mastication (Temporal WSM p=0.8; Temporal NWSM p=0.8; Masseter WSM p=0.6; Masseter NWSM p=0.2). Differences in the increase in electrical activity between the masseter and temporal muscles occurred on the working side, on the HMS and NHMS (p=0.0), but not on the non-working side: HMS (p=0.9) and NHMS (p=0.3). The increase in electrical activity was about 35% higher in the masseter than in the temporal muscle. Mastication side preference does not significantly impact electrical activity of the anterior temporal and masseter muscles during mastication or in postural position. Copyright © 2016. Published by Elsevier Ltd.

  7. Interplay between body stabilisation and quadriceps muscle activation capacity.

    Science.gov (United States)

    Bampouras, Theodoros M; Reeves, Neil D; Baltzopoulos, Vasilios; Maganaris, Constantinos N

    2017-03-22

    The study aimed to distinguish the effect of stabilisation and muscle activation on quadriceps maximal isometric voluntary contraction (MVC) torque generation. Nine subjects performed (a) an MVC with restrained leg and pelvis (Typical MVC), (b) a Typical MVC with handgrip (Handgrip MVC), (c) an MVC focusing on contracting the knee extensors only (Isolated knee extension MVC), and (d) an MVC with unrestrained leg and pelvis (Unrestrained MVC). Torque and activation capacity between conditions were compared with repeated measures ANOVA and dependent t-tests. EMG (from eleven remote muscles) was compared using Friedman's and Wilcoxon. Typical MVC (277.2±49.6Nm) and Handgrip MVC (261.0±55.4Nm) were higher than Isolated knee extension MVC (210.2±48.3Nm, pMVC (195.2±49.7Nm, pMVC (83.1±15.9%) activation was higher than Isolated knee extension MVC (68.9±24.3%, pMVC and Handgrip MVC (81.8±17.4%) were higher than Unrestrained MVC (64.9±16.2%, pMVC consistently lower than Typical MVC or Handgrip MVC. Stabilisation of the involved segments is the prime concern allowing fuller activation of the muscle, reinforcing the need for close attention to stabilisation during dynamometry-based knee joint functional assessment.

  8. Neurotransmitter GABA activates muscle but not α7 nicotinic receptors.

    Science.gov (United States)

    Dionisio, Leonardo; Bergé, Ignacio; Bravo, Matías; Esandi, María Del Carmen; Bouzat, Cecilia

    2015-01-01

    Cys-loop receptors are neurotransmitter-activated ion channels involved in synaptic and extrasynaptic transmission in the brain and are also present in non-neuronal cells. As GABAA and nicotinic receptors (nAChR) belong to this family, we explored by macroscopic and single-channel recordings whether the inhibitory neurotransmitter GABA has the ability to activate excitatory nAChRs. GABA differentially activates nAChR subtypes. It activates muscle nAChRs, with maximal peak currents of about 10% of those elicited by acetylcholine (ACh) and 15-fold higher EC50 with respect to ACh. At the single-channel level, the weak agonism is revealed by the requirement of 20-fold higher concentration of GABA for detectable channel openings, a major population of brief openings, and absence of clusters of openings when compared with ACh. Mutations at key residues of the principal binding-site face of muscle nAChRs (αY190 and αG153) affect GABA activation similarly as ACh activation, whereas a mutation at the complementary face (εG57) shows a selective effect for GABA. Studies with subunit-lacking receptors show that GABA can activate muscle nAChRs through the α/δ interface. Interestingly, single-channel activity elicited by GABA is similar to that elicited by ACh in gain-of-function nAChR mutants associated to congenital myasthenic syndromes, which could be important in the progression of the disorders due to steady exposure to serum GABA. In contrast, GABA cannot elicit single-channel or macroscopic currents of α7 or the chimeric α7-serotonin-type 3 receptor, a feature important for preserving an adequate excitatory/inhibitory balance in the brain as well as for avoiding activation of non-neuronal receptors by serum GABA. Copyright © 2015 by The American Society for Pharmacology and Experimental Therapeutics.

  9. Muscle activity and kinematics of forefoot and rearfoot strike runners

    OpenAIRE

    Ahn, A. N.; C. Brayton; Bhatia, T.; P.; Martin

    2014-01-01

    Background: Forefoot strike (FFS) and rearfoot strike (RFS) runners differ in their kinematics, force loading rates, and joint loading patterns, but the timing of their muscle activation is less clear. Methods: Forty recreational and highly trained runners ran at four speeds barefoot and shod on a motorized treadmill. “Barefoot” runners wore thin, five-toed socks and shod runners wore neutral running shoes. Subjects were instructed to run comfortably at each speed with no instructions abou...

  10. Dynamics of muscle activation during tonic-clonic seizures.

    Science.gov (United States)

    Conradsen, Isa; Moldovan, Mihai; Jennum, Poul; Wolf, Peter; Farina, Dario; Beniczky, Sándor

    2013-03-01

    The purpose of our study was to elucidate the dynamics of muscle activation during generalised tonic-clonic seizures (GTCS). We recorded surface electromyography (EMG) from the deltoid muscle during 26 GTCS from 13 patients and compared it with GTCS-like events acted by 10 control subjects. GTCS consisted of a sequence of phases best described quantitatively by dynamics of the low frequency (LF) wavelet component (2-8Hz). Contrary to the traditional view, the tonic phase started with a gradual increase in muscle activity. A longer clonic phase was associated with a shorter onset of the tonic phase and a higher seizure occurrence. Increase in LF occurred during the onset phase and during the transition from the tonic to the clonic phase, corresponding to the vibratory movements. The clonic phase consisted of EMG discharges of remarkably constant duration (0.2s) separated by silent periods (SP) of exponentially increasing duration - features that could not be reproduced voluntarily. The last SP was longer in seizures with higher EMG peak frequency whereas the energy of the last clonus was higher in seizures with a short clonic phase. We found specific features of muscle activation dynamics during GTCS. Our findings suggest that the same inhibitory mechanisms that contribute to GTCS termination counteract seizure initiation, accounting for the gradual onset. Both active inhibition and mechanisms related to metabolic depletion act synergistically to stop the seizure. Analysis of the ictal EMG dynamics is a valuable tool for monitoring the balance between pro-convulsive and anti-convulsive factors. Copyright © 2012 Elsevier B.V. All rights reserved.

  11. Adaptation of muscle gene expression to changes in contractile activity

    Science.gov (United States)

    Booth, F. W.; Babij, P.; Thomason, D. B.; Wong, T. S.; Morrison, P. R.

    1987-01-01

    A review of the existing literature regarding the effects of different types of physical activities on the gene expression of adult skeletal muscles leads us to conclude that each type of exercise training program has, as a result, a different phenotype, which means that there are multiple mechanisms, each producing a unique phenotype. A portion of the facts which support this position is presented and interpreted here. [Abstract translated from the original French by NASA].

  12. Muscle shortening velocity depends on tissue inertia and level of activation during submaximal contractions.

    Science.gov (United States)

    Ross, Stephanie A; Wakeling, James M

    2016-06-01

    In order to perform external work, muscles must do additional internal work to deform their tissue, and in particular, to overcome the inertia due to their internal mass. However, the contribution of the internal mass within a muscle to the mechanical output of that muscle has only rarely been studied. Here, we use a dynamic, multi-element Hill-type muscle model to examine the effects of the inertial mass within muscle on its contractile performance. We find that the maximum strain-rate of muscle is slower for lower activations and larger muscle sizes. As muscle size increases, the ability of the muscle to overcome its inertial load will decrease, as muscle tension is proportional to cross-sectional area and inertial load is proportional to mass. Thus, muscles that are larger in size will have a higher inertial cost to contraction. Similarly, when muscle size and inertial load are held constant, decreasing muscle activation will increase inertial cost to contraction by reducing muscle tension. These results show that inertial loads within muscle contribute to a slowing of muscle contractile velocities (strain-rates), particularly at the submaximal activations that are typical during animal locomotion.

  13. Corticospinal contribution to arm muscle activity during human walking

    DEFF Research Database (Denmark)

    Barthélemy, Dorothy; Nielsen, Jens Bo

    2010-01-01

    potentials (MEPs) elicited in the posterior deltoid muscle (PD) by transcranial magnetic stimulation (TMS) were modulated during the gait cycle in parallel with changes in the background EMG activity. There was no significant difference in the size of the MEPs at a comparable level of background EMG during...... walking and during static PD contraction. Short latency intracortical inhibition (SICI; 2 ms interval) studied by paired-pulse TMS was diminished during bursts of PD EMG activity. This could not be explained only by changes in background EMG activity and/or control MEP size, since SICI showed...... no correlation to the level of background EMG activity during static PD contraction. Finally, TMS at intensity below the threshold for activation of corticospinal tract fibres elicited a suppression of the PD EMG activity during walking. Since TMS at this intensity is likely to only activate intracortical...

  14. Neck and shoulder muscle activity of orthodontists in natural environments.

    Science.gov (United States)

    McNee, C; Kieser, J K; Antoun, J S; Bennani, H; Gallo, L M; Farella, M

    2013-06-01

    Work related musculoskeletal disorders (WMSDs) are common among dentists and possibly caused by prolonged static load. The aim of this study was to assess the contraction pattern of neck and shoulder muscles of orthodontists in natural environments. Electromyographic (EMG) activity of right sternocleidomastoid and trapezius muscles were recorded by means of portable recorders in eight orthodontists during working conditions, and both active and resting non-working conditions. Recordings were analysed in terms of contraction episode (CE) count, amplitude, and duration. The sternocleidomastoid and trapezius muscles contracted about 40-70times per hour in the natural environment. Their EMG activity pattern mainly consisted of short-lasting, low-amplitude CEs. The counts and amplitude of sternocleidomastoid CEs did not differ across vocational and non-vocational conditions. The number and amplitude of trapezius CEs were slightly but significantly higher during the vocational condition. There were highly significant (pmuscle contractions found in the vocational setting. During orthodontic work, operators commonly hold muscular contractions for significantly longer periods than are encountered in non-vocational settings. This behaviour may be associated causally with the increases seen in WMSDs through proposed pathophysiological mechanisms occurring at the motor unit level. Our findings may also be valid for other occupations characterised by seated static postures with precision hand and wrist movements.

  15. Fatigue resistance of rat extraocular muscles does not depend on creatine kinase activity.

    Science.gov (United States)

    McMullen, Colleen A; Hayess, Katrin; Andrade, Francisco H

    2005-08-17

    Creatine kinase (CK) links phosphocreatine, an energy storage system, to cellular ATPases. CK activity serves as a temporal and spatial buffer for ATP content, particularly in fast-twitch skeletal muscles. The extraocular muscles are notoriously fast and active, suggesting the need for efficient ATP buffering. This study tested the hypotheses that (1) CK isoform expression and activity in rat extraocular muscles would be higher, and (2) the resistance of these muscles to fatigue would depend on CK activity. We found that mRNA and protein levels for cytosolic and mitochondrial CK isoforms were lower in the extraocular muscles than in extensor digitorum longus (EDL). Total CK activity was correspondingly decreased in the extraocular muscles. Moreover, cytoskeletal components of the sarcomeric M line, where a fraction of CK activity is found, were downregulated in the extraocular muscles as was shown by immunocytochemistry and western blotting. CK inhibition significantly accelerated the development of fatigue in EDL muscle bundles, but had no major effect on the extraocular muscles. Searching for alternative ATP buffers that could compensate for the relative lack of CK in extraocular muscles, we determined that mRNAs for two adenylate kinase (AK) isoforms were expressed at higher levels in these muscles. Total AK activity was similar in EDL and extraocular muscles. These data indicate that the characteristic fatigue resistance of the extraocular muscles does not depend on CK activity.

  16. Fatigue resistance of rat extraocular muscles does not depend on creatine kinase activity

    Directory of Open Access Journals (Sweden)

    Hayeß Katrin

    2005-08-01

    Full Text Available Abstract Background Creatine kinase (CK links phosphocreatine, an energy storage system, to cellular ATPases. CK activity serves as a temporal and spatial buffer for ATP content, particularly in fast-twitch skeletal muscles. The extraocular muscles are notoriously fast and active, suggesting the need for efficient ATP buffering. This study tested the hypotheses that (1 CK isoform expression and activity in rat extraocular muscles would be higher, and (2 the resistance of these muscles to fatigue would depend on CK activity. Results We found that mRNA and protein levels for cytosolic and mitochondrial CK isoforms were lower in the extraocular muscles than in extensor digitorum longus (EDL. Total CK activity was correspondingly decreased in the extraocular muscles. Moreover, cytoskeletal components of the sarcomeric M line, where a fraction of CK activity is found, were downregulated in the extraocular muscles as was shown by immunocytochemistry and western blotting. CK inhibition significantly accelerated the development of fatigue in EDL muscle bundles, but had no major effect on the extraocular muscles. Searching for alternative ATP buffers that could compensate for the relative lack of CK in extraocular muscles, we determined that mRNAs for two adenylate kinase (AK isoforms were expressed at higher levels in these muscles. Total AK activity was similar in EDL and extraocular muscles. Conclusion These data indicate that the characteristic fatigue resistance of the extraocular muscles does not depend on CK activity.

  17. Distinct muscle apoptotic pathways are activated in muscles with different fiber types a rat model of critical illness myopathy

    Science.gov (United States)

    Barnes, Benjamin T.; Confides, Amy L.; Rich, Mark M.; Dupont-Versteegden, Esther E.

    2015-01-01

    Critical illness myopathy (CIM) is associated with severe muscle atrophy and fatigue in affected patients. Apoptotic signaling is involved in atrophy and is elevated in muscles from patients with CIM. In this study we investigated underlying mechanisms of apoptosis-related pathways in muscles with different fiber type composition in a rat model of CIM using denervation and glucocorticoid administration (denervation and steroid-induced myopathy, DSIM). Soleus and tibialis anterior (TA) muscles showed severe muscle atrophy (40–60% of control muscle weight) and significant apoptosis in interstitial as well as myofiber nuclei that was similar between the two muscles with DSIM. Caspase-3 and −8 activities, but not caspase-9 and −12, were elevated in TA and not in soleus muscle, while the caspase-independent proteins endonuclease G (EndoG) and apoptosis inducing factor (AIF) were not changed in abundance nor differentially localized in either muscle. Anti-apoptotic proteins HSP70, −27, and apoptosis repressor with a caspase recruitment domain (ARC) were elevated in soleus compared to TA muscle and ARC was significantly decreased with induction of DSIM in soleus. Results indicate that apoptosis is a significant process associated with DSIM in both soleus and TA muscles, and that apoptosis-associated processes are differentially regulated in muscles of different function and fiber type undergoing atrophy due to DSIM. We conclude that interventions combating apoptosis with CIM may need to be directed towards inhibiting caspase-dependent as well as -independent mechanisms to be able to affect muscles of all fiber types. PMID:25740800

  18. Distinct muscle apoptotic pathways are activated in muscles with different fiber types in a rat model of critical illness myopathy.

    Science.gov (United States)

    Barnes, Benjamin T; Confides, Amy L; Rich, Mark M; Dupont-Versteegden, Esther E

    2015-06-01

    Critical illness myopathy (CIM) is associated with severe muscle atrophy and fatigue in affected patients. Apoptotic signaling is involved in atrophy and is elevated in muscles from patients with CIM. In this study we investigated underlying mechanisms of apoptosis-related pathways in muscles with different fiber type composition in a rat model of CIM using denervation and glucocorticoid administration (denervation and steroid-induced myopathy, DSIM). Soleus and tibialis anterior (TA) muscles showed severe muscle atrophy (40-60% of control muscle weight) and significant apoptosis in interstitial as well as myofiber nuclei that was similar between the two muscles with DSIM. Caspase-3 and -8 activities, but not caspase-9 and -12, were elevated in TA and not in soleus muscle, while the caspase-independent proteins endonuclease G (EndoG) and apoptosis inducing factor (AIF) were not changed in abundance nor differentially localized in either muscle. Anti-apoptotic proteins HSP70, -27, and apoptosis repressor with a caspase recruitment domain (ARC) were elevated in soleus compared to TA muscle and ARC was significantly decreased with induction of DSIM in soleus. Results indicate that apoptosis is a significant process associated with DSIM in both soleus and TA muscles, and that apoptosis-associated processes are differentially regulated in muscles of different function and fiber type undergoing atrophy due to DSIM. We conclude that interventions combating apoptosis with CIM may need to be directed towards inhibiting caspase-dependent as well as -independent mechanisms to be able to affect muscles of all fiber types.

  19. The Assessment Methods of Laryngeal Muscle Activity in Muscle Tension Dysphonia: A Review

    Directory of Open Access Journals (Sweden)

    Seyyedeh Maryam Khoddami

    2013-01-01

    Full Text Available The purpose of this paper is to review the methods used for the assessment of muscular tension dysphonia (MTD. The MTD is a functional voice disorder associated with abnormal laryngeal muscle activity. Various assessment methods are available in the literature to evaluate the laryngeal hyperfunction. The case history, laryngoscopy, and palpation are clinical methods for the assessment of patients with MTD. Radiography and surface electromyography (EMG are objective methods to provide physiological information about MTD. Recent studies show that surface EMG can be an effective tool for assessing muscular tension in MTD.

  20. The assessment methods of laryngeal muscle activity in muscle tension dysphonia: a review.

    Science.gov (United States)

    Khoddami, Seyyedeh Maryam; Nakhostin Ansari, Noureddin; Izadi, Farzad; Talebian Moghadam, Saeed

    2013-11-04

    The purpose of this paper is to review the methods used for the assessment of muscular tension dysphonia (MTD). The MTD is a functional voice disorder associated with abnormal laryngeal muscle activity. Various assessment methods are available in the literature to evaluate the laryngeal hyperfunction. The case history, laryngoscopy, and palpation are clinical methods for the assessment of patients with MTD. Radiography and surface electromyography (EMG) are objective methods to provide physiological information about MTD. Recent studies show that surface EMG can be an effective tool for assessing muscular tension in MTD.

  1. Mitochondrial superoxide flashes: metabolic biomarkers of skeletal muscle activity and disease

    OpenAIRE

    2011-01-01

    Mitochondrial superoxide flashes (mSOFs) are stochastic events of quantal mitochondrial superoxide generation. Here, we used flexor digitorum brevis muscle fibers from transgenic mice with muscle-specific expression of a novel mitochondrial-targeted superoxide biosensor (mt-cpYFP) to characterize mSOF activity in skeletal muscle at rest, following intense activity, and under pathological conditions. Results demonstrate that mSOF activity in muscle depended on electron transport chain and aden...

  2. Electromyographic Study of Neck Muscle Activity According to Head Position in Rugby Tackles

    Science.gov (United States)

    Morimoto, Koji; Sakamoto, Masaaki; Fukuhara, Takashi; Kato, Kazuo

    2013-01-01

    [Purpose] This study examined differences in neck muscle activity in two different head positions during tackles with the aim of contributing to the prevention of sports injuries. [Subjects] The subjects were 28 male high-school rugby players. [Methods] Two tackle positions were considered: a head-up position and a head-down position. Muscle activities of the sternocleidomastoid muscles and the upper, middle, and lower parts of the trapezius muscles were measured. [Results] Muscle activities of the sternocleidomastoid muscles and the right upper trapezius muscle were significantly increased in the head-up position, and the activity of the lower trapezius was significantly increased in the head-down position. [Conclusion] Tackling with the head-up position increases neck muscle activity and stability of the head and the neck. PMID:24259802

  3. Activation of estrogen response elements is mediated both via estrogen and muscle contractions in rat skeletal muscle myotubes

    DEFF Research Database (Denmark)

    Wiik, A.; Hellsten, Ylva; Berthelson, P.

    2009-01-01

    The aim of the present study was to investigate the activation of estrogen response elements (EREs) by estrogen and muscle contractions in rat myotubes in culture and to assess whether the activation is dependent on the estrogen receptors (ERs). In addition, the effect of estrogen and contraction...... increased (P estrogen and attenuated (P estrogen-induced transactivation is mediated via ERs, the effect of muscle contraction...... is ER independent. The muscle contraction-induced transactivation of ERE and increase in ERbeta mRNA were instead found to be MAP kinase (MAPK) dependent. This study demonstrates for the first time that muscle contractions have a similar functional effect as estrogen in skeletal muscle myotubes, causing...

  4. The influence of induced shoulder muscle pain on rotator cuff and scapulothoracic muscle activity during elevation of the arm.

    Science.gov (United States)

    Castelein, Birgit; Cools, Ann; Parlevliet, Thierry; Cagnie, Barbara

    2017-03-01

    Altered recruitment of rotator cuff and scapulothoracic muscles has been identified in patients with subacromial impingement syndrome. To date, however, the cause-consequence relationship between pain and altered muscle recruitment has not been fully unraveled. The effect of experimental shoulder pain induced by injection of hypertonic saline in the supraspinatus on the activity of the supraspinatus, infraspinatus, subscapularis, trapezius, and serratus anterior activity was investigated during the performance of an elevation task by use of muscle functional magnetic resonance imaging in 25 healthy individuals. Measurements were taken at 4 levels (C6-C7, T2-T3, T3-T4, and T6-T7) at rest and after the elevation task performed without and with experimental shoulder pain. During arm elevation, experimentally induced pain caused a significant activity reduction, expressed as reduction in T2 shift of the IS (P = .029). No significant changes in T2 shift values were found for the other rotator cuff muscles or the scapulothoracic muscles. This study demonstrates that acute experimental shoulder pain has an inhibitory effect on the activity of the IS during arm elevation. Acute experimental shoulder pain did not seem to influence the scapulothoracic muscle activity significantly. The findings suggest that rotator cuff muscle function (infraspinatus) should be a consideration in the early management of patients with shoulder pain. Copyright © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.

  5. Model identification of stomatognathic muscle system activity during mastication

    Science.gov (United States)

    Kijak, Edward; Margielewicz, Jerzy; Lietz-Kijak, Danuta; Wilemska-Kucharzewska, Katarzyna; Kucharzewski, Marek; Śliwiński, Zbigniew

    2017-01-01

    The present study aimed to determine the numeric projection of the function of the mandible and muscle system during mastication. An experimental study was conducted on a healthy 47 year-old subject. On clinical examination no functional disorders were observed. To evaluate the activity of mastication during muscle functioning, bread cubes and hazelnuts were selected (2 cm2 and 1.2/1.3 cm in diameter, respectively) for condyloid processing. An assessment of the activity of mastication during muscle functioning was determined on the basis of numeric calculations conducted with a novel software programme, Kinematics 3D, designed specifically for this study. The efficacy of the model was verified by ensuring the experimentally recorded trajectories were concordant with those calculated numerically. Experimental measurements of the characteristic points of the mandible trajectory were recorded six times. Using the configuration coordinates that were calculated, the dominant componential harmonics of the amplitude-frequency spectrum were identified. The average value of the dominant frequency during mastication of the bread cubes was ~1.16±0.06 Hz, whereas in the case of the hazelnut, this value was nearly two-fold higher at 1.84±0.07 Hz. The most asymmetrical action during mastication was demonstrated to be carried out by the lateral pterygoid muscles, provided that their functioning was not influenced by food consistency. The consistency of the food products had a decisive impact on the frequency of mastication and the number of cycles necessary to grind the food. Model tests on the function of the masticatory organ serve as effective tools since they provide qualitative and quantitative novel information on the functioning of the human masticatory organ. PMID:28123482

  6. Late cortical disinhibition in relaxed versus active hand muscles.

    Science.gov (United States)

    Caux-Dedeystère, A; Derambure, P; Devanne, H

    2015-07-09

    Recent research suggests that long-interval intracortical inhibition (LICI) is followed by a transitory period of late cortical disinhibition (LCD) that can even lead to a net increase in cortical excitability. The relationship between LICI/LCD and voluntary drive remains poorly understood. Our study aims at investigating the influence of index abduction on LICI and LCD in an actively engaged muscle and a neighboring muscle, while varying the intensity of the conditioning stimulus (CS). Motor-evoked potentials (MEPs) were recorded from the first dorsal interosseus (FDI) and abductor digiti minimi (ADM) muscles in 13 subjects. Paired-pulses were delivered with 10 different interstimulus intervals (ranging from 60 to 290 ms). Whatever the condition (relaxed or active FDI), the test stimulus was set to evoke an MEP of 1mV. The time course of conditioned MEP amplitude was compared for relaxed and active conditions when the CS intensity was set to (i) 130% of the rest motor threshold (RMT) or (ii) to evoke the same size of MEP under both conditions. LICI lasted longer (i.e. disinhibition occurred later) at rest than during abduction when evoked either by similar or matched conditioning stimuli. No post-LICI facilitation was observed at rest - even when the CS intensity was set to 160% RMT. In contrast, long-interval intracortical facilitation (LICF) was observed in the quiescent ADM when FDI was active. LICF may then be associated with voluntary activity albeit with lack of topographic specificity. Copyright © 2015 IBRO. Published by Elsevier Ltd. All rights reserved.

  7. The Activity of Surface Electromyographic Signal of Selected Muscles during Classic Rehabilitation Exercise

    Directory of Open Access Journals (Sweden)

    Jinzhuang Xiao

    2016-01-01

    Full Text Available Objectives. Prone bridge, unilateral bridge, supine bridge, and bird-dog are classic rehabilitation exercises, which have been advocated as effective ways to improve core stability among healthy individuals and patients with low back pain. The aim of this study was to investigate the activity of seven selected muscles during rehabilitation exercises through the signal of surface electromyographic. Approaches. We measured the surface electromyographic signals of four lower limb muscles, two abdominal muscles, and one back muscle during rehabilitation exercises of 30 healthy students and then analyzed its activity level using the median frequency method. Results. Different levels of muscle activity during the four rehabilitation exercises were observed. The prone bridge and unilateral bridge caused the greatest muscle fatigue; however, the supine bridge generated the lowest muscle activity. There was no significant difference (P>0.05 between left and right body side muscles in the median frequency slope during the four rehabilitation exercises of seven muscles. Conclusions. The prone bridge can affect the low back and lower limb muscles of most people. The unilateral bridge was found to stimulate muscles much more active than the supine bridge. The bird-dog does not cause much fatigue to muscles but can make most selected muscles active.

  8. The effect of increase in baggage weight on elderly women's lower extremity muscle activation during gait.

    Science.gov (United States)

    Kim, Seong-Gil; Nam, Chan-Woo; Yong, Min-Sik

    2014-01-01

    The aim of the present study was to examine the effect of increased baggage weight on the muscle activation of elderly women's lower extremities during gait. A total of 24 elderly women who were residing in communities in Daegu, South Korea aged 79.6±6.2, 149.7±7.0cm in height, and 53.5±7.2kg in weight participated in this study. The muscle activation of each muscle was measured three times at 2kg, 3kg, and 4kg of baggage weight while the subjects were conducting treadmill walking wearing backpacks. Electrodes were placed on four muscles: the quadriceps muscle (rectus femoris), the hamstring muscle (semitendinosus), the tibialis anterior muscle, and the soleus muscle. The results show that the rates of increase in muscle activation in the tibialis anterior and soleus muscles according to baggage weight increase were higher than those in the quadriceps and hamstring muscles (<0.05). These results indicate that the heavier weight loads increase the activation of muscles that control the ankle joints causing muscle fatigue. Moreover, a decrease in balance ability through muscle fatigue can be a risk factor for falls. Thus, elderly people should be instructed not to carry heavy objects.

  9. Relation Between Muscle Activation Pattern and Pain : An Explorative Study in a Bassists Population

    NARCIS (Netherlands)

    Woldendorp, Kees H.; van de Werk, Pieter; Boonstra, Anne M.; Stewart, Roy E.; Otten, Egbert

    2013-01-01

    Objective: To explore the muscle activation patterns in relation to pain complaints in bassists studied during a musical task. This study was based on the assumption that pain complaints are caused by increased muscle activation during playing or relaxation and/or faster onset of fatigue of muscles.

  10. Muscle-Strengthening Activities and Participation among Adults in the United States

    Science.gov (United States)

    Loustalot, Fleetwood; Carlson, Susan A.; Kruger, Judy; Buchner, David M.; Fulton, Janet E.

    2013-01-01

    Purpose: To describe those who reported meeting the "2008 Physical Activity Guidelines for Americans" ("2008 Guidelines") muscle-strengthening standard of 2 or more days per week, including all seven muscle groups, and to assess the type and location of muscle-strengthening activities performed. Method: Data from HealthStyles…

  11. Muscle-Strengthening Activities and Participation among Adults in the United States

    Science.gov (United States)

    Loustalot, Fleetwood; Carlson, Susan A.; Kruger, Judy; Buchner, David M.; Fulton, Janet E.

    2013-01-01

    Purpose: To describe those who reported meeting the "2008 Physical Activity Guidelines for Americans" ("2008 Guidelines") muscle-strengthening standard of 2 or more days per week, including all seven muscle groups, and to assess the type and location of muscle-strengthening activities performed. Method: Data from HealthStyles…

  12. Relation Between Muscle Activation Pattern and Pain : An Explorative Study in a Bassists Population

    NARCIS (Netherlands)

    Woldendorp, Kees H.; van de Werk, Pieter; Boonstra, Anne M.; Stewart, Roy E.; Otten, Egbert

    Objective: To explore the muscle activation patterns in relation to pain complaints in bassists studied during a musical task. This study was based on the assumption that pain complaints are caused by increased muscle activation during playing or relaxation and/or faster onset of fatigue of muscles.

  13. Whole body and muscle energy metabolism in preruminant calves: effects of nutrient synchrony and physical activity

    NARCIS (Netherlands)

    Borne, van den J.J.G.C.; Hocquette, J.F.; Verstegen, M.W.A.; Gerrits, W.J.J.

    2007-01-01

    The effects of asynchronous availability of amino acids and glucose on muscle composition and enzyme activities in skeletal muscle were studied in preruminant calves. It was hypothesized that decreased oxidative enzyme activities in muscle would explain a decreased whole body heat production with

  14. On the origin of muscle synergies: invariant balance in the co-activation of agonist and antagonist muscle pairs

    Directory of Open Access Journals (Sweden)

    Hiroaki eHirai

    2015-11-01

    Full Text Available Investigation of neural representation of movement planning has attracted the attention of neuroscientists, as it may reveal the sensorimotor transformation essential to motor control. The analysis of muscle synergies based on the activity of agonist-antagonist (AA muscle pairs may provide insight into such transformations, especially for a reference frame in the muscle space. In this study, we examined the AA concept using the following explanatory variables: the AA ratio, which is related to the equilibrium-joint angle, and the AA sum, which is associated with joint stiffness. We formulated muscle synergies as a function of AA sums, positing that muscle synergies are composite units of mechanical impedance. The AA concept can be regarded as another form of the equilibrium-point (EP hypothesis, and it can be extended to the concept of EP-based synergies. We introduce here a novel tool for analyzing the neurological and motor functions underlying human movements and review some initial insights from our results about the relationships between muscle synergies, endpoint stiffness, and virtual trajectories (time series of EP. Our results suggest that (1 muscle synergies reflect an invariant balance in the co-activation of AA muscle pairs; (2 each synergy represents the basis for the radial, tangential, and null movements of the virtual trajectory in the polar coordinates centered on the specific joint at the base of the body; and (3 the alteration of muscle synergies (for example, due to spasticity or rigidity following neurological injury results in significant distortion of endpoint stiffness and concomitant virtual trajectories. These results indicate that muscle synergies (i.e., the balance of muscle mechanical impedance are essential for motor control.

  15. Cerebellar brain inhibition in the target and surround muscles during voluntary tonic activation.

    Science.gov (United States)

    Panyakaew, Pattamon; Cho, Hyun Joo; Srivanitchapoom, Prachaya; Popa, Traian; Wu, Tianxia; Hallett, Mark

    2016-04-01

    Motor surround inhibition is the neural mechanism that selectively favours the contraction of target muscles and inhibits nearby muscles to prevent unwanted movements. This inhibition was previously reported at the onset of a movement, but not during a tonic contraction. Cerebellar brain inhibition (CBI) is reduced in active muscles during tonic activation; however, it has not been studied in the surround muscles. CBI was evaluated in the first dorsal interosseus (FDI) muscle as the target muscle, and the abductor digiti minimi, flexor carpi radialis and extensor carpi radialis muscles as surround muscles, during rest and tonic activation of the FDI muscle in 21 subjects. Cerebellar stimulation was performed under magnetic resonance imaging-guided neuronavigation targeting lobule VIII of the cerebellar hemisphere. Stimulus intensities for cerebellar stimulation were based on the resting motor cortex threshold (RMT) and adjusted for the depth difference between the cerebellar and motor cortices. We used 90-120% of the adjusted RMT as the conditioning stimulus intensity during rest. The intensity that generated the best CBI at rest in the FDI muscle was selected for use during tonic activation. During selective tonic activation of the FDI muscle, CBI was significantly reduced only for the FDI muscle, and not for the surround muscles. Unconditioned motor evoked potential sizes were increased in all muscles during FDI muscle tonic activation as compared with rest, despite background electromyography activity increasing only for the FDI muscle. Our study suggests that the cerebellum may play an important role in selective tonic finger movement by reducing its inhibition in the motor cortex only for the relevant agonist muscle.

  16. The effect of fear of movement on muscle activation in posttraumatic neck pain disability

    NARCIS (Netherlands)

    Nederhand, Marc J.; Hermens, Hermie J.; IJzerman, Maarten J.; Groothuis, Karin G.M.; Turk, Dennis C.

    2006-01-01

    Studies using surface electromyography have demonstrated a reorganization of muscle activation patterns of the neck and shoulder muscles in patients with posttraumatic neck pain disability. The neurophysiologically oriented "pain adaptation" model explains this reorganization as a useful adaptation

  17. Changes in presumed motor cortical activity during fatiguing muscle contraction in humans

    DEFF Research Database (Denmark)

    Seifert, Thomas; Petersen, Nicolas Caesar

    2010-01-01

    AIM: Changes in sensory information from active muscles accompany fatiguing exercise and the force-generating capacity deteriorates. The central motor commands therefore must adjust depending on the task performed. Muscle potentials evoked by transcranial magnetic stimulation (TMS) change during...

  18. Time-dependent cortical activation in voluntary muscle contraction.

    Science.gov (United States)

    Yang, Qi; Wang, Xiaofeng; Fang, Yin; Siemionow, Vlodek; Yao, Wanxiang; Yue, Guang H

    2011-01-01

    This study was to characterize dynamic source strength changes estimated from high-density scalp electroencephalogram (EEG) at different phases of a submaximal voluntary muscle contraction. Eight healthy volunteers performed isometric handgrip contractions of the right arm at 20% maximal intensity. Signals of the handgrip force, electromyography (EMG) from the finger flexor and extensor muscles and 64-channel EEG were acquired simultaneously. Sources of the EEG were analyzed at 19 time points across preparation, execution and sustaining phases of the handgrip. A 3-layer boundary element model (BEM) based on the MNI (Montréal Neurological Institute) brain MRI was used to overlay the sources. A distributed current density model, LORETA L1 norm method was applied to the data that had been processed by independent component analysis (ICA). Statistical analysis based on a mixed-effects polynomial regression model showed a significant and consistent time-dependent non-linear source strength change pattern in different phases of the handgrip. The source strength increased at the preparation phase, peaked at the force onset time and decreased in the sustaining phase. There was no significant difference in the changing pattern of the source strength among Brodmann's areas 1, 2, 3, 4, and 6. These results show, for the first time, a high time resolution increasing-and-decreasing pattern of activation among the sensorimotor regions with the highest activity occurs at the muscle activity onset. The similarity in the source strength time courses among the cortical centers examined suggests a synchronized parallel function in controlling the motor activity.

  19. Gluteus medius and scapula muscle activations in youth baseball pitchers.

    Science.gov (United States)

    Oliver, Gretchen D; Weimar, Wendi H; Plummer, Hillary A

    2015-06-01

    The baseball pitching motion is a total kinetic chain activity that must efficiently use both the upper and lower extremity. Of particular importance is the scapular motion, which is critical for humeral positioning and proper alignment of shoulder musculature. It was hypothesized that scapular stability is enhanced by pelvic girdle stability. Therefore, it was the purpose of this study to determine the muscle activations of selected pelvic and scapular stabilizing muscles during a fastball pitch in youth baseball pitchers. Twenty youth baseball pitchers (age: 11.3 + 1.0 years; height: 152.4 + 9.0 cm; weight: 47.5 + 11.3 kg) were recorded throwing 4-seam fastballs for strikes. Data revealed moderate (20-39% maximum voluntary isometric contraction [MVIC]) to moderately strong (>40% MVIC) activation of the ipsilateral (throwing arm side) gluteus medius, upper trapezius, and serratus anterior throughout phases 2 (maximum shoulder external rotation to ball release) and 3 (ball release to maximum shoulder internal rotation). Moderately strong activation (>40% MVIC) of the upper trapezius and serratus anterior was noted during phases 2 and 3 of the pitching motion. Pearson's product-moment correlation revealed significant relationships between bilateral gluteus medius and the force couples about the scapula during all 3 phases of the pitching motion. The results of this study provide important data that improve the understanding of the muscular relationship between the pelvic and scapular stabilizers during the fastball pitch. Training and rehabilitation programs should consider focusing on lumbopelvic-hip and scapular muscle strengthening as well as coordinated strengthening of the pelvic and scapular stabilizers, in baseball pitchers.

  20. Muscle activity during functional coordination training: implications for strength gain and rehabilitation

    DEFF Research Database (Denmark)

    Jørgensen, Marie Birk; Andersen, Lars Louis; Kirk, Niels

    2010-01-01

    The purpose of this study was to evaluate if different types, body positions, and levels of progression of functional coordination exercises can provide sufficiently high levels of muscle activity to improve strength of the neck, shoulder, and trunk muscles. Nine untrained women were familiarized...... training can be performed with a muscle activity sufficient for strength gain. Functional coordination training may therefore be a good choice for prevention or rehabilitation of musculoskeletal pain or injury in the neck, shoulder, or trunk muscles....

  1. Surface electromyograph activity of submental muscles during swallowing and expiratory muscle training tasks in Huntington's disease patients.

    Science.gov (United States)

    Reyes, Alvaro; Cruickshank, Travis; Thompson, Jennifer; Ziman, Mel; Nosaka, Kazunori

    2014-02-01

    Huntington's disease (HD) patients have difficulty in swallowing, leading to aspiration pneumonia, which is a major cause of death. It seems possible that submental muscles that are crucial for preventing an escape of a bolus into the airway, are affected by HD, but no previous studies have investigated this. To assess surface electromyograph (sEMG) activity of submental muscles during swallowing and expiratory muscle training (EMT) tasks in HD patients in comparison to healthy volunteers. sEMG activities of submental muscles during saliva, water swallowing, EMT tasks performed at 25% and 75% of maximum expiratory pressure were recorded and normalised by the sEMG activity during an effortful swallow in 17 early to mid stage HD patients and 17 healthy volunteers. sEMG activity was greater (pswallowing, but was not significantly different between groups for saliva, water swallowing and EMT at 25%. HD patients had lower sEMG activity for EMT at 75% (p<0.05). Decreases in submental muscle activity were not evident in HD patients except during EMT at 75%. This suggests that relative submental muscle weakness is observed only during a high intensity task in early to mid stage HD patients. Copyright © 2013 Elsevier Ltd. All rights reserved.

  2. Direct optical activation of skeletal muscle fibres efficiently controls muscle contraction and attenuates denervation atrophy.

    Science.gov (United States)

    Magown, Philippe; Shettar, Basavaraj; Zhang, Ying; Rafuse, Victor F

    2015-10-13

    Neural prostheses can restore meaningful function to paralysed muscles by electrically stimulating innervating motor axons, but fail when muscles are completely denervated, as seen in amyotrophic lateral sclerosis, or after a peripheral nerve or spinal cord injury. Here we show that channelrhodopsin-2 is expressed within the sarcolemma and T-tubules of skeletal muscle fibres in transgenic mice. This expression pattern allows for optical control of muscle contraction with comparable forces to nerve stimulation. Force can be controlled by varying light pulse intensity, duration or frequency. Light-stimulated muscle fibres depolarize proportionally to light intensity and duration. Denervated triceps surae muscles transcutaneously stimulated optically on a daily basis for 10 days show a significant attenuation in atrophy resulting in significantly greater contractile forces compared with chronically denervated muscles. Together, this study shows that channelrhodopsin-2/H134R can be used to restore function to permanently denervated muscles and reduce pathophysiological changes associated with denervation pathologies.

  3. Electromyographic activities of the subscapularis, supraspinatus and infraspinatus muscles during passive shoulder and active elbow exercises.

    Science.gov (United States)

    Jung, Myung-Chul; Kim, Sung-Jae; Rhee, Jae-Jun; Lee, Doo-Hyung

    2016-07-01

    Postoperative exercises may increase load on repaired tendons. Differences in the activity of the rotator cuff muscles were assessed during several different types of passive shoulder and active elbow exercises. In 15 healthy subjects, passive forward flexion of the shoulder was performed using a table, pulley and rope, and a cane, and external rotation was performed using a cane and a wall. The active elbow flexion-extension exercise was also performed while holding the upper arm with the contralateral hand. Activation amplitudes of the supraspinatus, infraspinatus and subscapularis muscles were evaluated using electromyography with fine wires. During passive forward flexion, the supraspinatus and infraspinatus muscles exhibited lower activity when using a table compared with a cane (both P shoulder while using the cane and wall, there was no difference in the activity of any muscles. Electromyographic activity during the active elbow exercise was lower in the supraspinatus while holding the upper arm (P = 0.018). The table sliding exercise may reduce stress on the rotator cuff during passive forward flexion more than the other exercises do. Decreasing the range of motion to less than 90° in forward flexion activated the supraspinatus less. Moreover, movement of the elbow can be performed holding the upper arm to activate the rotator cuff to a lesser extent. Prognostic study, Level II.

  4. Improved identification of dystonic cervical muscles via abnormal muscle activity during isometric contractions

    NARCIS (Netherlands)

    De Bruijn, E.; Nijmeijer, S. W. R.; Forbes, P. A.; Koelman, J. H. T. M.; van der Helm, F. C. T.; Tijssen, M. A. J.; Happee, R.

    2015-01-01

    Background: The preferred treatment for cervical dystonia (CD) is injection of botulinum toxin in the dystonic muscles. Unfortunately, in the absence of reliable diagnostic methods it can be difficult to discriminate dystonic muscles from healthy muscles acting in compensation. We investigated if dy

  5. Improved identification of dystonic cervical muscles via abnormal muscle activity during isometric contractions

    NARCIS (Netherlands)

    De Bruijn, E; Nijmeijer, S W R; Forbes, P A; Koelman, J H T M; van der Helm, F C T; Tijssen, M A J; Happee, R

    2015-01-01

    BACKGROUND: The preferred treatment for cervical dystonia (CD) is injection of botulinum toxin in the dystonic muscles. Unfortunately, in the absence of reliable diagnostic methods it can be difficult to discriminate dystonic muscles from healthy muscles acting in compensation. We investigated if dy

  6. Associations between personality traits, physical activity level, and muscle strength.

    Science.gov (United States)

    Tolea, Magdalena I; Terracciano, Antonio; Simonsick, Eleanor M; Metter, E Jeffrey; Costa, Paul T; Ferrucci, Luigi

    2012-06-01

    Associations among personality as measured by the Five Factor Model, physical activity, and muscle strength were assessed using data from the Baltimore Longitudinal Study of Aging (N = 1220, age: mean = 58, SD = 16). General linear modeling with adjustment for age, sex, race, and body mass index, and bootstrapping for mediation were used. We found neuroticism and most of its facets to negatively correlate with strength. The extraversion domain and its facets of warmth, activity, and positive-emotions were positively correlated with strength, independent of covariates. Mediation analysis results suggest that these associations are partly explained by physical activity level. Findings extend the evidence of an association between personality and physical function to its strength component and indicate health behavior as an important pathway.

  7. Muscle activation during pedaling in different saddle position

    Directory of Open Access Journals (Sweden)

    Ana Paula Barcellos Karolczak

    2008-04-01

    Full Text Available The purpose of this study was to analyze the effects on muscle activation pattern of different saddle positions during cycling. Three elite cyclists followed a protocol that consisted of four different saddles positions, displaced forward, backward, upward and downward with relation to the reference position used in training and competition. In all tests the saddle was displaced by 1cm. The cyclists’ bicycles were mounted on a magnetic cycle simulator. The load was normalized at the second ventilatory threshold. Muscle activation of six lower limb muscles was registered: gluteus maximus, rectus femoris, biceps femoris, vastus lateralis, gastrocnemius medialis, and tibialis anterior. The results demonstrated that relatively small saddle adjustments can affect the pattern of muscle activation and probably cycling technique. Resumo ResumoO objetivo do presente estudo foi analisar os efeitos de diferentes posicionamentos do selim no padrão de ativação elétrica durante a pedalada. Três ciclistas de elite foram submetidos a um protocolo que constou da avaliação de quatro diferentes posições de selim (para frente, para trás, para cima e para baixo, assumindo como posição de referência a posição usada durante os treino e competição. O deslocamento do selim foi de 1 cm para todas as posições. As bicicletas dos ciclistas foram acopladas a um ciclossimulador magnético. A carga do teste foi normalizada utilizando um critério fisiológico, garantindo assim o mesmo nível de esforço para todos os sujeitos. A atividade elétrica de seis músculos do membro inferior foi mensurada: gluteus maximus, rectus femoris, biceps femoris, vastus lateralis, gastrocnemius medialis, e tibialis anterior. Os resultados demonstram que pequenos ajustes na posição do selim podem afetar os padrões de ativação elétrica e provavelmente a técnica de pedalada.

  8. The effects of surface condition on abdominal muscle activity during single-legged hold exercise.

    Science.gov (United States)

    Ha, Sung-min; Oh, Jae-seop; Jeon, In-cheol; Kwon, Oh-yun

    2015-02-01

    To treat low-back pain, various spinal stability exercises are commonly used to improve trunk muscle function and strength. Because human movement for normal daily activity occurs in multi-dimensions, the importance of exercise in multi-dimensions or on unstable surfaces has been emphasized. Recently, a motorized rotating platform (MRP) for facilitating multi-dimensions dynamic movement was introduced for clinical use. However, the abdominal muscle activity with this device has not been reported. The purpose of this study was to compare the abdominal muscle activity (rectus abdominis, external and internal oblique muscles) during an active single-leg-hold (SLH) exercise on a floor (stable surface), foam roll, and motorized rotating platform (MRP). Thirteen healthy male subjects participated in this study. Using electromyography, the abdominal muscle activity was measured while the subjects performed SLH exercises on floor (stable surface), foam roll, and MRP. There were significant differences in the abdominal muscle activities among conditions (P.05) (Fig. 2). After the Bonferroni correction, however, no significant differences among conditions remained, except for differences in both side IO muscle activity between the floor and foam roll conditions (padjabdominal muscles activity in the multiple comparison between conditions (mean difference were smaller than the standard deviation in the abdominal muscle activities) (padj>0.017), except for differences in both side IO muscle activity between the floor (stable surface) and foam roll (padj<0.017) (effect size: 0.79/0.62 (non-supporting/supporting leg) for foam-roll versus floor).

  9. Gait and muscle activation changes in men with knee osteoarthritis.

    Science.gov (United States)

    Liikavainio, Tuomas; Bragge, Timo; Hakkarainen, Marko; Karjalainen, Pasi A; Arokoski, Jari P

    2010-01-01

    The aim was to examine the biomechanics of level- and stair-walking in men with knee osteoarthritis (OA) at different pre-determined gait speeds and to compare the results with those obtained from healthy control subjects. Special emphasis was placed on the estimation of joint loading. Fifty-four men with knee OA (50-69 years) and 53 healthy age- and sex-matched controls were enrolled in the study. The participants walked barefoot in the laboratory (1.2 m/s+/-5%), corridor (1.2; 1.5 and 1.7 m/s+/-5%), and climbing and coming down stairs (0.5 and 0.8 m/s+/-5%) separately. Joint loading was assessed with skin mounted accelerometers (SMAs) attached just above and below the more affected knee joint. The 3-D ground reaction forces (GRFs) and muscle activation with surface-electromyography (EMG) from vastus medialis (VM) and biceps femoris (BF) were also measured simultaneously. There were no differences in SMA variables between groups during level-walking, but maximal loading rate (LR(max)) was higher bilaterally in the controls (Pstair descent at faster speed. The distinctions in muscle activation both at level- and stair ambulation in VM and BF muscles revealed that the patients used different strategies to execute the same walking tasks. It is concluded that the differences in measured SMA and GRF parameters between the knee OA patients and the controls were only minor at constant gait speeds. It is speculated that the faster speeds in the stair descent subjected the compensatory mechanisms to the maximum highlighting the differences between groups.

  10. Reorganized trunk muscle activity during multidirectional floor perturbations after experimental low back pain

    DEFF Research Database (Denmark)

    Larsen, Lars Henrik; Hirata, Rogerio Pessoto; Graven-Nielsen, Thomas

    2016-01-01

    each perturbation was extracted and averaged across perturbations. The difference (ΔRMS-EMG) and absolute difference (absolute ΔRMS-EMG) RMS from baseline conditions were extracted for each muscle during pain conditions and averaged bilaterally for back and abdominal muscle groups. Bilateral compared...... with unilateral pain induced higher VAS scores (P muscle activity during unilateral (P abdominal...... (P muscles during bilateral and decreased in the back (P abdominal (P muscles during unilateral pain. Bilateral pain caused greater absolute ΔRMS-EMG changes in the back (P abdominal (P muscle groups than unilateral pain. PERSPECTIVE: This study provided...

  11. Preventive effects of Chlorella on skeletal muscle atrophy in muscle-specific mitochondrial aldehyde dehydrogenase 2 activity-deficient mice.

    Science.gov (United States)

    Nakashima, Yuya; Ohsawa, Ikuroh; Nishimaki, Kiyomi; Kumamoto, Shoichiro; Maruyama, Isao; Suzuki, Yoshihiko; Ohta, Shigeo

    2014-10-11

    Oxidative stress is involved in age-related muscle atrophy, such as sarcopenia. Since Chlorella, a unicellular green alga, contains various antioxidant substances, we used a mouse model of enhanced oxidative stress to investigate whether Chlorella could prevent muscle atrophy. Aldehyde dehydrogenase 2 (ALDH2) is an anti-oxidative enzyme that detoxifies reactive aldehydes derived from lipid peroxides such as 4-hydroxy-2-nonenal (4-HNE). We therefore used transgenic mice expressing a dominant-negative form of ALDH2 (ALDH2*2 Tg mice) to selectively decrease ALDH2 activity in the muscles. To evaluate the effect of Chlorella, the mice were fed a Chlorella-supplemented diet (CSD) for 6 months. ALDH2*2 Tg mice exhibited small body size, muscle atrophy, decreased fat content, osteopenia, and kyphosis, accompanied by increased muscular 4-HNE levels. The CSD helped in recovery of body weight, enhanced oxidative stress, and increased levels of a muscle impairment marker, creatine phosphokinase (CPK) induced by ALDH2*2. Furthermore, histological and histochemical analyses revealed that the consumption of the CSD improved skeletal muscle atrophy and the activity of the mitochondrial cytochrome c oxidase. This study suggests that long-term consumption of Chlorella has the potential to prevent age-related muscle atrophy.

  12. In Graves' disease, increased muscle tension and reduced elasticity of affected muscles is primarily caused by active muscle contraction

    NARCIS (Netherlands)

    H.J. Simonsz (Huib); G. Kommerell (Guntram)

    1989-01-01

    textabstractIn three patients with Graves' disease of recent onset, length-tension diagrams were made during surgery for squint under eyedrop anesthesia, while the other eye looked ahead, into the field of action, or out of the field of action of the muscle that was measured. The affected muscles

  13. In Graves' disease, increased muscle tension and reduced elasticity of affected muscles is primarily caused by active muscle contraction

    NARCIS (Netherlands)

    H.J. Simonsz (Huib); G. Kommerell (Guntram)

    1989-01-01

    textabstractIn three patients with Graves' disease of recent onset, length-tension diagrams were made during surgery for squint under eyedrop anesthesia, while the other eye looked ahead, into the field of action, or out of the field of action of the muscle that was measured. The affected muscles we

  14. Methods for demonstration of enzyme activity in muscle fibres at the muscle/bone interface in demineralized tissue

    DEFF Research Database (Denmark)

    Kirkeby, S; Vilmann, H

    1981-01-01

    A method for demonstration of activity for ATPase and various oxidative enzymes (succinic dehydrogenase, alpha-glycerophosphate dehydrogenase, and lactic dehydrogenase) in muscle/bone sections of fixed and demineralized tissue has been developed. It was found that it is possible to preserve...... considerable amounts of the above mentioned enzymes in the muscle fibres at the muscle/bone interfaces. The best results were obtained after 20 min fixation, and 2-3 weeks of storage in MgNa2EDTA containing media. As the same technique previously has been used to describe patterns of resorption and deposition...

  15. Type and intensity of activity and risk of mobility limitation: the mediating role of muscle parameters

    NARCIS (Netherlands)

    Visser, M.; Simonsick, E.M.; Colbert, L.H.; Brach, J.S.; Rubin, S.M.; Kritchevsky, S.B.; Newman, A.B.; Harris, T.B.

    2005-01-01

    2,719 kcal/wk of total physical activity). The study outcome, incident mobility limitation, was defined as two consecutive, semiannual self-reports of any difficulty walking one quarter of a mile or climbing 10 steps. Thigh muscle area, thigh muscle attenuation (a marker of fat infiltration in muscl

  16. Active tension changes in frog skeletal muscle during and after mechanical extension

    NARCIS (Netherlands)

    Atteveldt, H. van; Crowe, Alan

    1980-01-01

    Isolated frog sartorious muscle at 4°C has been used to study the phenomenon whereby tetanically stimulated muscle, subjected to a mechanical extension, yields an active tension which is greater than that obtained during an isometric contraction in which the muscle is stretched prior to stimulation.

  17. Daily activity of the rabbit jaw muscles during early postnatal development

    NARCIS (Netherlands)

    van Wessel, T.; Langenbach, G.E.J.; Brugman, P.; Korfage, J.A.M.; van Eijden, T.M.G.J.

    2006-01-01

    Early postnatal development of the jaw muscles is characterized by the transition from suckling to chewing behavior. As chewing develops the jaw closing muscles become more powerful compared with the jaw openers. These changes are likely to affect the amount of daily muscle activity. Therefore, the

  18. Influence of botulinum toxin on rabbit jaw muscle activity and anatomy

    NARCIS (Netherlands)

    Korfage, J.A.M.; Wang, J.; Lie, S.H.J.T.J.; Langenbach, G.E.J.

    2012-01-01

    Introduction: Muscles can adapt their fiber properties to accommodate to new conditions. We investigated the extent to which a decrease in muscle activation can cause an adaptation of fiber properties in synergistic and antagonistic jaw muscles. Methods: Three months after the injection of botulinum

  19. Brachialis muscle activity can be assessed with surface electromyography.

    Science.gov (United States)

    Staudenmann, Didier; Taube, Wolfgang

    2015-04-01

    The brachialis muscle (BR) represents an important elbow flexor and its activity has so far mainly been measured with intramuscular electromyography (EMG). The aim of this study was to examine whether the activity of the BR can be assessed with surface EMG without interference from the biceps brachii (BB). With eight subjects we measured surface EMG of the arm flexor synergists, BR, BB, and brachioradialis (BRR) during two isometric voluntary contraction types: (1) pure elbow flexion and (2) elbow flexion with a superimposed forearm supination. Since the BR and BB have a distinct biomechanical function, an individual activity of the BR can be expected for the second contraction type, if the BR can be assessed independently from the BB. The correlation coefficients between EMG amplitudes and flexion force (supination torque) were determined. During pure flexion the activities of all synergists were similarly correlated with the flexion force (r = 0.96 ± 0.02). During flexion+supination the activity of the BR was distinct from the activity of the BB, with a 14% higher correlation for the BR with the flexion force and a 40-64% lower correlation with the supination torque. The BB predicted supination torque substantially better than the BR and BRR (r = 0.93 ± 0.02). The current results demonstrate that the activity of the BR can be assessed with surface EMG as it was distinct from the BB during flexion+supination but predicted flexion force equally well as BB during the pure flexion contraction.

  20. Fatiguing stimulation of one skeletal muscle triggers heat shock protein activation in several rat organs: the role of muscle innervation.

    Science.gov (United States)

    Jammes, Yves; Steinberg, Jean Guillaume; By, Youlet; Brerro-Saby, Christelle; Condo, Jocelyne; Olivier, Marine; Guieu, Regis; Delliaux, Stephane

    2012-11-15

    We hypothesised that activation of muscle afferents by fatigue triggers a widespread activation of heat shock proteins (HSPs) in resting muscles and different organs. In anaesthetised rats, HSP25 and HSP70 levels were determined in both tibialis anterior (TA) and extensor digitorum longus (EDL) muscles and in the diaphragm, kidney and brain by ELISA, which mostly identifies phosphorylated HSP, and western blotting. One TA muscle was electrically stimulated and tissues were sampled 10 or 60 min after the stimulation had ended. The nerve supply to the stimulated TA or its counterpart in the contralateral limb was left intact or suppressed. In control rats, no muscle stimulation was performed and tissues were sampled at the same time points (10 or 60 min). After TA stimulation, ELISA showed an increased HSP25 content in the contralateral TA, EDL and diaphragm at 10 min but not at 60 min, and HSP70 increased in all sampled tissues at 60 min. Western blotting did not show any changes in HSP25 and HSP70 at 10 min, while at 60 min HSP25 increased in all sampled tissues except the brain and HSP70 was elevated in all tissues. Denervation of the contralateral non-stimulated limb suppressed HSP changes in TA and after denervation of the stimulated TA the widespread activation of HSPs in other organs was absent. Our data suggest that fatigue-induced activation of skeletal muscle afferents triggers an early increase in phosphorylated HSP25 in muscles and a delayed elevation of non-phosphorylated HSP25 and HSP70 in skeletal and respiratory muscles, kidney and brain.

  1. Cortical activation associated with muscle synergies of the human male pelvic floor.

    Science.gov (United States)

    Asavasopon, Skulpan; Rana, Manku; Kirages, Daniel J; Yani, Moheb S; Fisher, Beth E; Hwang, Darryl H; Lohman, Everett B; Berk, Lee S; Kutch, Jason J

    2014-10-08

    Human pelvic floor muscles have been shown to operate synergistically with a wide variety of muscles, which has been suggested to be an important contributor to continence and pelvic stability during functional tasks. However, the neural mechanism of pelvic floor muscle synergies remains unknown. Here, we test the hypothesis that activation in motor cortical regions associated with pelvic floor activation are part of the neural substrate for such synergies. We first use electromyographic recordings to extend previous findings and demonstrate that pelvic floor muscles activate synergistically during voluntary activation of gluteal muscles, but not during voluntary activation of finger muscles. We then show, using functional magnetic resonance imaging (fMRI), that a region of the medial wall of the precentral gyrus consistently activates during both voluntary pelvic floor muscle activation and voluntary gluteal activation, but not during voluntary finger activation. We finally confirm, using transcranial magnetic stimulation, that the fMRI-identified medial wall region is likely to generate pelvic floor muscle activation. Thus, muscle synergies of the human male pelvic floor appear to involve activation of motor cortical areas associated with pelvic floor control.

  2. The activity pattern of shoulder muscles in subjects with and without subacromial impingement

    DEFF Research Database (Denmark)

    Diederichsen, Louise Pyndt; Nørregaard, Jesper; Dyhre-Poulsen, Poul

    2009-01-01

    motion. In the symptomatic shoulder, there was a significantly greater EMG activity during abduction in the supraspinatus and latissimus muscles and less activity in serratus anterior compared to the healthy subjects. During external rotation, there was significantly less activity of the infraspinatus...... and serratus anterior muscles on the symptomatic side compared to the healthy subjects. On the asymptomatic side, the groups showed different muscle activity during external rotation. Our findings of an altered shoulder muscle activity pattern on both the symptomatic and asymptomatic side in patients indicate...... in patients with SI. The aim of the study was to determine and compare the activity pattern of the shoulder muscles in subjects with and without SI. Twenty-one subjects with SI and 20 healthy controls were included. Electromyography (EMG) was assessed from eight shoulder muscles from both shoulders during...

  3. Differential activity patterns in the masseter muscle under simulated clenching and grinding forces.

    Science.gov (United States)

    Schindler, H J; Türp, J C; Blaser, R; Lenz, J

    2005-08-01

    The aim of this study was to investigate (i) whether the masseter muscle shows differential activation under experimental conditions which simulate force generation during clenching and grinding activities; and (ii) whether there are (a) preferentially active muscle regions or (b) force directions which show enhanced muscle activation. To answer these questions, the electromyographic (EMG) activity of the right masseter muscle was recorded with five intramuscular electrodes placed in two deep muscle areas and in three surface regions. Intraoral force transfer and force measurement were achieved by a central bearing pin device equipped with three strain gauges (SG). The activity distribution in the muscle was recorded in four different mandibular positions (central, left, right, anterior). In each position, maximum voluntary contraction (MVC) was exerted in vertical, posterior, anterior, medial and lateral directions. The investigated muscle regions showed different amount of EMG activity. The relative intensity of the activation, with respect to other regions, changed depending on the task. In other words, the muscle regions demonstrated heterogeneous changes of the EMG pattern for the various motor tasks. The resultant force vectors demonstrated similar amounts in all horizontal bite directions. Protrusive force directions revealed the highest relative activation of the masseter muscle. The posterior deep muscle region seemed to be the most active compartment during the different motor tasks. The results indicate a heterogeneous activation of the masseter muscle under test conditions simulating force generation during clenching and grinding. Protrusively directed bite forces were accompanied by the highest activation in the muscle, with the posterior deep region as the most active area.

  4. Simulating the activation, contraction and movement of skeletal muscles using the bidomain model.

    Science.gov (United States)

    Lopez Rincon, A; Cantu, C; Soto, R; Shimoda, S

    2016-08-01

    A simulation of the muscle activation, contraction and movement is here presented. This system was developed based on the Bidomain mathematical model of the electrical propagation in muscles. This study shows an electrical stimuli input to a muscle and how this behave. The comparison between healthy subject and patient with muscle activation impairment is depicted, depending on whether the signal reaches a threshold. A 3D model of a bicep muscle and a forearm bone connected was constructed using OpenGL. This platform could be used for development of controllers for biomechatronic systems in future works. This kind of bioinspired model could be used for a better understanding of the neuromotor system.

  5. Muscle networks: Connectivity analysis of EMG activity during postural control

    Science.gov (United States)

    Boonstra, Tjeerd W.; Danna-Dos-Santos, Alessander; Xie, Hong-Bo; Roerdink, Melvyn; Stins, John F.; Breakspear, Michael

    2015-12-01

    Understanding the mechanisms that reduce the many degrees of freedom in the musculoskeletal system remains an outstanding challenge. Muscle synergies reduce the dimensionality and hence simplify the control problem. How this is achieved is not yet known. Here we use network theory to assess the coordination between multiple muscles and to elucidate the neural implementation of muscle synergies. We performed connectivity analysis of surface EMG from ten leg muscles to extract the muscle networks while human participants were standing upright in four different conditions. We observed widespread connectivity between muscles at multiple distinct frequency bands. The network topology differed significantly between frequencies and between conditions. These findings demonstrate how muscle networks can be used to investigate the neural circuitry of motor coordination. The presence of disparate muscle networks across frequencies suggests that the neuromuscular system is organized into a multiplex network allowing for parallel and hierarchical control structures.

  6. Recovery of inspiratory intercostal muscle activity following high cervical hemisection.

    Science.gov (United States)

    Dougherty, B J; Lee, K Z; Gonzalez-Rothi, E J; Lane, M A; Reier, P J; Fuller, D D

    2012-09-30

    Anatomical and neurophysiological evidence indicates that thoracic interneurons can serve a commissural function and activate contralateral motoneurons. Accordingly, we hypothesized that respiratory-related intercostal (IC) muscle electromyogram (EMG) activity would be only modestly impaired by a unilateral cervical spinal cord injury. Inspiratory tidal volume (VT) was recorded using pneumotachography and EMG activity was recorded bilaterally from the 1st to 2nd intercostal space in anesthetized, spontaneously breathing rats. Studies were conducted at 1-3 days, 2 wks or 8 wks following C2 spinal cord hemisection (C2HS). Data were collected during baseline breathing and a brief respiratory challenge (7% CO(2)). A substantial reduction in inspiratory intercostal EMG bursting ipsilateral to the lesion was observed at 1-3 days post-C2HS. However, a time-dependent return of activity occurred such that by 2 wks post-injury inspiratory intercostal EMG bursts ipsilateral to the lesion were similar to age-matched, uninjured controls. The increases in ipsilateral intercostal EMG activity occurred in parallel with increases in VT following the injury (R=0.55; Pintercostal" circuitry enables a robust, spontaneous recovery of ipsilateral intercostal activity following C2HS in rats. Copyright © 2012. Published by Elsevier B.V.

  7. Transcriptional activation of muscle atrophy promotes cardiac muscle remodeling during mammalian hibernation.

    Science.gov (United States)

    Zhang, Yichi; Aguilar, Oscar A; Storey, Kenneth B

    2016-01-01

    upregulated only during late torpor by 2.4-fold. Protein levels of MAFbx and MuRF1 increased in late torpor as well as during early arousal by as much as 2.8-fold, and MAFbx levels remained elevated during interbout arousal, whereas MuRF1 levels returned to control levels. Discussion. The present results indicate that upregulation and activation of Foxo1 and 3a, in addition to the increase in MyoG levels at late torpor, may be upregulating the expression of MAFbx and MuRF1. These findings suggest that there is activation of the ubiquitin proteasome system (UPS) as ground squirrels arouse from torpor. Therefore, the signalling pathway involving MyoG, and the E3 ligases MAFbx and MuRF1, plays a significant role in cardiac muscle remodelling during hibernation. These findings provide insights into the regulation of protein degradation and turnover in the cardiac muscle of a hibernator model.

  8. Transcriptional activation of muscle atrophy promotes cardiac muscle remodeling during mammalian hibernation

    Directory of Open Access Journals (Sweden)

    Yichi Zhang

    2016-08-01

    upregulated only during late torpor by 2.4-fold. Protein levels of MAFbx and MuRF1 increased in late torpor as well as during early arousal by as much as 2.8-fold, and MAFbx levels remained elevated during interbout arousal, whereas MuRF1 levels returned to control levels. Discussion. The present results indicate that upregulation and activation of Foxo1 and 3a, in addition to the increase in MyoG levels at late torpor, may be upregulating the expression of MAFbx and MuRF1. These findings suggest that there is activation of the ubiquitin proteasome system (UPS as ground squirrels arouse from torpor. Therefore, the signalling pathway involving MyoG, and the E3 ligases MAFbx and MuRF1, plays a significant role in cardiac muscle remodelling during hibernation. These findings provide insights into the regulation of protein degradation and turnover in the cardiac muscle of a hibernator model.

  9. ORM Promotes Skeletal Muscle Glycogen Accumulation via CCR5-Activated AMPK Pathway in Mice

    Science.gov (United States)

    Qin, Zhen; Wan, Jing-Jing; Sun, Yang; Wang, Peng-Yuan; Su, Ding-Feng; Lei, Hong; Liu, Xia

    2016-01-01

    We found previously that acute phase protein orosomucoid reacts to fatigue and activates C-C chemokine receptor type 5 to increase muscle glycogen storage and enhance muscle endurance (Lei et al., 2016). To explore the underlying molecular mechanisms, we investigated the role of AMP-activated protein kinase, a critical fuel sensor in skeletal muscle, in C-C chemokine receptor type 5-mediated orosomucoid action. It was found orosomucoid increased skeletal muscle AMP-activated protein kinase activation in a time- and dose- dependent manner, which was largely prevented by pharmacological blocking or knockout of C-C chemokine receptor type 5. Administration of orosomucoid also significantly increased the de-phosphorylation and activity of muscle glycogen synthase, the rate-limiting enzyme for glycogen synthesis. The effect was largely absent in mice deficient in C-C chemokine receptor type 5−/− or AMP-activated protein kinase α2−/−, the predominant isoform in skeletal muscle. Moreover, deletion of AMP-activated protein kinase α2 abolished the effect of orosomucoid on fatigue and muscle glycogen. These findings indicate that orosomucoid may promote glycogen storage and enhance muscle function through C-C chemokine receptor type 5-mdiated activation of AMP-activated protein kinase, which in turn activates glycogen synthase and increases muscle glycogen. PMID:27679573

  10. Comparison of Orbicularis Oculi Muscle Activity during Computer Work with Single and Dual Monitors

    OpenAIRE

    Yoo, Won-gyu

    2014-01-01

    [Purpose] This study compared the orbicularis oculi muscle activity during computer work with single and dual monitors. [Subjects] Ten computer workers 22–27 years of age were included in this study. [Methods] Subjects performed computer work with single or dual monitors, and the activity of the right orbicularis oculi muscle was measured with a MP150 system. [Results] The muscle activity of the orbicularis oculi under condition 1 was significantly decreased compared with that under condition...

  11. SIRT1 Protein, by Blocking the Activities of Transcription Factors FoxO1 and FoxO3, Inhibits Muscle Atrophy and Promotes Muscle Growth*

    Science.gov (United States)

    Lee, Donghoon; Goldberg, Alfred L.

    2013-01-01

    In several cell types, the protein deacetylase SIRT1 regulates the activities of FoxO transcription factors whose activation is critical in muscle atrophy. However, the possible effects of SIRT1 on the activity of FoxOs in skeletal muscle and on the regulation of muscle size have not been investigated. Here, we show that after food deprivation, SIRT1 levels fall dramatically in type II skeletal muscles (tibialis anterior), which show marked atrophy, unlike in the liver (where SIRT1 rises) or heart or the soleus, a type I muscle (where SIRT1 is unchanged). Maintenance of high SIRT1 levels by electroporation in mouse muscle inhibits markedly the muscle wasting induced by fasting as well as by denervation, and these protective effects require its deacetylase activity. SIRT1 overexpression reduces muscle wasting by blocking the activation of FoxO1 and 3. It thus prevents the induction of key atrogenes, including the muscle-specific ubiquitin ligases, atrogin1 and MuRF1, and multiple autophagy (Atg) genes and the increase in overall proteolysis. In normal muscle, SIRT1 overexpression by electroporation causes rapid fiber hypertrophy without, surprisingly, activation of the PI3K-AKT signaling pathway. Thus, SIRT1 activation favors postnatal muscle growth, and its fall appears to be critical for atrophy during fasting. Consequently, SIRT1 activation represents an attractive possible pharmacological approach to prevent muscle wasting and cachexia. PMID:24003218

  12. Assessment of bioelectrical activity of synergistic muscles during pelvic floor muscles activation in postmenopausal women with and without stress urinary incontinence: a preliminary observational study

    Directory of Open Access Journals (Sweden)

    Ptaszkowski K

    2015-09-01

    Full Text Available Kuba Ptaszkowski,1 Małgorzata Paprocka-Borowicz,2 Lucyna Słupska,2 Janusz Bartnicki,1,3 Robert Dymarek,4 Joanna Rosińczuk,4 Jerzy Heimrath,5 Janusz Dembowski,6 Romuald Zdrojowy6 1Department of Obstetrics, 2Department of Clinical Biomechanics and Physiotherapy in Motor System Disorders, Wroclaw Medical University, Wroclaw, Poland; 3Department of Obstetrics and Gynecology, Health Center Bitterfeld/Wolfen gGmbH, Bitterfeld-Wolfen, Germany; 4Department of Nervous System Diseases, 5Department of Gynaecology and Obstetrics, Faculty of Health Science, 6Department and Clinic of Urology, Faculty of Postgraduate Medical Training, Wroclaw Medical University, Wroclaw, Poland Objective: Muscles such as adductor magnus (AM, gluteus maximus (GM, rectus abdominis (RA, and abdominal external and internal oblique muscles are considered to play an important role in the treatment of stress urinary incontinence (SUI, and the relationship between contraction of these muscles and pelvic floor muscles (PFM has been established in previous studies. Synergistic muscle activation intensifies a woman’s ability to contract the PFM. In some cases, even for continent women, it is not possible to fully contract their PFM without involving the synergistic muscles. The primary aim of this study was to assess the surface electromyographic activity of synergistic muscles to PFM (SPFM during resting and functional PFM activation in postmenopausal women with and without SUI.Materials and methods: This study was a preliminary, prospective, cross-sectional observational study and included volunteers and patients who visited the Department and Clinic of Urology, University Hospital in Wroclaw, Poland. Forty-two patients participated in the study and were screened for eligibility criteria. Thirty participants satisfied the criteria and were categorized into two groups: women with SUI (n=16 and continent women (n=14. The bioelectrical activity of PFM and SPFM (AM, RA, GM was

  13. Bed rest suppresses bioassayable growth hormone release in response to muscle activity

    Science.gov (United States)

    McCall, G. E.; Goulet, C.; Grindeland, R. E.; Hodgson, J. A.; Bigbee, A. J.; Edgerton, V. R.

    1997-01-01

    Hormonal responses to muscle activity were studied in eight men before (-13 or -12 and -8 or -7 days), during (2 or 3, 8 or 9, and 13 or 14 days) and after (+2 or +3 and +10 or +11 days) 17 days of bed rest. Muscle activity consisted of a series of unilateral isometric plantar flexions, including 4 maximal voluntary contractions (MVCs), 48 contractions at 30% MVC, and 12 contractions at 80% MVC, all performed at a 4:1-s work-to-rest ratio. Blood was collected before and immediately after muscle activity to measure plasma growth hormone by radioimmunoassay (IGH) and by bioassay (BGH) of tibia epiphyseal cartilage growth in hypophysectomized rats. Plasma IGH was unchanged by muscle activity before, during, or after bed rest. Before bed rest, muscle activity increased (P muscle activity, a pattern that persisted through 8 or 9 days of bed rest. However, after 13 or 14 days of bed rest, plasma concentration of BGH was significantly lower after than before muscle activity (2,594 +/- 211 to 2,085 +/- 109 microg/l). After completion of bed rest, muscle activity increased BGH by 31% at 2 or 3 days (1,807 +/- 117 to 2,379 +/- 473 microg/l; P muscle activity.

  14. Predicting the activation states of the muscles governing upper esophageal sphincter relaxation and opening.

    Science.gov (United States)

    Omari, Taher I; Jones, Corinne A; Hammer, Michael J; Cock, Charles; Dinning, Philip; Wiklendt, Lukasz; Costa, Marcello; McCulloch, Timothy M

    2016-03-15

    The swallowing muscles that influence upper esophageal sphincter (UES) opening are centrally controlled and modulated by sensory information. Activation and deactivation of neural inputs to these muscles, including the intrinsic cricopharyngeus (CP) and extrinsic submental (SM) muscles, results in their mechanical activation or deactivation, which changes the diameter of the lumen, alters the intraluminal pressure, and ultimately reduces or promotes flow of content. By measuring the changes in diameter, using intraluminal impedance, and the concurrent changes in intraluminal pressure, it is possible to determine when the muscles are passively or actively relaxing or contracting. From these "mechanical states" of the muscle, the neural inputs driving the specific motor behaviors of the UES can be inferred. In this study we compared predictions of UES mechanical states directly with the activity measured by electromyography (EMG). In eight subjects, pharyngeal pressure and impedance were recorded in parallel with CP- and SM-EMG activity. UES pressure and impedance swallow profiles correlated with the CP-EMG and SM-EMG recordings, respectively. Eight UES muscle states were determined by using the gradient of pressure and impedance with respect to time. Guided by the level and gradient change of EMG activity, mechanical states successfully predicted the activity of the CP muscle and SM muscle independently. Mechanical state predictions revealed patterns consistent with the known neural inputs activating the different muscles during swallowing. Derivation of "activation state" maps may allow better physiological and pathophysiological interpretations of UES function.

  15. Masseter Muscle Activity in Track and Field Athletes: A Pilot Study

    Science.gov (United States)

    Nukaga, Hideyuki; Takeda, Tomotaka; Nakajima, Kazunori; Narimatsu, Keishiro; Ozawa, Takamitsu; Ishigami, Keiichi; Funato, Kazuo

    2016-01-01

    Teeth clenching has been shown to improve remote muscle activity (by augmentation of the Hoffmann reflex), and joint fixation (by decreased reciprocal inhibition) in the entire body. Clenching could help maintain balance, improve systemic function, and enhance safety. Teeth clenching from a sports dentistry viewpoint was thought to be important and challenging. Therefore, it is quite important to investigate mastication muscles’ activity and function during sports events for clarifying a physiological role of the mastication muscle itself and involvement of mastication muscle function in whole body movement. Running is a basic motion of a lot of sports; however, a mastication muscles activity during this motion was not clarified. Throwing and jumping operation were in a same situation. The purpose of this study was to investigate the presence or absence of masseter muscle activity during track and field events. In total, 28 track and field athletes took part in the study. The Multichannel Telemetry system was used to monitor muscle activity, and the electromyograms obtained were synchronized with digital video imaging. The masseter muscle activity threshold was set 15% of maximum voluntary clenching. As results, with few exceptions, masseter muscle activity were observed during all analyzed phases of the 5 activities, and that phases in which most participants showed masseter muscle activity were characterized by initial acceleration, such as in the short sprint, from the commencement of throwing to release in both the javelin throw and shot put, and at the take-off and landing phases in both jumps. PMID:27708727

  16. Bed rest suppresses bioassayable growth hormone release in response to muscle activity

    Science.gov (United States)

    McCall, G. E.; Goulet, C.; Grindeland, R. E.; Hodgson, J. A.; Bigbee, A. J.; Edgerton, V. R.

    1997-01-01

    Hormonal responses to muscle activity were studied in eight men before (-13 or -12 and -8 or -7 days), during (2 or 3, 8 or 9, and 13 or 14 days) and after (+2 or +3 and +10 or +11 days) 17 days of bed rest. Muscle activity consisted of a series of unilateral isometric plantar flexions, including 4 maximal voluntary contractions (MVCs), 48 contractions at 30% MVC, and 12 contractions at 80% MVC, all performed at a 4:1-s work-to-rest ratio. Blood was collected before and immediately after muscle activity to measure plasma growth hormone by radioimmunoassay (IGH) and by bioassay (BGH) of tibia epiphyseal cartilage growth in hypophysectomized rats. Plasma IGH was unchanged by muscle activity before, during, or after bed rest. Before bed rest, muscle activity increased (P muscle activity, a pattern that persisted through 8 or 9 days of bed rest. However, after 13 or 14 days of bed rest, plasma concentration of BGH was significantly lower after than before muscle activity (2,594 +/- 211 to 2,085 +/- 109 microg/l). After completion of bed rest, muscle activity increased BGH by 31% at 2 or 3 days (1,807 +/- 117 to 2,379 +/- 473 microg/l; P muscle activity.

  17. [Participation of the primary motor cortex in programming of muscle activity during catching of falling object].

    Science.gov (United States)

    Kazennikov, O V; Lipshits, M I

    2011-01-01

    Object fell into the cup that sitting subject held between thumb and index fingers. Transcranial magnetic stimulation (TMS) of the primary motor cortex was performed early before and during anticipatory grip force increasing. Comparison of current EMG activity of adductor pollicis brevis and first dorsal interosseous muscles and responses of these muscles on TMS showed that responses were increased before the raising of muscle activity. From the other side only slight augmentation of responses was observed during subsequent strong muscle activation. It is assumed that the increasing of the TMS responses that occurred before the initiation of muscle activity reflects the enhancement ofthe motor cortex excitability associated to specific processes related to the motor cortex participation in programming of the muscles activities.

  18. A comparison of surgeon's postural muscle activity during robotic-assisted and laparoscopic rectal surgery.

    Science.gov (United States)

    Szeto, Grace P Y; Poon, Jensen T C; Law, Wai-Lun

    2013-09-01

    This study compared the muscular activity in the surgeon's neck and upper limbs during robotic-assisted laparoscopic (R-Lap) surgery and conventional laparoscopic (C-Lap) surgery. Two surgeons performed the same procedure of R-Lap and C-Lap low anterior resection, and real-time surface electromyography was recorded in bilateral cervical erector spinae, upper trapezius (UT) and anterior deltoid muscles for over 60 min in each procedure. In one surgeon, forearm muscle activities were also recorded during robotic surgery. Similar levels of cervical muscle activity were demonstrated in both types of surgery. One surgeon showed much higher activity in the left UT muscle during robotic surgery. In the second surgeon, C-Lap was associated with much higher levels of muscle activity in both UT muscles. This may be related to the bilateral abducted arm posture required in maneuvering the laparoscopic instruments. In the forearm region, the "ulnaris" muscles for wrist flexion and extension bilaterally showed high amplitudes during robotic-assisted surgery. Robotic-assisted surgery seemed to demand a higher level of muscle work in the forearm region while greater efforts of shoulder muscles were involved during laparoscopic surgery. There are also individual variations in postural habits and motor control that can affect the muscle activation patterns. This study demonstrated a method of objectively examining the surgeon's physical workload during real-time surgery in the operating theatre, and further research should explore the surgeon's workload in a larger group of surgeons performing different surgical procedures.

  19. Muscles provide protection during microbial infection by activating innate immune response pathways in Drosophila and zebrafish

    Directory of Open Access Journals (Sweden)

    Arunita Chatterjee

    2016-06-01

    Full Text Available Muscle contraction brings about movement and locomotion in animals. However, muscles have also been implicated in several atypical physiological processes including immune response. The role of muscles in immunity and the mechanism involved has not yet been deciphered. In this paper, using Drosophila indirect flight muscles (IFMs as a model, we show that muscles are immune-responsive tissues. Flies with defective IFMs are incapable of mounting a potent humoral immune response. Upon immune challenge, the IFMs produce anti-microbial peptides (AMPs through the activation of canonical signaling pathways, and these IFM-synthesized AMPs are essential for survival upon infection. The trunk muscles of zebrafish, a vertebrate model system, also possess the capacity to mount an immune response against bacterial infections, thus establishing that immune responsiveness of muscles is evolutionarily conserved. Our results suggest that physiologically fit muscles might boost the innate immune response of an individual.

  20. Fast skeletal muscle troponin activation increases force of mouse fast skeletal muscle and ameliorates weakness due to nebulin-deficiency.

    Directory of Open Access Journals (Sweden)

    Eun-Jeong Lee

    Full Text Available The effect of the fast skeletal muscle troponin activator, CK-2066260, on calcium-induced force development was studied in skinned fast skeletal muscle fibers from wildtype (WT and nebulin deficient (NEB KO mice. Nebulin is a sarcomeric protein that when absent (NEB KO mouse or present at low levels (nemaline myopathy (NM patients with NEB mutations causes muscle weakness. We studied the effect of fast skeletal troponin activation on WT muscle and tested whether it might be a therapeutic mechanism to increase muscle strength in nebulin deficient muscle. We measured tension-pCa relations with and without added CK-2066260. Maximal active tension in NEB KO tibialis cranialis fibers in the absence of CK-2066260 was ∼60% less than in WT fibers, consistent with earlier work. CK-2066260 shifted the tension-calcium relationship leftwards, with the largest relative increase (up to 8-fold at low to intermediate calcium levels. This was a general effect that was present in both WT and NEB KO fiber bundles. At pCa levels above ∼6.0 (i.e., calcium concentrations <1 µM, CK-2066260 increased tension of NEB KO fibers to beyond that of WT fibers. Crossbridge cycling kinetics were studied by measuring k(tr (rate constant of force redevelopment following a rapid shortening/restretch. CK-2066260 greatly increased k(tr at submaximal activation levels in both WT and NEB KO fiber bundles. We also studied the sarcomere length (SL dependence of the CK-2066260 effect (SL 2.1 µm and 2.6 µm and found that in the NEB KO fibers, CK-2066260 had a larger effect on calcium sensitivity at the long SL. We conclude that fast skeletal muscle troponin activation increases force at submaximal activation in both wildtype and NEB KO fiber bundles and, importantly, that this troponin activation is a potential therapeutic mechanism for increasing force in NM and other skeletal muscle diseases with loss of muscle strength.

  1. Arm movements can increase leg muscle activity during submaximal recumbent stepping in neurologically intact individuals.

    NARCIS (Netherlands)

    Kam, D. de; Rijken, H.; Manintveld, T.; Nienhuis, B.; Dietz, V.; Duysens, J.E.J.

    2013-01-01

    Facilitation of leg muscle activity by active arm movements during locomotor tasks could be beneficial during gait rehabilitation after spinal cord injury. The present study explored the effects of arm movements on leg muscle activity during submaximal recumbent stepping. Healthy subjects exercised

  2. The Changes of Muscle Strength and Functional Activities During Aging in Male and Female Populations

    Directory of Open Access Journals (Sweden)

    Shih-Jung Cheng

    2014-12-01

    Conclusion: We noted that the muscle strength and functional activities were decreased earlier in female than male individuals. The decrease of functional activities during the aging process seems to be earlier than the decrease of muscle strength. It is important to implement functional activities training in addition to strengthening exercise to maintain functional levels of the geriatric population.

  3. Intra-session repeatability of lower limb muscles activation pattern during pedaling.

    Science.gov (United States)

    Dorel, Sylvain; Couturier, Antoine; Hug, François

    2008-10-01

    Assessment of intra-session repeatability of muscle activation pattern is of considerable relevance for research settings, especially when used to determine changes over time. However, the repeatability of lower limb muscles activation pattern during pedaling is not fully established. Thus, we tested the intra-session repeatability of the activation pattern of 10 lower limb muscles during a sub-maximal cycling exercise. Eleven triathletes participated to this study. The experimental session consisted in a reference sub-maximal cycling exercise (i.e. 150 W) performed before and after a 53-min simulated training session (mean power output=200+/-12 W). Repeatability of EMG patterns was assessed in terms of muscle activity level (i.e. RMS of the mean pedaling cycle and burst) and muscle activation timing (i.e. onset and offset of the EMG burst) for the 10 following lower limb muscles: gluteus maximus (GMax), semimembranosus (SM), Biceps femoris (BF), vastus medialis (VM), rectus femoris (RF), vastus lateralis (VL), gastrocnemius medianus (GM) and lateralis (GL), soleus (SOL) and tibialis anterior (TA). No significant differences concerning the muscle activation level were found between test and retest for all the muscles investigated. Only VM, SOL and TA showed significant differences in muscle activation timing parameters. Whereas ICC and SEM values confirmed this weak repeatability, cross-correlation coefficients suggest a good repeatability of the activation timing parameters for all the studied muscles. Overall, the main finding of this work is the good repeatability of the EMG pattern during pedaling both in term of muscle activity level and muscle activation timing.

  4. Electromyographic activity of masticatory muscles in elderly women – a pilot study

    Science.gov (United States)

    Gaszynska, Ewelina; Kopacz, Karolina; Fronczek-Wojciechowska, Magdalena; Padula, Gianluca; Szatko, Franciszek

    2017-01-01

    Objectives To evaluate the effect of age and chosen factors related to aging such as dentition, muscle strength, and nutrition on masticatory muscles electromyographic activity during chewing in healthy elderly women. Background With longer lifespan there is a need for maintaining optimal quality of life and health in older age. Skeletal muscle strength deteriorates in older age. This deterioration is also observed within masticatory muscles. Methods A total of 30 women, aged 68–92 years, were included in the study: 10 individuals had natural functional dentition, 10 were missing posterior teeth in the upper and lower jaw reconstructed with removable partial dentures, and 10 were edontoulous, using complete removable dentures. Surface electromyography was performed to evaluate masticatory muscles activity. Afterwards, measurement of masseter thickness with ultrasound imaging was performed, body mass index and body cell mass index were calculated, and isometric handgrip strength was measured. Results Isometric maximal voluntary contraction decreased in active masseters with increasing age and in active and passive temporalis muscles with increasing age and increasing body mass index. In active masseter, mean electromyographic activity during the sequence (time from the start of chewing till the end when the test food became ready to swallow) decreased with increasing age and during the cycle (single bite time) decreased with increasing age and increasing body mass index. In active and passive temporalis muscles, mean electromyographic activity during the sequence and the cycle decreased with increasing age, increasing body mass index, and loss of natural dentition. Individuals with natural dentition had significantly higher mean muscle activity during sequence and cycle in active temporalis muscles than those wearing full dentures and higher maximal activity during cycle in individuals with active and passive temporalis muscles than in complete denture wearers

  5. Shoulder muscle activity and function in common shoulder rehabilitation exercises.

    Science.gov (United States)

    Escamilla, Rafael F; Yamashiro, Kyle; Paulos, Lonnie; Andrews, James R

    2009-01-01

    , posterior tilt and ER. The serratus anterior also helps stabilize the medial border and inferior angle of the scapular, preventing scapular IR (winging) and anterior tilt. If normal scapular movements are disrupted by abnormal scapular muscle firing patterns, weakness, fatigue, or injury, the shoulder complex functions less efficiency and injury risk increases. Scapula position and humeral rotation can affect injury risk during humeral elevation. Compared with scapular protraction, scapular retraction has been shown to both increase subacromial space width and enhance supraspinatus force production during humeral elevation. Moreover, scapular IR and scapular anterior tilt, both of which decrease subacromial space width and increase impingement risk, are greater when performing scaption with IR ('empty can') compared with scaption with ER ('full can'). There are several exercises in the literature that exhibit high to very high activity from the rotator cuff, deltoids and scapular muscles, such as prone horizontal abduction at 100 degrees abduction with ER, flexion and abduction with ER, 'full can' and 'empty can', D1 and D2 diagonal pattern flexion and extension, ER and IR at 0 degrees and 90 degrees abduction, standing extension from 90-0 degrees , a variety of weight-bearing upper extremity exercises, such as the push-up, standing scapular dynamic hug, forward scapular punch, and rowing type exercises. Supraspinatus activity is similar between 'empty can' and 'full can' exercises, although the 'full can' results in less risk of subacromial impingement. Infraspinatus and subscapularis activity have generally been reported to be higher in the 'full can' compared with the 'empty can', while posterior deltoid activity has been reported to be higher in the 'empty can' than the 'full can'.

  6. HDAC1 activates FoxO and is both sufficient and required for skeletal muscle atrophy

    Science.gov (United States)

    Beharry, Adam W.; Sandesara, Pooja B.; Roberts, Brandon M.; Ferreira, Leonardo F.; Senf, Sarah M.; Judge, Andrew R.

    2014-01-01

    ABSTRACT The Forkhead box O (FoxO) transcription factors are activated, and necessary for the muscle atrophy, in several pathophysiological conditions, including muscle disuse and cancer cachexia. However, the mechanisms that lead to FoxO activation are not well defined. Recent data from our laboratory and others indicate that the activity of FoxO is repressed under basal conditions via reversible lysine acetylation, which becomes compromised during catabolic conditions. Therefore, we aimed to determine how histone deacetylase (HDAC) proteins contribute to activation of FoxO and induction of the muscle atrophy program. Through the use of various pharmacological inhibitors to block HDAC activity, we demonstrate that class I HDACs are key regulators of FoxO and the muscle-atrophy program during both nutrient deprivation and skeletal muscle disuse. Furthermore, we demonstrate, through the use of wild-type and dominant-negative HDAC1 expression plasmids, that HDAC1 is sufficient to activate FoxO and induce muscle fiber atrophy in vivo and is necessary for the atrophy of muscle fibers that is associated with muscle disuse. The ability of HDAC1 to cause muscle atrophy required its deacetylase activity and was linked to the induction of several atrophy genes by HDAC1, including atrogin-1, which required deacetylation of FoxO3a. Moreover, pharmacological inhibition of class I HDACs during muscle disuse, using MS-275, significantly attenuated both disuse muscle fiber atrophy and contractile dysfunction. Together, these data solidify the importance of class I HDACs in the muscle atrophy program and indicate that class I HDAC inhibitors are feasible countermeasures to impede muscle atrophy and weakness. PMID:24463822

  7. Anticipatory and Reactive Response to Falls: Muscle Synergy Activation of Forearm Muscles.

    Science.gov (United States)

    Couzens, Greg; Kerr, Graham

    2015-10-01

    We investigated the surface electromyogram response of six forearm muscles to falls onto the outstretched hand. The extensor carpi radialis longus, extensor carpi radialis brevis, extensor carpi ulnaris, abductor pollicis longus, flexor carpi radialis and flexor carpi ulnaris muscles were sampled from eight volunteers who underwent ten self-initiated falls. All muscles initiated prior to impact. Co-contraction is the most obvious surface electromyogram feature. The predominant response is in the radial deviators. The surface electromyogram timing we recorded would appear to be a complex anticipatory response to falling modified by the effect on the forearm muscles following impact. The mitigation of the force of impact is probably more importantly through shoulder abduction and extension and elbow flexion rather than action of the forearm muscles.

  8. Chronic electromyographic analysis of circadian locomotor activity in crayfish.

    Science.gov (United States)

    Tomina, Yusuke; Kibayashi, Akihiro; Yoshii, Taishi; Takahata, Masakazu

    2013-07-15

    Animals generally exhibit circadian rhythms of locomotor activity. They initiate locomotor behavior not only reflexively in response to external stimuli but also spontaneously in the absence of any specific stimulus. The neuronal mechanisms underlying circadian locomotor activity can, therefore, be based on the rhythmic changes in either reflexive efficacy or endogenous activity. In crayfish Procambarus clarkii, it can be determined by analyzing electromyographic (EMG) patterns of walking legs whether the walking behavior is initiated reflexively or spontaneously. In this study, we examined quantitatively the leg muscle activity that underlies the locomotor behavior showing circadian rhythms in crayfish. We newly developed a chronic EMG recording system that allowed the animal to freely behave under a tethered condition for more than 10 days. In the LD condition in which the animals exhibited LD entrainment, the rhythmic burst activity of leg muscles for stepping behavior was preceded by non-rhythmic tonic activation that lasted for 1323±488ms when the animal initiated walking. In DD and LL free-running conditions, the pre-burst activation lasted for 1779±31 and 1517±39ms respectively. In the mechanical stimulus-evoked walking, the pre-burst activation ended within 79±6ms. These data suggest that periodic changes in the crayfish locomotor activity under the condition of LD entrainment or free-running are based on activity changes in the spontaneous initiation mechanism of walking behavior rather than those in the sensori-motor pathway connecting mechanoreceptors with leg movements.

  9. Activation patterns in forearm muscles during archery shooting.

    Science.gov (United States)

    Ertan, H; Kentel, B; Tümer, S T; Korkusuz, F

    2003-02-01

    A contraction and relaxation strategy with regard to forearm muscles during the release of the bowstring has often been observed during archery, but has not well been described. The purpose of this study was to analyze this strategy in archers with different levels of expertise; elite, beginner and non-archers. Electromyography (EMG) activity of the M. flexor digitorum superficialis and the M. extensor digitorum were recorded at a sampling frequency of 500 Hz, together with a pulse synchronized with the clicker snap, for twelve shots by each subject. Raw EMG records, 1-s before and after the clicker pulse, were rectified, integrated and normalized. The data was then averaged for successive shots of each subject and later for each group. All subjects including non-archers developed an active contraction of the M. extensor digitorum and a gradual relaxation of the M. flexor digitorum superficialis with the fall of the clicker. In elite archers release started about 100 ms after the fall of the clicker, whereas in beginners and non-archers release started after about 200 and 300 ms, respectively. Non-archers displayed a preparation phase involving extensive extensor activity before the release of the bowstring, which was not observed in elite and beginner archers. In conclusion, archers released the bowstring by active contraction of the forearm extensors, whereas a clear relaxation of the forearm flexors affecting the release movement was not observed.

  10. EMG analysis of peroneal and tibialis anterior muscle activity prior to foot contact during functional activities.

    Science.gov (United States)

    McLoda, T A; Hansen, A J; Birrer, D A

    2004-06-01

    The purpose of this investigation was to determine the pre-activity of the tibialis anterior (TA), peroneus longus (PL), and peroneus brevis (PB) prior to foot contact during three conditions. Twenty-six subjects (age 22 +/- 2 yrs; 15 male, 11 female) with no lower extremity injuries reported for data collection. Data were collected from each subject's dominant leg using surface electromyography (EMG). EMG electrodes were applied over the test muscles using a standard protocol. A heel-toe strike transducer was affixed to the bottom of the subject's shoe. The subject completed two randomized trials of walking on a treadmill (5.6 kph), jogging on a treadmill (9.3 kph) and drop landing from a 38 cm box. Isometric reference positions (IRPs) were recorded for the TA, PL, and PB. Muscle data were normalized to IRPs and the average processed EMG for the 200 ms prior to heel strike during walking and jogging and prior to toe strike when dropping from the box was used for analysis. A one-way repeated measures MANOVA was used to detect differences in pre-activity of the muscles between the three conditions. Univariate tests were used to determine differences for each muscle and Tukey's was applied post hoc to determine individual effect differences. The MANOVA revealed significant differences among the three conditions (F2.50 = 10.770; P < .0005). Average TA activity was significantly higher during jogging (Tukey's; P < .0005). Significant differences existed between each condition for the TA. Average PL and PB activity was significantly higher when drop landing (Tukey's; P < .0005). There was no significant difference between walking and jogging for the PL and PB. The amount of muscle pre-activity occurring before heel or toe strike provides useful information for the examination of reaction times to unexpected inversion during dynamic activities.

  11. Effect of contraction intensity on sympathetic nerve activity to active human skeletal muscle

    Directory of Open Access Journals (Sweden)

    Daniel eBoulton

    2014-06-01

    Full Text Available The effect of contraction intensity on muscle sympathetic nerve activity (MSNA to active human limbs has not been established. To address this, MSNA was recorded from the left peroneal nerve during and after dorsiflexion contractions sustained for two minutes by the left leg at ~10, 25 and 40 %MVC. To explore the involvement of the muscle metaboreflex, limb ischaemia was imposed midway during three additional contractions and maintained during recovery. Compared with total MSNA at rest (11.5 ± 4.1 mv.min-1, MSNA in the active leg increased significantly at the low (21.9 ± 13.6 mv.min-1, medium (30.5 ± 20.8 mv.min-1 and high (50.0 ± 24.5 mv.min-1 intensities. This intensity-dependent effect was more strongly associated with increases in MSNA burst amplitude than burst frequency. Total MSNA then returned to resting levels within the first minute of recovery. Limb ischaemia had no significant influence on the intensity-dependent rise in MSNA or its decline during recovery in the active leg. These findings reveal intensity-dependent increases in total MSNA and burst amplitude to contracting human skeletal muscle that do not appear to involve the muscle metaboreflex.

  12. Motor activity affects adult skeletal muscle re-innervation acting via tyrosine kinase receptors.

    Science.gov (United States)

    Sartini, Stefano; Bartolini, Fanny; Ambrogini, Patrizia; Betti, Michele; Ciuffoli, Stefano; Lattanzi, Davide; Di Palma, Michael; Cuppini, Riccardo

    2013-05-01

    Recently, muscle expression of brain-derived neurotrophic factor (BDNF) mRNA and protein under activity control has been reported. BDNF is a neurotrophin known to be involved in axon sprouting in the CNS. Hence, we set out to study the effect of chronic treadmill mid-intensity running on adult rat muscle re-innervation, and to explore the involvement of BDNF and tropomyosin-related kinase (Trk) receptors. After nerve crush, muscle re-innervation was evaluated using intracellular recordings, tension recordings, immunostaining and Western blot analyses. An enhanced muscle multiple innervation was found in running rats that was fully reversed to control values blocking Trk receptors or interrupting the running activity. An increase in muscle multiple innervation was also found in sedentary rats treated with a selective TrkB receptor agonist. The expression of TrkB receptors by intramuscular axons was demonstrated, and increased muscle expression of BDNF was found in running animals. The increase in muscle multiple innervation was consistent with the faster muscle re-innervation that we found in running animals. We conclude that, when regenerating axons contact muscle cells, muscle activity progressively increases modulating BDNF and possibly other growth factors, which in turn, acting via Trk receptors, induce axon sprouting to re-innervate skeletal muscle.

  13. Perceived exertion is related to muscle activity during leg extension exercise.

    Science.gov (United States)

    Duncan, Michael J; Al-Nakeeb, Yahya; Scurr, Joanna

    2006-01-01

    This study examined the relationship between ratings of perceived exertion and muscle activity during dynamic leg extension exercise using a resistance exercise specific OMNI-RPE scale. Twenty volunteers (10 males, 10 females, age 22.2 +/- 3.1 yr) performed one set of leg extension exercise at 30%, 60%, and 90% of their one-repetition maximum (1-RM). OMNI-RPE responses were assessed for both the active muscle (OMNI-AM) and the overall body (OMNI-O) following each intensity. Electromyography (EMG) data were collected from the rectus femoris, vastus lateralis, and vastus medialis muscles. A two-factor repeated measures ANOVA showed a significant OMNI-RPE (region) X intensity interaction (p muscle groups (all p Muscle activity was significantly and positively related to OMNI-RPE in both the active muscle and overall body (all p < 0.01). The OMNI-Res RPE scale may be a promising technique for regulating resistance training intensity.

  14. Inter-experimental discrepancy in facial muscle activity during vowel utterance.

    Science.gov (United States)

    Naik, Ganesh R; Kumar, Dinesh K

    2010-01-01

    This paper analyses the inter-experimental similarities in the muscle activation during vowel sound production by an individual. Surface electromyography has been used as an indicator of muscle activity and independent component analysis has been used to separate the electrical activity from different muscles. The results indicate that there is a 'reasonable' relationship between muscle activities of the corresponding muscles when the experiments are repeated. The results demonstrate that when people speak, they use a similar set of muscles when they repeat the same sound. The results also indicate that there is a variation when the same sound is spoken at different speeds of utterances. This can be attributable to the lack of audio feedback when the same sound is uttered.

  15. Neck and Shoulder Muscle Activation Among Experienced and Inexperienced Pilots in +Gz Exposure.

    Science.gov (United States)

    Honkanen, Tuomas; Oksa, Juha; Mäntysaari, Matti J; Kyröläinen, Heikki; Avela, Janne

    2017-02-01

    The aim of the present study was to compare differences in electromyography (EMG) activation of the neck and shoulder muscles between groups of inexperienced and experienced pilots during controlled +Gz exposure in a centrifuge. The subjects were volunteer cadets (inexperienced group) and lieutenants (experienced group) undergoing their first centrifuge training. The first group did not have any high performance aircraft (HPA) experience, while the latter one had a 1-yr experience of intense flying of HPA. During the centrifuge run, EMG activity was recorded from the left and right shoulder, neck flexor, and neck extensor muscles. The pilots without HPA experience had significantly higher muscle activity in the neck flexor and extensor muscles during the last 5 s of the recorded period at G levels exceeding +7.4. Muscle activity in the neck and shoulder muscles was gradually higher among the whole study group with increasing +Gz forces. Because pilots without any HPA experience had significantly higher muscle activity than their counterparts with experience of HPA, we suppose that the experience of high +Gz forces might lead to lower muscle activation in the same flight mission.Honkanen T, Oksa J, Mäntysaari MJ, Kyröläinen H, Avela J. Neck and shoulder muscle activation among experienced and inexperienced pilots in +Gz exposure. Aerosp Med Hum Perform. 2017; 88(2):90-95.

  16. Muscle Activation Profiles and Co-Activation of Quadriceps and Hamstring Muscles around Knee Joint in Indian Primary Osteoarthritis Knee Patients.

    Science.gov (United States)

    Sharma, Sanjeev Kumar; Yadav, Shiv Lal; Singh, U; Wadhwa, Sanjay

    2017-05-01

    Osteoarthritis (OA) of knee is a common joint disease. It is associated with reduced knee joint stability due to impaired quadriceps strength, pain, and an altered joint structure. There is altered muscle activation in knee OA patients, which interferes with normal load distribution around the knee and facilitates disease progression. Our primary aim was to determine activation patterns of the muscles i.e., quadriceps and hamstrings in knee OA patients during walking. We also studied co-activation of muscles around knee joint in primary OA knee patients including directed medial and lateral co-contractions. This observational study was done at Department of Physical Medicine and Rehabilitation, All India Institute of Medical Sciences, New Delhi, India. Fourty-four patients with medial compartment primary knee OA were included in study after satisfying inclusion and exclusion criteria. All the patients were assessed for mean, peak and integrated Root Mean Square (RMS), EMG values, muscle activation patterns and co-activation of muscles around knee joint by surface Electromyography (EMG) analysis of Vastus Medialis Obliques (VMO), Vastus Lateralis (VL), Semitendinosus (SMT) and Biceps Femoris (BF) muscles during gait cycle. The EMG waveform for each muscle was amplitude normalized and time normalized to 100% of gait cycle and plotted on graph. Quantitative variables were assessed for normal distribution and accordingly mean±SD or median (range), as appropriate, was computed. For primary OA knee, mean age 61±5 years, mean weight 63.7±10.1 kg, mean height 153.9±7.2 cm, and mean Body Mass Index (BMI) 26.8±3.0 kg/m(2) was found. The muscle activity of hamstrings (SMT muscle and BF) was increased during midstance, late stance and early swing phase of gait cycle as compared to quadriceps (VMO and VL) muscle activity respectively, suggesting co-contraction of opposing muscles around knee joint. Patients with knee OA walk with increased hamstring muscle activity (during

  17. The Effect of Whole-body Vibration on Muscle Activity in Active and Inactive Subjects.

    Science.gov (United States)

    Lienhard, K; Vienneau, J; Friesenbichler, B; Nigg, S; Meste, O; Nigg, B M; Colson, S S

    2015-06-01

    The purpose of this study was to compare lower limb muscle activity between physically active and inactive individuals during whole-body vibration exercises. Additionally, transmissibility of the vertical acceleration to the head was quantified. 30 active and 28 inactive participants volunteered to stand in a relaxed (20°) and a squat (60°) position on a side-alternating WBV platform that induced vibrations at 16 Hz and 4 mm amplitude. Surface electromyography (sEMG) was measured in selected lower limb muscles and was normalized to the corresponding sEMG recorded during a maximal voluntary contraction. The vertical acceleration on the head was evaluated and divided by the vertical platform acceleration to obtain transmissibility values. Control trials without vibration were also assessed. The outcomes of this study showed that (1) WBV significantly increased muscle activity in the active (absolute increase: +7%, P 0.05). However, (3), transmissibility to the head was greater in the active (0.080) than the inactive participants (0.065, P active counterparts, but are at lower risk for potential side-effects of vibration exposure. © Georg Thieme Verlag KG Stuttgart · New York.

  18. Respiratory muscle activity during asphyxic apnoea and opisthotonus in the rabbit.

    Science.gov (United States)

    Davis, P J; Macefield, G; Nail, B S

    1986-09-01

    The behaviour of submandibular, cervical, thoracic and abdominal respiratory muscles was examined in the pentobarbitone-urethane-anaesthetized rabbit during progressive asphyxia induced by rebreathing. During asphyxic hyperpnoea the external intercostal, interchondral and scalene inspiratory activities augmented until succeeded by the apnoeic period, in which all were inhibited with the diaphragm. Likewise, the genioglossus, sternohyoid and thyrohyoid muscles exhibited inspiratory augmentation during asphyxic hyperpnoea until the onset of apnoeic inhibition. However, late in the apnoea these muscles, together with the sternothyroid, sternomastoid and digastric muscles, generated an augmenting tonic discharge associated with an intense abdominal constriction, and with the extension of the limbs characteristic of opisthotonus. This intense tonic activity, which was never expressed by the diaphragm and thoracic inspiratory muscles, was immediately interrupted or terminated by the subsequent inspiratory efforts of gasping respiration, during which the abdominal muscles were inhibited but all the submandibular, cervical and thoracic inspiratory muscles greatly participated. The mylohyoid muscles presented augmenting expiratory activity during asphyxic hyperpnoea which declined during the apnoea. These muscles, however, did not exhibit the intense tonic discharge expressed by the expiratory abdominal and inspiratory submandibular and cervical muscles in late apnoea and were not active in gasping.

  19. Back posture and low back muscle activity in female computer workers: a field study.

    Science.gov (United States)

    Mork, Paul Jarle; Westgaard, Rolf H

    2009-02-01

    Few studies have investigated sitting posture and low back muscle activity in occupational settings. This study aims to determine back posture and its influence on low back muscle activity in computer workers, and to investigate whether the work situation is associated with exacerbation of low back pain. Twenty-one female computer workers participated. Surface electromyographic activity was recorded from lumbar multifidus, longissimus, and iliocostalis throughout the workday. Simultaneous inclinometer recordings from pelvis, upper trunk, and left thigh were used to determine back posture and identify periods with sitting, standing, and walking. Low back pain intensity was recorded by visual analogue scale every hour throughout the work and leisure periods. All subjects adopted a markedly flexed back posture while seated at work. Surface electromyographic activity was very low for all muscles during sitting (group median Back posture moderately influenced electromyographic activity, accounting for 19% (sitting) to 38% (standing) of intra-individual variation in muscle activity. Subjects reporting aggravating low back pain (n=10) during the workday were not distinguished by duration of sitting, sitting posture, or low back muscle activity. Low back pain was markedly reduced from the last hour of work to the first hour of leisure, accompanied by an increase in low back muscle activity. Low back muscle activity was very low during seated posture, presumably due to the flexion-relaxation phenomenon. Sustained stretch of passive lumbar structures in combination with essentially silent muscles may exacerbate low back pain in sedentary workers.

  20. Changes in joint angle, muscle-tendon complex length, muscle contractile tissue displacement, and modulation of EMG activity during acute whole-body vibration.

    Science.gov (United States)

    Cochrane, Darryl J; Loram, Ian D; Stannard, Stephen R; Rittweger, Jörn

    2009-09-01

    It has been suggested that vibration causes small changes in muscle length, but to the best of our knowledge, these have yet to be demonstrated during whole-body vibration (WBV). This was an observational study to determine whether acute WBV would result in muscle lengthening. We hypothesized that acute WBV would increase electromyography (EMG) activity concurrently with measurable changes in muscle contractile length. Nine healthy males performed two conditions on a Galileo vibration machine for 15 s at 0 HZ (resting) and 6 HZ at a set knee angle of 18 degrees. Muscle tendon complex length, contractile tissue displacement of the medial gastrocnemius muscle, and EMG of soleus, tibialis anterior, and vastus lateralis muscles were measured. At 6 HZ the medial gastrocnemius (MG) muscle tendon complex (MTC) amplitude (375 microm) was significantly greater (P EMG modulation were found for all muscles during the 6 HZ compared to the 0 HZ condition. The major finding was that approximately 50% of the elongation occurred within the muscle itself and was associated with preceding changes in EMG. This indicates muscle lengthening may be a prerequisite for eliciting stretch reflexes. In conclusion, there is a temporal association between EMG activity and muscle contractile tissue displacement where low-frequency WBV results in small muscle length changes and increases muscle activation.

  1. Altered lower leg muscle activation patterns in patients with cerebral palsy during cycling on an ergometer

    Science.gov (United States)

    Alves-Pinto, Ana; Blumenstein, Tobias; Turova, Varvara; Lampe, Renée

    2016-01-01

    Objective Cycling on a recumbent ergometer constitutes one of the most popular rehabilitation exercises in cerebral palsy (CP). However, no control is performed on how muscles are being used during training. Given that patients with CP present altered muscular activity patterns during cycling or walking, it is possible that an incorrect pattern of muscle activation is being promoted during rehabilitation cycling. This study investigated patterns of muscular activation during cycling on a recumbent ergometer in patients with CP and whether those patterns are determined by the degree of spasticity and of mobility. Methods Electromyographic (EMG) recordings of lower leg muscle activation during cycling on a recumbent ergometer were performed in 14 adult patients diagnosed with CP and five adult healthy participants. EMG recordings were done with an eight-channel EMG system built in the laboratory. The activity of the following muscles was recorded: Musculus rectus femoris, Musculus biceps femoris, Musculus tibialis anterior, and Musculus gastrocnemius. The degree of muscle spasticity and mobility was assessed using the Modified Ashworth Scale and the Gross Motor Function Classification System, respectively. Muscle activation patterns were described in terms of onset and duration of activation as well as duration of cocontractions. Results Muscle activation in CP was characterized by earlier onsets, longer periods of activation, a higher occurrence of agonist–antagonist cocontractions, and a more variable cycling tempo in comparison to healthy participants. The degree of altered muscle activation pattern correlated significantly with the degree of spasticity. Conclusion This study confirmed the occurrence of altered lower leg muscle activation patterns in patients with CP during cycling on a recumbent ergometer. There is a need to develop feedback systems that can inform patients and therapists of an incorrect muscle activation during cycling and support the training

  2. A continuum constitutive model for the active behaviour of skeletal muscle

    Science.gov (United States)

    Ehret, Alexander E.; Böl, Markus; Itskov, Mikhail

    2011-03-01

    In the present paper we propose a continuum constitutive model for the passive and active mechanical behaviour of skeletal muscle. Unlike most works in this field, the model is not based on an additive split between passive and active components but considers muscle tissue as one continuous biological material, which alters its properties when activated. This alteration also allows for a kinematic interpretation on the muscle fibre level and is described by a single activation-dependent model parameter. This as well as the other material parameters are obtained from standard experiments on resting and activated muscle or from microstructural information such as fibre type and twitch characteristics. In the passive state, the constitutive equations are governed by a transversely isotropic polyconvex and coercive strain-energy function. The model shows excellent agreement with experimental stress-stretch data of a passive and activated rat tibialis anterior muscle.

  3. Change of Muscle Activity as Well as Kinematic and Kinetic Parameters during Headers after Core Muscle Fatigue

    Directory of Open Access Journals (Sweden)

    Stephan Becker

    2017-01-01

    Full Text Available In soccer, headers are a tactical measure and influenced by numerous factors. The goal of this study was to identify whether changes in kinematics and muscular activity, especially of the head-stabilizing muscles, occur during headers when the core musculature is fatigued. In two subgroups, muscular activity (12 amateur players, age 23.6 ± 4.2 years and kinematics and dynamics (29 amateur players, age 23.7 ± 2.8 years were examined during straight headers on a pendulum header. Data were collected before and after the core muscles were fatigued by an exercise program. Telemetric surface EMG, 3D acceleration sensor, force plate, and video recordings were used. Under fatigue, the activity of M. erector spinae and M. rectus abdominis was significantly reduced in the preparation phase of the header. The activity of M. sternocleidomastoideus was significantly increased during the jump phase, and the hip extension angle during maximum arched body tension was significantly reduced under fatigue. Jumping height, acceleration force impulse, and linear head acceleration were also significantly reduced. We conclude that fatigue of the core muscles affects the motion technique of the header and the activity of the muscle groups stabilizing the head. Therefore, the necessity of specific training in soccer should be emphasized from a medical-preventive point of view.

  4. Transcriptional activation of the IL-6 gene in human contracting skeletal muscle: influence of muscle glycogen content.

    Science.gov (United States)

    Keller, C; Steensberg, A; Pilegaard, H; Osada, T; Saltin, B; Pedersen, B K; Neufer, P D

    2001-12-01

    In humans, the plasma interleukin 6 (IL-6) concentration increases dramatically during low-intensity exercise. Measurements across the working limb indicate that skeletal muscle is the source of IL-6 production. To determine whether energy availability influences the regulation of IL-6 expression during prolonged exercise, six male subjects completed two trials consisting of 180 min of two-legged dynamic knee extensor with either normal or low (~60% of control) pre-exercise muscle glycogen levels. Increases in plasma IL-6 during exercise were significantly higher (P<0.05) in the low-glycogen (16-fold) trial verses the control (10-fold) trial. Transcriptional activation of the IL-6 gene in skeletal muscle was also higher in the low-glycogen trial; it increased by about 40-fold after 90 min of exercise and about 60-fold after 180 min of exercise. Muscle IL-6 mRNA followed a similar but delayed pattern, increasing by more than 100-fold in the low-glycogen trial and by about 30-fold in the control trial. These data demonstrate that exercise activates transcription of the IL-6 gene in working skeletal muscle, a response that is dramatically enhanced when glycogen levels are low. These findings also support the hypothesis that IL-6 may be produced by contracting myofibers when glycogen levels become critically low as a means of signaling the liver to increase glucose production.

  5. On the glucokinase activity of extracts from normal and atrophic muscles

    NARCIS (Netherlands)

    Gerritsen, T.

    1952-01-01

    The glucokinase activity of extracts of muscles of various species (man, rabbit, guinea-pig, rat and chicken) has been determined. The activity of an extract prepared from a rabbit muscle, which had atrophied in the course of three to four weeks as a consequence of severance of the nerve, was alwa

  6. Synergistic Structure in the Speed Dependent Modulation of Muscle Activity in Human Walking

    NARCIS (Netherlands)

    Buurke, Tom J W; Lamoth, Claudine J C; van der Woude, Lucas H V; Otter, den A. Rob

    2016-01-01

    Recently, a modular organisation has been proposed to simplify control of the large number of muscles involved in human walking. Although previous research indicates that a single set of modular activation patterns can account for muscle activity at different speeds, these studies only provide indir

  7. Lower physical activity is associated with fat infiltration within skeletal muscle in young girls

    Science.gov (United States)

    Fat infiltration within skeletal muscle is strongly associated with obesity, type 2 diabetes mellitus, and metabolic syndrome. Lower physical activity may be a risk factor for greater fat infiltration within skeletal muscle, although whether lower physical activity is associated with fat infiltrati...

  8. Synergistic Structure in the Speed Dependent Modulation of Muscle Activity in Human Walking

    NARCIS (Netherlands)

    Buurke, Tom J. W.; Lamoth, Claudine J C; van der Woude, Lucas H V; Otter, den A. Rob

    2016-01-01

    Recently, a modular organisation has been proposed to simplify control of the large number of muscles involved in human walking. Although previous research indicates that a single set of modular activation patterns can account for muscle activity at different speeds, these studies only provide

  9. DEVELOPMENTAL REGULATION OF PROTEIN KINASE B ACTIVATION IS ISOFORM SPECIFIC IN SKELETAL MUSCLE OF NEONATAL PIGS

    Science.gov (United States)

    The postprandial activation of the insulin signaling pathway that leads to translation initiation is enhanced in skeletal muscle of the neonate and decreases with development in parallel with the developmental decline in muscle protein synthesis. Our previous study showed that the activity of protei...

  10. Association of Orofacial Muscle Activity and Movement during Changes in Speech Rate and Intensity

    Science.gov (United States)

    McClean, Michael D.; Tasko, Stephen M.

    2003-01-01

    Understanding how orofacial muscle activity and movement covary across changes in speech rate and intensity has implications for the neural control of speech production and the use of clinical procedures that manipulate speech prosody. The present study involved a correlation analysis relating average lower-lip and jaw-muscle activity to lip and…

  11. Association of Orofacial Muscle Activity and Movement during Changes in Speech Rate and Intensity

    Science.gov (United States)

    McClean, Michael D.; Tasko, Stephen M.

    2003-01-01

    Understanding how orofacial muscle activity and movement covary across changes in speech rate and intensity has implications for the neural control of speech production and the use of clinical procedures that manipulate speech prosody. The present study involved a correlation analysis relating average lower-lip and jaw-muscle activity to lip and…

  12. Electromyographic effect of mat Pilates exercise on the back muscle activity of healthy adult females.

    Science.gov (United States)

    Menacho, Maryela O; Obara, Karen; Conceição, Josilene S; Chitolina, Matheus L; Krantz, Daniel R; da Silva, Rubens A; Cardoso, Jefferson R

    2010-01-01

    The purpose of this study was to examine back muscle activity during 3 traditional mat Pilates exercises. Eleven healthy female volunteers, aged between 18 and 30 years, participated in this cross-sectional study. Surface electromyography (sEMG) of lumbar extensor muscles was recorded simultaneously with kinematics data to identify the phases of movement. Three mat Pilates back exercises were compared: (1) swimming, (2) single leg kick with static prone back extension, and (3) double leg kick. Root mean square values of each muscle were recorded with 2 pairs of surface electrodes placed bilaterally on one lumbar extensor muscle (at L5). During phases of each exercise, sEMG signals were identified by video analysis. Electrical muscle activation was normalized by the maximal voluntary isometric contraction and used to compare back muscle activity among exercises. A 2-way repeated measures analysis of variance was performed to assess the differences in activation level during the exercises. The value of electrical muscle activity in the lumbar extensors ranged between 15% and 61% of MIVC for the 3 types of Pilates mat work exercise. The swimming exercise increased lumbar extensor activity (29% on average) in comparison to the other 2 Pilates conditions. Interestingly, the double leg kick exercise generated significantly more lumbar extensor activity (26% on average) than the single leg kick. For this group of participants, the swimming exercise increased muscle activation relative to the other 2 exercise modes. Copyright © 2010 National University of Health Sciences. Published by Mosby, Inc. All rights reserved.

  13. A comparison of hamstring muscle activity during different screening tests for non-contact ACL injury

    DEFF Research Database (Denmark)

    Husted, Rasmus S; Bencke, Jesper; Andersen, Lars Louis

    2016-01-01

    BACKGROUND: Reduced ability to activate the medial hamstring muscles during a sports-specific sidecutting movement has been found to be a potential risk factor for non-contact ACL injury. However, whether a reduced ability to activate the medial hamstring muscle is a general neuromuscular phenome...

  14. Heterogeneity of muscle activation in relation to force direction: a multi-channel surface electromyography study on the triceps surae muscle.

    NARCIS (Netherlands)

    Staudenmann, D.; Kingma, I.; Daffertshofer, A.; Stegeman, D.F.; Dieen, J.H. van

    2009-01-01

    Several skeletal muscles can be divided into sub-modules, called neuromuscular compartments (NMCs), which are thought to be controlled independently and to have distinct biomechanical functions. We looked for distinct muscle activation patterns in the triceps surae muscle (TS) using surface electrom

  15. Role of diacylglycerol activation of PKCθ in lipid-induced muscle insulin resistance in humans

    Science.gov (United States)

    Szendroedi, Julia; Yoshimura, Toru; Phielix, Esther; Koliaki, Chrysi; Marcucci, Mellissa; Zhang, Dongyan; Jelenik, Tomas; Müller, Janette; Herder, Christian; Nowotny, Peter; Shulman, Gerald I.; Roden, Michael

    2014-01-01

    Muscle insulin resistance is a key feature of obesity and type 2 diabetes and is strongly associated with increased intramyocellular lipid content and inflammation. However, the cellular and molecular mechanisms responsible for causing muscle insulin resistance in humans are still unclear. To address this question, we performed serial muscle biopsies in healthy, lean subjects before and during a lipid infusion to induce acute muscle insulin resistance and assessed lipid and inflammatory parameters that have been previously implicated in causing muscle insulin resistance. We found that acute induction of muscle insulin resistance was associated with a transient increase in total and cytosolic diacylglycerol (DAG) content that was temporally associated with protein kinase (PKC)θ activation, increased insulin receptor substrate (IRS)-1 serine 1101 phosphorylation, and inhibition of insulin-stimulated IRS-1 tyrosine phosphorylation and AKT2 phosphorylation. In contrast, there were no associations between insulin resistance and alterations in muscle ceramide, acylcarnitine content, or adipocytokines (interleukin-6, adiponectin, retinol-binding protein 4) or soluble intercellular adhesion molecule-1. Similar associations between muscle DAG content, PKCθ activation, and muscle insulin resistance were observed in healthy insulin-resistant obese subjects and obese type 2 diabetic subjects. Taken together, these data support a key role for DAG activation of PKCθ in the pathogenesis of lipid-induced muscle insulin resistance in obese and type 2 diabetic individuals. PMID:24979806

  16. Biofeedback effectiveness to reduce upper limb muscle activity during computer work is muscle specific and time pressure dependent

    DEFF Research Database (Denmark)

    Vedsted, Pernille; Søgaard, Karen; Blangsted, Anne Katrine

    2011-01-01

    Continuous electromyographic (EMG) activity level is considered a risk factor in developing muscle disorders. EMG biofeedback is known to be useful in reducing EMG activity in working muscles during computer work. The purpose was to test the following hypotheses: (1) unilateral biofeedback from...... trapezius (TRA) can reduce bilateral TRA activity but not extensor digitorum communis (EDC) activity; (2) biofeedback from EDC can reduce activity in EDC but not in TRA; (3) biofeedback is more effective in no time constraint than in the time constraint working condition. Eleven healthy women performed...... computer work during two different working conditions (time constraint/no time constraint) while receiving biofeedback. Biofeedback was given from right TRA or EDC through two modes (visual/auditory) by the use of EMG or mechanomyography as biofeedback source. During control sessions (no biofeedback), EMG...

  17. Biofeedback effectiveness to reduce upper limb muscle activity during computer work is muscle specific and time pressure dependent

    DEFF Research Database (Denmark)

    Vedsted, Pernille; Søgaard, Karen; Blangsted, Anne Katrine

    2011-01-01

    Continuous electromyographic (EMG) activity level is considered a risk factor in developing muscle disorders. EMG biofeedback is known to be useful in reducing EMG activity in working muscles during computer work. The purpose was to test the following hypotheses: (1) unilateral biofeedback from...... trapezius (TRA) can reduce bilateral TRA activity but not extensor digitorum communis (EDC) activity; (2) biofeedback from EDC can reduce activity in EDC but not in TRA; (3) biofeedback is more effective in no time constraint than in the time constraint working condition. Eleven healthy women performed...... computer work during two different working conditions (time constraint/no time constraint) while receiving biofeedback. Biofeedback was given from right TRA or EDC through two modes (visual/auditory) by the use of EMG or mechanomyography as biofeedback source. During control sessions (no biofeedback), EMG...

  18. An Active Learning Mammalian Skeletal Muscle Lab Demonstrating Contractile and Kinetic Properties of Fast- and Slow-Twitch Muscle

    Science.gov (United States)

    Head, S. I.; Arber, M. B.

    2013-01-01

    The fact that humans possess fast and slow-twitch muscle in the ratio of approximately 50% has profound implications for designing exercise training strategies for power and endurance activities. With the growth of exercise and sport science courses, we have seen the need to develop an undergraduate student laboratory that demonstrates the basic…

  19. An Active Learning Mammalian Skeletal Muscle Lab Demonstrating Contractile and Kinetic Properties of Fast- and Slow-Twitch Muscle

    Science.gov (United States)

    Head, S. I.; Arber, M. B.

    2013-01-01

    The fact that humans possess fast and slow-twitch muscle in the ratio of approximately 50% has profound implications for designing exercise training strategies for power and endurance activities. With the growth of exercise and sport science courses, we have seen the need to develop an undergraduate student laboratory that demonstrates the basic…

  20. The influence of different sitting postures on head/neck posture and muscle activity.

    Science.gov (United States)

    Caneiro, Joao Paulo; O'Sullivan, Peter; Burnett, Angus; Barach, Avi; O'Neil, David; Tveit, Orjan; Olafsdottir, Karolina

    2010-02-01

    To date the influence that specific sitting posture has on the head/neck posture and cervico-thoracic muscle activity has been insufficiently investigated. Therefore the aim of this study was to investigate whether three different thoraco-lumbar sitting postures affect head/neck posture and cervico-thoracic muscle activity. Twenty (10 men, 10 women) asymptomatic subjects were placed in 3 standardized thoraco-lumbar sitting postures (lumbo-pelvic, thoracic upright and slump) to investigate their influence on cervico-thoracic muscle activity and head/neck posture. There were significant differences in lumbar and thoracic curvatures in the 3 different sitting postures (Ppostures (P=0.015). Upper trapezius (UT) demonstrated no significant difference in muscle activation in the 3 sitting postures (Ppostures affect head/neck posture and cervico-thoracic muscle activity. It highlights the potential importance of thoraco-lumbar spine postural adjustment when training head/neck posture.

  1. Temporal muscle activation assessment by ultrasound imaging during flexor withdrawal reflex and voluntary contraction.

    Science.gov (United States)

    Jose, Gomez-Tames; Shuto, Nakamura; Jose, Gonzalez; Wenwei, Yu

    2013-01-01

    Activating flexor reflexes by electrical stimulation has been used as a mechanism to initiate the swing phase or to enhance it for spinal cord injured patients. However, it is necessary to know their contraction dynamics in order to artificially induce them at the right moment of a walking cycle. This requires understanding the temporal activation pattern of both surface and deep muscles simultaneously. This study aimed at developing a system to measure and analyze the temporal activation of both surface and deep muscles during voluntary contraction and flexor reflexes (also called withdrawal reflexes) using ultrasound imaging. A set of experiments were done to verify the validity of the system, while exploring the temporal pattern of muscle activation during flexor reflexes. As a result, we were able to quantify the surface and deep muscle activity by measuring the muscle thickness, pennation angle and long-axis displacement, from the ultrasound images.

  2. Quantification of muscle activity during sleep for patients with neurodegenerative diseases

    DEFF Research Database (Denmark)

    Hanif, Umaer; Trap, Lotte; Jennum, Poul;

    2015-01-01

    Idiopathic REM sleep behavior disorder (iRBD) is a very strong predictor for later development of Parkinson's disease (PD), and is characterized by REM sleep without atonia (RSWA), resulting in increased muscle activity during REM sleep. Abundant studies have shown the loss of atonia during REM...... sleep, but our aim was to investigate whether iRBD and PD patients have increased muscle activity in both REM and NREM sleep compared to healthy controls. This was achieved by developing a semi-automatic algorithm for quantification of mean muscle activity per second during all sleep stages...... to the different sleep stages and muscle activity beyond the threshold was counted. The results were evaluated statistically using the two-sided Mann-Whitney U-test. The results suggested that iRBD patients also exhibit distinctive muscle activity characteristics in NREM sleep, however not as evident as in REM...

  3. Effect of sprint cycle training on activities of antioxidant enzymes in human skeletal muscle

    DEFF Research Database (Denmark)

    Hellsten, Ylva; Apple, F. S.; Sjödin, B.

    1996-01-01

    The effect of intermittent sprint cycle training on the level of muscle antioxidant enzyme protection was investigated. Resting muscle biopsies, obtained before and after 6 wk of training and 3, 24, and 72 h after the final session of an additional 1 wk of more frequent training, were analyzed...... for activities of the antioxidant enzymes glutathione peroxidase (GPX), glutathione reductase (GR), and superoxide dismutase (SOD). Activities of several muscle metabolic enzymes were determined to assess the effectiveness of the training. After the first 6-wk training period, no change in GPX, GR, or SOD...... the level of antioxidant protection in the muscle....

  4. Perceived loading and muscle activity during hip strengthening exercises

    DEFF Research Database (Denmark)

    Brandt, Mikkel; Jakobsen, Markus Due; Thorborg, Kristian;

    2013-01-01

    OBJECTIVE: Decreased hip muscle strength is frequently reported in patients with hip injury or pathology. Furthermore, soccer players suffering from groin injury show decreased strength of hip muscles. Estimating 10-repetition maximum can be time-consuming and difficult, thus, using the Borg cate...

  5. Thoracic posture, shoulder muscle activation patterns and isokinetic ...

    African Journals Online (AJOL)

    determined at 60°/sec by measuring the concentric and eccentric forces during internal rotation (IR) and ... muscle was observed prior to impact, compared with the pectoralis major ... tight shoulder internal rotators and adductors, high body mass and ..... EMG analysis of rugby players' scapulothoracic muscles is limited, but.

  6. Single motor unit activity in human extraocular muscles during the vestibulo-ocular reflex.

    Science.gov (United States)

    Weber, Konrad P; Rosengren, Sally M; Michels, Rike; Sturm, Veit; Straumann, Dominik; Landau, Klara

    2012-07-01

    Motor unit activity in human eye muscles during the vestibulo-ocular reflex (VOR) is not well understood, since the associated head and eye movements normally preclude single unit recordings. Therefore we recorded single motor unit activity following bursts of skull vibration and sound, two vestibular otolith stimuli that elicit only small head and eye movements. Inferior oblique (IO) and inferior rectus (IR) muscle activity was measured in healthy humans with concentric needle electrodes. Vibration elicited highly synchronous, short-latency bursts of motor unit activity in the IO (latency: 10.5 ms) and IR (14.5 ms) muscles. The activation patterns of the two muscles were similar, but reciprocal, with delayed activation of the IR muscle. Sound produced short-latency excitation of the IO muscle (13.3 ms) in the eye contralateral to the stimulus. Simultaneous needle and surface recordings identified the IO as the muscle of origin of the vestibular evoked myogenic potential (oVEMP) thus validating the physiological basis of this recently developed clinical test of otolith function. Single extraocular motor unit recordings provide a window into neural activity in humans that can normally only be examined using animal models and help identify the pathways of the translational VOR from otoliths to individual eye muscles.

  7. Effect of Neck Muscle Strength and Anticipatory Cervical Muscle Activation on the Kinematic Response of the Head to Impulsive Loads

    Science.gov (United States)

    Eckner, James T.; Oh, Youkeun K.; Joshi, Monica S.; Richardson, James K.; Ashton-Miller, James A.

    2015-01-01

    Background Greater neck strength and activating the neck muscles to brace for impact are both thought to reduce an athlete's risk of concussion during a collision by attenuating the head's kinematic response after impact. However, the literature reporting the neck's role in controlling postimpact head kinematics is mixed. Furthermore, these relationships have not been examined in the coronal or transverse planes or in pediatric athletes. Hypotheses In each anatomic plane, peak linear velocity (DV) and peak angular velocity (Dv) of the head are inversely related to maximal isometric cervical muscle strength in the opposing direction (H1). Under impulsive loading, DV and Dv will be decreased during anticipatory cervical muscle activation compared with the baseline state (H2). Study Design Descriptive laboratory study. Methods Maximum isometric neck strength was measured in each anatomic plane in 46 male and female contact sport athletes aged 8 to 30 years. A loading apparatus applied impulsive test forces to athletes' heads in flexion, extension, lateral flexion, and axial rotation during baseline and anticipatory cervical muscle activation conditions. Multivariate linear mixed models were used to determine the effects of neck strength and cervical muscle activation on head DV and Dv. Results Greater isometric neck strength and anticipatory activation were independently associated with decreased head DV and Dv after impulsive loading across all planes of motion (all P\\.001). Inverse relationships between neck strength and head DV and Dv presented moderately strong effect sizes (r = 0.417 to r = 0.657), varying by direction of motion and cervical muscle activation. Conclusion In male and female athletes across the age spectrum, greater neck strength and anticipatory cervical muscle activation (“bracing for impact”) can reduce the magnitude of the head's kinematic response. Future studies should determine whether neck strength contributes to the observed sex and

  8. Increased Stiffness in Aged Skeletal Muscle Impairs Muscle Progenitor Cell Proliferative Activity.

    Directory of Open Access Journals (Sweden)

    Grégory Lacraz

    Full Text Available Skeletal muscle aging is associated with a decreased regenerative potential due to the loss of function of endogenous stem cells or myogenic progenitor cells (MPCs. Aged skeletal muscle is characterized by the deposition of extracellular matrix (ECM, which in turn influences the biomechanical properties of myofibers by increasing their stiffness. Since the stiffness of the MPC microenvironment directly impacts MPC function, we hypothesized that the increase in muscle stiffness that occurs with aging impairs the behavior of MPCs, ultimately leading to a decrease in regenerative potential.We showed that freshly isolated individual myofibers from aged mouse muscles contain fewer MPCs overall than myofibers from adult muscles, with fewer quiescent MPCs and more proliferative and differentiating MPCs. We observed alterations in cultured MPC behavior in aged animals, where the proliferation and differentiation of MPCs were lower and higher, respectively. These alterations were not linked to the intrinsic properties of aged myofibers, as shown by the similar values for the cumulative population-doubling values and fusion indexes. However, atomic force microscopy (AFM indentation experiments revealed a nearly 4-fold increase in the stiffness of the MPC microenvironment. We further showed that the increase in stiffness is associated with alterations to muscle ECM, including the accumulation of collagen, which was correlated with higher hydroxyproline and advanced glycation end-product content. Lastly, we recapitulated the impaired MPC behavior observed in aging using a hydrogel substrate that mimics the stiffness of myofibers.These findings provide novel evidence that the low regenerative potential of aged skeletal muscle is independent of intrinsic MPC properties but is related to the increase in the stiffness of the MPC microenvironment.

  9. Musculoskeletal modelling of muscle activation and applied external forces for the correction of scoliosis.

    Science.gov (United States)

    Curtin, Maurice; Lowery, Madeleine M

    2014-04-07

    This study uses biomechanical modelling and computational optimization to investigate muscle activation in combination with applied external forces as a treatment for scoliosis. Bracing, which incorporates applied external forces, is the most popular non surgical treatment for scoliosis. Non surgical treatments which make use of muscle activation include electrical stimulation, postural control, and therapeutic exercises. Electrical stimulation has been largely dismissed as a viable treatment for scoliosis, although previous studies have suggested that it can potentially deliver similarly effective corrective forces to the spine as bracing. The potential of muscle activation for scoliosis correction was investigated over different curvatures both with and without the addition of externally applied forces. The five King's classifications of scoliosis were investigated over a range of Cobb angles. A biomechanical model of the spine was used to represent various scoliotic curvatures. Optimization was applied to the model to reduce the curves using combinations of both deep and superficial muscle activation and applied external forces. Simulating applied external forces in combination with muscle activation at low Cobb angles (forces were applied in combination, lower levels of muscle activation or less external force was required to reduce the curvature of the spine, when compared with either muscle activation or external force applied in isolation. The results of this study suggest that activation of superficial and deep muscles may be effective in reducing spinal curvature at low Cobb angles when muscle groups are selected for activation based on the curve type. The findings further suggest the potential for a hybrid treatment involving combined muscle activation and applied external forces at larger Cobb angles.

  10. Resistance exercise-induced fluid shifts: change in active muscle size and plasma volume

    Science.gov (United States)

    Ploutz-Snyder, L. L.; Convertino, V. A.; Dudley, G. A.

    1995-01-01

    The purpose of this study was to test the hypothesis that the reduction in plasma volume (PV) induced by resistance exercise reflects fluid loss to the extravascular space and subsequently selective increase in cross-sectional area (CSA) of active but not inactive skeletal muscle. We compared changes in active and inactive muscle CSA and PV after barbell squat exercise. Magnetic resonance imaging (MRI) was used to quantify muscle involvement in exercise and to determine CSA of muscle groups or individual muscles [vasti (VS), adductor (Add), hamstring (Ham), and rectus femoris (RF)]. Muscle involvement in exercise was determined using exercise-induced contrast shift in spin-spin relaxation time (T2)-weighted MR images immediately postexercise. Alterations in muscle size were based on the mean CSA of individual slices. Hematocrit, hemoglobin, and Evans blue dye were used to estimate changes in PV. Muscle CSA and PV data were obtained preexercise and immediately postexercise and 15 and 45 min thereafter. A hierarchy of muscle involvement in exercise was found such that VS > Add > Ham > RF, with the Ham and RF showing essentially no involvement. CSA of the VS and Add muscle groups were increased 10 and 5%, respectively, immediately after exercise in each thigh with no changes in Ham and RF CSA. PV was decreased 22% immediately following exercise. The absolute loss of PV was correlated (r2 = 0.75) with absolute increase in muscle CSA immediately postexercise, supporting the notion that increased muscle size after resistance exercise reflects primarily fluid movement from the vascular space into active but not inactive muscle.

  11. The effect of postural correction on muscle activation amplitudes recorded from the cervicobrachial region.

    Science.gov (United States)

    McLean, Linda

    2005-12-01

    In clinical practice, postural correction is a common treatment approach for individuals with neck and shoulder pain. As chronic static muscle use is thought to be associated with the onset of some neck and shoulder pain syndromes, it is important to understand the impact a postural correction program might have on muscle activation amplitudes in the neck and shoulder regions. Normalized surface electromyographic data were recorded from the levator scapulae, upper trapezius, supraspinatus, posterior deltoid, masseter, rhomboid major, cervical erector spinae, and sternocleidomastoid muscles of the dominant side of each of eighteen healthy subjects. Subjects performed five repetitions of each of four seated typing postures (habitual, corrected, head-forward and slouched) and four standing postures (habitual, corrected, and head-forward and slouched). Repeated-measures analysis of variance models (alpha=0.05) revealed that in sitting postural correction tended to decreased the level of muscle activation required in all muscles studied during seated computer work, however this finding was not statistically significant. Corrected posture in sitting did, however produce a statistically significant reduction in muscle activity compared to forward head posture. Corrected posture in standing required more muscle activity than habitual or forward head posture in the majority of cervicobrachial and jaw muscles, suggesting that a graduated approach to postural correction exercises might be required in order to train the muscles to appropriately withstand the requirements of the task. A surprising finding was that muscle activity levels and postural changes had the largest impact on the masseter muscle, which demonstrated activation levels in the order of 20% maximum voluntary electrical activation.

  12. Frowning and jaw clenching muscle activity reflects the perception of effort during incremental workload cycling.

    Science.gov (United States)

    Huang, Ding-Hau; Chou, Shih-Wei; Chen, Yi-Lang; Chiou, Wen-Ko

    2014-12-01

    The present study aimed to investigate whether facial electromyography (EMG) recordings reflect the perception of effort and primary active lower limb muscle activity during incremental workload cycling. The effects of exercise intensity on EMG activity of the corrugator supercilii (CS), masseter and vastus lateralis (VL) muscles, heart rate (HR) and the rating of perceived exertion (RPE) were investigated, and the correlations among these parameters were determined. Eighteen males and 15 females performed continuous incremental workload cycling exercise until exhaustion. CS, masseter and VL muscle activities were continuously recorded using EMG during exercise. HR was also continuously monitored during the test. During the final 30 s of each stage of cycle ergometer exercise, participants were asked to report their feeling of exertion on the adult OMNI-Cycle RPE. HR and EMG activity of the facial muscles and the primary active lower limb muscle were strongly correlated with RPE; they increased with power output. Furthermore, facial muscle activity increased significantly during high-intensity exercise. Masseter muscle activity was strongly and positively correlated with HR, RPE and VL activity. The present investigation supports the view that facial EMG activity reflects the perception of effort. The jaw clenching facial expression can be considered an important factor for improving the reporting of perceived effort during high-intensity exercise in males and females. Key pointsFrowning and jaw clenching muscle activity reflects the perception of effort during incremental workload cycling.EMG activity of the masseter muscle was strongly and positively correlated with RPE, HR and lower limb EMG activity during incremental workload cycling.The jaw clenching facial expression can be considered an important factor for estimating the intensity of effort.

  13. Impaired voluntary neuromuscular activation limits muscle power in mobility-limited older adults

    Science.gov (United States)

    Background. Age-related alterations of neuromuscular activation may contribute to deficits in muscle power and mobility function. This study assesses whether impaired activation of the agonist quadriceps and antagonist hamstrings, including amplitude- and velocity-dependent characteristics of activa...

  14. Discovery of Novel Small Molecules that Activate Satellite Cell Proliferation and Enhance Repair of Damaged Muscle.

    Science.gov (United States)

    Billin, Andrew N; Bantscheff, Marcus; Drewes, Gerard; Ghidelli-Disse, Sonja; Holt, Jason A; Kramer, Henning F; McDougal, Alan J; Smalley, Terry L; Wells, Carrow I; Zuercher, William J; Henke, Brad R

    2016-02-19

    Skeletal muscle progenitor stem cells (referred to as satellite cells) represent the primary pool of stem cells in adult skeletal muscle responsible for the generation of new skeletal muscle in response to injury. Satellite cells derived from aged muscle display a significant reduction in regenerative capacity to form functional muscle. This decrease in functional recovery has been attributed to a decrease in proliferative capacity of satellite cells. Hence, agents that enhance the proliferative abilities of satellite cells may hold promise as therapies for a variety of pathological settings, including repair of injured muscle and age- or disease-associated muscle wasting. Through phenotypic screening of isolated murine satellite cells, we identified a series of 2,4-diaminopyrimidines (e.g., 2) that increased satellite cell proliferation. Importantly, compound 2 was effective in accelerating repair of damaged skeletal muscle in an in vivo mouse model of skeletal muscle injury. While these compounds were originally prepared as c-Jun N-terminal kinase 1 (JNK-1) inhibitors, structure-activity analyses indicated JNK-1 inhibition does not correlate with satellite cell activity. Screening against a broad panel of kinases did not result in identification of an obvious molecular target, so we conducted cell-based proteomics experiments in an attempt to identify the molecular target(s) responsible for the potentiation of the satellite cell proliferation. These data provide the foundation for future efforts to design improved small molecules as potential therapeutics for muscle repair and regeneration.

  15. Modulation of muscle activity and force fluctuations in the plantarflexors after bedrest depends on knee position.

    Science.gov (United States)

    Yoshitake, Yasuhide; Kouzaki, Motoki; Fukuoka, Hideoki; Fukunaga, Tetsuo; Shinohara, Minoru

    2007-06-01

    Force fluctuations in leg muscles increase after bedrest, perhaps due to modulation of the neural strategy that is specific to a muscle or common to agonist muscles. The purpose of this study was to examine the modulation of muscle activity and force fluctuations during steady contractions with variable involvement of plantarflexor muscles after bedrest at knee-flexed (FLX) and extended (EXT) positions. Before and after 20-day bedrest, plantarflexion force and surface electromyogram (EMG) in the medial gastrocnemius (MG), lateral gastrocnemius, and soleus muscles were measured during steady isometric contractions in five young men. In EXT, power EMG of MG increased significantly after bedrest. This low-frequency modulation of muscle activity in MG accompanied a 29% increase in the standard deviation of force. There was no change in EMG in other muscles. In FLX, there was no adjustment in EMG or force fluctuations. These results suggest that low-frequency modulation of MG plays a role in increasing force fluctuations during steady plantarflexion in EXT after bedrest. The findings indicate task/muscle specificity in the modulation of neural strategy during steady contractions after bedrest and underscore the importance of designing a specific training regimen targeted to particular tasks/muscles with regard to force fluctuations in multiple-agonist systems.

  16. Analysis of scapular muscle EMG activity in patients with idiopathic neck pain: a systematic review.

    Science.gov (United States)

    Castelein, Birgit; Cools, Ann; Bostyn, Emma; Delemarre, Jolien; Lemahieu, Trees; Cagnie, Barbara

    2015-04-01

    It is proposed that altered scapular muscle function can contribute to abnormal loading of the cervical spine. However, it is not clear if patients with idiopathic neck pain show altered activity of the scapular muscles. The aim of this paper was to systematically review the literature regarding the differences or similarities in scapular muscle activity, measured by electromyography ( = EMG), between patients with chronic idiopathic neck pain compared to pain-free controls. Case-control (neck pain/healthy) studies investigating scapular muscle EMG activity (amplitude, timing and fatigue parameters) were searched in Pubmed and Web of Science. 25 articles were included in the systematic review. During rest and activities below shoulder height, no clear differences in mean Upper Trapezius ( = UT) EMG activity exist between patients with idiopathic neck pain and a healthy control group. During overhead activities, no conclusion for scapular EMG amplitude can be drawn as a large variation of results were reported. Adaptation strategies during overhead tasks are not the same between studies. Only one study investigated timing of the scapular muscles and found a delayed onset and shorter duration of the SA during elevation in patients with idiopathic neck pain. For scapular muscle fatigue, no definite conclusions can be made as a wide variation and conflicting results are reported. Further high quality EMG research on scapular muscles (broader than the UT) is necessary to understand/draw conclusions on how scapular muscles react in the presence of idiopathic neck pain.

  17. An Analysis of Muscle Activities of Healthy Women during Pilates Exercises in a Prone Position.

    Science.gov (United States)

    Kim, Bo-In; Jung, Ju-Hyeon; Shim, Jemyung; Kwon, Hae-Yeon; Kim, Haroo

    2014-01-01

    [Purpose] This study analyzed the activities of the back and hip muscles during Pilates exercises conducted in a prone position. [Subjects] The subjects were 18 healthy women volunteers who had practiced at a Pilates center for more than three months. [Methods] The subjects performed three Pilates exercises. To examine muscle activity during the exercises, 8-channel surface electromyography (Noraxon USA, Inc., Scottsdale, AZ) was used. The surface electrodes were attached to the bilateral latissimus dorsi muscle, multifidus muscle, gluteus maximus, and semitendinous muscle. Three Pilates back exercises were compared: (1) double leg kick (DLK), (2) swimming (SW), and (3) leg beat (LB). Electrical muscle activation was normalized to maximal voluntary isometric contraction. Repeated measures analysis of variance was performed to assess the differences in activation levels among the exercises. [Results] The activity of the multifidus muscle was significantly high for the SW (52.3±11.0, 50.9±9.8) and LB exercises(51.8±12.8, 48.3±13.9) and the activity of the semitendinosus muscle was higher for the LB exercise (49.2±8.7, 52.9±9.3) than for the DLK and SW exercises. [Conclusion] These results may provide basic material for when Pilates exercises are performed in a prone position and may be useful information on clinical Pilates for rehabilitation programs.

  18. Upper Extremity Muscle Activation during Recovery of Reaching in Subjects with Post-stroke Hemiparesis

    Science.gov (United States)

    Wagner, Joanne M.; Dromerick, Alexander W.; Sahrmann, Shirley A.; Lang, Catherine E.

    2007-01-01

    Objective To investigate upper extremity muscle activation and recovery during the first few months after stroke. Methods Subjects with hemiparesis following stroke were studied performing a reaching task at an acute time point (mean = 9 days post-stroke) and then again at a subacute time point (mean = 109 days post-stroke). We recorded kinematics and electromyographic activity of 6 upper extremity muscles. Results At the acute time point, the hemiparetic group had delayed muscle onsets, lower modulation ratios, and higher relative levels of muscle activation (%MVIC) during reaching than controls. From the acute to the subacute time points, improvements were noted in all three variables. By the subacute phase, muscle onsets were similar to controls, while modulation ratios remained lower than controls and %MVIC showed a trend toward being greater in the hemiparetic group. Changes in muscle activation were differentially related to changes in reaching performance. Conclusions Our data show that improvements in muscle timing and decreases in the relative level of volitional activation may underlie improved reaching performance in the early months after stroke. Significance Given that stroke is one of the leading causes of persistent physical disability, it is important to understand how the ability to activate muscles changes during the early phases of recovery after injury. PMID:17097340

  19. Comparison of muscles activity of abled bodied and amputee subjects for around shoulder movement.

    Science.gov (United States)

    Kaur, Amanpreet; Agarwal, Ravinder; Kumar, Amod

    2016-05-12

    Worldwide, about 56% of the amputees are upper limb amputees. This research deals a method with two-channel surface electromyogram (SEMG) signal recorded from around shoulder to estimate the changes in muscle activity in non-amputee and the residual limb of trans humeral amputees with different movements of arm. Identification of different muscles activity of near shoulder amputee and non-amputee persons. SEMG signal were acquired during three distinct exercises from three-selected muscles location around shoulder. The participants were asked to move their dominant arm from an assigned position to record their muscles activity recorded with change in position. Results shows the muscles activity in scalene is more than the other muscles like pectoralis and infraspinatus with the same shoulder motion. In addition, STFT (Short-Time Fourier Transform) spectrogram with window length of 256 samples at maximum of 512 frequency bins using hamming window has used to identify the signal for the maximum muscles activity with best resolution in spectrum plot. The results suggest that one can use this analysis for making a suitable device for around shoulder prosthetic users based on muscles activation of amputee persons.

  20. [Mechanical stimulation of soles' support zones: non-invasive method of activation of generators of stepping movements in man].

    Science.gov (United States)

    Tomilovskaia, E S; Moshonkina, T R; Gorodnichev, R M; Shigueva, T A; Zakirova, A Z; Pivovarova, E A; Savokhin, A A; Selionov, V A; Semenov, Iu S; Brevnov, V V; Kitov, V V; Gerasimenko, Iu P; Kozlovskaia, I B

    2013-01-01

    The effects of mechanical stimulation of the soles' support zones in regimens of slow and fastwalking (75 and 120 steps per minute) were studied using the model of supportlessness (legs suspension). 20 healthy subjects participated in the study. EMG activity of hip and shin muscles was recorded. Kinematic of leg movements was assessed with the use of videoanalysis system. Support stimulation was followed by leg movements in 80% of cases, in 53% it was a locomotion-like movement. EMG bursts accompanied the movements. Involvement order and alteration of bursts in muscles were similar to voluntary walking. EMG activity occurred with a delay of 5.17 ± 1.08 seconds for hip muscles and 14.01 ± 2.82 seconds for shin muscles, frequency of bursts differed from stimulation frequency. Support stimulation was followed by leg movements in 80% of cases, in 53% of which they had characteristics of locomotions being accompanied by the burst-like electromyographic activities. Involvement order of the leg muscles and organization of antagonistic muscles activities were analogous to that of voluntary walking. The latencies of electromyographic activity in hip muscles composed 5.17 ± 1.083 s and 14.01 ± 2.82 s - for shin muscles, frequency of bursts differed significantly from stimulation frequency. In 31% of cases the electromyographical activity following the stimulation of the soles' support zones was not burst-like. Its amplitude rose smoothly reaching a certain level that was subsequently maintained. Results of the study showed that soles' support zones stimulation in regimen of locomotion can activate a locomotor generator and that effect evoked by this stimulation includes not only rhythmical but also non-rhythmical (probably postural) components of walking.

  1. Optogenetic Activation of the Sublaterodorsal (SLD) Nucleus Induces Rapid Muscle Inhibition

    Science.gov (United States)

    2015-09-01

    Optogenetic Activation of the Sublaterodorsal (SLD) Nucleus Induces Rapid Muscle Inhibition 5a. CONTRACT NUMBER 1120-1120-99 5b. GRANT NUMBER 5c...eye movement (NREM/REM) sleep, involves rapid state changes that are physiologically distinct in their impact on sensory perception, muscle tone... Muscle Inhibition prepared by Cameron H Good ORISE 4502 Darlington St, Aberdeen Proving Ground, Maryland Thomas Jhou and Nathan Burnham

  2. Comparing trapezius muscle activity in the different planes of shoulder elevation.

    Science.gov (United States)

    Ishigaki, Tomonobu; Ishida, Tomoya; Samukawa, Mina; Saito, Hiroshi; Hirokawa, Motoki; Ezawa, Yuya; Sugawara, Makoto; Tohyama, Harukazu; Yamanaka, Masanori

    2015-05-01

    [Purpose] The purpose of this study was to compare the upper, middle, and lower trapezius muscles' activity in the different planes of shoulder elevation. [Subjects] Twenty male subjects volunteered for this study. [Methods] Surface electromyographic (EMG) activity for each of the three regions of the trapezius muscles in the three different planes of elevation were collected while the participants maintained 30, 60, and 90 degrees of elevation in each plane. The EMG data were normalized with maximum voluntary isometric contraction (%MVIC), and compared among the planes at each angle of elevation. [Results] There were significantly different muscle activities among the elevation planes at each angle. [Conclusion] This study found that the three regions of the trapezius muscles changed their activity depending on the planes of shoulder elevation. These changes in the trapezius muscles could induce appropriate scapular motion to face the glenoid cavity in the correct directions in different planes of shoulder elevation.

  3. Nitric oxide and Na,K-ATPase activity in rat skeletal muscle

    DEFF Research Database (Denmark)

    Juel, Carsten

    2016-01-01

    Aim: It has been suggested that nitric oxide (NO) stimulates the Na,K-ATPase in cardiac myocytes. Therefore, the aims of this study were to investigate whether NO increases Na,K-ATPase activity in skeletal muscle and, if that is the case, to identify the underlying mechanism. Method: The study used...... activity was depressed by oxidized glutathione. Conclusion: NO and cGMP stimulate the Na,K-ATPase in glycolytic skeletal muscle. Direct S-nitrosylation and interference with S-glutathionylation seem to be excluded. In addition, phosphorylation of phospholemman at serine 68 is not involved. Most likely...... isolated rat muscle, muscle homogenates and purified membranes as model systems. Na,K-ATPase activity was quantified from phosphate release due to ATP hydrolysis. Results: Exposure to the NO donor spermine NONOate (10 μm) increased the maximal Na,K-ATPase activity by 27% in isolated glycolytic muscles...

  4. Force enhancement during and following muscle stretch of maximal voluntarily activated human quadriceps femoris.

    Science.gov (United States)

    Hahn, Daniel; Seiberl, Wolfgang; Schwirtz, Ansgar

    2007-08-01

    Force enhancement during and following muscle stretch has been observed for electrically and voluntarily activated human muscle. However, especially for voluntary contractions, the latter observation has only been made for adductor pollicis and the ankle joint muscles, but not for large muscles like quadriceps femoris. Therefore, the aim of this study was to investigate the effects of active muscle stretch on force production for maximal voluntary contractions of in vivo human quadriceps femoris (n = 15). Peak torques during and torques at the end of stretch, torques following stretch, and passive torques following muscle deactivation were compared to the isometric torques at corresponding muscle length. In addition, muscle activation of rectus femoris, vastus medialis and vastus lateralis was obtained using surface EMG. Stretches with different amplitudes (15, 25 and 35 degrees at a velocity of 60 degrees s(-1)) were performed on the plateau region and the descending limb of the force-length relation in a random order. Data analysis showed four main results: (1) peak torques did not occur at the end of the stretch, but torques at the end of the stretch exceeded the corresponding isometric torque; (2) there was no significant force enhancement following muscle stretch, but a small significant passive force enhancement persisted for all stretch conditions; (3) forces during and following stretch were independent of stretch amplitude; (4) muscle activation during and following muscle stretch was significantly reduced. In conclusion, although our results showed passive force enhancement, we could not provide direct evidence that there is active force enhancement in voluntarily activated human quadriceps femoris.

  5. Application of Pilates principles increases paraspinal muscle activation.

    Science.gov (United States)

    Andrade, Letícia Souza; Mochizuki, Luís; Pires, Flávio Oliveira; da Silva, Renato André Sousa; Mota, Yomara Lima

    2015-01-01

    To analyze the effect of Pilates principles on the EMG activity of abdominal and paraspinal muscles on stable and unstable surfaces. Surface EMG data about the rectus abdominis (RA), iliocostalis (IL) and lumbar multifidus (MU) of 19 participants were collected while performing three repetitions of a crunch exercise in the following conditions: 1) with no Pilates technique and stable surface (nP + S); 2) with no Pilates technique and unstable surface (nP + U); 3) with Pilates technique and stable surface (P + S); 4) with Pilates and unstable surface (P + U). The EMG Fanalysis was conducted using a custom-made Matlab(®) 10. There was no condition effect in the RA iEMG with stable and unstable surfaces (F(1,290) = 0 p = 0.98) and with and without principles (F(1,290) = 1.2 p = 0.27). IL iEMG was higher for the stable surface condition (F(1,290) = 32.3 p Pilates principles (F(1,290) = 21.9 p Pilates principles (F(1,290) = 84.9 p < 0.001). Copyright © 2014 Elsevier Ltd. All rights reserved.

  6. Muscle relaxant and neurotoxic activities of intrathecal baclofen in rats.

    Science.gov (United States)

    Kuroiwa, Miho; Kitano, Yutaka; Takasuna, Kiyoshi; Manabe, Sunao; Saito, Takao

    2009-11-01

    Intrathecal baclofen therapy by the continuous intrathecal infusion of baclofen has been shown to be an effective treatment for spasticity in patients with spinal cord injury, cerebral palsy, traumatic brain injury, multiple sclerosis and other disorders. To demonstrate the efficacy and safety of intrathecal baclofen therapy, we investigated the muscle relaxant and neurotoxic activities of intrathecal baclofen in rats, compared with intravenous baclofen. Intrathecal and intravenous administration of baclofen dose-dependently inhibited the anemic decerebrate rigidity with ED(50) values of 0.31microg/animal (=1.1-1.3microg/kg) and 0.43mg/kg, respectively. Intrathecal administration of baclofen induced no noticeable changes in a spontaneous electroencephalogram at 30microg/animal. Intravenous administration of baclofen induced an abnormal electroencephalogram with flat waves in all the animals and the no-observed-effect level was estimated to be 5mg/kg. In some animals, intravenous administration of baclofen induced sporadic spikes or sharp waves with background flat waves, indicating inhibitory and excitatory effects on the central nervous system. In conclusion, intrathecal administration of baclofen dose-dependently inhibited anemic decerebrate rigidity in rats and the effective dose was more than 300 times lower than that of intravenous baclofen. The safety margin of intrathecal baclofen was greater than that of intravenous baclofen (> or =97 versus 12). These results suggest that intrathecal baclofen therapy is superior to systemic baclofen therapy in both efficacy and safety.

  7. Arterial Myogenic Activation through Smooth Muscle Filamin A

    Directory of Open Access Journals (Sweden)

    Kevin Retailleau

    2016-03-01

    Full Text Available Mutations in the filamin A (FlnA gene are frequently associated with severe arterial abnormalities, although the physiological role for this cytoskeletal element remains poorly understood in vascular cells. We used a conditional mouse model to selectively delete FlnA in smooth muscle (sm cells at the adult stage, thus avoiding the developmental effects of the knockout. Basal blood pressure was significantly reduced in conscious smFlnA knockout mice. Remarkably, pressure-dependent tone of the resistance caudal artery was lost, whereas reactivity to vasoconstrictors was preserved. Impairment of the myogenic behavior was correlated with a lack of calcium influx in arterial myocytes upon an increase in intraluminal pressure. Notably, the stretch activation of CaV1.2 was blunted in the absence of smFlnA. In conclusion, FlnA is a critical upstream element of the signaling cascade underlying the myogenic tone. These findings allow a better understanding of the molecular basis of arterial autoregulation and associated disease states.

  8. Active pauses induce more variable electromyographic pattern of the trapezius muscle activity during computer work

    DEFF Research Database (Denmark)

    Samani, Afshin; Holtermann, Andreas; Søgaard, Karen

    2009-01-01

    , with passive (relax) and active (30% maximum voluntary contraction of shoulder elevation) pauses given every 2 min at two different work paces (low/high). Bipolar SEMG from four parts of the trapezius muscle was recorded. The relative rest time was higher for the lower parts compared with the upper......The aim of this laboratory study was to evaluate effects of active and passive pauses and investigate the distribution of the trapezius surface electromyographic (SEMG) activity during computer mouse work. Twelve healthy male subjects performed four sessions of computer work for 10 min in one day...... of the trapezius (pactive pause compared with passive one (p

  9. [Cellular mechanism of the generation of spontaneous activity in gastric muscle].

    Science.gov (United States)

    Nakamura, Eri; Kito, Yoshihiko; Fukuta, Hiroyasu; Yanai, Yoshimasa; Hashitani, Hikaru; Yamamoto, Yoshimichi; Suzuki, Hikaru

    2004-03-01

    In gastric smooth muscles, interstitial cells of Cajal (ICC) might be the pacemaker cells of spontaneous activities since ICC are rich in mitochondria and are connected with smooth muscle cells via gap junctions. Several types of ICC are distributed widely in the stomach wall. A group of ICC distributed in the myenteric layer (ICC-MY) were the pacemaker cells of gastrointestinal smooth muscles. Pacemaker potentials were generated in ICC-MY, and the potentials were conducted to circular smooth muscles to trigger slow waves and also conducted to longitudinal muscles to form follower potentials. In circular muscle preparations, interstitial cells distributed within muscle bundles (ICC-IM) produced unitary potentials, which were conducted to circular muscles to form slow potentials by summation. In mutant mice lacking inositol trisphosphate (IP(3)) receptor, slow waves were absent in gastric smooth muscles. The generation of spontaneous activity was impaired by the inhibition of Ca(2+)-release from internal stores through IP(3) receptors, inhibition of mitochondrial Ca(2+)-handling with proton pump inhibitors, and inhibition of ATP-sensitive K(+)-channels at the mitochondrial inner membrane. These results suggested that mitochondrial Ca(2+)-handling causes the generation of spontaneous activity in pacemaker cells. Possible involvement of protein kinase C (PKC) in the Ca(2+) signaling system was also suggested.

  10. Superficial shoulder muscle co-activations during lifting tasks: Influence of lifting height, weight and phase.

    Science.gov (United States)

    Blache, Y; Dal Maso, F; Desmoulins, L; Plamondon, A; Begon, M

    2015-04-01

    This study aimed to assess the level of co-activation of the superficial shoulder muscles during lifting movement. Boxes containing three different loads (6, 12, and 18 kg) were lifted by fourteen subjects from the waist to shoulder or eye level. The 3D kinematics and electromyograms of the three deltoids, latissimus dorsi and pectoralis major were recorded. A musculoskeletal model was used to determine direction of the moment arm of these muscles. Finally an index of muscle co-activation named the muscle focus was used to evaluate the effects of lifting height, weight lifted and phase (pulling, lifting and dropping phases) on superficial shoulder muscle coactivation. The muscle focus was lower (more co-contraction) during the dropping phase compared to the two other phases (-13%, pmuscle activations and by a change in the direction of the muscle moment arm as a function of glenohumeral joint position. Consequently, the function of the shoulder superficial muscles varied with respect to the glenohumeral joint position. To increase the superficial muscle coactivation during the dropping phase may be a solution to increase glenohumeral joint stiffness. Copyright © 2014 Elsevier Ltd. All rights reserved.

  11. Muscle activation during four Pilates core stability exercises in quadruped position.

    Science.gov (United States)

    Queiroz, Bergson C; Cagliari, Mariana F; Amorim, César F; Sacco, Isabel C

    2010-01-01

    Queiroz BC, Cagliari MF, Amorim CF, Sacco IC. Muscle activation during four Pilates core stability exercises in quadruped position. To compare the activity of stabilizing trunk and hip muscles in 4 variations of Pilates stabilizing exercises in the quadruped position. Repeated-measures descriptive study. A biomechanics laboratory at a university school of medicine. Healthy subjects (N=19; mean age +/- SD, 31+/-5y; mean weight +/- SD, 60+/-11kg; mean height +/- SD, 166+/-9cm) experienced in Pilates routines. Surface electromyographic signals of iliocostalis, multifidus, gluteus maximus, rectus abdominis, and external and internal oblique muscles were recorded in 4 knee stretch exercises: retroverted pelvis with flexed trunk; anteverted pelvis with extended trunk; neutral pelvis with inclined trunk; and neutral pelvis with trunk parallel to the ground. Root mean square values of each muscle and exercise in both phases of hip extension and flexion, normalized by the maximal voluntary isometric contraction. The retroverted pelvis with flexed trunk position led to significantly increased external oblique and gluteus maximus muscle activation. The anteverted pelvis with trunk extension significantly increased multifidus muscle activity. The neutral pelvis position led to significantly lower activity of all muscles. Rectus abdominis muscle activation to maintain body posture was similar in all exercises and was not influenced by position of the pelvis and trunk. Variations in the pelvic and trunk positions in the knee stretch exercises change the activation pattern of the multifidus, gluteus maximus, rectus abdominis, and oblique muscles. The lower level of activation of the rectus abdominis muscle suggests that pelvic stability is maintained in the 4 exercise positions. Copyright (c) 2010 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

  12. Oral glucose ingestion attenuates exercise-induced activation of 5'-AMP-activated protein kinase in human skeletal muscle

    DEFF Research Database (Denmark)

    Åkerström, Thorbjörn; Birk, Jesper Bratz; Klein, Ditte Kjærsgaard

    2006-01-01

    5'-AMP-activated protein kinase (AMPK) has been suggested to be a 'metabolic master switch' regulating various aspects of muscle glucose and fat metabolism. In isolated rat skeletal muscle, glucose suppresses the activity of AMPK and in human muscle glycogen loading decreases exercise-induced AMPK...... activation. We hypothesized that oral glucose ingestion during exercise would attenuate muscle AMPK activation. Nine male subjects performed two bouts of one-legged knee-extensor exercise at 60% of maximal workload. The subjects were randomly assigned to either consume a glucose containing drink or a placebo...... drink during the two trials. Muscle biopsies were taken from the vastus lateralis before and after 2 h of exercise. Plasma glucose was higher (6.0 +/- 0.2 vs. 4.9 +/- 0.1 mmol L-1, P

  13. Arm movements can increase leg muscle activity during submaximal recumbent stepping in neurologically intact individuals.

    Science.gov (United States)

    de Kam, Digna; Rijken, Hennie; Manintveld, Toos; Nienhuis, Bart; Dietz, Volker; Duysens, Jacques

    2013-07-01

    Facilitation of leg muscle activity by active arm movements during locomotor tasks could be beneficial during gait rehabilitation after spinal cord injury. The present study explored the effects of arm movements on leg muscle activity during submaximal recumbent stepping. Healthy subjects exercised on a recumbent stepping machine both with and without arm movements. Activity of five leg muscles was recorded and compared for stepping with and without arm movements. To determine which arm movements are optimal for leg muscle facilitation, subjects were instructed to step with 1) mechanically coupled vs. decoupled arm and leg movements, 2) synchronous vs. asynchronous arm movements, and 3) at 50 vs. 70 RPM. Leg muscle activity was increased by active arm movements in all muscles, except the vastus lateralis muscle. Activity of other extensors (soleus, medial gastrocnemius, and biceps femoris) was primarily increased during the extension phase, whereas activity of flexors (tibialis anterior) was also increased during the flexion phase. Facilitation was more or less consistent for both frequencies and for synchronous and asynchronous movements. For coupled arm movements, facilitation tended to be diminished or absent. The observed facilitation in the present study is probably of neuromuscular rather than biomechanical origin, since the arms are probably hardly involved in postural control or weight-bearing during recumbent stepping. Further studies in patients should explore the possibility to integrate neuromuscular facilitation in rehabilitation programs.

  14. PPARβ/δ regulates glucocorticoid- and sepsis-induced FOXO1 activation and muscle wasting.

    Directory of Open Access Journals (Sweden)

    Estibaliz Castillero

    Full Text Available FOXO1 is involved in glucocorticoid- and sepsis-induced muscle wasting, in part reflecting regulation of atrogin-1 and MuRF1. Mechanisms influencing FOXO1 expression in muscle wasting are poorly understood. We hypothesized that the transcription factor peroxisome proliferator-activated receptor β/δ (PPARβ/δ upregulates muscle FOXO1 expression and activity with a downstream upregulation of atrogin-1 and MuRF1 expression during sepsis and glucocorticoid treatment and that inhibition of PPARβ/δ activity can prevent muscle wasting. We found that activation of PPARβ/δ in cultured myotubes increased FOXO1 activity, atrogin-1 and MuRF1 expression, protein degradation and myotube atrophy. Treatment of myotubes with dexamethasone increased PPARβ/δ expression and activity. Dexamethasone-induced FOXO1 activation and atrogin-1 and MuRF1 expression, protein degradation, and myotube atrophy were inhibited by PPARβ/δ blocker or siRNA. Importantly, muscle wasting induced in rats by dexamethasone or sepsis was prevented by treatment with a PPARβ/δ inhibitor. The present results suggest that PPARβ/δ regulates FOXO1 activation in glucocorticoid- and sepsis-induced muscle wasting and that treatment with a PPARβ/δ inhibitor may ameliorate loss of muscle mass in these conditions.

  15. Effects of experimental nasal obstruction on human masseter and suprahyoid muscle activities during sleep.

    Science.gov (United States)

    Hiyama, Shigetoshi; Ono, Takashi; Ishiwata, Yasuo; Kuroda, Takayuki; Ohyama, Kimie

    2003-04-01

    The effect of nasal obstruction on nocturnal masseter and suprahyoid muscle activities using a newly developed portable electromygram (EMG)-recording unit was examined. Ten healthy Japanese males participated in this study. EMG activities of both the right masseter and bilateral suprahyoid muscles were recorded with a portable EMG-recording unit. At midnight, the subject was asked to lie on a bed after complete preparation with surface electrodes. After maximal clenching and jaw-opening effort (100% maximum voluntary contribution), the subject was allowed to fall asleep. In the first half of the night, EMG activities were recorded for about three hours of sleep without nasal obstruction. In the second half of the night, EMG activities were recorded for about three hours of sleep with nasal obstruction. In both muscles, there were no significant changes in either the maximal EMG activities or the number of events beyond 40% MVC with nasal obstruction. But in an evaluation based on the distribution of muscle activities, the EMG activity of the masseter muscle tended to decrease (P = .07) and that of the suprahyoid muscles increased significantly (P = .02) with nasal obstruction. These results suggest that nasal obstruction could modulate the activities of the masseter and suprahyoid muscles during sleep.

  16. The variability of co-activation pattern of antagonist muscles in human infant crawling.

    Science.gov (United States)

    Xiong, Qi L; Wu, Xiao Y; Nong Xiao; Zeng, Si Y; Zheng, Xiao L; Di Wu; Hou, Wen S

    2016-08-01

    Infant crawling is part of normal human gross motor development, and a 4-beat gait that involves rhythmical flexion and extension of limbs and the underlying muscle co-activation of antagonist muscle around the joint. However, detection the co-activation pattern of antagonist muscle are sparse due to the general difficulty of measuring locomotion in human infants. In this paper, sEMG of antagonist muscles and the corresponding kinematics data of limbs were collected when infants were crawling on hands and knees at their self-selected speed. The infant's gross motor developmental status was assessed by the global Gross Motor Function Measure Scale (GMFM-88) as well. The method based on EMG-EMG plots was used to quantify the variability of co-activation pattern of antagonist muscle. After that, we observed that antagonist muscles of upper limb (triceps brachii and biceps brachii) showed less variability of co-activation pattern of muscles than lower limb(quadriceps femoris and hamstrings) during crawling, and this variability was also varied in different crawling phases (stance and swing). Furthermore, we found some varied behaviors in the co-activation patterns of antagonist muscles when gross motor developmental level increased. The preliminary work suggests that such adaptive changes may be related to the adjustment of neuromuscular in the early stage of gross motor development.

  17. Does posture of the cervical spine influence dorsal neck muscle activity when lifting?

    Science.gov (United States)

    Peolsson, Anneli; Marstein, Eivind; McNamara, Timothy; Nolan, Damien; Sjaaberg, Espen; Peolsson, Michael; Jull, Gwendolen; O'Leary, Shaun

    2014-02-01

    Previous studies have shown that postural orientations of the neck, such as flexed or forward head postures, are associated with heightened activity of the dorsal neck muscles. While these studies describe the impact of variations in neck posture alone, there is scant literature regarding the effect of neck posture on muscle activity when combined with upper limb activities such as lifting. The purpose of this study was to evaluate the effect of three different neck postures on the activity of the different layers of the dorsal neck muscles during a lifting task. Ultrasound measurements of dorsal neck muscle deformation were compared over two time points (rest, during lift) during a lifting task performed in three different neck postural conditions (neutral, flexed and forward head posture) in 21 healthy subjects. Data were analysed by post-process speckle tracking analysis. Results demonstrated significantly greater muscle deformation induced by flexed and forward head postures, compared to the neutral posture, for all dorsal neck muscles at rest (pposture of the cervical spine influenced the level of muscle deformation not only at rest, but also when lifting. The findings of the study suggest that neck posture should be considered during the evaluation or design of lifting activities as it may contribute to excessive demands on dorsal neck muscles with potential detrimental consequences. Copyright © 2013 Elsevier Ltd. All rights reserved.

  18. Muscle cells challenged with saturated fatty acids mount an autonomous inflammatory response that activates macrophages

    Directory of Open Access Journals (Sweden)

    Pillon Nicolas J

    2012-10-01

    Full Text Available Abstract Obesity is associated with chronic low-grade inflammation. Within adipose tissue of mice fed a high fat diet, resident and infiltrating macrophages assume a pro-inflammatory phenotype characterized by the production of cytokines which in turn impact on the surrounding tissue. However, inflammation is not restricted to adipose tissue and high fat-feeding is responsible for a significant increase in pro-inflammatory cytokine expression in muscle. Although skeletal muscle is the major disposer of dietary glucose and a major determinant of glycemia, the origin and consequence of muscle inflammation in the development of insulin resistance are poorly understood. We used a cell culture approach to investigate the vectorial crosstalk between muscle cells and macrophages upon exposure to physiological, low levels of saturated and unsaturated fatty acids. Inflammatory pathway activation and cytokine expression were analyzed in L6 muscle cells expressing myc-tagged GLUT4 (L6GLUT4myc exposed to 0.2 mM palmitate or palmitoleate. Conditioned media thereof, free of fatty acids, were then tested for their ability to activate RAW264.7 macrophages. Palmitate -but not palmitoleate- induced IL-6, TNFα and CCL2 expression in muscle cells, through activation of the NF-κB pathway. Palmitate (0.2 mM alone did not induce insulin resistance in muscle cells, yet conditioned media from palmitate-challenged muscle cells selectively activated macrophages towards a pro-inflammatory phenotype. These results demonstrate that low concentrations of palmitate activate autonomous inflammation in muscle cells to release factors that turn macrophages pro-inflammatory. We hypothesize that saturated fat-induced, low-grade muscle cell inflammation may trigger resident skeletal muscle macrophage polarization, possibly contributing to insulin resistance in vivo.

  19. Passive muscle stiffness may be influenced by active contractility of intramuscular connective tissue.

    Science.gov (United States)

    Schleip, Robert; Naylor, Ian L; Ursu, Daniel; Melzer, Werner; Zorn, Adjo; Wilke, Hans-Joachim; Lehmann-Horn, Frank; Klingler, Werner

    2006-01-01

    The article introduces the hypothesis that intramuscular connective tissue, in particular the fascial layer known as the perimysium, may be capable of active contraction and consequently influence passive muscle stiffness, especially in tonic muscles. Passive muscle stiffness is also referred to as passive elasticity, passive muscular compliance, passive extensibility, resting tension, or passive muscle tone. Evidence for the hypothesis is based on five indications: (1) tonic muscles contain more perimysium and are therefore stiffer than phasic muscles; (2) the specific collagen arrangement of the perimysium is designed to fit a load-bearing function; (3) morphological considerations as well as histological observations in our laboratory suggest that the perimysium is characterized by a high density of myofibroblasts, a class of fibroblasts with smooth muscle-like contractile kinetics; (4) in vitro contraction tests with fascia have demonstrated that fascia, due to the presence of myofibroblasts, is able to actively contract, and that the resulting contraction forces may be strong enough to influence musculoskeletal dynamics; (5) the pronounced increase of the perimysium in muscle immobilization and in the surgical treatment of distraction osteogenesis indicates that perimysial stiffness adapts to mechanical stimulation and hence influences passive muscle stiffness. In conclusion, the perimysium seems capable of response to mechanostimulation with a myofibroblast facilitated active tissue contraction, thereby adapting passive muscle stiffness to increased tensional demands, especially in tonic musculature. If verified, this new concept may lead to novel pharmaceutical or mechanical approaches to complement existing treatments of pathologies which are accompanied by an increase or decrease of passive muscle stiffness (e.g., muscle fibroses such as torticollis, peri-partum pelvic pain due to pelvic instability, and many others). Methods for testing this new concept

  20. The Effect of Plyometric Training on Trunk Muscle Pre-activation in Active Females with Trunk Neuromuscular Control Deficit

    Directory of Open Access Journals (Sweden)

    M Hadadnezhad

    2014-02-01

    Results: the results of independent sample T-test indicated that there are significant differences between post-test of control and experimental groups in regard to Gluteus Medius (p=0.021, Quadratus Lumborum (p=0.011, Transverse Abdominis/Internal oblique (p=0.006, External Oblique (p=0.023 muscles activations which reveals effectiveness of plyometric training on pre-activation of muscles. Conclusion: Based on the study results, plyometric training affects the activation of muscles and thus improving the pre-activation can prevent mechanisms related to anterior cruciate ligament injury. Therefore, plyometric training can reduce incidence of anterior cruciate ligament injury.

  1. Muscle activation during selected strength exercises in women with chronic neck muscle pain

    DEFF Research Database (Denmark)

    Andersen, L.L.; Kjaer, M.; Andersen, C.H.

    2008-01-01

    ) (luring selected strengthening exercises in women undergoing rehabilitation for chronic neck muscle pain (defined as a clinical diagnosis of trapezins myalgia). Subjects. The subjects were 12 female workers (age = 30-60 years) with a clinical diagnosis of trapezius myalgia and a mean baseline pain...

  2. Muscle activation during selected strength exercises in women with chronic neck muscle pain

    DEFF Research Database (Denmark)

    Andersen, Lars L; Kjaer, Michael; Andersen, Christoffer H

    2008-01-01

    selected strengthening exercises in women undergoing rehabilitation for chronic neck muscle pain (defined as a clinical diagnosis of trapezius myalgia). SUBJECTS: The subjects were 12 female workers (age=30-60 years) with a clinical diagnosis of trapezius myalgia and a mean baseline pain intensity of 5...

  3. An Acute Bout of Barefoot Running Alters Lower-limb Muscle Activation for Minimalist Shoe Users.

    Science.gov (United States)

    Snow, N J; Basset, F A; Byrne, J

    2016-05-01

    Despite the abundance of barefoot running-related research, there have been no electromyography studies evaluating the effects of this mode of exercise on habitual users of minimalist footwear. The present study investigated differences in muscle activation during acute bouts of barefoot and shod running, in minimalist shoe users. 8 male participants ran on a motorized treadmill for 10 min under both conditions, at 70% maximal aerobic speed. Electromyographic data were sampled from the biceps femoris, gluteus maximus, gastrocnemius medialis, tibialis anterior, and vastus lateralis during both swing and stance. Root-mean-square analysis of electromyographic data was conducted to compare muscle activation between conditions. During stance, barefoot running resulted in greater muscle activity in gastrocnemius medialis and gluteus maximus, and lower muscle activity in tibialis anterior. During swing, barefoot running resulted in increased muscle activity in vastus lateralis and gastrocnemius medialus. These results indicate that, for minimalist shoe users, an acute bout of barefoot running results in significantly different lower-limb muscle activity. Increased activation in the above muscles presents a possible mechanism for injury, which should be considered during exercise prescription.

  4. Muscles Activity in the elderly with Balance Impairments in walking under Dual tasks

    Directory of Open Access Journals (Sweden)

    Elaheh Azadian

    2016-09-01

    Full Text Available Objectives: Each step during gait requires different attention demands that will affect muscles activity. The study of changes in the timing and intensity of the muscles activity in walking with dual task has received less attention from researchers. The purpose of this study was to evaluate changes in electromyography patterns of gait with cognitive dual tasks in balance impaired elderly. Methods: Thirty older adults were recruited for this study. People were selected through berg balance test. Subjects walked 12-meters in two conditions, normal walking and walking with a cognitive dual task. Spatial-temporal kinematic parameters were recorded through the motion analysis and muscles activities were recorded through electromyography system. The data obtained was analyzed using repeated measures ANOVA at a significant level of p< 0.05.  Results: The results showed that walking under dual tasks would decrease gait speed and increase stride time and stance time. Also muscle activity in Tibialis anterior and Vastus lateralis in stance-phase would decrease significantly in dual tasks as compared with single task (p< 0.05, but timing of muscle activity would not change in dual task conditions.  Conclusions: Based on the results, it can be argued that walking under a dual task can change spatial-temporal parameters and muscle activity in gait pattern in the elderly with balance impairment. One explanation could be that the decreased control of the central nervous system on muscle activity in stance phase due to the performing of a dual task.

  5. Rapid knee-extensions to increase quadriceps muscle activity in patients with total knee arthroplasty

    DEFF Research Database (Denmark)

    Husted, Rasmus Skov; Wilquin, Lousia; Jakobsen, Thomas Linding

    2017-01-01

    BACKGROUND: Inhibition of the quadriceps muscle and reduced knee-extension strength is common shortly following total knee arthroplasty (weeks to months), due to reduced voluntary activation of the quadriceps muscle. In healthy subjects, strength training with heavy loads is known to increase...... agonist muscle activity, especially if the exercise is conducted using rapid muscle contractions. PURPOSE: The purpose of this study was to examine if patients with total knee arthroplasty could perform rapid knee-extensions using a 10 RM load four to eight weeks after surgery, and the degree to which...... rapid knee-extensions were associated with greater voluntary quadriceps muscle activity during an experimental strength training session, compared to that elicited using slow knee-extensions. STUDY DESIGN: A randomized cross-over study. METHODS: Twenty-four patients (age 66.5) 4-8 weeks post total knee...

  6. Is fast fiber innervation responsible for increased acetylcholinesterase activity in reinnervating soleus muscles?

    Science.gov (United States)

    Misulis, K. E.; Dettbarn, W. D.

    1985-01-01

    An investigation was conducted as to whether the predominantly slow SOL, which is low in AChE activity, is initially reinnervated by axons that originally innervated fast muscle fibers with high AChE activity, such as those of the EDL. Local denervation of the SOL in the guinea pig was performed because this muscle is composed solely of slow (type I) fibers; thereby virtually eliminating the possibility of homologous muscle fast fiber innervation. The overshoot in this preparation was qualitatively similar to that seen with distal denervation in the guinea pig and local and distal denervation in the rat. Thus, initial fast fiber innvervation is not responsible for the patterns of change in AChE activity seen with reinnervation in the SOL. It is concluded that the neural control of AChe is different in these two muscles and may reflect specific differences in the characteristics of AChE regulation in fast and slow muscle.

  7. Gene expression profiling of porcine skeletal muscle in the early recovery phase following acute physical activity

    DEFF Research Database (Denmark)

    Hansen, Jeanette; Conley, Lene; Hedegaard, Jakob

    2012-01-01

    of unaccustomed exercise on global transcriptional profiles in porcine skeletal muscles. Using a combined microarray and candidate gene approach, we identified a suite of genes that are differentially expressed in muscles during postexercise recovery. Several members of the heat shock protein family and proteins...... of adenosine-to-inosine edited mRNAs in the ribonucleoprotein bodies called paraspeckles. These findings expand the complexity of pathways affected by acute contractile activity of skeletal muscle, contributing to a better understanding of the molecular processes that occur in muscle tissue in the recovery...

  8. Contraction-induced muscle fiber damage is increased in soleus muscle of streptozotocin-diabetic rats and is associated with elevated expression of brain-derived neurotrophic factor mRNA in muscle fibers and activated satellite cells

    NARCIS (Netherlands)

    Copray, S; Liem, R; Brouwer, N; Greenhaff, P; Habens, F; Fernyhough, P

    The expression of brain-derived neurotrophic factor (BDNF) is elevated in the soleus muscle of streptozotocin-diabetic rats. To determine whether this diabetes-induced elevation was associated with or enhanced by muscle activity we have induced high-intensity muscle contraction by electrically

  9. Contraction-induced muscle fiber damage is increased in soleus muscle of streptozotocin-diabetic rats and is associated with elevated expression of brain-derived neurotrophic factor mRNA in muscle fibers and activated satellite cells

    NARCIS (Netherlands)

    Copray, S; Liem, R; Brouwer, N; Greenhaff, P; Habens, F; Fernyhough, P

    2000-01-01

    The expression of brain-derived neurotrophic factor (BDNF) is elevated in the soleus muscle of streptozotocin-diabetic rats. To determine whether this diabetes-induced elevation was associated with or enhanced by muscle activity we have induced high-intensity muscle contraction by electrically stimu

  10. p53 increases caspase-6 expression and activation in muscle tissue expressing mutant huntingtin

    DEFF Research Database (Denmark)

    Ehrnhoefer, Dagmar E; Skotte, Niels H; Ladha, Safia

    2014-01-01

    a role in the peripheral phenotypes, such as muscle wasting observed in HD. We assessed skeletal muscle tissue from HD patients and well-characterized mouse models of HD. Cleavage of the caspase-6 specific substrate lamin A is significantly increased in skeletal muscle obtained from HD patients as well...... as in muscle tissues from two different HD mouse models. p53, a transcriptional activator of caspase-6, is upregulated in neuronal cells and tissues expressing mutant huntingtin. Activation of p53 leads to a dramatic increase in levels of caspase-6 mRNA, caspase-6 activity and cleavage of lamin A. Using mouse......-6 expression and activation is exacerbated in cells and tissues of both neuronal and peripheral origin expressing mutant huntingtin (Htt). These findings suggest that the presence of the mutant Htt protein enhances p53 activity and lowers the apoptotic threshold, which activates caspase-6...

  11. Muscle activity during knee-extension strengthening exercise performed with elastic tubing and isotonic resistance

    DEFF Research Database (Denmark)

    Jakobsen, Markus Due; Sundstrup, Emil; Andersen, Christoffer H;

    2012-01-01

    While elastic resistance training, targeting the upper body is effective for strength training, the effect of elastic resistance training on lower body muscle activity remains questionable. The purpose of this study was to evaluate the EMG-angle relationship of the quadriceps muscle during 10-RM ...

  12. Submovement organization, pen pressure, and muscle activity are modulated to precision demands in 2D tracking

    NARCIS (Netherlands)

    Huysmans, M.A.; Hoozemans, M.J.M.; Beek, A.J. van der; Looze, M.P. de; Dien, J.H. van

    2012-01-01

    The authors investigated how tracking performance, submovement organization, pen pressure and muscle activity in forearm and shoulder muscles were affected by target size in a 2D tracking task performed with a pen on a digitizer tablet. Twenty-six subjects took part in an experiment, in which either

  13. Predominant alpha2/beta2/gamma3 AMPK activation during exercise in human skeletal muscle

    DEFF Research Database (Denmark)

    Birk, Jesper Bratz; Wojtaszewski, Jørgen

    2006-01-01

    5'AMP-activated protein kinase (AMPK) is a key regulator of cellular metabolism and is regulated in muscle during exercise. We have previously established that only three of 12 possible AMPK a/ß/¿-heterotrimers are present in human skeletal muscle. Previous studies describe discrepancies between ...

  14. Single Dose of Fluoxetine Increases Muscle Activation in Chronic Stroke Patients

    NARCIS (Netherlands)

    Genderen, van Hanneke Irene; Nijlant, Juliette M.M.; Putten, van Michel J.A.M; Movig, Kris L.L.; IJzerman, Maarten J.

    2009-01-01

    Objectives: This pilot study explores the influence of a single dose of fluoxetine (20 mg) on the muscle activation patterns and functional ability of the muscles in the lower part of the arm in chronic stroke patients. Methods: A crossover, placebo-controlled clinical trial was conducted in 10

  15. Circadian and individual variations in duration of spontaneous activity among ankle muscles of the cat

    NARCIS (Netherlands)

    Hensbergen, E; Kernell, D

    This article concerns the spontaneous motor behavior of cat hindlimb muscles and muscle regions using 24-h electromyographic (EMG) recordings. Previously, we found marked differences in average daily "duty time" (i.e., the percentage of total sampling time filled with EMG activity) between different

  16. Preliminary rapport on head posture and muscle activity in subjects with class I and II.

    Science.gov (United States)

    Gadotti, I C; Bérzin, F; Biasotto-Gonzalez, D

    2005-11-01

    Forward head posture may cause alterations in the stomatognathic system, including changes in the muscle activity of the masticatory muscles and dental occlusion alterations. Considering the need for further understanding of the relationship between the stomatognathic system and the cervical region, the purpose of this study was to analyse the head posture and the electromyographic (EMG) activity of the anterior portion of temporal and masseter muscles bilaterally among bruxist's subjects with different dental occlusion classifications using the Angle method. The study consisted of 20 female volunteers, between the ages of 17 and 27 years. They were separated into two groups (class I and class II occlusions) according to a dentist-performed evaluation. An assessment of forward head posture was conducted using a photographic technique (angular calculus) combined with a clinical analysis. In the EMG analyses, active differential surface electrodes (Ag) were utilized and were placed bilaterally on the belly of masseter and temporal muscles, perpendicular to the muscles fibres. The EMG signal recorded during bilateral isotonic mastication, was presented using the Root Mean Square and was processed by Matlab software. The results indicated that the EMG responses of temporal and masseter muscles tend to be modified by occlusion alteration class II. Subjects with class II occlusion tended to present more occurrence of forward head posture with alterations in the muscle activity pattern between masseter and temporal muscles.

  17. Troponin activator augments muscle force in nemaline myopathy patients with nebulin mutations.

    Science.gov (United States)

    de Winter, Josine Marieke; Buck, Danielle; Hidalgo, Carlos; Jasper, Jeffrey R; Malik, Fady I; Clarke, Nigel F; Stienen, Ger J M; Lawlor, Michael W; Beggs, Alan H; Ottenheijm, Coen A C; Granzier, Henk

    2013-06-01

    Nemaline myopathy-the most common non-dystrophic congenital myopathy-is caused by mutations in thin filament genes, of which the nebulin gene is the most frequently affected one. The nebulin gene codes for the giant sarcomeric protein nebulin, which plays a crucial role in skeletal muscle contractile performance. Muscle weakness is a hallmark feature of nemaline myopathy patients with nebulin mutations, and is caused by changes in contractile protein function, including a lower calcium-sensitivity of force generation. To date no therapy exists to treat muscle weakness in nemaline myopathy. Here, we studied the ability of the novel fast skeletal muscle troponin activator, CK-2066260, to augment force generation at submaximal calcium levels in muscle cells from nemaline myopathy patients with nebulin mutations. Contractile protein function was determined in permeabilised muscle cells isolated from frozen patient biopsies. The effect of 5 μM CK-2066260 on force production was assessed. Nebulin protein concentrations were severely reduced in muscle cells from these patients compared to controls, while myofibrillar ultrastructure was largely preserved. Both maximal active tension and the calcium-sensitivity of force generation were lower in patients compared to controls. Importantly, CK-2066260 greatly increased the calcium-sensitivity of force generation-without affecting the cooperativity of activation-in patients to levels that exceed those observed in untreated control muscle. Fast skeletal troponin activation is a therapeutic mechanism to augment contractile protein function in nemaline myopathy patients with nebulin mutations and with other neuromuscular diseases.

  18. RAPID KNEE-EXTENSIONS TO INCREASE QUADRICEPS MUSCLE ACTIVITY IN PATIENTS WITH TOTAL KNEE ARTHROPLASTY

    DEFF Research Database (Denmark)

    Husted, Rasmus Skov; Wilquin, Lousia; Jakobsen, Thomas Linding

    2017-01-01

    BACKGROUND: Inhibition of the quadriceps muscle and reduced knee-extension strength is common shortly following total knee arthroplasty (weeks to months), due to reduced voluntary activation of the quadriceps muscle. In healthy subjects, strength training with heavy loads is known to increase ago...

  19. Different ways to balance the spine: subtle changes in sagittal spinal curves affect regional muscle activity.

    Science.gov (United States)

    Claus, Andrew P; Hides, Julie A; Moseley, G Lorimer; Hodges, Paul W

    2009-03-15

    Exploratory study of regional muscle activity in different postures. To detail the relationship between spinal curves and regional muscle activity. Sagittal balanced spinal posture (C7 above S1 in the sagittal plane) is a goal for spinal surgery and conservative ergonomics. Three combinations of thoracolumbar and lumbar spinal curves can be considered sagittal balanced postures: (i) flat-at both regions, (ii) long lordosis-lordotic at both regions, and (iii) short lordosis-thoracic kyphosis and lumbar lordosis. This study compares regional muscle activity between these 3 sagittal balanced postures in sitting, as well as a slump posture. Fine-wire electromyography (EMG) electrodes were inserted into the lumbar multifidus (deep and superficial), iliocostalis (lateral and medial), longissimus thoracis, and transversus abdominis in 14 healthy male volunteers. Fine-wire or surface EMG electrodes were also used to record activity of the obliquus internus, obliquus externus, and rectus abdominis muscles. Root mean square EMG amplitude in the flat, long lordosis, short lordosis, and slump sitting postures were normalized to maximal voluntary contraction, and also to the peak activity across the sitting postures. Muscle activity was compared between postures with a linear mixed model analysis. Of the extensor muscles, it was most notable that activity of the deep and superficial fibers of lumbar multifidus increased incrementally in the 3 sagittal balanced postures; flat, long lordosis, and short lordosis (P sagittal balanced postures, the flat posture showed the least muscle activity (similar to the slump posture at most muscles examined). Discrete combinations of muscle activity supported the 3 different sagittal balanced postures in sitting, providing new detail for surgeons, researchers, and therapists to distinguish between different sagittal balanced postures.

  20. Kinesiology Taping does not Modify Electromyographic Activity or Muscle Flexibility of Quadriceps Femoris Muscle: A Randomized, Placebo-Controlled Pilot Study in Healthy Volleyball Players.

    Science.gov (United States)

    Halski, Tomasz; Dymarek, Robert; Ptaszkowski, Kuba; Słupska, Lucyna; Rajfur, Katarzyna; Rajfur, Joanna; Pasternok, Małgorzata; Smykla, Agnieszka; Taradaj, Jakub

    2015-08-01

    Kinesiology taping (KT) is a popular method of supporting professional athletes during sports activities, traumatic injury prevention, and physiotherapeutic procedures after a wide range of musculoskeletal injuries. The effectiveness of KT in muscle strength and motor units recruitment is still uncertain. The objective of this study was to assess the effect of KT on surface electromyographic (sEMG) activity and muscle flexibility of the rectus femoris (RF), vastus lateralis (VL), and vastus medialis (VM) muscles in healthy volleyball players. Twenty-two healthy volleyball players (8 men and 14 women) were included in the study and randomly assigned to 2 comparative groups: "kinesiology taping" (KT; n=12; age: 22.30 ± 1.88 years; BMI: 22.19 ± 4.00 kg/m(2)) in which KT application over the RF muscle was used, and "placebo taping" (PT; n=10; age: 21.50 ± 2.07 years; BMI: 22.74 ± 2.67 kg/m(2)) in which adhesive nonelastic tape over the same muscle was used. All subjects were analyzed for resting sEMG activity of the VL and VM muscles, resting and functional sEMG activity of RF muscle, and muscle flexibility of RF muscle. No significant differences in muscle flexibility of the RF muscle and sEMG activity of the RF, VL, and VM muscles were registered before and after interventions in both groups, and between the KT and PT groups (p>0.05). The results show that application of the KT to the RF muscle is not useful to improve sEMG activity.

  1. Determination of the Timing and Level of Activities of Lumbopelvic Muscles in Response to Postural Perturbations

    Directory of Open Access Journals (Sweden)

    S Ebrahimi Takamjani

    2005-05-01

    Full Text Available Background: One of the most important concerns in orthopedic medicine is the low back. Considering the importance of muscle function in preventing LBT by controlling too much load and stress applied on the spinal joints and ligaments. Materials and Methods: The aim of this research was to determine the timing and level of activities of lumbopelvic muscles in response to postural perturbations caused by unexpected loading of the upper limbs in standing on three different supporting surfaces (neutral, positive slope, negative slope in 20 healthy females 18 to 30 years old ( = 23.20 SD = 2.55 . The electromyographic signals were recorded from the deltoid, gluteus maximus, internal oblique abdominis and lumbar paraspinal muscles of the dominant side of the body to evaluate the onset time, end time, level of muscle activity (RMS and duration of different muscles in one task and one muscle in different tasks. Results: The results showed that the agonists (posterior muscles activated at first to compensate the flexor torque caused by loading and then the antagonists (anterior muscles switched-on to compensate the reaction forces caused by agonist activities. With regards to continuous activity of internal oblique and its attachments via thoracalumbar fascia to the transverse processes of the lumbar vertebrae, it can be considered as one of the major stabilizer muscles of the trunk . Conclusion: Finally the results indicated that supporting surface type didn’t have any effect on timing and scaling of muscle activities in different tasks suggesting that probably spinal and trunk priprioceptors are just responsible for triggering postural responses and they don’t have any role in determining timing and scaling.

  2. Modulation of jaw muscle spindle afferent activity following intramuscular injections with hypertonic saline.

    Science.gov (United States)

    Ro, J Y; Capra, N F

    2001-05-01

    Transient noxious chemical stimulation of small diameter muscle afferents modulates jaw movement-related responses of caudal brainstem neurons. While it is likely that the effect is mediated from the spindle afferents in the mesencephalic nucleus (Vmes) via the caudally projecting Probst's tract, the mechanisms of pain induced modulations of jaw muscle spindle afferents is not known. In the present study, we tested the hypothesis that jaw muscle nociceptors gain access to muscle spindle afferents in the same muscle via central mechanisms and alter their sensitivity. Thirty-five neurons recorded from the Vmes were characterized as muscle spindle afferents based on their responses to passive jaw movements, muscle palpation, and electrical stimulation of the masseter nerve. Each cell was tested by injecting a small volume (250 microl) of either 5% hypertonic and/or isotonic saline into the receptor-bearing muscle. Twenty-nine units were tested with 5% hypertonic saline, of which 79% (23/29) showed significant modulation of mean firing rates (MFRs) during one or more phases of ramp-and-hold movements. Among the muscle spindle primary-like units (n = 12), MFRs of 4 units were facilitated, five reduced, two showed mixed responses and one unchanged. In secondary-like units (n = 17), MFRs of 9 were facilitated, three reduced and five unchanged. Thirteen units were tested with isotonic saline, of which 77% showed no significant changes of MFRs. Further analysis revealed that the hypertonic saline not only affected the overall output of muscle spindle afferents, but also increased the variability of firing and altered the relationship between afferent signal and muscle length. These results demonstrated that activation of muscle nociceptors significantly affects proprioceptive properties of jaw muscle spindles via central neural mechanisms. The changes can have deleterious effects on oral motor function as well as kinesthetic sensibility.

  3. Circadian force and EMG activity in hindlimb muscles of rhesus monkeys

    Science.gov (United States)

    Hodgson, J. A.; Wichayanuparp, S.; Recktenwald, M. R.; Roy, R. R.; McCall, G.; Day, M. K.; Washburn, D.; Fanton, J. W.; Kozlovskaya, I.; Edgerton, V. R.; Rumbaugh, D. M. (Principal Investigator)

    2001-01-01

    Continuous intramuscular electromyograms (EMGs) were recorded from the soleus (Sol), medial gastrocnemius (MG), tibialis anterior (TA), and vastus lateralis (VL) muscles of Rhesus during normal cage activity throughout 24-h periods and also during treadmill locomotion. Daily levels of MG tendon force and EMG activity were obtained from five monkeys with partial datasets from three other animals. Activity levels correlated with the light-dark cycle with peak activities in most muscles occurring between 08:00 and 10:00. The lowest levels of activity generally occurred between 22:00 and 02:00. Daily EMG integrals ranged from 19 mV/s in one TA muscle to 3339 mV/s in one Sol muscle: average values were 1245 (Sol), 90 (MG), 65 (TA), and 209 (VL) mV/s. The average Sol EMG amplitude per 24-h period was 14 microV, compared with 246 microV for a short burst of locomotion. Mean EMG amplitudes for the Sol, MG, TA, and VL during active periods were 102, 18, 20, and 33 microV, respectively. EMG amplitudes that approximated recruitment of all fibers within a muscle occurred for 5-40 s/day in all muscles. The duration of daily activation was greatest in the Sol [151 +/- 45 (SE) min] and shortest in the TA (61 +/- 19 min). The results show that even a "postural" muscle such as the Sol was active for only approximately 9% of the day, whereas less active muscles were active for approximately 4% of the day. MG tendon forces were generally very low, consistent with the MG EMG data but occasionally reached levels close to estimates of the maximum force generating potential of the muscle. The Sol and TA activities were mutually exclusive, except at very low levels, suggesting very little coactivation of these antagonistic muscles. In contrast, the MG activity usually accompanied Sol activity suggesting that the MG was rarely used in the absence of Sol activation. The results clearly demonstrate a wide range of activation levels among muscles of the same animal as well as among different

  4. Girls with generalized joint hypermobility display changed muscle activity and postural sway during static balance tasks

    DEFF Research Database (Denmark)

    Juul-Kristensen, B; Johansen, Kl; Hendriksen, P;

    2016-01-01

    OBJECTIVES: To study knee muscle activity and static postural sway in girls with generalized joint hypermobility (GJH). METHOD: Sixteen girls with GJH and 11 girls with non-GJH (NGJH) aged 14 years, randomly recruited among schoolchildren, participated in this study. GJH inclusion criteria were: ......, compared with NGJH, static balance tasks with higher medial knee muscle activity relative to the lateral activity, and larger postural sway when vision was eliminated. The short- and long-term consequences should be studied further....

  5. Motor imagery muscle contraction strength influences spinal motor neuron excitability and cardiac sympathetic nerve activity

    OpenAIRE

    2015-01-01

    [Purpose] The aim of this study was to investigate the changes in spinal motor neuron excitability and autonomic nervous system activity during motor imagery of isometric thenar muscle activity at 10% and 50% maximal voluntary contraction (MVC). [Methods] The F-waves and low frequency/high frequency (LF/HF) ratio were recorded at rest, during motor imagery, and post-trial. For motor imagery trials, subjects were instructed to imagine thenar muscle activity at 10% and 50% MVC while holding the...

  6. Comparison of excitatory currents activated by different transmitters on crustacean muscle. II. Glutamate-activated currents and comparison with acetylcholine currents present on the same muscle.

    Science.gov (United States)

    Lingle, C; Auerbach, A

    1983-04-01

    The properties of glutamate-activated excitatory currents on the gm6 muscle from the foregut of the spiny lobsters Panulirus argus and interruptus and the crab Cancer borealis were examined using either noise analysis, analysis of synaptic current decays, or slow iontophoretic currents. The properties of acetylcholine currents activated in nonjunctional regions of the gm6 muscle were also examined. At 12 degrees C and -80 mV, the predominant time constant of power spectra from glutamate-activated current noise was approximately 7 ms and the elementary conductance was approximately 34 pS. At 12 degrees C and -80 mV, the predominant time constant of acetylcholine-activated channels was approximately 11 ms with a conductance of approximately 12 pS. Focally recorded glutamatergic extracellular synaptic currents on the gm6 muscle decayed with time constants of approximately 7-8 ms at 12 degrees C and -80 mV. The decay time constant was prolonged e-fold about every 225-mV hyperpolarization in membrane potential. The Q10 of the time constant of the synaptic current decay was approximately 2.6. The voltage dependence of the steady-state conductance increase activated by iontophoretic application of glutamate has the opposite direction of the steady-state conductance activated by cholinergic agonists when compared on the gm6 muscles. The glutamate-activated conductance increase is diminished with hyperpolarization. The properties of the marine crustacean glutamate channels are discussed in relation to glutamate channels in other organisms and to the acetylcholine channels found on the gm6 muscle and the gm1 muscle of the decapod foregut (Lingle and Auerbach, 1983).

  7. Are muscle activation patterns altered during shod and barefoot running with a forefoot footfall pattern?

    Science.gov (United States)

    Ervilha, Ulysses Fernandes; Mochizuki, Luis; Figueira, Aylton; Hamill, Joseph

    2016-09-14

    This study aimed to investigate the activation of lower limb muscles during barefoot and shod running with forefoot or rearfoot footfall patterns. Nine habitually shod runners were asked to run straight for 20 m at self-selected speed. Ground reaction forces and thigh and shank muscle surface electromyographic (EMG) were recorded. EMG outcomes (EMG intensity [iEMG], latency between muscle activation and ground reaction force, latency between muscle pairs and co-activation index between muscle pairs) were compared across condition (shod and barefoot), running cycle epochs (pre-strike, strike, propulsion) and footfall (rearfoot and forefoot) by ANOVA. Condition affected iEMG at pre-strike epoch. Forefoot and rearfoot strike patterns induced different EMG activation time patterns affecting co-activation index for pairs of thigh and shank muscles. All these timing changes suggest that wearing shoes or not is less important for muscle activation than the way runners strike the foot on the ground. In conclusion, the guidance for changing external forces applied on lower limbs should be pointed to the question of rearfoot or forefoot footfall patterns.

  8. Muscle activation described with a differential equation model for large ensembles of locally coupled molecular motors.

    Science.gov (United States)

    Walcott, Sam

    2014-10-01

    Molecular motors, by turning chemical energy into mechanical work, are responsible for active cellular processes. Often groups of these motors work together to perform their biological role. Motors in an ensemble are coupled and exhibit complex emergent behavior. Although large motor ensembles can be modeled with partial differential equations (PDEs) by assuming that molecules function independently of their neighbors, this assumption is violated when motors are coupled locally. It is therefore unclear how to describe the ensemble behavior of the locally coupled motors responsible for biological processes such as calcium-dependent skeletal muscle activation. Here we develop a theory to describe locally coupled motor ensembles and apply the theory to skeletal muscle activation. The central idea is that a muscle filament can be divided into two phases: an active and an inactive phase. Dynamic changes in the relative size of these phases are described by a set of linear ordinary differential equations (ODEs). As the dynamics of the active phase are described by PDEs, muscle activation is governed by a set of coupled ODEs and PDEs, building on previous PDE models. With comparison to Monte Carlo simulations, we demonstrate that the theory captures the behavior of locally coupled ensembles. The theory also plausibly describes and predicts muscle experiments from molecular to whole muscle scales, suggesting that a micro- to macroscale muscle model is within reach.

  9. Activation of selected shoulder muscles during unilateral wall and bench press tasks under submaximal isometric effort.

    Science.gov (United States)

    Tucci, Helga T; Ciol, Marcia A; de Araújo, Rodrigo C; de Andrade, Rodrigo; Martins, Jaqueline; McQuade, Kevin J; Oliveira, Anamaria S

    2011-07-01

    Controlled laboratory study. To assess the activation of 7 shoulder muscles under 2 closed kinetic chain (CKC) tasks for the upper extremity using submaximal isometric effort, thus providing relative quantification of muscular isometric effort for these muscles across the CKC exercises, which may be applied to rehabilitation protocols for individuals with shoulder weakness. CKC exercises favor joint congruence, reduce shear load, and promote joint dynamic stability. Additionally, knowledge about glenohumeral and periscapular muscle activity elicited during CKC exercises may help clinicians to design protocols for shoulder rehabilitation. Using surface electromyography, activation level was measured across 7 shoulder muscles in 20 healthy males, during the performance of a submaximal isometric wall press and bench press. Signals were normalized to the maximal voluntary isometric contraction, and, using paired t tests, data were analyzed between the exercises for each muscle. Compared to the wall press, the bench press elicited higher activity for most muscles, except for the upper trapezius. Levels of activity were usually low but were above 20% maximal voluntary isometric contraction for the serratus anterior on both tasks, and for the long head triceps brachii on the bench press. Both the bench press and wall press, as performed in this study, led to relatively low EMG activation levels for the muscles measured and may be considered for use in the early phases of rehabilitation.

  10. Antero-posterior activity changes in the superficial masseter muscle after exposure to experimental pain.

    Science.gov (United States)

    Türp, Jens C; Schindler, Hans J; Pritsch, Maria; Rong, Qiguo

    2002-04-01

    The aim of this randomized, controlled, double-blind study was to examine how the activation pattern of the masseter muscle changes during natural function when experimental pain is induced in a discrete anterior area of the muscle. In 20 subjects, three bipolar surface electrodes and three intramuscular fine-wire electrodes (antero-posterior mapping) were simultaneously attached above and in the right masseter muscle to record the electromyographic (EMG) activity during unilateral chewing before and after infusion of a 0.9% isotonic and 5% hypertonic saline bolus in the anterior area of the muscle. The activity of the contralateral masseter muscle was registered by surface electrodes. In addition, the development of pain intensity was quantitatively measured with a numerical rating scale (NRS). While both saline concentrations caused pain, the hypertonic solution evoked stronger pain. The experiments also provided evidence of a significant although differential activity reduction of the ipsilateral masseter muscle in the antero-posterior direction. The activity reduction decreased with increasing distance from the location of the infusion. The results support the idea that the strategy of differential activation protects the injured muscle while simultaneously maintaining optimal function.

  11. Effect of postural angle on back muscle activities in aging female workers performing computer tasks.

    Science.gov (United States)

    Kamil, Nabilla Sofia Mohd; Dawal, Siti Zawiah Md

    2015-06-01

    [Purpose] This study investigated the effects of postural angle on back muscle activity during a computer task in aging women. [Subjects] Seventeen women ≥50 years old participated. [Methods] The participants were instructed to perform computer-related tasks for 20 minutes on a workstation that simulated typical office working conditions. Back posture was measured from the measured trunk and pelvic angles. Electromyography activities were recorded simultaneously from the cervical erector spinae, longissimus, and multifidus muscles. [Results] The lowest mean percentages of maximum voluntary contraction for the cervical erector spinae and longissimus muscles were obtained when the upper trunk and pelvic angles were between 0° to -5° from the sagittal plane. The back muscle activities increased as the upper trunk and pelvic angles exceeded 0°. Statistical analysis showed significant correlations between upper trunk angle and cervical erector spinae and longissimus muscle activities. Similarly, pelvic angle was significantly correlated with cervical erector spinae and multifidus muscle activities. [Conclusion] A neutral back posture minimizes muscle activities in aging women performing computer tasks.

  12. Spontaneous jaw muscle activity in patients with acquired brain injuries - preliminary findings

    DEFF Research Database (Denmark)

    Kothari, Mohit; Madsen, Vibeke Louise Funch; Castrillon, Eduardo E.

    2017-01-01

    High or excessive parafunctional jaw muscle activity is a frequent complication of acquired brain injury (ABI) and may have some similarities to bruxism. Bruxism has been associated with increased tooth wear, masseter hypertrophy and headaches. The aim of this observational study was to identify...... the levels of jaw muscle activity from fourteen ABI patients having different functional and cognitive levels in their early phase of neurological rehabilitation (according to their Ranchos Los Amigos Scale (RLAS) score). Nine patients were severely cognitive impairement (RLAS score 1-3): with no or little...... (EMG) device was used to assess the jaw muscle EMG activity in ABI patients for two hours continuously at two different days....

  13. The effects of age and muscle contraction on AMPK activity and heterotrimer composition.

    Science.gov (United States)

    Hardman, Shalene E; Hall, Derrick E; Cabrera, Alyssa J; Hancock, Chad R; Thomson, David M

    2014-07-01

    Sarcopenia is characterized by increased skeletal muscle atrophy due in part to alterations in muscle metabolism. AMP-activated protein kinase (AMPK) is a master regulator of skeletal muscle metabolic pathways which regulate many cellular processes that are disrupted in old-age. Functional AMPK is a heterotrimer composed of α, β and γ subunits, and each subunit can be represented in the heterotrimer by one of two (α1/α2, β1/β2) or three (γ1/γ2/γ3) isoforms. Altered isoform composition affects AMPK localization and function. Previous work has shown that overall AMPK activation with endurance-type exercise is blunted in old vs. young skeletal muscle. However, details regarding the activation of the specific isoforms of AMPK, as well as the heterotrimeric composition of AMPK in old skeletal muscle, are unknown. Our purpose here, therefore, was to determine the effect of old-age on 1) the activation of the α1 and α2 catalytic subunits of AMPK in skeletal muscle by a continuous contraction bout, and 2) the heterotrimeric composition of skeletal muscle AMPK. We studied gastrocnemius (GAST) and tibialis anterior (TA) muscles from young adult (YA; 8months old) and old (O; 30months old) male Fischer344×Brown Norway F1 hybrid rats after an in situ bout of endurance-type contractions produced via electrical stimulation of the sciatic nerve (STIM). AMPKα phosphorylation and AMPKα1 and α2 activities were unaffected by age at rest. However, AMPKα phosphorylation and AMPKα2 protein content and activity were lower in O vs. YA after STIM. Conversely, AMPKα1 content was greater in O vs. YA muscle, and α1 activity increased with STIM in O but not YA muscles. AMPKγ3 overall concentration and its association with AMPKα1 and α2 were lower in O vs. YA GAST. We conclude that activation of AMPKα1 is enhanced, while activation of α2 is suppressed immediately after repeated skeletal muscle contractions in O vs. YA skeletal muscle. These changes are associated with

  14. Synaptic and functional linkages between spinal premotor interneurons and hand-muscle activity during precision grip

    Directory of Open Access Journals (Sweden)

    Tomohiko eTakei

    2013-04-01

    Full Text Available Grasping is a highly complex movement that requires the coordination of a number of hand joints and muscles. Previous studies showed that spinal premotor interneurons (PreM-INs in the primate cervical spinal cord have divergent synaptic effects on hand motoneurons and that they might contribute to hand-muscle synergies. However, the extent to which these PreM-IN synaptic connections functionally contribute to modulating hand-muscle activity is not clear. In this paper, we explored the contribution of spinal PreM-INs to hand-muscle activation by quantifying the synaptic linkage (SL and functional linkage (FL of the PreM-INs with hand-muscle activities. The activity of 23 PreM-INs was recorded from the cervical spinal cord (C6–T1, with EMG signals measured simultaneously from hand and arm muscles in two macaque monkeys performing a precision grip task. Spike-triggered averages (STAs of rectified EMGs were compiled for 456 neuron–muscle pairs; 63 pairs showed significant post-spike effects (i.e., SL. Conversely, 231 of 456 pairs showed significant cross-correlations between the IN firing rate and rectified EMG (i.e., FL. Importantly, a greater proportion of the neuron–muscle pairs with SL showed FL (43/63 pairs, 68% compared with the pairs without SL (203/393, 52%, and the presence of SL was significantly associated with that of FL. However, a significant number of pairs had SL without FL (SL∩!FL, n = 20 or FL without SL (!SL∩FL, n = 203, and the proportions of these incongruities exceeded the number expected by chance. These results suggested that spinal PreM-INs function to significantly modulate hand-muscle activity during precision grip, but the contribution of other neural structures is also needed to recruit an adequate combination of hand-muscle motoneurons.

  15. Muscle activation patterns during walking from transtibial amputees recorded within the residual limb-prosthetic interface

    Directory of Open Access Journals (Sweden)

    Huang Stephanie

    2012-08-01

    Full Text Available Abstract Background Powered lower limb prostheses could be more functional if they had access to feedforward control signals from the user’s nervous system. Myoelectric signals are one potential control source. The purpose of this study was to determine if muscle activation signals could be recorded from residual lower limb muscles within the prosthetic socket-limb interface during walking. Methods We recorded surface electromyography from three lower leg muscles (tibilias anterior, gastrocnemius medial head, gastrocnemius lateral head and four upper leg muscles (vastus lateralis, rectus femoris, biceps femoris, and gluteus medius of 12 unilateral transtibial amputee subjects and 12 non-amputee subjects during treadmill walking at 0.7, 1.0, 1.3, and 1.6 m/s. Muscle signals were recorded from the amputated leg of amputee subjects and the right leg of control subjects. For amputee subjects, lower leg muscle signals were recorded from within the limb-socket interface and from muscles above the knee. We quantified differences in the muscle activation profile between amputee and control groups during treadmill walking using cross-correlation analyses. We also assessed the step-to-step inter-subject variability of these profiles by calculating variance-to-signal ratios. Results We found that amputee subjects demonstrated reliable muscle recruitment signals from residual lower leg muscles recorded within the prosthetic socket during walking, which were locked to particular phases of the gait cycle. However, muscle activation profile variability was higher for amputee subjects than for control subjects. Conclusion Robotic lower limb prostheses could use myoelectric signals recorded from surface electrodes within the socket-limb interface to derive feedforward commands from the amputee’s nervous system.

  16. Physical activity is associated with retained muscle metabolism in human myotubes challenged with palmitate

    DEFF Research Database (Denmark)

    Green, C J; Bunprajun, T; Pedersen, B K

    2013-01-01

      The aim of this study was to investigate whether physical activity is associated with preserved muscle metabolism in human myotubes challenged with saturated fatty acids. Human muscle satellite cells were isolated from sedentary or active individuals and differentiated into myocytes in culture...... and correlated positively to JNK phosphorylation. In conclusion, muscle satellite cells retain metabolic differences associated with physical activity. Physical activity partially protects myocytes from fatty acid-induced insulin resistance and inactivity is associated with dysregulation of metabolism...... in satellite cells challenged with palmitate. Although the benefits of physical activity on whole body physiology have been well investigated, this paper presents novel findings that both diet and exercise impact satellite cells directly. Given the fact that satellite cells are important for muscle maintenance...

  17. Effect of mouth breathing on masticatory muscle activity during chewing food.

    Science.gov (United States)

    Ikenaga, N; Yamaguchi, K; Daimon, S

    2013-06-01

    The aim of this study was to examine the effect of mouth breathing on masticatory muscle activity during chewing food. Masseter muscle activity during chewing of a rice ball was recorded in 45 adult volunteers (three women), identified as nose breathers. Surface electrodes were placed on the skin according to the orientation of the masseter muscle to record the activity of this muscle while the subjects chewed the food until swallowing. Each activity was recorded twice, once with nose breathing and once with mouth breathing induced by nasal obstruction. The integrated and mean electromyography values for mouth breathing were significantly lower than the values for nose breathing (P breathing through the mouth compared with the nose. Significantly more chewing strokes were counted for mouth breathing compared with nose breathing (P breathing decreases chewing activity and reduces the vertical effect upon the posterior teeth. © 2013 John Wiley & Sons Ltd.

  18. Stretch-activated channels in stretch-induced muscle damage: role in muscular dystrophy.

    Science.gov (United States)

    Yeung, Ella W; Allen, David G

    2004-08-01

    1. Stretch-induced muscle injury results in the damage that causes reduced force and increased membrane permeability. This muscle damage is caused, in part, by ionic entry through stretch-activated channels and blocking these channels with Gd3+ or streptomycin reduces the force deficit associated with damage. 2. Dystrophin-deficient muscles are more susceptible to stretch-induced muscle injury and the recovery from injury can be incomplete. We have found that Na+ entry associated with stretch-induced injury is enhanced in dystrophin-deficient muscles and that blockers of stretch-activated channels are capable of preventing ionic entry and reducing muscle damage. 3. A model is presented that proposes links between stretch-induced injury, opening of stretch-activated channels, increased levels of intracellular ions and various forms of muscle damage. Although changes in Na+ accompany stretch-induced muscle injury, we believe that changes in Ca2+ probably have a more central role in the damage process.

  19. AMP-activated kinase α2 deficiency protects mice from denervation-induced skeletal muscle atrophy.

    Science.gov (United States)

    Guo, Yuting; Meng, Jin; Tang, Yinglong; Wang, Ting; Wei, Bin; Feng, Run; Gong, Bing; Wang, Huiwen; Ji, Guangju; Lu, Zhongbing

    2016-06-15

    AMP-activated protein kinase (AMPK) is a master regulator of skeletal muscle metabolic pathways. Recently, AMPK activation by AICAR has been shown to increase myofibrillar protein degradation in C2C12 myotubes via stimulating autophagy and ubiquitin proteasome system. However, the impact of AMPKα on denervation induced muscle atrophy has not been tested. In this study, we performed sciatic denervation on hind limb muscles in both wild type (WT) and AMPKα2(-/-) mice. We found that AMPKα was phosphorylated in atrophic muscles following denervation. In addition, deletion of AMPKα2 significantly attenuated denervation induced skeletal muscle wasting and protein degradation, as evidenced by preserved muscle mass and myofiber area, as well as lower levels of ubiquitinated protein, Atrogin-1 and MuRF-1 expression, and LC3-II/I ratio in tibial anterior (TA) muscles. Interestingly, the phosphorylated FoxO3a at Ser253 was significantly decreased in atrophic TA muscles, which was preserved in AMPKα2(-/-) mice. Collectively, our data support the notion that the activation of AMPKα2 contributes to the atrophic effects of denervation. Copyright © 2016 Elsevier Inc. All rights reserved.

  20. A Longitudinal Electromyography Study of Complex Movements in Poststroke Therapy. 2: Changes in Coordinated Muscle Activation

    Directory of Open Access Journals (Sweden)

    Negin Hesam-Shariati

    2017-07-01

    Full Text Available Fine motor control is achieved through the coordinated activation of groups of muscles, or “muscle synergies.” Muscle synergies change after stroke as a consequence of the motor deficit. We investigated the pattern and longitudinal changes in upper limb muscle synergies during therapy in a largely unconstrained movement in patients with a broad spectrum of poststroke residual voluntary motor capacity. Electromyography (EMG was recorded using wireless telemetry from 6 muscles acting on the more-affected upper body in 24 stroke patients at early and late therapy during formal Wii-based Movement Therapy (WMT sessions, and in a subset of 13 patients at 6-month follow-up. Patients were classified with low, moderate, or high motor-function. The Wii-baseball swing was analyzed using a non-negative matrix factorization (NMF algorithm to extract muscle synergies from EMG recordings based on the temporal activation of each synergy and the contribution of each muscle to a synergy. Motor-function was clinically assessed immediately pre- and post-therapy and at 6-month follow-up using the Wolf Motor Function Test, upper limb motor Fugl-Meyer Assessment, and Motor Activity Log Quality of Movement scale. Clinical assessments and game performance demonstrated improved motor-function for all patients at post-therapy (p < 0.01, and these improvements were sustained at 6-month follow-up (p > 0.05. NMF analysis revealed fewer muscle synergies (mean ± SE for patients with low motor-function (3.38 ± 0.2 than those with high motor-function (4.00 ± 0.3 at early therapy (p = 0.036 with an association trend between the number of synergies and the level of motor-function. By late therapy, there was no significant change between groups, although there was a pattern of increase for those with low motor-function over time. The variability accounted for demonstrated differences with motor-function level (p < 0.05 but not time. Cluster

  1. Exploring Muscle Activation during Nordic Walking: A Comparison between Conventional and Uphill Walking

    Science.gov (United States)

    Pellegrini, Barbara; Peyré-Tartaruga, Leonardo Alexandre; Zoppirolli, Chiara; Bortolan, Lorenzo; Bacchi, Elisabetta; Figard-Fabre, Hélène; Schena, Federico

    2015-01-01

    Nordic Walking (NW) owes much of its popularity to the benefits of greater energy expenditure and upper body engagement than found in conventional walking (W). Muscle activation during NW is still understudied, however. The aim of the present study was to assess differences in muscle activation and physiological responses between NW and W in level and uphill walking conditions. Nine expert Nordic Walkers (mean age 36.8±11.9 years; BMI 24.2±1.8 kg/m2) performed 5-minute treadmill trials of W and NW at 4 km/h on inclines of 0% and 15%. The electromyographic activity of seven upper body and five leg muscles and oxygen consumption (VO2) were recorded and pole force during NW was measured. VO2 during NW was 22.3% higher at 0% and only 6.9% higher at 15% than during W, while upper body muscle activation was 2- to 15-fold higher under both conditions. Lower body muscle activation was similarly increased during NW and W in the uphill condition, whereas the increase in erector spinae muscle activity was lower during NW than W. The lack of a significant increase in pole force during uphill walking may explain the lower extra energy expenditure of NW, indicating less upper body muscle activation to lift the body against gravity. NW seemed to reduce lower back muscle contraction in the uphill condition, suggesting that walking with poles may reduce effort to control trunk oscillations and could contribute to work production during NW. Although the difference in extra energy expenditure between NW and W was smaller in the uphill walking condition, the increased upper body muscle involvement during exercising with NW may confer additional benefit compared to conventional walking also on uphill terrains. Furthermore, people with low back pain may gain benefit from pole use when walking uphill. PMID:26418339

  2. Role of support afferentation in control of the tonic muscle activity

    Science.gov (United States)

    Kozlovskaya, I. B.; Sayenko, I. V.; Sayenko, D. G.; Miller, T. F.; Khusnutdinova, D. R.; Melnik, K. A.

    2007-02-01

    The paper summarizes the results of experimental studies advocating for the leading role of support afferentation in control of the functional organization of the tonic muscle system. It is shown that transition to supportless conditions is followed by a significant decline of transverse stiffness and maximal voluntary force of postural (extensor) muscles limiting their participation in locomotion and increasing involvement of phasic muscles. Mechanical stimulation of the support zones of the soles under the supportless conditions eliminates all the above-mentioned effects, including changes in transverse stiffness and maximal voluntary forces of postural muscles, and consequent loss of influence of postural muscles in the locomotor activity. It is suggested that support afferentation, facilitating (support is present) or suppressing (support is absent) the tonic motor units (MUs) activities, defines the coordination patterns of postural synergies, and ensures the optimal strategy of corrective postural responses.

  3. Influence of relative blood flow restriction pressure on muscle activation and muscle adaptation.

    Science.gov (United States)

    Counts, Brittany R; Dankel, Scott J; Barnett, Brian E; Kim, Daeyeol; Mouser, J Grant; Allen, Kirsten M; Thiebaud, Robert S; Abe, Takashi; Bemben, Michael G; Loenneke, Jeremy P

    2016-03-01

    The aim of this study was to investigate the acute and chronic skeletal muscle response to differing levels of blood flow restriction (BFR) pressure. Fourteen participants completed elbow flexion exercise with pressures from 40% to 90% of arterial occlusion. Pre/post torque measurements and electromyographic (EMG) amplitude of each set were quantified for each condition. This was followed by a separate 8-week training study of the effect of high (90% arterial occlusion) and low (40% arterial occlusion) pressure on muscle size and function. For the acute study, decreases in torque were similar between pressures [-15.5 (5.9) Nm, P = 0.344]. For amplitude of the first 3 and last 3 reps there was a time effect. After training, increases in muscle size (10%), peak isotonic strength (18%), peak isokinetic torque (180°/s = 23%, 60°/s = 11%), and muscular endurance (62%) changed similarly between pressures. We suggest that higher relative pressures may not be necessary when exercising under BFR. © 2015 Wiley Periodicals, Inc.

  4. Carnitine palmitoyl transferase activity and whole muscle oxidation rates vary with fatty acid substrate in avian flight muscles.

    Science.gov (United States)

    Price, Edwin R; Staples, James F; Milligan, C Louise; Guglielmo, Christopher G

    2011-05-01

    Birds primarily fuel migratory flights with fat, and the composition of that fat has the potential to affect overall lipid oxidation rates. We measured the whole muscle lipid oxidation rates in extensor digitorum communis muscles from white-throated sparrows (Zonotrichia albicollis Gmelin) incubated for 20 min at 20°C with radiolabeled stearate (18:0), oleate (18:1ω9), or linoleate (18:2ω6). Lipid oxidation rates were ~40% higher with linoleate than oleate (oleate: 36 ± 8.54 μmol CO(2) g(-1) h(-1)), and ~75% lower with stearate compared with oleate, indicating that maximal lipid oxidation rates can indeed be affected by the type of fatty acid supplied to the muscle. Additionally, we investigated the activity of the mitochondrial fatty acid transport-associated enzyme carnitine palmitoyl transferase (CPT) in pectoralis muscles of 5 bird species (Zonotrichia albicollis, Philomachus pugnax, Sturnus vulgaris, Taeniopygia guttata, Passer domesticus). Activity was measured in homogenized samples using various fatty acyl-CoA substrates (16:0, 16:1, 18:0, 18:1ω9, 18:2ω6, 18:3ω3, 18:3ω6, 20:0, 20:4ω6, 22:6ω3) in a spectrophotometric assay. CPT activity increased with the degree of unsaturation and decreased with chain length. CPT activity did not differ between ω3 and ω6 isomers of 18:3, nor was the pattern of CPT substrate preference different between captive white-throated sparrows in a migratory (i.e., displaying Zugunruhe) or non-migratory state. These findings can explain previously observed differences in peak performance induced by dietary fat composition and suggest that lipid supply is limiting to maximal exercise performance in birds.

  5. Motor unit activity after eccentric exercise and muscle damage in humans.

    Science.gov (United States)

    Semmler, J G

    2014-04-01

    It is well known that unaccustomed eccentric exercise leads to muscle damage and soreness, which can produce long-lasting effects on muscle function. How this muscle damage influences muscle activation is poorly understood. The purpose of this brief review is to highlight the effect of eccentric exercise on the activation of muscle by the nervous system, by examining the change in motor unit activity obtained from surface electromyography (EMG) and intramuscular recordings. Previous research shows that eccentric exercise produces unusual changes in the EMG–force relation that influences motor performance during isometric, shortening and lengthening muscle contractions and during fatiguing tasks. When examining the effect of eccentric exercise at the single motor unit level, there are substantial changes in recruitment thresholds, discharge rates, motor unit conduction velocities and synchronization, which can last for up to 1 week after eccentric exercise. Examining the time course of these changes suggests that the increased submaximal EMG after eccentric exercise most likely occurs through a decrease in motor unit conduction velocity and an increase in motor unit activity related to antagonist muscle coactivation and low-frequency fatigue. Furthermore, there is a commonly held view that eccentric exercise produces preferential damage to high-threshold motor units, but the evidence for this in humans is limited. Further research is needed to establish whether there is preferential damage to high-threshold motor units after eccentric exercise in humans, preferably by linking changes in motor unit activity with estimates of motor unit size using selective intramuscular recording techniques.

  6. The muscle activation patterns of lower limb during stair climbing at different backpack load.

    Science.gov (United States)

    Yali, Han; Aiguo, Song; Haitao, Gao; Songqing, Zhu

    2015-01-01

    Stair climbing under backpack load condition is a challenging task. Understanding muscle activation patterns of lower limb during stair climbing with load furthers our understanding of the factors involved in joint pathology and the effects of treatment. At the same time, stair climbing under backpack load requires adjustments of muscle activations and increases joint moment compared to level walking, which with muscle activation patterns are altered as a result of using an assistive technology, such as a wearable exoskeleton leg for human walking power augmentation. Therefore, the aim of this study was to analyze lower limb muscles during stair climbing under different backpack load. Nine healthy volunteers ascended a four-step staircase at different backpack load (0 kg, 10 kg, 20 kg, 30 kg). Electromyographic (EMG) signals were recorded from four lower limb muscles (gastrocnemius, tibialis anterior, hamstring, rectus femoris). The results showed that muscle activation amplitudes of lower limb increase with increasing load during stair climbing, the maximum RMS of gastrocnemius are greater than tibialis anterior, hamstring and rectus femoris whether stair climbing or level walking under the same load condition. However, the maximum RMS of hamstring are smaller than gastrocnemius, tibialis anterior and rectus femoris. The study of muscle activation under different backpack load during stair climbing can be used to design biomechanism and explore intelligent control based on EMG for a wearable exoskeleton leg for human walking power augmentation.

  7. An Eectromyographic Ccomparison Between the Activities of Temporal and Masseter Muscles in Class III Skeletal

    Directory of Open Access Journals (Sweden)

    T Hossein-Zadeh-Nik

    2002-02-01

    Full Text Available Electromyographic (EMG investigations about the activities of the muscles have been the focus of attention for many years. In the field of orthodontics, investigators, among other things, tried to evaluate correlation between EMG activity, occlusal relationships and craniofacial morphology to analyze the effect of muscular activity, as an etiological factor in malocclusion. The purpose of the present investigation is to analyze the effect of EMG activity of temporal and masseter muscles quantitatively in skeletal class III malocclusion. 26 patients (9 to If years old, with class III malocclusion were selected and their EMG activity of temporal and masseter muscles in rest position, centric occlusion, clenching, mastication and swallowing were compared with 20 normal children at the same age range. Then the statistical correlation between 13 cephalometric parameters and EMG activities were analyzed and then the regression analysis was performed and the results were as follows:1- The mean amplitude of masseter and temporal muscles activity in rest position, centric occlusion, mastication, and clenching in class III samples were greater than normal group (PO.05.2- The mean duration of masseter and temporal muscles activity in rest position and centric occlusion in class III samples were more than normal group (PO.05.3- According to regression analysis, a linear correlation was observed between ANB angle and temporal muscle activity in rest and centric occlusion that was not observed in other cases.The findings of this study showed that difference in temporal muscle activity in class III malocclusion, in comparison with the normal group, is correlated with skeletal morphology of the face, but according to other investigations it is not ture for the masseter muscle.

  8. Na+-K+-ATPase in rat skeletal muscle: muscle fiber-specific differences in exercise-induced changes in ion affinity and maximal activity

    DEFF Research Database (Denmark)

    Juel, Carsten

    2008-01-01

    other muscles tested. In conclusion, muscle activity induces fiber type-specific changes both in Na(+) affinity and maximal in vitro activity of the Na(+)-K(+)-ATPase. The underlying mechanisms may involve translocation of subunits and increased association between PLM units and the alphabeta complex...

  9. EMG Activity of Selected Trunk and Hip Muscles During a Squat Lift: Effect of Varying the Lumbar Posture

    Science.gov (United States)

    1990-01-01

    Analysis of the electromyographic (EMG) signal of a muscle group during lifting can provide insight into the force developed by that muscle (Anderrson, 1977...Jonsson, 1985). Myoelectric activity of a muscle has been found to vary linearly with the tension developed, in similar activities and non-fatigue...the lumbar spine in a kyphotic position would result in a significant increase in the amount of myoelectric activity seen in the hip extensor muscles

  10. The Masticatory Contractile Load Induced Expression and Activation of Akt1/PKBα in Muscle Fibers at the Myotendinous Junction within Muscle-Tendon-Bone Unit

    Science.gov (United States)

    Korkmaz, Yüksel; Klinz, Franz J.; Moghbeli, Mehrnoush; Addicks, Klaus; Raab, Wolfgang H. -M.; Bloch, Wilhelm

    2010-01-01

    The cell specific detection of enzyme activation in response to the physiological contractile load within muscle-tendon-bone unit is essential for understanding of the mechanical forces transmission from muscle cells via tendon to the bone. The hypothesis that the physiological mechanical loading regulates activation of Akt1/PKBα at Thr308 and at Ser473 in muscle fibers within muscle-tendon-bone unit was tested using quantitative immunohistochemistry, confocal double fluorescence analysis, and immunoblot analysis. In comparison to the staining intensities in peripheral regions of the muscle fibers, Akt1/PKBα was detected with a higher staining intensity in muscle fibers at the myotendinous junction (MTJ) areas. In muscle fibers at the MTJ areas, Akt1/PKBα is dually phosphorylated at Thr308 and Ser473. The immunohistochemical results were confirmed by immunoblot analysis. We conclude that contractile load generated by masticatory muscles induces local domain-dependent expression of Akt1/PKBα as well as activation by dually phosphorylation at Thr308 and Ser473 in muscle fibers at the MTJ areas within muscle-tendon-bone unit. PMID:20454577

  11. The masticatory contractile load induced expression and activation of Akt1/PKBalpha in muscle fibers at the myotendinous junction within muscle-tendon-bone unit.

    Science.gov (United States)

    Korkmaz, Yüksel; Klinz, Franz J; Moghbeli, Mehrnoush; Addicks, Klaus; Raab, Wolfgang H-M; Bloch, Wilhelm

    2010-01-01

    The cell specific detection of enzyme activation in response to the physiological contractile load within muscle-tendon-bone unit is essential for understanding of the mechanical forces transmission from muscle cells via tendon to the bone. The hypothesis that the physiological mechanical loading regulates activation of Akt1/PKBalpha at Thr308 and at Ser473 in muscle fibers within muscle-tendon-bone unit was tested using quantitative immunohistochemistry, confocal double fluorescence analysis, and immunoblot analysis. In comparison to the staining intensities in peripheral regions of the muscle fibers, Akt1/PKBalpha was detected with a higher staining intensity in muscle fibers at the myotendinous junction (MTJ) areas. In muscle fibers at the MTJ areas, Akt1/PKBalpha is dually phosphorylated at Thr308 and Ser473. The immunohistochemical results were confirmed by immunoblot analysis. We conclude that contractile load generated by masticatory muscles induces local domain-dependent expression of Akt1/PKBalpha as well as activation by dually phosphorylation at Thr308 and Ser473 in muscle fibers at the MTJ areas within muscle-tendon-bone unit.

  12. The Masticatory Contractile Load Induced Expression and Activation of Akt1/PKBα in Muscle Fibers at the Myotendinous Junction within Muscle-Tendon-Bone Unit

    Directory of Open Access Journals (Sweden)

    Yüksel Korkmaz

    2010-01-01

    Full Text Available The cell specific detection of enzyme activation in response to the physiological contractile load within muscle-tendon-bone unit is essential for understanding of the mechanical forces transmission from muscle cells via tendon to the bone. The hypothesis that the physiological mechanical loading regulates activation of Akt1/PKBα at Thr308 and at Ser473 in muscle fibers within muscle-tendon-bone unit was tested using quantitative immunohistochemistry, confocal double fluorescence analysis, and immunoblot analysis. In comparison to the staining intensities in peripheral regions of the muscle fibers, Akt1/PKBα was detected with a higher staining intensity in muscle fibers at the myotendinous junction (MTJ areas. In muscle fibers at the MTJ areas, Akt1/PKBα is dually phosphorylated at Thr308 and Ser473. The immunohistochemical results were confirmed by immunoblot analysis. We conclude that contractile load generated by masticatory muscles induces local domain-dependent expression of Akt1/PKBα as well as activation by dually phosphorylation at Thr308 and Ser473 in muscle fibers at the MTJ areas within muscle-tendon-bone unit.

  13. Muscle activity during mandibular movements in normal and mandibular retrognathic subjects.

    Science.gov (United States)

    Harper, R P; de Bruin, H; Burcea, I

    1997-03-01

    The masticatory muscles function as a unit during precise mandibular positioning movements that occur during such activities as speech, singing, or playing musical instruments. This investigation was designed to assess jaw muscle recruitment patterns during controlled mandibular movement in normal subjects and in patients with mandibular retrognathism. A computer-integrated electromyography (EMG) and movement monitoring (Selspot) system was used to collect data over 7 seconds of a sagittal border movement (Posselt envelope) of the mandible and 4 seconds each of rest position, light tooth contact, and maximum clench. Fine wire bipolar electrodes were placed into the inferior belly of the lateral pterygoid muscles bilaterally and surface electrodes were placed bilaterally over the anterior belly of the temporalis muscles and the masseter muscles. Ten subjects with Class I occlusion, normal cephalometric values, and an absence of temporomandibular joint (TMJ) dysfunction were compared with 12 patients with mandibular retrognathism, Class II malocclusion, and an absence of clinical signs of TMJ internal derangement before and after a bilateral sagittal split and advancement of the mandible. There was a wide variation in standard deviations of EMG activity for the lateral pterygoid muscles in the retrognathic patients compared with normal controls before surgery (P EMG activity levels during the forward movement phase of the envelope, before surgery compared with controls (P < .001). After surgery, the lateral pterygoid muscle showed early recruitment in the forward movement similar to control levels. The masticatory muscles function as a unit during mandibular positioning movements. Patients with mandibular retrognathism have different muscle recruitment patterns from those of normal subjects with the mandible at rest and during mandibular movement. After orthognathic surgery, adaptation occurs in the phasic timing of jaw muscle activity.

  14. Task-dependent spatial distribution of neural activation pattern in human rectus femoris muscle.

    Science.gov (United States)

    Watanabe, Kohei; Kouzaki, Motoki; Moritani, Toshio

    2012-04-01

    Compartmentalization of skeletal muscle by multiple motor nerve branches, named as neuromuscular compartment (NMC), has been demonstrated in animals as well as humans. While different functional roles among individual NMCs were reported in the animal studies, no studies have clarified the region-specific functional role within a muscle related with NMCs arrangement in human skeletal muscle. It was reported that the rectus femoris (RF) muscle is innervated by two nerve branches attached at proximal and distal parts of the muscle. The purpose of the present study is to clarify the possible region-specific functional role in the human RF muscle. Multi-channel surface electromyography (SEMG) were recorded from the RF muscle by using 128 electrodes during two different submaximal isometric contractions that the muscle contributes, i.e. isometric knee extension and hip flexion, at 20%, 40%, 60% and 80% of maximal voluntary contraction (MVC). Results indicated that the central locus activation for the amplitude map of SEMG during hip flexion located at more proximal region compared with that during knee extension. Significant higher normalized root mean square (RMS) values were observed at the proximal region during the hip flexion in comparison to those at middle and distal regions at 60% and 80% of MVC (pMVC (p<0.05). The results of the present study suggest possible region-specific functional role in the human RF muscle.

  15. An embryonic myosin isoform enables stretch activation and cyclical power in Drosophila jump muscle.

    Science.gov (United States)

    Zhao, Cuiping; Swank, Douglas M

    2013-06-18

    The mechanism behind stretch activation (SA), a mechanical property that increases muscle force and oscillatory power generation, is not known. We used Drosophila transgenic techniques and our new muscle preparation, the jump muscle, to determine if myosin heavy chain isoforms influence the magnitude and rate of SA force generation. We found that Drosophila jump muscles show very low SA force and cannot produce positive power under oscillatory conditions at pCa 5.0. However, we transformed the jump muscle to be moderately stretch-activatable by replacing its myosin isoform with an embryonic isoform (EMB). Expressing EMB, jump muscle SA force increased by 163% and it generated net positive power. The rate of SA force development decreased by 58% with EMB expression. Power generation is Pi dependent as >4 mM Pi was required for positive power from EMB. Pi increased EMB SA force, but not wild-type SA force. Our data suggest that when muscle expressing EMB is stretched, EMB is more easily driven backward to a weakly bound state than wild-type jump muscle. This increases the number of myosin heads available to rapidly bind to actin and contribute to SA force generation. We conclude that myosin heavy chain isoforms influence both SA kinetics and SA force, which can determine if a muscle is capable of generating oscillatory power at a fixed calcium concentration. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  16. Benefits of detailed models of muscle activation and mechanics

    Science.gov (United States)

    Lehman, S. L.; Stark, L.

    1981-01-01

    Recent biophysical and physiological studies identified some of the detailed mechanisms involved in excitation-contraction coupling, muscle contraction, and deactivation. Mathematical models incorporating these mechanisms allow independent estimates of key parameters, direct interplay between basic muscle research and the study of motor control, and realistic model behaviors, some of which are not accessible to previous, simpler, models. The existence of previously unmodeled behaviors has important implications for strategies of motor control and identification of neural signals. New developments in the analysis of differential equations make the more detailed models feasible for simulation in realistic experimental situations.

  17. Volitional muscle activity paired with transcranial magnetic stimulation increases corticospinal excitability

    Directory of Open Access Journals (Sweden)

    Matthew A Edwardson

    2015-01-01

    Full Text Available Studies of activity-dependent stimulation in non-human primates suggest that pairing each instance of volitional muscle activity with immediate intracortical stimulation causes long-term-potentiation-like effects. This technique holds promise for clinical rehabilitation, yet few investigators have tested activity-dependent stimulation in human subjects. In addition, no one has studied activity-dependent stimulation on the cortical representation for two separate target muscles in human subjects. We hypothesized that 40 min of transcranial magnetic stimulation (TMS triggered from ballistic muscle activity at a mean repetition rate of 1 Hz would cause greater increases in corticospinal excitability than TMS-cued muscle activity, and that these changes would be specific to the muscle of study. Ten healthy human subjects participated in 4 separate sessions in this crossover study: (1 visually cued volitional activation of the abductor pollicis brevis (APB muscle triggering TMS (APB-Triggered TMS, (2 volitional activation of APB in response to TMS delivered from a recording of the prior APB-Triggered TMS session (TMS-Cued APB, (3 visually cued volitional activation of the extensor digitorum (ED triggering TMS (ED-Triggered TMS, and (4 volitional activation of ED in response to TMS delivered from a recording of the prior ED-Triggered TMS session (TMS-Cued ED. Contrary to our hypothesis, we discovered evidence of increased corticospinal excitability for all conditions as measured by change in area of the motor evoked potential. We conclude that single TMS pulses paired either before or after muscle activity may increase corticospinal excitability and that further studies are needed to clarify the optimal time window for inducing neural plasticity with activity-dependent stimulation. These findings will inform the design of future activity-dependent stimulation protocols for clinical rehabilitation.

  18. Electromyographic activity of selected trunk muscles during stabilization exercises using a gym ball.

    Science.gov (United States)

    Mori, A

    2004-01-01

    Trunk stabilization is very important for the injured lower back. The use of a gym ball, the surface of which is labile, is becoming more popular for strengthening the trunk muscles and challenging the motor control system in trunk stabilization exercises. However, little is known about the activity of the trunk muscles during such exercises. The purpose of this study was to compare the electromyographic (EMG) activity of the trunk muscles during seven stabilization exercises using a gym ball. Eleven healthy men (19.9 +/- 1.8 years old) without low back pain volunteered to participate in the study. Bipolar surface electrodes were attached to the right side of the upper and lower rectus abdominis, the obliquus externus abdominis and the upper and lower back extensor muscles. EMG signals were recorded during seven types of stabilization exercises using a gym ball and normalized to maximal voluntary contraction (% MVC). A two-way analysis of variance (ANOVA) was performed on % MVC from each task for each of the five trunk muscle sites (p gym ball and toes on the floor in prone position, resulted in the highest activity of all abdominal muscles, and an exercise of the lifting the gym ball up, holding it actively between both legs with both knees flexed in supine position resulted in the lowest. Lifting up of the pelvis in a bridged position exercise, supporting the head with the gym ball and with the feet on the floor in supine position, resulted in higher muscle activity of the back extensor muscles than another exercise. It is very important for physical therapists to make clear the purpose of the trunk stabilization exercises, because different kinds of exercises with the gym ball demand various levels of muscular activity and use of various parts of the trunk muscles.

  19. The Body Action Coding System II: Muscle activations during the perception and expression of emotion

    Directory of Open Access Journals (Sweden)

    Elisabeth M.J. Huis in 't Veld

    2014-09-01

    Full Text Available Research into the expression and perception of emotions has mostly focused on facial expressions. Recently, body postures have become increasingly important in research, but knowledge on muscle activity during the perception or expression of emotion is lacking. The current study continues the development of a Body Action Coding System (BACS, which was initiated in a previous study, and described the involvement of muscles in the neck, shoulders and arms during expression of fear and anger. The current study expands the BACS by assessing the activity patterns of three additional muscles. Surface electromyography of muscles in the neck (upper trapezius descendens, forearms (extensor carpi ulnaris, lower back (erector spinae longissimus and calves (peroneus longus were measured during active expression and passive viewing of fearful and angry body expressions. The muscles in the forearm were strongly active for anger expression and to a lesser extent for fear expression. In contrast, muscles in the calves were recruited slightly more for fearful expressions. It was also found that muscles automatically responded to the perception of emotion, without any overt movement. The observer’s forearms responded to the perception of fear, while the muscles used for leaning backwards were activated when faced with an angry adversary. Lastly, the calf responded immediately when a fearful person was seen, but responded slower to anger. There is increasing interest in developing systems that are able to create or recognize emotional body language for the development of avatars, robots, and online environments. To that end, multiple coding systems have been developed that can either interpret or create bodily expressions based on static postures, motion capture data or videos. However, the BACS is the first coding system based on muscle activity.

  20. The Body Action Coding System II: muscle activations during the perception and expression of emotion.

    Science.gov (United States)

    Huis In 't Veld, Elisabeth M J; van Boxtel, Geert J M; de Gelder, Beatrice

    2014-01-01

    Research into the expression and perception of emotions has mostly focused on facial expressions. Recently, body postures have become increasingly important in research, but knowledge on muscle activity during the perception or expression of emotion is lacking. The current study continues the development of a Body Action Coding System (BACS), which was initiated in a previous study, and described the involvement of muscles in the neck, shoulders and arms during expression of fear and anger. The current study expands the BACS by assessing the activity patterns of three additional muscles. Surface electromyography of muscles in the neck (upper trapezius descendens), forearms (extensor carpi ulnaris), lower back (erector spinae longissimus) and calves (peroneus longus) were measured during active expression and passive viewing of fearful and angry body expressions. The muscles in the forearm were strongly active for anger expression and to a lesser extent for fear expression. In contrast, muscles in the calves were recruited slightly more for fearful expressions. It was also found that muscles automatically responded to the perception of emotion, without any overt movement. The observer's forearms responded to the perception of fear, while the muscles used for leaning backwards were activated when faced with an angry adversary. Lastly, the calf responded immediately when a fearful person was seen, but responded slower to anger. There is increasing interest in developing systems that are able to create or recognize emotional body language for the development of avatars, robots, and online environments. To that end, multiple coding systems have been developed that can either interpret or create bodily expressions based on static postures, motion capture data or videos. However, the BACS is the first coding system based on muscle activity.

  1. The effects of Pilates breathing trainings on trunk muscle activation in healthy female subjects: a prospective study.

    Science.gov (United States)

    Kim, Sung-Tae; Lee, Joon-Hee

    2017-02-01

    [Purpose] To investigate the effects of Pilates breathing on trunk muscle activation. [Subjects and Methods] Twenty-eight healthy female adults were selected for this study. Participants' trunk muscle activations were measured while they performed curl-ups, chest-head lifts, and lifting tasks. Pilates breathing trainings were performed for 60 minutes per each session, 3 times per week for 2 weeks. Post-training muscle activations were measured by the same methods used for the pre-training muscle activations. [Results] All trunk muscles measured in this study had increased activities after Pilates breathing trainings. All activities of the transversus abdominis/internal abdominal oblique, and multifidus significantly increased. [Conclusion] Pilates breathing increased activities of the trunk stabilizer muscles. Activation of the trunk muscle indicates that practicing Pilates breathing while performing lifting tasks will reduce the risk of trunk injuries.

  2. Activation of rectus capitis posterior major muscles during voluntary retraction of the head in asymptomatic subjects.

    Science.gov (United States)

    Hallgren, Richard C; Rowan, Jacob J; Bai, Peng; Pierce, Steven J; Shafer-Crane, Gail A; Prokop, Lawrence L

    2014-01-01

    The purpose of this study was to assess levels of electromyographic activity measured from rectus capitis posterior major (RCPM) muscles of asymptomatic subjects as their heads moved from a self-defined neutral position to a retracted position. A 2 × 2 within-subjects factorial research design was used. Disposable, intramuscular electrodes were used to collect electromyographic data from asymptomatic subjects between the ages of 20 and 40 years old. Data analysis was performed using mixed effects β regression models. Activation of RCPM muscles was found to significantly increase (P < .0001) as the head moved from a self-defined neutral position to a retracted position. Rectus capitis posterior major muscle activation levels, measured as a function of head position, have not been previously reported. The findings from this study showed that RCPM muscle activation significantly increases during voluntary retraction of the head. Copyright © 2014 National University of Health Sciences. Published by Elsevier Inc. All rights reserved.

  3. Patterns of Lower Limb Muscle Activity in Young Boys During a One Foot Static Balance Task.

    Science.gov (United States)

    Layne, Charles S.; Abraham, Lawrence D.

    1987-01-01

    This study of 10 seven- to nine-year-old boys was undertaken to determine the electromyographic activity of four muscles in the supporting leg during one foot static balancing. Results are presented and analyzed. (Author/MT)

  4. Upper extremity kinematics and muscle activation patterns in subjects with facioscapulohumeral dystrophy

    NARCIS (Netherlands)

    Bergsma, A.; Murgia, A.; Cup, E.H.C.; Verstegen, P.P.; Meijer, K.; Groot, I.J.M. de

    2014-01-01

    OBJECTIVE: To compare the kinematics and muscle activity of subjects with facioscapulohumeral dystrophy (FSHD) and healthy control subjects during the performance of standardized upper extremity tasks. DESIGN: Exploratory case-control study. SETTING: A movement laboratory. PARTICIPANTS: Subjects

  5. Upper Extremity Kinematics and Muscle Activation Patterns in Subjects With Facioscapulohumeral Dystrophy

    NARCIS (Netherlands)

    Bergsma, Arjen; Murgia, Alessio; Cup, Edith H.; Verstegen, Paul P.; Meijer, Kenneth; de Groot, Imelda J.

    Objective: To compare the kinematics and muscle activity of subjects with facioscapulohumeral dystrophy (FSHD) and healthy control subjects during the performance of standardized upper extremity tasks. Design: Exploratory case-control study. Setting: A movement laboratory. Participants: Subjects

  6. Upper Extremity Kinematics and Muscle Activation Patterns in Subjects With Facioscapulohumeral Dystrophy

    NARCIS (Netherlands)

    Bergsma, Arjen; Murgia, Alessio; Cup, Edith H.; Verstegen, Paul P.; Meijer, Kenneth; de Groot, Imelda J.

    2014-01-01

    Objective: To compare the kinematics and muscle activity of subjects with facioscapulohumeral dystrophy (FSHD) and healthy control subjects during the performance of standardized upper extremity tasks. Design: Exploratory case-control study. Setting: A movement laboratory. Participants: Subjects (N=

  7. The influence of the training program on muscle activity of lower limb muscles in relation to the risk factors of hamstring injury at soccer players

    OpenAIRE

    Hnátová, Iva

    2013-01-01

    CHARLES UNIVERSITY IN PRAG Faculty of Physical Educational and Sport Department of Physiotherapy THE INFLUENCE OF THE TRAINING PROGRAM ON MUSCLE ACTIVITY OF LOWER LIMB MUSCLES IN RELATION TO THE RISK FACTORS OF HAMSTRING INJURY AT SOCCER PLAYERS Dissertation thesis Supervisor: Author: Doc. PaedDr. Dagmar Pavlů, CSc. Mgr. Iva Hnátová Consultant: PhDr. Aleš Kaplan, PhD. November 2012 SUMMARY Titel: The influence of the training program on muscle activity of lower limb muscles in relation to the...

  8. Spatial variation and inconsistency between estimates of onset of muscle activation from EMG and ultrasound.

    Science.gov (United States)

    Dieterich, Angela V; Botter, Alberto; Vieira, Taian Martins; Peolsson, Anneli; Petzke, Frank; Davey, Paul; Falla, Deborah

    2017-02-08

    Delayed onset of muscle activation can be a descriptor of impaired motor control. Activation onset can be estimated from electromyography (EMG)-registered muscle excitation and from ultrasound-registered muscle motion, which enables non-invasive measurements in deep muscles. However, in voluntary activation, EMG- and ultrasound-detected activation onsets may not correspond. To evaluate this, ten healthy men performed isometric elbow flexion at 20% to 70% of their maximal force. Utilising a multi-channel electrode transparent to ultrasound, EMG and M(otion)-mode ultrasound were recorded simultaneously over the biceps brachii muscle. The time intervals between automated and visually estimated activation onsets were correlated with the regional variation of EMG and muscle motion onset, contraction level and speed. Automated and visual onsets indicated variable time intervals between EMG- and motion onset, median (interquartile range) 96 (121) ms and 48 (72) ms, respectively. In 17% (computed analysis) or 23% (visual analysis) of trials, motion onset was detected before local EMG onset. Multi-channel EMG and M-mode ultrasound revealed regional differences in activation onset, which decreased with higher contraction speed (Spearman ρ ≥ 0.45, P explain the high variation of the time intervals between local EMG- and ultrasound-detected activation onset.

  9. Spontaneous locomotor activity in late-stage chicken embryos is modified by stretch of leg muscles.

    Science.gov (United States)

    Bradley, Nina S; Ryu, Young U; Yeseta, Marie C

    2014-03-15

    Chicks initiate bilateral alternating steps several days before hatching and adaptively walk within hours of hatching, but emergence of precocious walking skills is not well understood. One of our aims was to determine whether interactions between environment and movement experience prior to hatching are instrumental in establishing precocious motor skills. However, physiological evidence of proprioceptor development in the chick has yet to be established; thus, one goal of this study was to determine when in embryogenesis proprioception circuits can code changes in muscle length. A second goal was to determine whether proprioception circuits can modulate leg muscle activity during repetitive limb movements for stepping (RLMs). We hypothesized that proprioception circuits code changes in muscle length and/or tension, and modulate locomotor circuits producing RLMs in anticipation of adaptive locomotion at hatching. To this end, leg muscle activity and kinematics were recorded in embryos during normal posture and after fitting one ankle with a restraint that supported the limb in an atypical posture. We tested the hypotheses by comparing leg muscle activity during spontaneous RLMs in control posture and ankle extension restraint. The results indicated that proprioceptors detect changes in muscle length and/or muscle tension 3 days before hatching. Ankle extension restraint produced autogenic excitation of the ankle flexor and reciprocal inhibition of the ankle extensor. Restraint also modified knee extensor activity during RLMs 1 day before hatching. We consider the strengths and limitations of these results and propose that proprioception contributes to precocious locomotor development during the final 3 days before hatching.

  10. Effects of muscle activity and fiber composition on glucose transport and GLUT-4.

    Science.gov (United States)

    Megeney, L A; Neufer, P D; Dohm, G L; Tan, M H; Blewett, C A; Elder, G C; Bonen, A

    1993-04-01

    We examined glucose uptake and GLUT-4 in rat muscles [soleus (Sol), plantaris (PL), extensor digitorum longus (EDL), tibialis anterior, and the red and white gastrocnemius (WG)]. In the normally innervated perfused rat hindlimb muscles the proportion of oxidative fibers was highly correlated with the muscle's insulin-stimulated 3-O-methyl-D-glucose (3-MG) uptake (R2 = 0.78) and GLUT-4 content (r = 0.94). Insulin-stimulated 3-MG uptake and GLUT-4 were also highly correlated (R2 = 0.996). In 3-day denervated muscles, insulin-stimulated 3-MG uptake was reduced in all six muscles (-41 to -14.6%, P 0.05). A very high correlation was observed between the decrements in GLUT-4 (%) and the decrements in 3-MG uptake (%; r = 0.99). The relatively greater loss in muscle activity (%) due to denervation in the Sol compared with the PL coincided with the reductions (%) in GLUT-4 and 3-MG uptake. These studies demonstrate that glucose uptake and GLUT-4 are regulated by insulin-independent means, namely the oxidative capacity of the muscle and the normal activity level of the muscle.

  11. Methods for dynamic characterization of the major muscles activating the lower limb joints in cycling motion

    Directory of Open Access Journals (Sweden)

    Navit Roth

    2014-09-01

    Full Text Available The functional activation, through electrical stimulation, of the lower limb consisting of several deficient muscles requires well-patterned and coordinated activation of these muscles. This study presents a method for characterizing the parameters of the major muscle groups controlling the ankle and knee joints in cycling motion, the latter having particular significance in the rehabilitation of locomotion. To lower mechanical indeterminacy in the joints the system is reduced by grouping the muscles acting in synergism. The joint torques were calculated by inverse dynamics methods from cycling motion data, including kinematics and foot/pedal reaction loads (forces, moments. The mechanical indeterminacy was resolved by applying optimization criteria and the individual muscle torques were parceled-out from the joint torques. System identification of the individual muscles, part of which being bi-articular, in this non-isometric condition was performed from the relationship between the evaluated force and the measured EMG of each the muscles, using both first and second order linear transfer functions. Feasibility of the presented method was demonstrated through the computation of the coefficients of the muscles involved and validating the results on the experimental data obtained from one subject.

  12. Muscle relaxant activity of Elaeagnus angustifolia L. fruit seeds in mice.

    Science.gov (United States)

    Hosseinzadeh, Hossein; Ramezani, Mohammad; Namjo, Nazanin

    2003-02-01

    Muscle relaxant effect of Elaeagnus angustifolia L. (Elaeagnaceae) fruit seeds was studied in mice using traction test. The aqueous and ethanolic extracts (i.p) induced a muscle relaxant effect in a dose dependent manner as effective as diazepam (1 mg/kg). The aqueous extract was partitioned with methanol-chloroform (MeCh) and n-butanol (Bu.) saturated with water. The MeCh and Bu. fractions did not show activity. Preliminary phytochemical tests showed that the extract contains flavonoid. The results suggested that E. angustifolia fruit seeds exerted muscle relaxant activity via flavonoid component(s).

  13. Bed rest suppresses bioassayable growth hormone release in response to muscle activity

    Science.gov (United States)

    McCall, G. E.; Goulet, C.; Grindeland, R. E.; Hodgson, J. A.; Bigbee, A. J.; Edgerton, V. R.

    1997-01-01

    Hormonal responses to muscle activity were studied in eight men before (-13 or -12 and -8 or -7 days), during (2 or 3, 8 or 9, and 13 or 14 days) and after (+2 or +3 and +10 or +11 days) 17 days of bed rest. Muscle activity consisted of a series of unilateral isometric plantar flexions, including 4 maximal voluntary contractions (MVCs), 48 contractions at 30% MVC, and 12 contractions at 80% MVC, all performed at a 4:1-s work-to-rest ratio. Blood was collected before and immediately after muscle activity to measure plasma growth hormone by radioimmunoassay (IGH) and by bioassay (BGH) of tibia epiphyseal cartilage growth in hypophysectomized rats. Plasma IGH was unchanged by muscle activity before, during, or after bed rest. Before bed rest, muscle activity increased (P pattern that persisted through 8 or 9 days of bed rest. However, after 13 or 14 days of bed rest, plasma concentration of BGH was significantly lower after than before muscle activity (2,594 +/- 211 to 2,085 +/- 109 microg/l). After completion of bed rest, muscle activity increased BGH by 31% at 2 or 3 days (1,807 +/- 117 to 2,379 +/- 473 microg/l; P < 0.05), and by 10 or 11 days the BGH response was similar to that before bed rest (1,881 +/- 75 to 4,160 +/- 315 microg/l; P < 0.05). These data demonstrate that the ambulatory state of an individual can have a major impact on the release of BGH, but not IGH, in response to a single bout of muscle activity.

  14. Muscle activation and heart rate responses to a side-step interval exercise.

    Science.gov (United States)

    Thiebaud, Robert S; Abe, Takashi; Bravo, Jonathan C; Giovannitti, Nicolas; Sullivan, Avery P

    2017-02-16

    The side-step test is commonly used to assess agility. Side-step interval exercise may also be a potential way to improve cardiorespiratory and muscular fitness. However, the acute heart rate and muscle activation response to this type of exercise is not well established. In addition, different tempos can influence these responses. The purpose of this study was to determine the acute heart rate and muscle activation responses of a side-step interval exercise to different exercise tempos. Ten participants completed a V˙O2 max test and performed a side-step interval exercise for 4 × 1 min intervals separated by 1-min rest intervals at a slow (84 bpm) and fast (112 bpm) tempo. Muscle activation of the vastus lateralis and vastus medialis and heart rate were measured during exercise. During the slow tempo, vastus lateralis muscle activation varied from 45% to 48% of maximum muscle activation (EMGmax ) while vastus medialis muscle activation varied from 51% to 54% EMGmax . During the fast tempo, vastus lateralis muscle activation varied from 53% to 65% EMGmax while vastus medialis muscle activation varied from 64% to 76% EMGmax . Heart rates varied from 80-84% HRmax from set 1 to set 4 for the fast tempo and varied from 67% to 72% HRmax from set 1 to set 4 for the slow speeds. Exercise intensity of a side-step interval exercise reached adequate levels to suggest that it may be possible to use this type of exercise to improve cardiorespiratory and muscular fitness. © 2017 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.

  15. Lower limb antagonist muscle co-activation and its relationship with gait parameters in cerebellar ataxia.

    Science.gov (United States)

    Mari, Silvia; Serrao, Mariano; Casali, Carlo; Conte, Carmela; Martino, Giovanni; Ranavolo, Alberto; Coppola, Gianluca; Draicchio, Francesco; Padua, Luca; Sandrini, Giorgio; Pierelli, Francesco

    2014-04-01

    Increased antagonist muscle co-activation, seen in motor-impaired individuals, is an attempt by the neuromuscular system to provide mechanical stability by stiffening joints. The aim of this study was to investigate the co-activation pattern of the antagonist muscles of the ankle and knee joints during walking in patients with cerebellar ataxia, a neurological disease that strongly affects stability. Kinematic and electromyographic parameters of gait were recorded in 17 patients and 17 controls. Ankle and knee antagonist muscle co-activation indexes were measured throughout the gait cycle and during the sub-phases of gait. The indexes of ataxic patients were compared with those of controls and correlated with clinical and gait variables. Patients showed increased co-activity indexes of both ankle and knee muscles during the gait cycle as well as during the gait sub-phases. Both knee and ankle muscle co-activation indexes were positively correlated with disease severity, while ankle muscle co-activation was also positively correlated with stance and swing duration variability. Significant negative correlations were observed between the number of self-reported falls per year and knee muscle co-activation. The increased co-activation observed in these cerebellar ataxia patients may represent a compensatory strategy serving to reduce gait instability. Indeed, this mechanism allows patients to reduce the occurrence of falls. The need for this strategy, which results in excessive muscle co-contraction, increased metabolic costs and cartilage degeneration processes, could conceivably be overcome through the use of supportive braces specially designed to provide greater joint stability.

  16. Skeletal Muscle Satellite Cell Activation Following Cutaneous Burn in Rats

    Science.gov (United States)

    2013-12-01

    Satellite cell isolation and culture Satellite cells were isolated similar as described by Allen et al. [30]. Following euthanasia , muscles were...satellite cell cultures. Methods Cell Biol 1997;52:155–76. [31] Tatsumi R, Liu X, Pulido A, Morales M, Sakata T, Dial S, Hattori A, Ikeuchi Y, Allen RE

  17. EMG-normalised kinase activation during exercise is higher in human gastrocnemius compared to soleus muscle.

    Directory of Open Access Journals (Sweden)

    Thomas E Jensen

    Full Text Available In mice, certain proteins show a highly confined expression in specific muscle groups. Also, resting and exercise/contraction-induced phosphorylation responses are higher in rat skeletal muscle with low mitochondrial content compared to muscles with high mitochondrial content, possibly related to differential reactive oxygen species (ROS-scavenging ability or resting glycogen content. To evaluate these parameters in humans, biopsies from soleus, gastrocnemius and vastus lateralis muscles were taken before and after a 45 min inclined (15% walking exercise bout at 69% VO2(max aimed at simultaneously activating soleus and gastrocnemius in a comparable dynamic work-pattern. Hexokinase II and GLUT4 were 46-59% and 26-38% higher (p<0.05 in soleus compared to the two other muscles. The type I muscle fiber percentage was highest in soleus and lowest in vastus lateralis. No differences were found in protein expression of signalling proteins (AMPK subunits, eEF2, ERK1/2, TBC1D1 and 4, mitochondrial markers (F1 ATPase and COX1 or ROS-handling enzymes (SOD2 and catalase. Gastrocnemius was less active than soleus measured as EMG signal and glycogen use yet gastrocnemius displayed larger increases than soleus in phosphorylation of AMPK Thr172, eEF2 Thr56 and ERK 1/2 Thr202/Tyr204 when normalised to the mean relative EMG-signal. In conclusion, proteins with muscle-group restricted expression in mice do not show this pattern in human lower extremity muscle groups. Nonetheless the phosphorylation-response is greater for a number of kinase signalling pathways in human gastrocnemius than soleus at a given activation-intensity. This may be due to the combined subtle effects of a higher type I muscle fiber content and higher training status in soleus compared to gastrocnemius muscle.

  18. The effect of stretch rate and activation state on skeletal muscle force in the anatomical range.

    Science.gov (United States)

    Grover, Joel P; Corr, David T; Toumi, Hechmi; Manthei, David M; Oza, Ashish L; Vanderby, Ray; Best, Thomas M

    2007-03-01

    The effects of stretch rate and activation state on muscle mechanics require further clarification. This subject is of particular interest because of the role of skeletal muscle undergoing eccentric contractions in musculoskeletal injuries. The present study investigated the force-displacement behavior of rabbit tibialis anterior muscle at three stretch rates (2.5, 10, 25 cm/s) and three activation states (passive, tetanic, denervated). A phenomenological power law model and a dynamic systems model were used to describe the mechanical responses. The power law model showed excellent agreement with the passive and denervated responses to stretch (R(mean)=0.97). Repeated measures analysis of variance found a difference (P=0.042) in peak force between the passive and denervated states at a stretch rate of 2.5 cm/s. The dynamic systems model closely fit the tetanized muscle responses (R(mean)=0.95). There was no difference in the displacement at yield (P=0.83) for the three stretch rates of the tetanized muscle undergoing stretch. Differences between the passive and denervated responses suggest that mechanoreceptors may play a role in stimulating the muscle as it is stretched through the anatomical range. The displacement at yield did not change significantly over a decade range of stretch velocities, suggesting that a strain threshold exists beyond which cross bridges cannot remain bound. The power law and dynamic systems models presented offer mathematically tractable approaches to interpret the response of lengthening skeletal muscle. These findings on active, passive, and denervated muscle point to a possible role of the muscle spindle to tissue mechanical behavior that should be accounted for in future studies of force-elongation behavior of skeletal muscle.

  19. Non-invasive monitoring of functionally distinct muscle activations during swallowing.

    Science.gov (United States)

    McKeown, Martin J; Torpey, Dana C; Gehm, Wendy C

    2002-03-01

    Dysphagia is an important consequence of many diseases. As some of the muscles of deglutition tend to be deep to the surface, needle electrodes are typically used, but this limits the number of muscles that can be simultaneously recorded. Since control of swallowing involves central pattern generators (CPGs) which distribute commands to several muscles, monitoring several muscles simultaneously is desirable. Here we describe a novel method, based on computing the independent components (ICs) of the simultaneous sEMG recordings (Muscle Nerve Suppl 9 (2000) 9) to detect the underlying functional muscle activations during swallowing using only surface EMG (sEMG) electrodes. Seven normal subjects repeatedly swallowed liquids of varying consistency while sEMG was recorded from 15 electrodes from the face and throat. Active areas of EMG were excised from the recordings and the ICs of the sEMG were calculated. The ICs demonstrated less swallow-to-swallow variability than the raw sEMG. The ICs, each consisting of a unique temporal waveform and a spatial distribution, provided a means to segregate the complex sequence of muscle activation into rigorously defined separate functional units. The temporal profiles of the ICs and their spatial distribution were consistent with prior needle EMG studies of the cricopharyngeal, superior pharyngeal constrictor, submental and possibly arytenoid muscles. Other components appeared to correspond to EKG artifact contaminating the EMG recordings, laryngeal excursion, tongue movement and activation of the buccal and/or masseter musculature At least two of the components were affected by the consistency of the liquids swallowed. Re-testing one subject a week later demonstrated good intertrial reliability. We propose that the ICs of the sEMG provide a non-invasive means to assess the complex muscle sequence activation of deglutition.

  20. POST-EXERCISE MUSCLE GLYCOGEN REPLETION IN THE EXTREME: EFFECT OF FOOD ABSENCE AND ACTIVE RECOVERY

    Directory of Open Access Journals (Sweden)

    Paul A. Fournier

    2004-09-01

    Full Text Available Glycogen plays a major role in supporting the energy demands of skeletal muscles during high intensity exercise. Despite its importance, the amount of glycogen stored in skeletal muscles is so small that a large fraction of it can be depleted in response to a single bout of high intensity exercise. For this reason, it is generally recommended to ingest food after exercise to replenish rapidly muscle glycogen stores, otherwise one's ability to engage in high intensity activity might be compromised. But what if food is not available? It is now well established that, even in the absence of food intake, skeletal muscles have the capacity to replenish some of their glycogen at the expense of endogenous carbon sources such as lactate. This is facilitated, in part, by the transient dephosphorylation-mediated activation of glycogen synthase and inhibition of glycogen phosphorylase. There is also evidence that muscle glycogen synthesis occurs even under conditions conducive to an increased oxidation of lactate post-exercise, such as during active recovery from high intensity exercise. Indeed, although during active recovery glycogen resynthesis is impaired in skeletal muscle as a whole because of increased lactate oxidation, muscle glycogen stores are replenished in Type IIa and IIb fibers while being broken down in Type I fibers of active muscles. This unique ability of Type II fibers to replenish their glycogen stores during exercise should not come as a surprise given the advantages in maintaining adequate muscle glycogen stores in those fibers that play a major role in fight or flight responses

  1. Arm position influences the activation patterns of trunk muscles during trunk range-of-motion movements.

    Science.gov (United States)

    Siu, Aaron; Schinkel-Ivy, Alison; Drake, Janessa Dm

    2016-10-01

    To understand the activation patterns of the trunk musculature, it is also important to consider the implications of adjacent structures such as the upper limbs, and the muscles that act to move the arms. This study investigated the effects of arm positions on the activation patterns and co-activation of the trunk musculature and muscles that move the arm during trunk range-of-motion movements (maximum trunk axial twist, flexion, and lateral bend). Fifteen males and fifteen females, asymptomatic for low back pain, performed maximum trunk range-of-motion movements, with three arm positions for axial twist (loose, crossed, abducted) and two positions for flexion and lateral bend (loose, crossed). Electromyographical data were collected for eight muscles bilaterally, and activation signals were cross-correlated between trunk muscles and the muscles that move the arms (upper trapezius, latissimus dorsi). Results revealed consistently greater muscle co-activation (higher cross-correlation coefficients) between the trunk muscles and upper trapezius for the abducted arm position during maximum trunk axial twist, while results for the latissimus dorsi-trunk pairings were more dependent on the specific trunk muscles (either abdominal or back) and latissimus dorsi muscle (either right or left side), as well as the range-of-motion movement. The findings of this study contribute to the understanding of interactions between the upper limbs and trunk, and highlight the influence of arm positions on the trunk musculature. In addition, the comparison of the present results to those of individuals with back or shoulder conditions may ultimately aid in elucidating underlying mechanisms or contributing factors to those conditions.

  2. Depressant effect of active shortening in the anterior byssus retractor muscle of Mytilus edulis.

    Science.gov (United States)

    Ekelund, M C

    1983-03-01

    The effect of shortening during activity, previously characterized in vertebrate striated muscle, was investigated in the anterior byssus retractor muscle (ABRM) of the mollusc Mytilus edulis. This muscle is considered to have an essentially myosin-linked Ca2+-regulatory system. Release steps of different amplitude were performed during isometric phasic contraction, and force redevelopment was recorded at a muscle length L1, defined as 90% of the muscle length at which a slight resting tension, approximately 1 mN, appeared in the presence of 2.5 X 10(-5) M 5-HT. Active shortening caused a graded depression of the contractile force without affecting the total duration of the mechanical response. Peak redeveloped force after muscle shortening of 0.06 L1 and 0.18 L1 was reduced by approximately 1.5% and 7.0%, respectively, of the isometric tension value at L1. The shortening effect was fully reversible, and had a lifetime of approximately 8 to 9 s. The depressant effect of active shortening was augmented at a reduced degree of activation of the muscle. The presence of caffeine and dantrolene and altered tonicity of the extracellular medium (0.9 T-1.2 T) did not significantly affect the shortening induced depression obtained at maximum phasic activation of the preparation. The nature of the shortening effect is compared to that obtained in vertebrate striated muscle and is discussed on the basis of differences in Ca2+-regulation of the contractile system in these two muscles.

  3. Muscle activation and blood flow do not explain the muscle length-dependent variation in quadriceps isometric endurance.

    Science.gov (United States)

    Kooistra, R D; de Ruiter, C J; de Haan, A

    2005-03-01

    We investigated the role of central activation in muscle length-dependent endurance. Central activation ratio (CAR) and rectified surface electromyogram (EMG) were studied during fatigue of isometric contractions of the knee extensors at 30 and 90 degrees knee angles (full extension = 0 degree). Subjects (n = 8) were tested on a custom-built ergometer. Maximal voluntary isometric knee extension with supramaximal superimposed burst stimulation (three 100-mus pulses; 300 Hz) was performed to assess CAR and maximal torque capacity (MTC). Surface EMG signals were obtained from vastus lateralis and rectus femoris muscles. At each angle, intermittent (15 s on 6 s off) isometric exercise at 50% MTC with superimposed stimulation was performed to exhaustion. During the fatigue task, a sphygmomanometer cuff around the upper thigh ensured full occlusion (400 mmHg) of the blood supply to the knee extensors. At least 2 days separated fatigue tests. MTC was not different between knee angles (30 degrees : 229.6 +/- 39.3 N.m vs. 90 degrees: 215.7 +/- 13.2 N.m). Endurance times, however, were significantly longer (P muscle length-related differences in metabolic cost.

  4. Post-exercise muscle glycogen repletion in the extreme: effect of food absence and active recovery.

    Science.gov (United States)

    Fournier, Paul A; Fairchild, Timothy J; Ferreira, Luis D; Bräu, Lambert

    2004-09-01

    Glycogen plays a major role in supporting the energy demands of skeletal muscles during high intensity exercise. Despite its importance, the amount of glycogen stored in skeletal muscles is so small that a large fraction of it can be depleted in response to a single bout of high intensity exercise. For this reason, it is generally recommended to ingest food after exercise to replenish rapidly muscle glycogen stores, otherwise one's ability to engage in high intensity activity might be compromised. But what if food is not available? It is now well established that, even in the absence of food intake, skeletal muscles have the capacity to replenish some of their glycogen at the expense of endogenous carbon sources such as lactate. This is facilitated, in part, by the transient dephosphorylation-mediated activation of glycogen synthase and inhibition of glycogen phosphorylase. There is also evidence that muscle glycogen synthesis occurs even under conditions conducive to an increased oxidation of lactate post-exercise, such as during active recovery from high intensity exercise. Indeed, although during active recovery glycogen resynthesis is impaired in skeletal muscle as a whole because of increased lactate oxidation, muscle glycogen stores are replenished in Type IIa and IIb fibers while being broken down in Type I fibers of active muscles. This unique ability of Type II fibers to replenish their glycogen stores during exercise should not come as a surprise given the advantages in maintaining adequate muscle glycogen stores in those fibers that play a major role in fight or flight responses. Key PointsEven in the absence of food intake, skeletal muscles have the capacity to replenish some of their glycogen at the expense of endogenous carbon sources such as lactate.During active recovery from exercise, skeletal muscles rich in type II fibers replenish part of their glycogen stores even in the absence of food intake.Post-exercise muscle glycogen synthesis in the

  5. Altered lower leg muscle activation patterns in patients with cerebral palsy during cycling on an ergometer

    Directory of Open Access Journals (Sweden)

    Alves-Pinto A

    2016-06-01

    Full Text Available Ana Alves-Pinto,1,* Tobias Blumenstein,1,* Varvara Turova,1 Renée Lampe1,2 1Research Unit of the Buhl-Strohmaier Foundation for Cerebral Palsy and Paediatric Neuroorthopaedics, Orthopaedic Department, Klinikum rechts der Isar, 2Markus Würth Professorship, Technical University of Munich, Munich, Germany *These authors contributed equally to this work Objective: Cycling on a recumbent ergometer constitutes one of the most popular rehabilitation exercises in cerebral palsy (CP. However, no control is performed on how muscles are being used during training. Given that patients with CP present altered muscular activity patterns during cycling or walking, it is possible that an incorrect pattern of muscle activation is being promoted during rehabilitation cycling. This study investigated patterns of muscular activation during cycling on a recumbent ergometer in patients with CP and whether those patterns are determined by the degree of spasticity and of mobility.Methods: Electromyographic (EMG recordings of lower leg muscle activation during cycling on a recumbent ergometer were performed in 14 adult patients diagnosed with CP and five adult healthy participants. EMG recordings were done with an eight-channel EMG system built in the laboratory. The activity of the following muscles was recorded: Musculus rectus femoris, Musculus biceps femoris, Musculus tibialis anterior, and Musculus gastrocnemius. The degree of muscle spasticity and mobility was assessed using the Modified Ashworth Scale and the Gross Motor Function Classification System, respectively. Muscle activation patterns were described in terms of onset and duration of activation as well as duration of cocontractions.Results: Muscle activation in CP was characterized by earlier onsets, longer periods of activation, a higher occurrence of agonist–antagonist cocontractions, and a more variable cycling tempo in comparison to healthy participants. The degree of altered muscle activation

  6. Estrogen effect on post-exercise skeletal muscle neutrophil infiltration and calpain activity.

    Science.gov (United States)

    Tiidus, P M; Holden, D; Bombardier, E; Zajchowski, S; Enns, D; Belcastro, A

    2001-05-01

    We hypothesized that estrogen administration would attenuate skeletal muscle neutrophil infiltration, indices of muscle membrane disruption, and muscle calpain activity shortly after the termination of exercise. Ovariectomized female rats were implanted with either an estogen pellet (25 mg beta-estradiol) or a placebo pellet. Two weeks postimplant, animals were killed either at rest or 1 h after running exercise (60 min at 21 m x min(-1), 12% grade). The 4 experimental groups (n = 12) used were: unexercised placebo (UP), unexercised estrogen (UE), exercised placebo (EP), and exercised estrogen (EE). Blood samples were analyzed for creatine kinase (CK) activity and estradiol content. Plantaris and gastrocnemius muscles were removed and histochemical determination of neutrophil content or biochemical determination of myeloperoxidase (MPO), glucose-6-phosphate dehydrogenase (G6PD), and calpain-like activity determined. Estrogen supplemented animals had 10-20-fold higher circulating estradiol levels than placebo animals. EP animals had significantly higher (P estrogen supplementation in ovariectomized rats attenuated 1-h post-exercise serum CK activities, muscle neutrophil infiltration, MPO activities, and calpain-like activities when compared with exercised, unsupplemented animals. This supports the possibility of a relationship between estrogen, calpain dependent production of neutrophil chemo-attractant peptides, and 1-h post-exercise skeletal muscle neutrophil infiltration.

  7. Activated protein C attenuates acute ischaemia reperfusion injury in skeletal muscle.

    LENUS (Irish Health Repository)

    Dillon, J P

    2012-02-03

    Activated protein C (APC) is an endogenous anti-coagulant with anti-inflammatory properties. The purpose of the present study was to evaluate the effects of activated protein C in the setting of skeletal muscle ischaemia reperfusion injury (IRI). IRI was induced in rats by applying rubber bands above the levels of the greater trochanters bilaterally for a period of 2h followed by 12h reperfusion. Treatment groups received either equal volumes of normal saline or activated protein C prior to tourniquet release. Following 12h reperfusion, muscle function was assessed electrophysiologically by electrical field stimulation. The animals were then sacrificed and skeletal muscle harvested for evaluation. Activated protein C significantly attenuated skeletal muscle reperfusion injury as shown by reduced myeloperoxidase content, wet to dry ratio and electrical properties of skeletal muscle. Further in vitro work was carried out on neutrophils isolated from healthy volunteers to determine the direct effect of APC on neutrophil function. The effects of APC on TNF-alpha stimulated neutrophils were examined by measuring CD18 expression as well as reactive oxygen species generation. The in vitro work demonstrated a reduction in CD18 expression and reactive oxygen species generation. We conclude that activated protein C may have a protective role in the setting of skeletal muscle ischaemia reperfusion injury and that this is in part mediated by a direct inhibitory effect on neutrophil activation.

  8. Muscle activity and acceleration during whole body vibration: effect of frequency and amplitude.

    Science.gov (United States)

    Pollock, Ross D; Woledge, Roger C; Mills, Kerry R; Martin, Finbarr C; Newham, Di J

    2010-10-01

    Whole body vibration may improve muscle and bone strength, power and balance although contradictory findings have been reported. Prolonged exposure may result in adverse effects. We investigated the effects of high (5.5 mm) and low (2.5mm) amplitude whole body vibration at various frequencies (5-30 Hz) on muscle activity and acceleration throughout the body. Surface electromyographic activity was recorded from 6 leg muscles in 12 healthy adults (aged 31.3 (SD 12.4) years). The average rectified acceleration of the toe, ankle, knee, hip and head was recorded from 15 healthy adults (36 (SD 12.1) years) using 3D motion analysis. Whole body vibration increased muscle activity 5-50% of maximal voluntary contraction with the greatest increase in the lower leg. Activity was greater with high amplitude at all frequencies, however this was not always significant (P 15 Hz acceleration decreased with distance from the platform. This was associated with increased muscle activity, presumably due to postural control and muscle tuning mechanisms. The minimal acceleration at the head reduces the likelihood of adverse reactions. The levels of activation are unlikely to cause hypertrophy in young healthy individuals but may be sufficient in weak and frail people. 2010 Elsevier Ltd. All rights reserved.

  9. A novel spatiotemporal muscle activity imaging approach based on the Extended Kalman Filter.

    Science.gov (United States)

    Wang, Jing; Zhang, Yingchun; Zhu, Xiangjun; Zhou, Ping; Liu, Chenguang; Rymer, William Z

    2012-01-01

    A novel spatiotemporal muscle activity imaging (sMAI) approach has been developed using the Extended Kalman Filter (EKF) to reconstruct internal muscle activities from non-invasive multi-channel surface electromyogram (sEMG) recordings. A distributed bioelectric dipole source model is employed to describe the internal muscle activity space, and a linear relationship between the muscle activity space and the sEMG measurement space is then established. The EKF is employed to recursively solve the ill-posed inverse problem in the sMAI approach, in which the weighted minimum norm (WMN) method is utilized to calculate the initial state and a new nonlinear method is developed based on the propagating features of muscle activities to predict the recursive state. A series of computer simulations was conducted to test the performance of the proposed sMAI approach. Results show that the localization error rapidly decreases over 35% and the overlap ratio rapidly increases over 45% compared to the results achieved using the WMN method only. The present promising results demonstrate the feasibility of utilizing the proposed EKF-based sMAI approach to accurately reconstruct internal muscle activities from non-invasive sEMG recordings.

  10. Effect of extensor muscle activation on the response to lumbar posteroanterior forces.

    Science.gov (United States)

    Lee, M; Esler, M A; Mildren, J; Herbert, R

    1993-05-01

    The purpose of this study was to examine the responses of normal subjects to the application of cyclical lumbar posteroanterior forces which simulated a manipulative therapy technique known as mobilization. The specific aim was to determine whether increases in spinal extensor muscle activity could modify the stiffness of lumbar posteroanterior movements. The lumbar posteroanterior stiffness was measured in eleven asymptomatic subjects in the prone position, both in the relaxed condition and during maximal voluntary isometric muscle contractions. The electromyographic activity of lumbar extensor muscles was measured in the relaxed and maximal contraction conditions during the application of mobilization. The posteroanterior stiffness was found to be significantly greater during maximum activation of the extensor muscles. The results indicate that muscle activity can significantly alter lumbar posteroanterior stiffness. Clinicians often apply posteroanterior forces over a spinous process of a vertebra to assess the resistance to movement. Information about the degree and nature of perceived resistance to posteroanterior movement is used to help make a diagnosis and select treatment techniques. This study has shown that increased activity of the spinal extensor muscles can increase the stiffness of lumbar posteroanterior movements, compared with the case where the subject is relaxed. When interpreting the posteroanterior responses of patients, clinicians should be aware that spinal extensor mucle activity can influence resistance to posteroanterior movement.

  11. A consistent muscle activation strategy underlies crawling and swimming in Caenorhabditis elegans.

    Science.gov (United States)

    Butler, Victoria J; Branicky, Robyn; Yemini, Eviatar; Liewald, Jana F; Gottschalk, Alexander; Kerr, Rex A; Chklovskii, Dmitri B; Schafer, William R

    2015-01-06

    Although undulatory swimming is observed in many organisms, the neuromuscular basis for undulatory movement patterns is not well understood. To better understand the basis for the generation of these movement patterns, we studied muscle activity in the nematode Caenorhabditis elegans. Caenorhabditis elegans exhibits a range of locomotion patterns: in low viscosity fluids the undulation has a wavelength longer than the body and propagates rapidly, while in high viscosity fluids or on agar media the undulatory waves are shorter and slower. Theoretical treatment of observed behaviour has suggested a large change in force-posture relationships at different viscosities, but analysis of bend propagation suggests that short-range proprioceptive feedback is used to control and generate body bends. How muscles could be activated in a way consistent with both these results is unclear. We therefore combined automated worm tracking with calcium imaging to determine muscle activation strategy in a variety of external substrates. Remarkably, we observed that across locomotion patterns spanning a threefold change in wavelength, peak muscle activation occurs approximately 45° (1/8th of a cycle) ahead of peak midline curvature. Although the location of peak force is predicted to vary widely, the activation pattern is consistent with required force in a model incorporating putative length- and velocity-dependence of muscle strength. Furthermore, a linear combination of local curvature and velocity can match the pattern of activation. This suggests that proprioception can enable the worm to swim effectively while working within the limitations of muscle biomechanics and neural control.

  12. Salamander limb regeneration involves the activation of a multipotent skeletal muscle satellite cell population.

    Science.gov (United States)

    Morrison, Jamie I; Lööf, Sara; He, Pingping; Simon, András

    2006-01-30

    In contrast to mammals, salamanders can regenerate complex structures after injury, including entire limbs. A central question is whether the generation of progenitor cells during limb regeneration and mammalian tissue repair occur via separate or overlapping mechanisms. Limb regeneration depends on the formation of a blastema, from which the new appendage develops. Dedifferentiation of stump tissues, such as skeletal muscle, precedes blastema formation, but it was not known whether dedifferentiation involves stem cell activation. We describe a multipotent Pax7+ satellite cell population located within the skeletal muscle of the salamander limb. We demonstrate that skeletal muscle dedifferentiation involves satellite cell activation and that these cells can contribute to new limb tissues. Activation of salamander satellite cells occurs in an analogous manner to how the mammalian myofiber mobilizes stem cells during skeletal muscle tissue repair. Thus, limb regeneration and mammalian tissue repair share common cellular and molecular programs. Our findings also identify satellite cells as potential targets in promoting mammalian blastema formation.

  13. Evaluation of muscle activity during a standardized shoulder resistance training bout in novice individuals

    DEFF Research Database (Denmark)

    Jakobsen, Markus D; Sundstrup, Emil; Andersen, Christoffer H

    2012-01-01

    training bout. The purpose of this study was to evaluate muscle activity during a shoulder resistance training bout with 15 repetitions maximum (RM) loadings in novice individuals. Twelve healthy sedentary women (age = 27-58 years; weight = 54-85 kg; height = 160-178 cm) were recruited for this study...... to the third set (averaged for all muscles: 38.1 ± 23.6 vs. 47.6 ± 28.8% and 88.4 ± 21.3 vs. 82.1 ± 18.1 Hz, respectively). In conclusion, during a shoulder resistance training bout in novice individuals using 15RM loading muscle activity of the upper, medial, and lower trapezius, the medial deltoid...... of exercises, nEMG activity was high (>60% of maximal isometric contractions). From the first to the last repetition of each set nEMG-averaged for all muscles-increased 10. 0 ± 0.4% (p

  14. Work related perceived stress and muscle activity during standardized computer work among female computer users

    DEFF Research Database (Denmark)

    Larsman, P; Thorn, S; Søgaard, K

    2009-01-01

    The current study investigated the associations between work-related perceived stress and surface electromyographic (sEMG) parameters (muscle activity and muscle rest) during standardized simulated computer work (typing, editing, precision, and Stroop tasks). It was part of the European case......-control study, NEW (Neuromuscular assessment in the Elderly Worker). The present cross-sectional study was based on a questionnaire survey and sEMG measurements among Danish and Swedish female computer users aged 45 or older (n=49). The results show associations between work-related perceived stress...... and trapezius muscle activity and rest during standardized simulated computer work, and provide partial empirical support for the hypothesized pathway of stress induced muscle activity in the association between an adverse psychosocial work environment and musculoskeletal symptoms in the neck and shoulder....

  15. Changes in transverse relaxation time of quadriceps femoris muscles after active recovery exercises with different intensities.

    Science.gov (United States)

    Mukaimoto, Takahiro; Semba, Syun; Inoue, Yosuke; Ohno, Makoto

    2014-01-01

    The purpose of this study was to examine the changes in the metabolic state of quadriceps femoris muscles using transverse relaxation time (T2), measured by muscle functional magnetic resonance (MR) imaging, after inactive or active recovery exercises with different intensities following high-intensity knee-extension exercise. Eight healthy men performed recovery sessions with four different conditions for 20 min after high-intensity knee-extension exercise on separate days. During the recovery session, the participants conducted a light cycle exercise for 20 min using a cycle (50%, 70% and 100% of the lactate threshold (LT), respectively: active recovery), and inactive recovery. The MR images of quadriceps femoris muscles were taken before the trial and after the recovery session every 30 min for 120 min. The percentage changes in T2 for the rectus femoris and vastus medialis muscles after the recovery session in 50% LT and 70% LT were significantly lower than those in either inactive recovery or 100% LT. There were no significant differences in those for vastus lateralis and vastus intermedius muscles among the four trials. The percentage changes in T2 of rectus femoris and vastus medialis muscles after the recovery session in 50% LT and 70% LT decreased to the values before the trial faster than those in either inactive recovery or 100% LT. Those of vastus lateralis and vastus intermedius muscles after the recovery session in 50% LT and 70% LT decreased to the values before the trial faster than those in 100% LT. Although the changes in T2 after active recovery exercises were not uniform in exercised muscles, the results of this study suggest that active recovery exercise with the intensities below LT are more effective to recover the metabolic state of quadriceps femoris muscles after intense exercise than with either intensity at LT or inactive recovery.

  16. The role of MyoD1 and histone modifications in the activation of muscle enhancers.

    Science.gov (United States)

    Blum, Roy; Dynlacht, Brian D

    2013-08-01

    MyoD1 is a key regulator that orchestrates skeletal muscle differentiation through the regulation of gene expression. Although many studies have focused on its role in transcriptional control at gene promoters, less is known regarding the role of MyoD1 in the assembly of active enhancers. Here, we discuss novel data that point to the ability of MyoD1 to mediate the assembly of active enhancers that augment the transcription of genes essential for muscle development and lineage specification. Based on genome-wide studies of epigenetic marks that typify active enhancers, we recently identified the compendium of distal regulatory elements that dictate transcriptional programs during myogenesis. Superimposition of MyoD1 binding sites upon the locations of muscle enhancers revealed its unequivocal binding to a core region of nearly a third of condition-specific muscle enhancers. Further studies exploring deposition of enhancer-related epigenetic marks in myoblasts lacking MyoD1 demonstrate the dependence of muscle enhancer assembly on the presence of MyoD1. We propose a model wherein MyoD1 mediates recruitment of Set7, H3K4me1, H3K27ac, p300, and RNAP II to MyoD1-bound enhancers to establish condition-specific activation of muscle genes. Moreover, muscle enhancers are modulated through coordinated binding of transcription factors, including c-Jun, Jdp2, Meis, and Runx1, which are recruited to muscle enhancers in a MyoD1-dependent manner. Thus, MyoD1 and enhancer-associated transcription factors function coordinately to assemble and regulate enhancers, thereby augmenting expression of muscle-related genes.

  17. The effect of trunk stabilization exercises with a swiss ball on core muscle activation in the elderly.

    Science.gov (United States)

    Kim, Seong Gil; Yong, Min Sik; Na, Sang Su

    2014-09-01

    [Purpose] The purpose of this study was to investigate the effects of trunk stabilization exercise on the muscle EMG activations related to core stability. [Subjects and Methods] Fifteen elderly people in a geriatric hospital performed trunk stabilization exercises with a Swiss ball for 20 minutes five times per week for 8 weeks. Trunk muscle activations were measured using electromyography before and after the intervention. [Results] After the intervention, the muscle activations of the rectus abdominis, erector spinae, lateral low-back (quadratus lumborum and external oblique), and gluteus medius muscles increased significantly. [Conclusion] The trunk stabilization exercise with a Swiss ball significantly increased the muscle activities of the elderly.

  18. [Familial spastic paraplegia with syndrome of continuous muscle fiber activity (Isaacs)].

    Science.gov (United States)

    Yokota, T; Matsunaga, T; Furukawa, T; Tsukagoshi, H

    1989-06-01

    A woman aged fifty-three developed paraparesis at the age of 4, which progressed slowly and required crutches by the age of 30. At the age of 51, muscle stiffness involved bilateral hands and arms gradually. At the age of 53, she suffered from painful spasms in right deltoid muscle. Her two brothers had spastic paraplegia without other neurological deficits. Her paternal grandfather and maternal grandmother were cousins. Slight dementia was noted (WAIS: IQ, 79). Her posture was stiff and muscles of upper limbs were in a persistent contraction; Subcutaneous tissue was thin, and muscles were well-defined and firm. There was moderate muscle weakness of legs and hands. Continuous fasciculations and myokymias were recognized in muscles of the arms and the limb girdles. Muscle tone was considerably increased especially in the bilateral arms. The deep tendon reflexes were exaggerated with extensor plantar responses. Profuse sweating affected palms, soles and backs. No sensory disturbance was appreciated. There was no myotonic responses to percussion of muscles. Following laboratory data were normal; thyroid functions, CSF studies, anti HTLV-I antibody and long chain fatty acid in red blood cells, myelography and brain CT except for increased basal metabolic rate (53%). Electromyographic study in the arms and hands revealed spontaneous motor unit activities including doublets at rest and increased proportion of polyphasic potentials and high amplitude potentials in voluntary contraction. Biopsy of right quadriceps femoris muscle showed hypertrophy of type I fibers and angulated atrophy of type II fibers. Continuous muscle activities in upper limbs did not change at sleep or with intravenous administration of 7 mg diazepam.(ABSTRACT TRUNCATED AT 250 WORDS)

  19. Variations in activities of human jaw muscles depend on tooth-tipping moments.

    Science.gov (United States)

    Uchida, S; Iwasaki, L R; Marx, D B; Yotsui, Y; Inoue, H; Nickel, J C

    2008-02-01

    Static mechanical analyses of the masticatory apparatus often assume that jaw muscle activity, as measured using electromyography (EMG), is linearly and constantly related to magnitude of bite force during biting, regardless of bite force-induced tooth-tipping moments. The objective of this study was to test the hypothesis that the relationship between EMG of the jaw muscles and bite force varies with the magnitude and sign of tooth-tipping moments. Seven healthy male subjects produced unilateral static occlusal forces at five biting positions, resulting in sequential changes from buccal (+) to lingual (-) tipping moments on the mandibular first molar. Jaw muscle activities were recorded bilaterally using surface (for temporalis and masseter muscles) and indwelling (for lateral pterygoid muscles) electrodes. Bite forces were recorded and controlled using custom devices. EMG versus bite force data were plotted and regression relationships were calculated for each subject, muscle and biting position. Linear regression analysis, analysis of variance and Bonferroni adjusted least significant difference tests were used to determine the effects of muscle, side (ipsilateral, contralateral) and biting position within subjects. It was found that the relationship between EMG and bite force for different tipping moments differed significantly within a subject and muscle. This was most common in the lateral pterygoid and temporalis muscles (all PEMG:bite force relationship varied between 3:1 and >25:1. In the masseter muscle, the EMG:bite force relationship for different tipping moments differed significantly in one subject (PEMG and bite force was linear. However, the slopes of the relationship changed significantly depending on sign (+, -) and magnitude of tipping moments acting on the molars.

  20. Differential activation of sympathetic discharge to skin and skeletal muscle in humans.

    Science.gov (United States)

    Vissing, S F

    1997-01-01

    The present work provides insight into the relative contribution of different mechanisms in regulating sympathetic discharge to skin and skeletal muscle in humans. Activation of sympathetic nerve activity during common behaviours such as orthostasis and exercise was shown to be highly selective, depending on the specific sympathetic outflow under study. Regarding orthostasis, data from experiments in this thesis revoked the concept that cardiopulmonary afferents only regulate muscle vascular resistance in the forearm, not in the leg. Also the concept that the cutaneous circulation is under baroreceptor control has been challenged. Unloading cardiopulmonary afferents with lower body negative pressure elicited intensity dependent increases in peroneal sympathetic discharge to skeletal muscle, and increases in forearm and calf vascular resistances. Therefore, it was concluded that cardiopulmonary afferents regulate vascular resistance in skeletal muscle of both forearm and calf, suggesting an important role for these afferents in the reflex adjustments to upright posture. In contrast to muscle sympathetic nerve activity, baroreceptor deactivation with lower body negative pressure had no effect on skin sympathetic nerve activity or skin vascular resistance. However, assumption of upright posture increased skin vascular resistance, this increase was abolished when increased vascular transmural pressure was avoided by elevating the arm. Local cutaneous nerve blockade, but not blockade of efferent sympathetic nerve traffic, abolished the vasoconstrictor response to upright posture. Based on these experiments, it was concluded that baroreceptor afferents do not regulate sympathetic vasoconstrictor outflow to the cutaneous circulation. During upright posture at normothermia cutaneous vasoconstriction is mainly driven by a local reflex. To explain activation of sympathetic outflow during exercise two theories have been proposed. One is that a "central motor command" signal

  1. Effect of cadence regulation on muscle activation patterns during robot assisted gait: a dynamic simulation study.

    Science.gov (United States)

    Hussain, Shahid; Xie, Sheng Q; Jamwal, Prashant K

    2013-03-01

    Cadence or stride frequency is an important parameter being controlled in gait training of neurologically impaired subjects. The aim of this study was to examine the effects of cadence variation on muscle activation patterns during robot assisted unimpaired gait using dynamic simulations. A twodimensional (2-D) musculoskeletal model of human gait was developed considering eight major muscle groups along with existing ground contact force (GCF) model. A 2-D model of a robotic orthosis was also developed which provides actuation to the hip, knee and ankle joints in the sagittal plane to guide subjects limbs on reference trajectories. A custom inverse dynamics algorithm was used along with a quadratic minimization algorithm to obtain a feasible set of muscle activation patterns. Predicted patterns of muscle activations during slow, natural and fast cadence were compared and the mean muscle activations were found to be increasing with an increase in cadence. The proposed dynamic simulation provide important insight into the muscle activation variations with change in cadence during robot assisted gait and provide the basis for investigating the influence of cadence regulation on neuromuscular parameters of interest during robot assisted gait.

  2. Muscle activation patterns in the Nordic hamstring exercise: Impact of prior strain injury.

    Science.gov (United States)

    Bourne, M N; Opar, D A; Williams, M D; Al Najjar, A; Shield, A J

    2016-06-01

    This study aimed to determine: (a) the spatial patterns of hamstring activation during the Nordic hamstring exercise (NHE); (b) whether previously injured hamstrings display activation deficits during the NHE; and (c) whether previously injured hamstrings exhibit altered cross-sectional area (CSA). Ten healthy, recreationally active men with a history of unilateral hamstring strain injury underwent functional magnetic resonance imaging of their thighs before and after six sets of 10 repetitions of the NHE. Transverse (T2) relaxation times of all hamstring muscles [biceps femoris long head (BFlh); biceps femoris short head (BFsh); semitendinosus (ST); semimembranosus (SM)] were measured at rest and immediately after the NHE and CSA was measured at rest. For the uninjured limb, the ST's percentage increase in T2 with exercise was 16.8%, 15.8%, and 20.2% greater than the increases exhibited by the BFlh, BFsh, and SM, respectively (P < 0.002 for all). Previously injured hamstring muscles (n = 10) displayed significantly smaller increases in T2 post-exercise than the homonymous muscles in the uninjured contralateral limb (mean difference -7.2%, P = 0.001). No muscles displayed significant between-limb differences in CSA. During the NHE, the ST is preferentially activated and previously injured hamstring muscles display chronic activation deficits compared with uninjured contralateral muscles. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  3. Noninvasive imaging of internal muscle activities from multi-channel surface EMG recordings.

    Science.gov (United States)

    Zhang, Yingchun

    2013-01-01

    Surface Electromyogram (sEMG) technology provides a non-invasive way for rapid monitoring muscle activities, but its poor spatial resolution and specificity limit its application in clinic. To overcome these limitations, a noninvasive muscle activity imaging (MAI) approach has been developed and used to reconstruct internal muscle activities from multi-channel sEMG recordings. A realistic geometric hand model is developed from high-resolution MR images and a distributed bioelectric dipole source model is employed to describe the internal muscle activity space of the muscles. The finite element method and weighted minimum norm method are utilized solve the forward and inverse problems respectively involved in the proposed MAI technique. A series of computer simulations was conducted to test the performance of the proposed MAI approach. Results show that reconstruction results achieved by the MAI technique indeed provide us more detailed and dynamic information of internal muscle activities, which enhance our understanding of the mechanisms underlying the surface EMG recordings.

  4. Skeletal muscle Ca(2+)-independent kinase activity increases during either hypertrophy or running

    Science.gov (United States)

    Fluck, M.; Waxham, M. N.; Hamilton, M. T.; Booth, F. W.

    2000-01-01

    Spikes in free Ca(2+) initiate contractions in skeletal muscle cells, but whether and how they might signal to transcription factors in skeletal muscles of living animals is unknown. Since previous studies in non-muscle cells have shown that serum response factor (SRF) protein, a transcription factor, is phosphorylated rapidly by Ca(2+)/calmodulin (CaM)-dependent protein kinase after rises in intracellular Ca(2+), we measured enzymatic activity that phosphorylates SRF (designated SRF kinase activity). Homogenates from 7-day-hypertrophied anterior latissimus dorsi muscles of roosters had more Ca(2+)-independent SRF kinase activity than their respective control muscles. However, no differences were noted in Ca(2+)/CaM-dependent SRF kinase activity between control and trained muscles. To determine whether the Ca(2+)-independent and Ca(2+)/CaM-dependent forms of Ca(2+)/CaM-dependent protein kinase II (CaMKII) might contribute to some of the SRF kinase activity, autocamtide-3, a synthetic substrate that is specific for CaMKII, was employed. While the Ca(2+)-independent form of CaMKII was increased, like the Ca(2+)-independent form of SRF kinase, no alteration in CaMKII occurred at 7 days of stretch overload. These observations suggest that some of SRF phosphorylation by skeletal muscle extracts could be due to CaMKII. To determine whether this adaptation was specific to the exercise type (i.e., hypertrophy), similar measurements were made in the white vastus lateralis muscle of rats that had completed 2 wk of voluntary running. Although Ca(2+)-independent SRF kinase was increased, no alteration occurred in Ca(2+)/CaM-dependent SRF kinase activity. Thus any role of Ca(2+)-independent SRF kinase signaling has downstream modulators specific to the exercise phenotype.

  5. Neck posture and muscle activity are different when upside down: a human volunteer study.

    Science.gov (United States)

    Newell, Robyn S; Blouin, Jean-Sébastien; Street, John; Cripton, Peter A; Siegmund, Gunter P

    2013-11-15

    Rollover crashes are dynamic and complex events in which head impacts with the roof can cause catastrophic neck injuries. Ex vivo and computational models are valuable in understanding, and ultimately preventing, these injuries. Although neck posture and muscle activity influence the resulting injury, there is currently no in vivo data describing these parameters immediately prior to a head-first impact. The specific objectives of this study were to determine the in vivo neck vertebral alignment and muscle activation levels when upside down, a condition that occurs during a rollover. Eleven human subjects (6F, 5M) were tested while seated upright and inverted in a custom-built apparatus. Vertebral alignment was measured using fluoroscopy and muscle activity was recorded using surface and indwelling electrodes in eight superficial and deep neck muscles. In vivo vertebral alignment and muscle activation levels differed between the upright and inverted conditions. When inverted and relaxed, the neck was more lordotic, C1 was aligned posterior to C7, the Frankfort plane was extended, and the activity of six muscles increased compared to upright and relaxed. When inverted subjects were asked to look forward to eliminate head extension, flexor muscle activity increased, C7 was more flexed, and C1 was aligned anterior to C7 versus upright and relaxed. Combined with the large inter-subject variability observed, these findings indicate that cadaveric or computational models designed to study injuries and prevention devices while inverted need to consider a variety of postures and muscle conditions to be relevant to the in vivo situation.

  6. Skeletal muscle Ca(2+)-independent kinase activity increases during either hypertrophy or running

    Science.gov (United States)

    Fluck, M.; Waxham, M. N.; Hamilton, M. T.; Booth, F. W.

    2000-01-01

    Spikes in free Ca(2+) initiate contractions in skeletal muscle cells, but whether and how they might signal to transcription factors in skeletal muscles of living animals is unknown. Since previous studies in non-muscle cells have shown that serum response factor (SRF) protein, a transcription factor, is phosphorylated rapidly by Ca(2+)/calmodulin (CaM)-dependent protein kinase after rises in intracellular Ca(2+), we measured enzymatic activity that phosphorylates SRF (designated SRF kinase activity). Homogenates from 7-day-hypertrophied anterior latissimus dorsi muscles of roosters had more Ca(2+)-independent SRF kinase activity than their respective control muscles. However, no differences were noted in Ca(2+)/CaM-dependent SRF kinase activity between control and trained muscles. To determine whether the Ca(2+)-independent and Ca(2+)/CaM-dependent forms of Ca(2+)/CaM-dependent protein kinase II (CaMKII) might contribute to some of the SRF kinase activity, autocamtide-3, a synthetic substrate that is specific for CaMKII, was employed. While the Ca(2+)-independent form of CaMKII was increased, like the Ca(2+)-independent form of SRF kinase, no alteration in CaMKII occurred at 7 days of stretch overload. These observations suggest that some of SRF phosphorylation by skeletal muscle extracts could be due to CaMKII. To determine whether this adaptation was specific to the exercise type (i.e., hypertrophy), similar measurements were made in the white vastus lateralis muscle of rats that had completed 2 wk of voluntary running. Although Ca(2+)-independent SRF kinase was increased, no alteration occurred in Ca(2+)/CaM-dependent SRF kinase activity. Thus any role of Ca(2+)-independent SRF kinase signaling has downstream modulators specific to the exercise phenotype.

  7. Muscle activation patterns of the upper and lower extremity during the windmill softball pitch.

    Science.gov (United States)

    Oliver, Gretchen D; Plummer, Hillary A; Keeley, David W

    2011-06-01

    Fast-pitch softball has become an increasingly popular sport for female athletes. There has been little research examining the windmill softball pitch in the literature. The purpose of this study was to describe the muscle activation patterns of 3 upper extremity muscles (biceps, triceps, and rhomboids [scapular stabilizers]) and 2 lower extremity muscles (gluteus maximus and medius) during the 5 phases of the windmill softball pitch. Data describing muscle activation were collected on 7 postpubescent softball pitchers (age 17.7 ± 2.6 years; height 169 ± 5.4 cm; mass 69.1 ± 5.4 kg). Surface electromyographic data were collected using a Myopac Jr 10-channel amplifier (RUN Technologies Scientific Systems, Laguna Hills, CA, USA) synchronized with The MotionMonitor™ motion capture system (Innovative Sports Training Inc, Chicago IL, USA) and presented as a percent of maximum voluntary isometric contraction. Gluteus maximus activity reached (196.3% maximum voluntary isometric contraction [MVIC]), whereas gluteus medius activity was consistent during the single leg support of phase 3 (101.2% MVIC). Biceps brachii activity was greatest during phase 4 of the pitching motion. Triceps brachii activation was consistently >150% MVIC throughout the entire pitching motion, whereas the scapular stabilizers were most active during phase 2 (170.1% MVIC). The results of this study indicate the extent to which muscles are activated during the windmill softball pitch, and this knowledge can lead to the development of proper preventative and rehabilitative muscle strengthening programs. In addition, clinicians will be able to incorporate strengthening exercises that mimic the timing of maximal muscle activation most used during the windmill pitching phases.

  8. Muscle Activation Differs between Three Different Knee Joint-Angle Positions during a Maximal Isometric Back Squat Exercise

    Directory of Open Access Journals (Sweden)

    Paulo Henrique Marchetti

    2016-01-01

    Full Text Available The purpose of this study was to compare muscle activation of the lower limb muscles when performing a maximal isometric back squat exercise over three different positions. Fifteen young, healthy, resistance-trained men performed an isometric back squat at three knee joint angles (20°, 90°, and 140° in a randomized, counterbalanced fashion. Surface electromyography was used to measure muscle activation of the vastus lateralis (VL, vastus medialis (VM, rectus femoris (RF, biceps femoris (BF, semitendinosus (ST, and gluteus maximus (GM. In general, muscle activity was the highest at 90° for the three quadriceps muscles, yet differences in muscle activation between knee angles were muscle specific. Activity of the GM was significantly greater at 20° and 90° compared to 140°. The BF and ST displayed similar activation at all joint angles. In conclusion, knee position alters muscles activation of the quadriceps and gluteus maximus muscles. An isometric back squat at 90° generates the highest overall muscle activation, yet an isometric back squat at 140° generates the lowest overall muscle activation of the VL and GM only.

  9. Glycogen content regulates peroxisome proliferator activated receptor-∂ (PPAR-∂) activity in rat skeletal muscle.

    Science.gov (United States)

    Philp, Andrew; MacKenzie, Matthew G; Belew, Micah Y; Towler, Mhairi C; Corstorphine, Alan; Papalamprou, Angela; Hardie, D Grahame; Baar, Keith

    2013-01-01

    Performing exercise in a glycogen depleted state increases skeletal muscle lipid utilization and the transcription of genes regulating mitochondrial β-oxidation. Potential candidates for glycogen-mediated metabolic adaptation are the peroxisome proliferator activated receptor (PPAR) coactivator-1α (PGC-1α) and the transcription factor/nuclear receptor PPAR-∂. It was therefore the aim of the present study to examine whether acute exercise with or without glycogen manipulation affects PGC-1α and PPAR-∂ function in rodent skeletal muscle. Twenty female Wistar rats were randomly assigned to 5 experimental groups (n = 4): control [CON]; normal glycogen control [NG-C]; normal glycogen exercise [NG-E]; low glycogen control [LG-C]; and low glycogen exercise [LG-E]). Gastrocnemius (GTN) muscles were collected immediately following exercise and analyzed for glycogen content, PPAR-∂ activity via chromatin immunoprecipitation (ChIP) assays, AMPK α1/α2 kinase activity, and the localization of AMPK and PGC-1α. Exercise reduced muscle glycogen by 47 and 75% relative to CON in the NG-E and LG-E groups, respectively. Exercise that started with low glycogen (LG-E) finished with higher AMPK-α2 activity (147%, pexercise. Our data would suggest that a factor associated with muscle contraction and/or glycogen depletion activates PPAR-∂ and initiates AMPK translocation in skeletal muscle in response to exercise.

  10. Investigation of Cervical Fleksor and Extensor Muscle Activation During Isometric Neck Extension Applied by Therraband

    Science.gov (United States)

    Önal, Sercan; Can, Filiz; Yakut, Yavuz; Baltacı, Gül

    2014-01-01

    Objectives: Therrabands are commonly used for resistive exercises, streching and stabilization exercises and also isometric exercises. However, principles of practice of therrabands are mostly focused on exercise variety. Likewise it is only given point to exercise variety during therrabands’ usage at cervical region. Nevertheless, for effective usage of therrabands and for proper assessment of effectiveness response, it is necessary to know the amount of resistance being given or muscle activation response against the resistance given. The aim of this study was to compare activations of cervical flexor and extensor muscles during isometric extension exercise against the resistance of therraband in healthy individuals. Methods: 14 healthy subjects (8 female,6 male)aged between 19-32 have been included in the study. Subjects with neck problems, systemic diseases, history of trauma or operation were excluded. Neck isometric exercises with therraband was 2 sets with 2 minutes’ intervals and EMG records have been taken during exercises. After preparation of the skin, surface electrodes placed on the motor points of sternocleidomastoideus(SCM) and erector spinae(ES) muscles. After taking the average of 3 measures, the first 10 seconds of muscular activations were recorded. The average of integrated EMG(iEMG) values of each records was used for statistical data. Independent T test and Mann Whitney U test were used for the analysis of findings. Results: There was no significant difference between the right ES and left ES’s mean iEMG during isometric neck extension against therraband (p=0.06). Although there was no difference between right SCM and right ES muscles action potentials(t=-0.895; p=0.379), there was a significant difference between left SCM and left ES muscles’ action potentials (z= -2.435; p=0.01). When all the right and left SCM and ES muscle activations were compared, a significant difference was detected in favour of ES muscles ( t= -2.133; p= 0

  11. Inhibition of FoxO transcriptional activity prevents muscle fiber atrophy during cachexia and induces hypertrophy

    Science.gov (United States)

    Reed, Sarah A.; Sandesara, Pooja B.; Senf, Sarah M.; Judge, Andrew R.

    2012-01-01

    Cachexia is characterized by inexorable muscle wasting that significantly affects patient prognosis and increases mortality. Therefore, understanding the molecular basis of this muscle wasting is of significant importance. Recent work showed that components of the forkhead box O (FoxO) pathway are increased in skeletal muscle during cachexia. In the current study, we tested the physiological significance of FoxO activation in the progression of muscle atrophy associated with cachexia. FoxO-DNA binding dependent transcription was blocked in the muscles of mice through injection of a dominant negative (DN) FoxO expression plasmid prior to inoculation with Lewis lung carcinoma cells or the induction of sepsis. Expression of DN FoxO inhibited the increased mRNA levels of atrogin-1, MuRF1, cathepsin L, and/or Bnip3 and inhibited muscle fiber atrophy during cancer cachexia and sepsis. Interestingly, during control conditions, expression of DN FoxO decreased myostatin expression, increased MyoD expression and satellite cell proliferation, and induced fiber hypertrophy, which required de novo protein synthesis. Collectively, these data show that FoxO-DNA binding-dependent transcription is necessary for normal muscle fiber atrophy during cancer cachexia and sepsis, and further suggest that basal levels of FoxO play an important role during normal conditions to depress satellite cell activation and limit muscle growth.—Reed, S. A., Sandesara, P. B., Senf, S. F., Judge, A. R. Inhibition of FoxO transcriptional activity prevents muscle fiber atrophy during cachexia and induces hypertrophy. PMID:22102632

  12. Length adaptation of smooth muscle contractile filaments in response to sustained activation.

    Science.gov (United States)

    Stålhand, Jonas; Holzapfel, Gerhard A

    2016-05-21

    Airway and bladder smooth muscles are known to undergo length adaptation under sustained contraction. This adaptation process entails a remodelling of the intracellular actin and myosin filaments which shifts the peak of the active force-length curve towards the current length. Smooth muscles are therefore able to generate the maximum force over a wide range of lengths. In contrast, length adaptation of vascular smooth muscle has attracted very little attention and only a handful of studies have been reported. Although their results are conflicting on the existence of a length adaptation process in vascular smooth muscle, it seems that, at least, peripheral arteries and arterioles undergo such adaptation. This is of interest since peripheral vessels are responsible for pressure regulation, and a length adaptation will affect the function of the cardiovascular system. It has, e.g., been suggested that the inward remodelling of resistance vessels associated with hypertension disorders may be related to smooth muscle adaptation. In this study we develop a continuum mechanical model for vascular smooth muscle length adaptation by assuming that the muscle cells remodel the actomyosin network such that the peak of the active stress-stretch curve is shifted towards the operating point. The model is specialised to hamster cheek pouch arterioles and the simulated response to stepwise length changes under contraction. The results show that the model is able to recover the salient features of length adaptation reported in the literature.

  13. Effect of the upper limbs muscles activity on the mechanical energy gain in pole vaulting.

    Science.gov (United States)

    Frère, Julien; Göpfert, Beat; Slawinski, Jean; Tourny-chollet, Claire

    2012-04-01

    The shoulder muscles are highly solicited in pole vaulting and may afford energy gain. The objective of this study was to determine the bilateral muscle activity of the upper-limbs to explain the actions performed by the vaulter to bend the pole and store elastic energy. Seven experienced athletes performed 5-10 vaults which were recorded using two video cameras (50Hz). The mechanical energy of the centre of gravity (CG) was computed, while surface electromyographic (EMG) profiles were recorded from 5 muscles bilateral: deltoideus, infraspinatus, biceps brachii, triceps, and latissimus dorsi muscles. The level of intensity from EMG profile was retained in four sub phases between take-off (TO1) and complete pole straightening (PS). The athletes had a mean mechanical energy gain of 22% throughout the pole vault, while the intensities of deltoideus, biceps brachii, and latissimus dorsi muscles were sub phases-dependent (pmechanical energy of the vaulter could be linked to an increase in muscle activation, especially from latissimusdorsi muscles. Copyright © 2011 Elsevier Ltd. All rights reserved.

  14. Activation and tremor of the shoulder muscles to the demands of an archery task.

    Science.gov (United States)

    Lin, Jiu-Jenq; Hung, Cheng-Ju; Yang, Ching-Ching; Chen, Hsing-Yu; Chou, Feng-Ching; Lu, Tung-Wu

    2010-02-01

    Physiological tremor and strength during the maintenance of shoulder position occur during a precision aiming task, such as archery. It is unclear how positions for precision demands affect physiological tremor and associated muscular activities. The purpose of this study was to assess the tremor amplitude and muscular activities of the shoulder between the various positions for precision demands. Ten males (age 21.9 +/- 2.0 years) participated in the study. Electromyography (EMG) was quantified on eight humeral/scapular muscles. The tremor was measured by the acceleration component of a motion tracking sensor in the 3-7 Hz and 8-12 Hz frequency bands. Participants simulated six preparatory archery shooting positions (3 arm angles x 2 arm draw positions) and performed isometric contractions. The relative root mean square (RMS) amplitudes of the shoulder muscles were significantly greater for the full drawing position compared with the partial position (humeral muscles: P = 0.011; scapular muscles: P = 0.026). In the full drawing position, increased humeral/scapular muscle EMG amplitude was moderately associated with an increased power spectrum of 8-12/3-7 Hz tremor in humerus/scapula motion (R = 0.43-0.57). To minimize fluctuations in high strength muscle performance, 90 degrees of elevation in the full drawing position may be a suitable position for demands in archery. In addition, scapular muscle amplitude is important for stability to reduce humerus tremor during archery performance.

  15. Calcium and stretch activation modulate power generation in Drosophila flight muscle.

    Science.gov (United States)

    Wang, Qian; Zhao, Cuiping; Swank, Douglas M

    2011-11-02

    Many animals regulate power generation for locomotion by varying the number of muscle fibers used for movement. However, insects with asynchronous flight muscles may regulate the power required for flight by varying the calcium concentration ([Ca(2+)]). In vivo myoplasmic calcium levels in Drosophila flight muscle have been found to vary twofold during flight and to correlate with aerodynamic power generation and wing beat frequency. This mechanism can only be possible if [Ca(2+)] also modulates the flight muscle power output and muscle kinetics to match the aerodynamic requirements. We found that the in vitro power produced by skinned Drosophila asynchronous flight muscle fibers increased with increasing [Ca(2+)]. Positive muscle power generation started at pCa = 5.8 and reached its maximum at pCa = 5.25. A twofold variation in [Ca(2+)] over the steepest portion of this curve resulted in a two- to threefold variation in power generation and a 1.2-fold variation in speed, matching the aerodynamic requirements. To determine the mechanism behind the variation in power, we analyzed the tension response to muscle fiber-lengthening steps at varying levels of [Ca(2+)]. Both calcium-activated and stretch-activated tensions increased with increasing [Ca(2+)]. However, calcium tension saturated at slightly lower [Ca(2+)] than stretch-activated tension, such that as [Ca(2+)] increased from pCa = 5.7 to pCa = 5.4 (the range likely used during flight), stretch- and calcium-activated tension contributed 80% and 20%, respectively, to the total tension increase. This suggests that the response of stretch activation to [Ca(2+)] is the main mechanism by which power is varied during flight. Copyright © 2011 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  16. Contractions activate hormone-sensitive lipase in rat muscle by protein kinase C and mitogen-activated protein kinase

    DEFF Research Database (Denmark)

    Donsmark, Morten; Langfort, Jozef; Holm, Cecilia

    2003-01-01

    Intramuscular triacylglycerol is an important energy store and is also related to insulin resistance. The mobilization of fatty acids from this pool is probably regulated by hormone-sensitive lipase (HSL), which has recently been shown to exist in muscle and to be activated by both adrenaline...... and contractions. Adrenaline acts via cAMP-dependent protein kinase (PKA). The signalling mediating the effect of contractions is unknown and was explored in this study. Incubated soleus muscles from 70 g male rats were electrically stimulated to perform repeated tetanic contractions for 5 min. The contraction...... of the inhibitors reduced adrenaline-induced HSL activation in soleus muscle. Both phorbol-12-myristate-13-acetate (PMA), which activates PKC and, in turn, ERK, and caffeine, which increases intracellular Ca2+ without eliciting contraction, increased HSL activity. Activated ERK increased HSL activity in supernatant...

  17. Exercise induces transient transcriptional activation of the PGC-1a gene in human skeletal muscle

    DEFF Research Database (Denmark)

    Pilegaard, Henriette; Saltin, Bengt; Neufer, P. Darrell

    2003-01-01

    Endurance exercise training induces mitochondrial biogenesis in skeletal muscle. The peroxisome proliferator activated receptor co-activator 1a (PGC-1a) has recently been identified as a nuclear factor critical for coordinating the activation of genes required for mitochondrial biogenesis in cell...

  18. Effect of eccentric contraction on satellite cell activation in human vastus lateralis muscle.

    Science.gov (United States)

    Imaoka, Yoko; Kawai, Minako; Mori, Futoshi; Miyata, Hirofumi

    2015-09-01

    We compared the time-course of satellite cell (SC) activation between eccentric and concentric contractions in the vastus lateralis (VL) muscle after step exercise. Young adults participated in a 30-min step up/down exercise which mainly involved concentric contractions with the right VL muscle and eccentric contractions with the left VL muscle. The concentric and eccentric contraction phases of the VL muscles were identified by changes in the electromyogram (EMG) and knee joint angle. Biopsy samples were taken from both VL muscles at three time periods: before the exercise and 2 and 5 days after the exercise. We found that the numbers of SCs were significantly increased in the type IIa fibers of the left VL at 2 and 5 days after the exercise. The expression of both hepatocyte growth factor (HGF) and myogenic differentiation 1 (MyoD) mRNA had significantly increased in the left VL at 2 and 5 days after the exercise and in the right VL at 5 days after the exercise. The expression of transient receptor potential canonical (TRPC) 1 mRNA also increased in the left VL at 2 days after exercise. These results indicate that eccentric contraction can effectively activate SC proliferation for up to 5 days after exercise. Similar changes in HGF, MyoD and TRPC1 mRNA expression suggest that HGF/c-Met signal activation through cation influx has a major impact on skeletal muscle SC activation in response to eccentric exercise.

  19. Lower Extremity Muscle Activation and Kinematics of Catchers When Throwing Using Various Squatting and Throwing Postures

    Directory of Open Access Journals (Sweden)

    Yi-Chien Peng, Kuo-Cheng Lo, Lin-Hwa Wang

    2015-09-01

    Full Text Available This study investigated the differences in joint motions and muscle activities of the lower extremities involved in various squatting postures. The motion capture system with thirty-one reflective markers attached on participants was used for motion data collection. The electromyography system was applied over the quadriceps, biceps femoris, tibialis anterior, and gastrocnemius muscles of the pivot and stride leg. The joint extension and flexion in wide squatting are greater than in general squatting (p = 0.005. Knee joint extension and flexion in general squatting are significantly greater than in wide squatting (p = 0.001. The adduction and abduction of the hip joint in stride passing are significantly greater than in step squatting (p = 0.000. Furthermore, the adduction and abduction of the knee joint in stride passing are also significantly greater than in step squatting (p = 0.000. When stride passing is performed, the muscle activation of the hamstring of the pivot foot in general squatting is significantly greater than in wide squatting (p < 0.05, and this difference continues to the stride period. Most catchers use a general or wide squatting width, exclusive of a narrow one. Therefore, the training design for strengthening the lower extremity muscles should consider the appropriateness of the common squat width to enhance squat-up performance. For lower limb muscle activation, wide squatting requires more active gastrocnemius and tibialis anterior muscles. Baseball players should extend the knee angle of the pivot foot before catching the ball.

  20. Metabolic stabilization of acetylcholine receptors in vertebrate neuromuscular junction by muscle activity

    Energy Technology Data Exchange (ETDEWEB)

    Rotzler, S.; Brenner, H.R. (Univ. of Basel (Switzerland))

    1990-08-01

    The effects of muscle activity on the growth of synaptic acetylcholine receptor (AChR) accumulations and on the metabolic AChR stability were investigated in rat skeletal muscle. Ectopic end plates induced surgically in adult soleus muscle were denervated early during development when junctional AChR number and stability were still low and, subsequently, muscles were either left inactive or they were kept active by chronic exogenous stimulation. AChR numbers per ectopic AChR cluster and AChR stabilities were estimated from the radioactivity and its decay with time, respectively, of end plate sites whose AChRs had been labeled with {sup 125}I-alpha-bungarotoxin (alpha-butx). The results show that the metabolic stability of the AChRs in ectopic clusters is reversibly increased by muscle activity even when innervation is eliminated very early in development. 1 d of stimulation is sufficient to stabilize the AChRs in ectopic AChR clusters. Muscle stimulation also produced an increase in the number of AChRs at early denervated end plates. Activity-induced cluster growth occurs mainly by an increase in area rather than in AChR density, and for at least 10 d after denervation is comparable to that in normally developing ectopic end plates. The possible involvement of AChR stabilization in end plate growth is discussed.

  1. The Relationships Between Muscle Power and Physical Activity in Older Men With Chronic Obstructive Pulmonary Disease.

    Science.gov (United States)

    Hernández, María; Zambom-Ferraresi, Fabrício; Cebollero, Pilar; Hueto, Javier; Cascante, José Antonio; Antón, María M

    2017-07-01

    The purpose of this study was to determine the potential relationship between muscle power of the lower extremities and the physical activity in older men with chronic obstructive pulmonary disease (COPD). Forty-four men (70.3 ± 6.7 years old) with moderate-to-severe COPD completed the 6-min walk test (6MWT), BODE (body mass index, obstruction, dyspnea, and exercise), a one-repetition maximum strength of the quadriceps femoris (1RMQF), and muscle power at 50% and 70% 1RMQF. Physical activity was measured using an accelerometer. The 6MWT was associated with muscle power at 50% 1RMQF (r = .40; P = .013) but not muscle power at 70% 1RMQF (r = .24; P = .15) or 1RMQF (r = .13; P = .44). Light-intensity activity was positively correlated with muscle power at 50% 1RMQF (r = .52; P = .001). Lower limb muscle power is associated with the 6MWT and light-intensity activities in older men with COPD.

  2. A fully resolved fluid-structure-muscle-activation model for esophageal transport

    Science.gov (United States)

    Kou, Wenjun; Bhalla, Amneet P. S.; Griffith, Boyce E.; Johnson, Mark; Patankar, Neelesh A.

    2013-11-01

    Esophageal transport is a mechanical and physiological process that transfers the ingested food bolus from the pharynx to the stomach through a multi-layered esophageal tube. The process involves interactions between the bolus, esophageal wall composed of mucosal, circular muscle (CM) and longitudinal muscle (LM) layers, and neurally coordinated muscle activation including CM contraction and LM shortening. In this work, we present a 3D fully-resolved model of esophageal transport based on the immersed boundary method. The model describes the bolus as a Newtonian fluid, the esophageal wall as a multi-layered elastic tube represented by springs and beams, and the muscle activation as a traveling wave of sequential actuation/relaxation of muscle fibers, represented by springs with dynamic rest lengths. Results on intraluminal pressure profile and bolus shape will be shown, which are qualitatively consistent with experimental observations. Effects of activating CM contraction only, LM shortening only or both, for the bolus transport, are studied. A comparison among them can help to identify the role of each type of muscle activation. The support of grant R01 DK56033 and R01 DK079902 from NIH is gratefully acknowledged.

  3. Changes in muscle activity determine progression of clinical symptoms in patients with chronic spine-related muscle pain. A complex clinical and neurophysiological approach.

    Science.gov (United States)

    Wytrazek, Marcin; Huber, Juliusz; Lisinski, Przemyslaw

    2011-01-01

    Spine-related muscle pain can affect muscle strength and motor unit activity. This study was undertaken to investigate whether surface electromyographic (sEMG) recordings performed during relaxation and maximal contraction reveal differences in the activity of muscles with or without trigger points (TRPs). We also analyzed the possible coexistence of characteristic spontaneous activity in needle electromyographic (eEMG) recordings with the presence of TRPs. Thirty patients with non-specific cervical and back pain were evaluated using clinical, neuroimaging and electroneurographic examinations. Muscle pain was measured using a visual analog scale (VAS), and strength using Lovett's scale; trigger points were detected by palpation. EMG was used to examine motor unit activity. Trigger points were found mainly in the trapezius muscles in thirteen patients. Their presence was accompanied by increased pain intensity, decreased muscle strength, increased resting sEMG amplitude, and decreased sEMG amplitude during muscle contraction. eEMG revealed characteristic asynchronous discharges in TRPs. The results of EMG examinations point to a complexity of muscle pain that depends on progression of the myofascial syndrome.

  4. Bone and muscle structure and quality preserved by active versus passive muscle exercise on a new stepper device in 21 days tail-suspended rats.

    Science.gov (United States)

    Sun, L W; Blottner, D; Luan, H Q; Salanova, M; Wang, C; Niu, H J; Felsenberg, D; Fan, Y B

    2013-06-01

    Human performance in microgravity is characterized by reversed skeletal muscle actions in terms of active vs. passive mode contractions of agonist/antagonist groups that may challenge principal biodynamics (biomechanical forces translated from muscle to bone) of the skeletal muscle-bone unit. We investigated active vs. passive muscle motions of the unloaded hindlimb skeletal muscle-bone unit in the 21 days tail-suspended (TS) rat using a newly designed stepper exercise device. The regimen included both active mode motions (TSA) and passive mode motions (TSP). A TS-only group and a normal cage group (CON) served as positive or negative controls. The muscle and bone decrements observed in TS-only group were not seen in the other groups except TSP. Active mode motions supported femur and tibia bone quality (5% BMD, 10% microtrabecular BV/TV, Tb.Th., Tb.N. parameters), whole soleus muscle/myofiber size and type II distribution, 20% increased sarcolemma NOS1 immunosignals vs. CON, with 25% more hybrid fiber formation (remodeling sign) for all TS groups. We propose a new custom-made stepper device to be used in the TS rat model that allows for detailed investigations of the unique biodynamic properties of the muscle-bone unit during resistive-load exercise countermeasure trials on the ground or in microgravity.

  5. Effects of strength and endurance training of superficial and deep neck muscles on muscle activities and pain levels of females with chronic neck pain.

    Science.gov (United States)

    Borisut, Sudarat; Vongsirinavarat, Mantana; Vachalathiti, Roongtiwa; Sakulsriprasert, Prasert

    2013-09-01

    [Purpose] To compare muscle activities and pain levels of females with chronic neck pain receiving different exercise programs. [Subjects and Methods] One hundred females with chronic neck pain participated in this study. They were randomly allocated into 4 groups (n = 25) on the basis of the exercises performed as follows: strength-endurance exercise, craniocervical flexion exercise, combination of strength-endurance and craniocervical flexion exercise and control groups. Pain, disability levels and changes in the muscle activities of the cervical erector spinae (CE), sternocleidomastoid (SCM), anterior scalenes (AS) and upper trapezius (UT) muscles were evaluated before and after the interventions. [Results] After 12 weeks of exercise intervention, all three exercise groups showed improvements in pain and disability. The muscle activities during the typing task were significantly different from the control group in all three exercise groups for all muscles except those of the extensor muscles in the craniocervical flexion exercise group. [Conclusion] The results of this study indicate that exercises for the cervical muscles improve pain and disability. The exercise programs reduced the activities of almost all cervical muscles.

  6. [Influence of preliminary information about mass on anticipatory muscle activity during catching of falling object].

    Science.gov (United States)

    Kazennikov, O V; Lipshits, M I

    2010-01-01

    Heavy or light object fell into the cup held between thumb and index fingers of sitting subject. The anticipatory muscle activity and the grip force applied to cup depended on the mass of object while the temporal parameters (time of beginning of muscle activity, duration of the activity, the time of grip force maximum) were constant. The preliminary verbal information about mass of the falling object was enough for predictive force programming. Without such information, i.e. during fall the object of unknown mass the anticipatory activity was planned in expectation of heavy weight.

  7. Effect of aging on performance, muscle activation and perceived stress during mentally demanding computer tasks

    DEFF Research Database (Denmark)

    Alkjaer, Tine; Pilegaard, Marianne; Bakke, Merete

    2005-01-01

    OBJECTIVES: This study examined the effects of age on performance, muscle activation, and perceived stress during computer tasks with different levels of mental demand. METHODS: Fifteen young and thirteen elderly women performed two computer tasks [color word test and reference task] with different...... demands affect young and elderly women differently. Thus the mentally demanding computer task had a more pronounced effect on the elderly than on the young. In contrast to the results in the reference task, the same level of muscle activity for most muscles and the same level of self-reported difficulty...... levels of mental demand but similar physical demands. The performance (clicking frequency, percentage of correct answers, and response time for correct answers) and electromyography from the forearm, shoulder, and neck muscles were recorded. Visual analogue scales were used to measure the participants...

  8. Glycogen stability and glycogen phosphorylase activities in isolated skeletal muscles from rat and toad.

    Science.gov (United States)

    Goodman, C A; Stephenson, G M

    2000-01-01

    There is increasing evidence that endogenous glycogen depletion may affect excitation-contraction (E-C) coupling events in vertebrate skeletal muscle. One approach employed in physiological investigations of E-C coupling involves the use of mechanically skinned, single fibre preparations obtained from tissues stored under paraffin oil, at room temperature (RT: 20-24 degrees C) and 4 degrees C for several hours. In the present study, we examined the effect of these storage conditions on the glycogen content in three muscles frequently used in research on E-C coupling: rat extensor digitorum longus (EDL) and soleus (SOL) and toad iliofibularis (IF). Glycogen content was determined fluorometrically in homogenates prepared from whole muscles, stored under paraffin oil for up to 6 h at RT or 4 degrees C. Control muscles and muscles stored for 0.5 and 6 h were also analysed for total phosphorylase (Phos(total)) and phosphorylase a (Phos a) activities. No significant change was observed in the glycogen content of EDL and SOL muscles stored at RT for 0.5 h. In rat muscles stored at RT for longer than 0.5 h, the glycogen content decreased to 67.6% (EDL) and 78.7% (SOL) of controls after 3 h and 25.3% (EDL) and 37.4% (SOL) after 6 h. Rat muscles stored at 4 degrees C retained 79.0% (EDL) and 92.5% (SOL) of glycogen after 3 h and 75.2% (EDL) and 61.1% (SOL) after 6 h. The glycogen content of IF muscles stored at RT or 4 degrees C for 6 h was not significantly different from controls. Phos(total) was unchanged in all muscles over the 6 h period, at both temperatures. Phos a was also unchanged in the toad IF muscles, but in rat muscles it decreased rapidly, particularly in EDL (4.1-fold after 0.5 h at RT). Taken together these results indicate that storage under paraffin oil for up to 6 h at RT or 4 degrees C is accompanied by minimal glycogen loss in toad IF muscles and by a time- and temperature-dependent glycogen loss in EDL and SOL muscles of the rat.

  9. Ultrasonographic assessment of the swelling of the human masseter muscle after static and dynamic activity

    DEFF Research Database (Denmark)

    Bakke, M; Thomsen, C E; Vilmann, A

    1996-01-01

    Work-related fatigue, pain and disorders in skeletal muscles have been related to prolonged static and dynamic activity. Such contractions have been shown to impair blood flow and increase muscle thickness and fluid. In the present study the effect of static and dynamic activity was evaluated from...... changes in masseter thickness as a measure of oedema, simultaneously with assessment of perceived pain/discomfort and cardiovascular responses. As static activity, fourteen young healthy women bit at 15% maximal voluntary contraction on bite-force transducers in the molar regions until exhaustion or 20.......5%) than dynamic activity (4.3%), whereas heart rate rose significantly only during dynamic exercise (13.3%). Hence, activity was associated with muscular swelling and pain, and, despite the relatively small size of the masticatory muscles, also with general cardiovascular responses....

  10. Association between maximal hamstring muscle strength and hamstring muscle pre-activity during a movement associated with non-contact ACL injury

    DEFF Research Database (Denmark)

    Zebis, M. K.; Sorensen, R. S.; Thorborg, K.

    2015-01-01

    Background: Reduced hamstring pre-activity during sidecutting increases the risk for non-contact ACL injury. During the last decade resistance training of the lower limb muscles has become an integral part ofACLinjury prevention in e.g. soccer and handball. However, it is not known whether a strong...... levels of muscle pre-activity during movements like the sidecutting maneuver. Implications: Other exercise modalities (i.e. neuromuscular training) are needed to optimize hamstring muscle pre-activity during movements associated with non-contact ACL injury....

  11. Posterior muscle chain activity during various extension exercises: an observational study

    OpenAIRE

    De Ridder, Eline MD; Oosterwijck, Jessica O; Vleeming, Andry; Vanderstraeten, Guy G.; Danneels, Lieven A

    2013-01-01

    Background: Back extension exercises are often used in the rehabilitation of low back pain. However, at present it is not clear how the posterior muscles are recruited during different types of extension exercises. Therefore, the present study will evaluate the myoelectric activity of thoracic, lumbar and hip extensor muscles during different extension exercises in healthy persons. Based on these physiological observations we will make recommendations regarding the use of extensions exercises...

  12. Lingual muscle activity across sleep-wake states in rats with surgically altered upper airway

    Directory of Open Access Journals (Sweden)

    Irma eRukhadze

    2014-04-01

    Full Text Available Obstructive sleep apnea (OSA patients have increased upper airway muscle activity, including such lingual muscles as the genioglossus (GG, geniohyoid (GH and hyoglossus (HG. This adaptation partially protects their upper airway against obstructions. Rodents are used to study the central neural control of sleep and breathing but they do not naturally exhibit OSA. We investigated whether, in chronically instrumented, behaving rats, disconnecting the GH and HG muscles from the hyoid (H apparatus would result in a compensatory increase of other upper airway muscle activity (EMG and/or other signs of upper airway instability. We first determined that, in intact rats, lingual (GG and intrinsic muscles maintained stable activity levels when quantified based on 2 h-long recordings conducted on days 6 through 22 after instrumentation. We then studied 5 rats in which the tendons connecting the GH and HG muscles to the H apparatus were experimentally severed. When quantified across all recording days, lingual EMG during SWS was modestly but significantly increased in rats with surgically altered upper airway (8.6% ±0.7(SE vs. 6.2% ±0.7 of the mean during wakefulness; p=0.012. Respiratory modulation of lingual EMG occurred mainly during SWS and was similarly infrequent in both groups, and the incidence of sighs and central apneas also was similar. Thus, a weakened action of selected lingual muscles did not produce sleep-disordered breathing but resulted in a relatively elevated activity in other lingual muscles during SWS. These results encourage more extensive surgical manipulations with the aim to obtain a rodent model with collapsible upper airway.

  13. Rate of force generation in muscle: correlation with actomyosin ATPase activity in solution.

    OpenAIRE

    Brenner, B; Eisenberg, E

    1986-01-01

    Crossbridge models of muscle contraction based on biochemical studies predict that there may be a relationship between the rate-limiting step in the actomyosin ATPase cycle in vitro and the rate of force development in vivo. In the present study, we measured the rate of force redevelopment in skinned rabbit muscle fibers following unloaded isotonic shortening and a rapid restretch. For comparison, ATPase activity was measured under identical conditions, using myosin subfragment-1 chemically c...

  14. Increased muscle activation following motor imagery during the rehabilitation of the anterior cruciate ligament.

    Science.gov (United States)

    Lebon, Florent; Guillot, Aymeric; Collet, Christian

    2012-03-01

    Motor imagery (MI) is the mental representation of an action without any concomitant movement. MI has been used frequently after peripheral injuries to decrease pain and facilitate rehabilitation. However, little is known about the effects of MI on muscle activation underlying the motor recovery. This study aimed to assess the therapeutic effects of MI on the activation of lower limb muscles, as well as on the time course of functional recovery and pain after surgery of the anterior cruciate ligament (ACL). Twelve patients with a torn ACL were randomly assigned to a MI or control group, who both received a series of physiotherapy. Electromyographic activity of the quadriceps, pain, anthropometrical data, and lower limb motor ability were measured throughout a 12-session therapy. The data provided evidence that MI elicited greater muscle activation, even though imagery practice did not result in pain decrease. Muscle activation increase might originate from a redistribution of the central neuronal activity, as there was no anthropometric change in lower limb muscles after imagery practice. This study confirmed the effectiveness of integrating MI in a rehabilitation process by facilitating muscular properties recovery following motor impairment. MI may thus be considered a reliable adjunct therapy to help injured patients to recover motor functions after reconstructive surgery of ACL.

  15. Do Changes in Muscle Architecture Affect Post-Activation Potentiation?

    Directory of Open Access Journals (Sweden)

    Danielle Reardon, Jay R. Hoffman, Gerald T. Mangine, Adam J. Wells, Adam M. Gonzalez, Adam R. Jajtner, Jeremy R. Townsend, William P. McCormack, Jeffrey R. Stout, Maren S. Fragala, David H. Fukuda

    2014-09-01

    Full Text Available The purpose of this randomized, cross-over design study was to examine the effect of three different muscle potentiation protocols on acute changes in muscle architecture and vertical jump performance. Eleven experienced, resistance trained men (25.2±3.6y completed three potentiation squat protocols using moderate intensity (MI; 75%, 3 sets x 10 repetitions, high intensity (HI; 90%, 3 sets x 3 repetitions and 100% (1RM; 1 set x 1repetition of their 1RM. In addition, all participants completed a control session (CTL in which no protocol was performed. During each testing session, muscle architecture and vertical jump testing were assessed at baseline (BL, 8min post (8P and 20min post (20P workout. Ultrasound measures included cross sectional area (CSA and pennation angle (PANG of both the rectus femoris (RF and vastus lateralis (VL. Following each ultrasound measure, peak vertical jump power (PVJP and mean (MVJP power was assessed using an accelerometer. Magnitude based inferences were used to make comparisons between trials. The MI trial resulted in a likely greater increase from BL to 8P and 20P in RF-CSA and VL-CSA, while the HI trial resulted in a likely greater change from BL to 20P in both RF-CSA and VL-CSA. Meanwhile, changes in PVJP and MVJP for the MI trial was likely decreased at BL-8P and BL–20P, while the HI trial was shown to result in a likely or possible decrease compared to CTL at BL-8P and BL–20P, respectively. A likely negative relationship was observed between changes in VL-PANG and MVJP (r = -0.35; p , 0.018 at BL-8P, and between changes in PVJP and RF-CSA (r = -0.37; p , 0.014 at BL–20P. Results of this study were unable to demonstrate any potentiation response from the trials employed, however these protocols did result in acute muscle architectural changes.

  16. Evaluation of methods for extraction of the volitional EMG in dynamic hybrid muscle activation

    Directory of Open Access Journals (Sweden)

    Mizrahi Joseph

    2006-11-01

    Full Text Available Abstract Background Hybrid muscle activation is a modality used for muscle force enhancement, in which muscle contraction is generated from two different excitation sources: volitional and external, by means of electrical stimulation (ES. Under hybrid activation, the overall EMG signal is the combination of the volitional and ES-induced components. In this study, we developed a computational scheme to extract the volitional EMG envelope from the overall dynamic EMG signal, to serve as an input signal for control purposes, and for evaluation of muscle forces. Methods A "synthetic" database was created from in-vivo experiments on the Tibialis Anterior of the right foot to emulate hybrid EMG signals, including the volitional and induced components. The database was used to evaluate the results obtained from six signal processing schemes, including seven different modules for filtration, rectification and ES component removal. The schemes differed from each other by their module combinations, as follows: blocking window only, comb filter only, blocking window and comb filter, blocking window and peak envelope, comb filter and peak envelope and, finally, blocking window, comb filter and peak envelope. Results and conclusion The results showed that the scheme including all the modules led to an excellent approximation of the volitional EMG envelope, as extracted from the hybrid signal, and underlined the importance of the artifact blocking window module in the process. The results of this work have direct implications on the development of hybrid muscle activation rehabilitation systems for the enhancement of weakened muscles.

  17. Time-varying identification of ankle dynamic joint stiffness during movement with constant muscle activation.

    Science.gov (United States)

    Guarin, Diego L; Kearney, Robert E

    2015-01-01

    Dynamic joint stiffness defines the torque generated at the joint in response to position perturbations. Dynamic stiffness is modulated by the angular position and the muscle activation level, making it difficult to estimate during large movements and/or time-varying muscle contractions. This paper presents a new methodology for estimating dynamic joint stiffness during movement and muscle activation. For this, we formulate a novel, nonlinear, dynamic joint stiffness model and present a new algorithm to estimate its parameters. The algorithm assumes that the variability in the model parameters is a function of the mean joint position. Using this methodology we estimated the dynamic joint stiffness at the ankle throughout ramp and hold displacements during a constant muscle contraction. The estimated model accurately predicted the intrinsic and reflex torques produced at the ankle as a response to small position perturbations during large displacement with muscle activation. Preliminary results show that during muscle contraction, ankle intrinsic stiffness estimated during movement is significantly lower than that estimated during quasi-stationary experiments.

  18. Changes in electrical activity in muscles resulting from chiropractic adjustment: a pilot study.

    Science.gov (United States)

    Shambaugh, P

    1987-12-01

    This study examines the effects of chiropractic adjustment on the muscles of the back. Vertebrae that are hypomobile may be held in that state by the erector spinae muscle group; adjusting such vertebrae should result in less muscle tension. By measuring the change in electrical activity, such relaxation can be observed. Hypomobile vertebrae were found by motion palpation. The patient was then placed prone and surface electrodes were placed over the upper trapezius, upper erector spinae (T3-T5), and lumbar erector spinae (L1-L3) muscle groups on both sides of the body. The patient was adjusted using full spine toggle recoil thrusts, and postadjustment readings were taken. Results from this study show that significant changes in muscle electrical activity occur as a consequence of adjusting. On average, a 25% reduction in muscle activity was observed across the 20 subjects tested, while no significant reductions were observed with the control group of 14 subjects. Significant reductions in side-to-side imbalances were also observed.

  19. Changes in the activity of the muscles surrounding the neck according to the angles of movement of the neck in adults in their 20s

    OpenAIRE

    Lee , Tae-Ho; Lee, Joon-Hyuk; Lee, Yun-seob; Kim, Myoung-Kwon; Kim, Seong-Gil

    2015-01-01

    [Purpose] The aim of this study was to examine changes in the muscle activity around the neck according to the neck movement angle during neck flexion and extension. [Subjects and Methods] Activities of the sternocleidomastoid muscle (SCM), splenius capitis and splenius cervicis muscles, upper trapezius muscle, and middle trapezius muscle during flexion and extension were assessed in 24 college students. [Results] SCM muscle activation significantly increased at every angle during flexion and...

  20. Unilateral eccentric exercise of the knee flexors affects muscle activation during gait.

    Science.gov (United States)

    Dover, Geoffrey C; Legge, Laura; St-Onge, Nancy

    2012-05-01

    Uni-lateral muscle soreness is common yet the effects on gait or electromyographic (EMG) activity are unknown. The purpose of our study was to induce delayed onset muscle soreness (DOMS) in the knee flexor group and measure the resultant change in EMG activity and knee motion during gait. Nine healthy subjects participated in the study. Measures of function, evoked tenderness of the biceps femoris, as well as knee angle, and EMG activity during gait were assessed prior and 48 h after an eccentric exercise protocol. DOMS was induced unilaterally in the knee flexors using an isokinetic dynamometer and subjects exercised until they could not generate 50% of their maximal voluntary isometric contraction (MVIC). There was a significant decrease in biceps femoris activity after DOMS during the last phase of gait. Moreover, there was a day × phase interaction for gastrocnemius activity with the last two phases displaying an increase in activity. There was no significant change in knee angle during gait. The decrease in biceps femoris activity as well as the increase in gastrocnemius activity could be evidence of a protective mechanism designed to decrease activity of the sore muscle while increasing the activity of a synergistic muscle. Copyright © 2012 Elsevier B.V. All rights reserved.

  1. Assessment of muscle electrical activity in spinal cord injury subjects during quiet standing.

    Science.gov (United States)

    Lewko, J P

    1996-03-01

    Disturbed motor control due to a spinal cord lesion is generally considered to be the cause of unusual standing utilized by those people suffering from spinal cord injury (SCI). Electromyographic (EMG) leg muscle activity during quiet standing was analyzed in four functional groups of SCI subjects and compared to the data of healthy people. A rating system for visual assessment of the stripchart recording was developed and its adequacy was confirmed by comparison of the rating system with computerized integrated EMG values of some of the recordings. The division of 47 subjects into functional groups was based on their ambulatory capabilities ie a non-support group, crutches, cane and walker user groups. Mean total muscle EMG activity was the highest in the group of subjects standing without support and it was significantly higher when compared to the other groups including the control group. Comparison between more and less active legs within each group showed significant differences in the non-support and crutches groups, whereas cane, walker and control groups showed nearly symmetric EMG patterns during standing. Analysis of the contribution of single muscles to the asymmetry of standing showed significantly higher activity in hamstring and triceps surae muscles than in other muscles in the non-support group. No significant differences in the activity of single muscles compared to their contralateral pair between more and less active leg were obtained in the remaining groups. It is evident, however, that different support devices used by SCI subjects greatly influence EMG patterns of postural muscles. The present findings suggest that disturbed conduction in the spinal cord is related to altered motor strategies employed by SCI subjects in attempts to perform the same volitional act as before the injury.

  2. Trunk Muscle Activation at the Initiation and Braking of Bilateral Shoulder Flexion Movements of Different Amplitudes

    Science.gov (United States)

    Eriksson Crommert, M.; Halvorsen, K.; Ekblom, M. M.

    2015-01-01

    The aim of this study was to investigate if trunk muscle activation patterns during rapid bilateral shoulder flexions are affected by movement amplitude. Eleven healthy males performed shoulder flexion movements starting from a position with arms along sides (0°) to either 45°, 90° or 180°. EMG was measured bilaterally from transversus abdominis (TrA), obliquus internus (OI) with intra-muscular electrodes, and from rectus abdominis (RA), erector spinae (ES) and deltoideus with surface electrodes. 3D kinematics was recorded and inverse dynamics was used to calculate the reactive linear forces and torque about the shoulders and the linear and angular impulses. The sequencing of trunk muscle onsets at the initiation of arm movements was the same across movement amplitudes with ES as the first muscle activated, followed by TrA, RA and OI. All arm movements induced a flexion angular impulse about the shoulders during acceleration that was reversed during deceleration. Increased movement amplitude led to shortened onset latencies of the abdominal muscles and increased level of activation in TrA and ES. The activation magnitude of TrA was similar in acceleration and deceleration where the other muscles were specific to acceleration or deceleration. The findings show that arm movements need to be standardized when used as a method to evaluate trunk muscle activation patterns and that inclusion of the deceleration of the arms in the analysis allow the study of the relationship between trunk muscle activation and direction of perturbing torque during one and the same arm movement. PMID:26562017

  3. Coordination of intrinsic and extrinsic hand muscle activity as a function of wrist joint angle during two-digit grasping.

    Science.gov (United States)

    Johnston, Jamie A; Bobich, Lisa R; Santello, Marco

    2010-04-26

    Fingertip forces result from the activation of muscles that cross the wrist and muscles whose origins and insertions reside within the hand (extrinsic and intrinsic hand muscles, respectively). Thus, tasks that involve changes in wrist angle affect the moment arm and length, hence the force-producing capabilities, of extrinsic muscles only. If a grasping task requires the exertion of constant fingertip forces, the Central Nervous System (CNS) may respond to changes in wrist angle by modulating the neural drive to extrinsic or intrinsic muscles only or by co-activating both sets of muscles. To distinguish between these scenarios, we recorded electromyographic (EMG) activity of intrinsic and extrinsic muscles of the thumb and index finger as a function of wrist angle during a two-digit object hold task. We hypothesized that changes in wrist angle would elicit EMG amplitude modulation of the extrinsic and intrinsic hand muscles. In one experimental condition we asked subjects to exert the same digit forces at each wrist angle, whereas in a second condition subjects could choose digit forces for holding the object. EMG activity was significantly modulated in both extrinsic and intrinsic muscles as a function of wrist angle (both pmuscles. We conclude that the CNS controlled both extrinsic and intrinsic muscles as a muscle synergy. These findings are discussed within the theoretical frameworks of synergies and common neural input across motor nuclei of hand muscles. Copyright 2010 Elsevier Ireland Ltd. All rights reserved.

  4. Alternative exon-encoding regions of Locusta migratoria muscle myosin modulate the pH dependence of ATPase activity.

    Science.gov (United States)

    Li, J; Lu, Z; He, J; Chen, Q; Wang, X; Kang, L; Li, X-D

    2016-12-01

    Whereas the vertebrate muscle myosin heavy chains (MHCs) are encoded by a family of Mhc genes, most insects examined to date contain a single Mhc gene and produce all of the different MHC isoforms by alternative RNA splicing. Here, we found that the migratory locust, Locusta migratoria, has one Mhc gene, which contains 41 exons, including five alternative exclusive exons and one differently included penultimate exon, and potentially encodes 360 MHC isoforms. From the adult L. migratoria, we identified 14 MHC isoforms (including two identical isoforms): four from flight muscle (the thorax dorsal longitudinal muscle), three from jump muscle (the hind leg extensor tibiae muscle) and seven from the abdominal intersegmental muscle. We purified myosins from flight muscle and jump muscle and characterized their motor activities. At neutral pH, the flight and the jump muscle myosins displayed similar levels of in vitro actin-gliding activity, whereas the former had a slightly higher actin-activated ATPase activity than the latter. Interestingly, the pH dependences of the actin-activated ATPase activity of these two myosins are different. Because the dominant MHC isoforms in these two muscles are identical except for the two alternative exon-encoding regions, we propose that these two alternative regions modulate the pH dependence of L. migratoria muscle myosin.

  5. Estimation of muscle forces in gait using a simulation of the electromyographic activity and numerical optimization.

    Science.gov (United States)

    Ravera, Emiliano Pablo; Crespo, Marcos José; Braidot, Ariel Andrés Antonio

    2016-01-01

    Clinical gait analysis provides great contributions to the understanding of gait patterns. However, a complete distribution of muscle forces throughout the gait cycle is a current challenge for many researchers. Two techniques are often used to estimate muscle forces: inverse dynamics with static optimization and computer muscle control that uses forward dynamics to minimize tracking. The first method often involves limitations due to changing muscle dynamics and possible signal artefacts that depend on day-to-day variation in the position of electromyographic (EMG) electrodes. Nevertheless, in clinical gait analysis, the method of inverse dynamics is a fundamental and commonly used computational procedure to calculate the force and torque reactions at various body joints. Our aim was to develop a generic musculoskeletal model that could be able to be applied in the clinical setting. The musculoskeletal model of the lower limb presents a simulation for the EMG data to address the common limitations of these techniques. This model presents a new point of view from the inverse dynamics used on clinical gait analysis, including the EMG information, and shows a similar performance to another model available in the OpenSim software. The main problem of these methods to achieve a correct muscle coordination is the lack of complete EMG data for all muscles modelled. We present a technique that simulates the EMG activity and presents a good correlation with the muscle forces throughout the gait cycle. Also, this method showed great similarities whit the real EMG data recorded from the subjects doing the same movement.

  6. Regulation of the muscle fiber microenvironment by activated satellite cells during hypertrophy.

    Science.gov (United States)

    Fry, Christopher S; Lee, Jonah D; Jackson, Janna R; Kirby, Tyler J; Stasko, Shawn A; Liu, Honglu; Dupont-Versteegden, Esther E; McCarthy, John J; Peterson, Charlotte A

    2014-04-01

    Our aim in the current study was to determine the necessity of satellite cells for long-term muscle growth and maintenance. We utilized a transgenic Pax7-DTA mouse model, allowing for the conditional depletion of > 90% of satellite cells with tamoxifen treatment. Synergist ablation surgery, where removal of synergist muscles places functional overload on the plantaris, was used to stimulate robust hypertrophy. Following 8 wk of overload, satellite cell-depleted muscle demonstrated an accumulation of extracellular matrix (ECM) and fibroblast expansion that resulted in reduced specific force of the plantaris. Although the early growth response was normal, an attenuation of hypertrophy measured by both muscle wet weight and fiber cross-sectional area occurred in satellite cell-depleted muscle. Isolated primary myogenic progenitor cells (MPCs) negatively regulated fibroblast ECM mRNA expression in vitro, suggesting a novel role for activated satellite cells/MPCs in muscle adaptation. These results provide evidence that satellite cells regulate the muscle environment during growth.

  7. Trunk muscle activity during the simultaneous performance of two motor tasks.

    Science.gov (United States)

    Farley, B G; Koshland, G F

    2000-12-01

    A unique feature of trunk muscles is that they can be activated to meet functional requirements for combined behaviors, including those related to posture and breathing. Trunk muscles therefore may have developed mechanisms for dealing with simultaneous inputs for different task requirements. This study was designed to test the hypothesis that a linear addition in trunk muscle activities would occur when an isometric trunk task and a pulsed expiration task was performed simultaneously. Surface electromyograms (EMG) were recorded from four trunk regions (medial and lateral back, upper and lower lateral abdomen) in sitting during the performance of the individual isometric trunk task, the individual pressure task, and the combined task (isometric trunk and pressure task). The direction of static holding for the isometric trunk task was varied between flexion and extension positions. For the pressure task subjects produced two consecutive pressure pulses (2/s) to a target oral pressure. For each muscle recording, a linear prediction was calculated from the mathematical addition of the EMG recorded from the individual trunk and pressure tasks. This linear prediction was compared to the actual muscle activity recorded during the combined task. Typically the EMG from two muscles showed linear addition, such that the relative contribution of muscle activity did not change for the combined task. This suggests that the motor commands for each task reached these motor neuron pools essentially unmodified. The other two muscles showed nonlinear combination of two EMG patterns. That is, qualitatively both EMG patterns, specific to each command, were evident in the measured EMG traces for the combined task, but quantitatively the muscle did not meet all criteria for linear addition. Linear addition may provide a simple mechanism for combining breathing-related behaviors (expiratory efforts) with other trunk behaviors (holding against gravity). This suggests that some muscles can

  8. Association of circulating angiotensin converting enzyme activity with respiratory muscle function in infants

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    Onufriou Anny

    2010-05-01

    Full Text Available Abstract Background Angiotensin converting enzyme (ACE gene contains a polymorphism, consisting of either the presence (I or absence (D of a 287 base pair fragment. Deletion (D is associated with increased circulating ACE (cACE activity. It has been suggested that the D-allele of ACE genotype is associated with power-oriented performance and that cACE activity is correlated with muscle strength. Respiratory muscle function may be similarly influenced. Respiratory muscle strength in infants can be assessed specifically by measurement of the maximum inspiratory pressure during crying (Pimax. Pressure-time index of the respiratory muscles (PTImus is a non-invasive method, which assesses the load to capacity ratio of the respiratory muscles. The objective of this study was to determine whether increased cACE activity in infants could be related to greater respiratory muscle strength and to investigate the potential association of cACE with PTImus measurements as well as the association of ACE genotypes with cACE activity and respiratory muscle strength in this population. Methods Serum ACE activity was assayed by using a UV-kinetic method. ACE genotyping was performed by polymerase chain reaction amplification, using DNA from peripheral blood. PTImus was calculated as (Pimean/Pimax × (Ti/Ttot, where Pimean was the mean inspiratory pressure estimated from airway pressure, generated 100 milliseconds after an occlusion (P0.1, Pimax was the maximum inspiratory pressure and Ti/Ttot was the ratio of the inspiratory time to the total respiratory cycle time. Pimax was the largest pressure generated during brief airway occlusions performed at the end of a spontaneous crying effort. Results A hundred and ten infants were studied. Infants with D/D genotype had significantly higher serum ACE activity than infants with I/I or I/D genotypes. cACE activity was significantly related to Pimax and inversely related to PTImus. No association between ACE genotypes and

  9. Abdominal muscle activity during breathing in different postures in COPD "Stage 0" and healthy subjects.

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    Mesquita Montes, António; Maia, Joana; Crasto, Carlos; de Melo, Cristina Argel; Carvalho, Paulo; Santos, Rita; Pereira, Susana; Vilas-Boas, João Paulo

    2017-04-01

    This study aims to evaluate the effect of different postures on the abdominal muscle activity during breathing in subjects "at risk" for the development of chronic obstructive pulmonary disease (COPD) and healthy. Twenty-nine volunteers, divided in "At Risk" for COPD (n=16; 47.38±5.08years) and Healthy (n=13; 47.54±6.65years) groups, breathed at the same rhythm in supine, standing, tripod and 4-point-kneeling positions. Surface electromyography was performed to assess the activation intensity of rectus abdominis, external oblique and transversus abdominis/internal oblique (TrA/IO) muscles, during inspiration and expiration. From supine to standing, an increased activation of all abdominal muscles was observed in "At Risk" for COPD group; however, in Healthy group, TrA/IO muscle showed an increased activation. In both groups, the TrA/IO muscle activation in tripod and 4-point kneeling positions was higher than in supine and lower than in standing. Subjects "at risk" for the development of COPD seemed to have a specific recruitment of the superficial layer of ventrolateral abdominal wall for the synchronization of postural function and mechanics of breathing.

  10. The effects of sling exercise using vibration on trunk muscle activities of healthy adults.

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    Choi, Youngin; Kang, Hyungkyu

    2013-10-01

    [Purpose] This study compared the effects of sling exercises with and without vibration on the muscular activity of the internal oblique (IO), rectus abdominis (RA), multifidus (MF), and erector spinae (ES) muscles of healthy adults. [Methods] Eleven healthy university students (11 men) with a mean age of 22.8 years were enrolled in this study. Subjects performed supine and prone bridge exercises with the knees flexed using a sling suspension system with and without vibration. The amplitudes of the EMG activities of selected trunk muscles (internal oblique, rectus abdominis, erector spinae, multifidus) were recorded. Two types of exercise conditions were executed in a random sequence for 5 seconds each. The signals detected from the middle 3 seconds (after discarding the signals of the first and the last one seconds) were used in the analysis. A 3-minute break was given after each exercise to minimize muscle fatigue. [Results] During the supine bridge exercise with vibration, the activities of the IO, RA, MF, and ES muscles were significantly higher than those of the supine bridge exercise without vibration. Additionally, during the prone bridge exercise with vibration, the activities of the IO, RA, MF, and ES were significantly higher than those of the prone bridge exercise without vibration. [Conclusion] Sling exercises with vibration improved the trunk muscle activities of healthy adults compared to the sling exercises without vibration. The information presented here is important for clinicians who use lumbar stabilization exercises as an evaluation tool or a rehabilitation exercise.

  11. Are cervical multifidus muscles active during whiplash and startle? An initial experimental study

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    Carpenter Mark G

    2008-06-01

    Full Text Available Abstract Background The cervical multifidus muscles insert onto the lower cervical facet capsular ligaments and the cervical facet joints are the source of pain in some chronic whiplash patients. Reflex activation of the multifidus muscle during a whiplash exposure could potentially contribute to injuring the facet capsular ligament. Our goal was to determine the onset latency and activation amplitude of the cervical multifidus muscles to a simulated rear-end collision and a loud acoustic stimuli. Methods Wire electromyographic (EMG electrodes were inserted unilaterally into the cervical multifidus muscles of 9 subjects (6M, 3F at the C4 and C6 levels. Seated subjects were then exposed to a forward acceleration (peak acceleration 1.55 g, speed change 1.8 km/h and a loud acoustic tone (124 dB, 40 ms, 1 kHz. Results Aside from one female, all subjects exhibited multifidus activity after both stimuli (8 subjects at C4, 6 subjects at C6. Neither onset latencies nor EMG amplitude varied with stimulus type or spine level (p > 0.13. Onset latencies and amplitudes varied widely, with EMG activity appearing within 160 ms of stimulus onset (for at least one of the two stimuli in 7 subjects. Conclusion These data indicate that the multifidus muscles of some individuals are active early enough to potentially increase the collision-induced loading of the facet capsular ligaments.

  12. Effects of increasing physical activity on foot structure and ankle muscle strength in adults with obesity

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    Zhao, Xiaoguang; Tsujimoto, Takehiko; Kim, Bokun; Katayama, Yasutomi; Wakaba, Kyousuke; Wang, Zhennan; Tanaka, Kiyoji

    2016-01-01

    [Purpose] The purpose of this study was to examine the effects of increasing physical activity on foot structure and ankle muscle strength in adults with obesity and to verify whether the rate of change in foot structure is related to that in ankle muscle strength. [Subjects and Methods] Twenty-seven adults with obesity completed a 12-week program in which the intensity of physical activity performed was gradually increased. Physical activity was monitored using a three-axis accelerometer. Foot structure was assessed using a three-dimensional foot scanner, while ankle muscle strength was measured using a dynamometry. [Results] With the increasing physical activity, the participants’ feet became thinner (the rearfoot width, instep height, and girth decreased) and the arch became higher (the arch height index increased) and stiffer (the arch stiffness index increased); the ankle muscle strength also increased after the intervention. Additionally, the changes in the arch height index and arch stiffness index were not associated with changes in ankle muscle strength. [Conclusion] Increasing physical activity may be one possible approach to improve foot structure and function in individuals with obesity. PMID:27630426

  13. Mapping ECoG channel contributions to trajectory and muscle activity prediction in human sensorimotor cortex

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    Nakanishi, Yasuhiko; Yanagisawa, Takufumi; Shin, Duk; Kambara, Hiroyuki; Yoshimura, Natsue; Tanaka, Masataka; Fukuma, Ryohei; Kishima, Haruhiko; Hirata, Masayuki; Koike, Yasuharu

    2017-01-01

    Studies on brain-machine interface techniques have shown that electrocorticography (ECoG) is an effective modality for predicting limb trajectories and muscle activity in humans. Motor control studies have also identified distributions of “extrinsic-like” and “intrinsic-like” neurons in the premotor (PM) and primary motor (M1) cortices. Here, we investigated whether trajectories and muscle activity predicted from ECoG were obtained based on signals derived from extrinsic-like or intrinsic-like neurons. Three participants carried objects of three different masses along the same counterclockwise path on a table. Trajectories of the object and upper arm muscle activity were predicted using a sparse linear regression. Weight matrices for the predictors were then compared to determine if the ECoG channels contributed more information about trajectory or muscle activity. We found that channels over both PM and M1 contributed highly to trajectory prediction, while a channel over M1 was the highest contributor for muscle activity prediction. PMID:28361947

  14. Globular adiponectin activates motility and regenerative traits of muscle satellite cells.

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    Tania Fiaschi

    Full Text Available Regeneration of adult injured skeletal muscle is due to activation of satellite cells, a population of stem cells resident beneath the basal lamina. Thus, information on soluble factors affecting satellite cell activation, as well as migration towards injury and fusion into new myofibers are essential. Here, we show that globular adiponectin (gAd, positively affects several features of muscle satellite cells. gAd activates satellite cells to exit quiescence and increases their recruitment towards myotubes. gAd elicits in satellite cells a specific motility program, involving activation of the small GTPase Rac1, as well as expression of Snail and Twist transcription factors driving a proteolytic motility, useful to reach the site of injury. We show that satellite cells produce autocrine full length adiponectin (fAd, which is converted to gAd by activated macrophages. In turns, gAd concurs to attract to the site of injury both satellite cells and macrophages and induces myogenesis in muscle satellite cells. Thus, these findings add a further role for gAd in skeletal muscle, including the hormone among factors participating in muscle regeneration.

  15. Physical activity counteracts tumor cell growth in colon carcinoma C26-injected muscles: an interim report

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    Charlotte Hiroux

    2016-06-01

    Full Text Available Skeletal muscle tissue is a rare site of tumor metastasis but is the main target of the degenerative processes occurring in cancer-associated cachexia syndrome. Beneficial effects of physical activity in counteracting cancer-related muscle wasting have been described in the last decades. Recently it has been shown that, in tumor xeno-transplanted mouse models, physical activity is able to directly affect tumor growth by modulating inflammatory responses in the tumor mass microenvironment. Here, we investigated the effect of physical activity on tumor cell growth in colon carcinoma C26 cells injected tibialis anterior muscles of BALB/c mice. Histological analyses revealed that 4 days of voluntary wheel running significantly counteracts tumor cell growth in C26-injected muscles compared to the non-injected sedentary controls. Since striated skeletal muscle tissue is the site of voluntary contraction, our results confirm that physical activity can also directly counteract tumor cell growth in a metabolically active tissue that is usually not a target for metastasis.

  16. Effects of a myofunctional appliance on orofacial muscle activity and structures.

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    Tallgren, A; Christiansen, R L; Ash, M; Miller, R L

    1998-06-01

    The aim of the study was to examine the effect of an oral shield treatment on orofacial muscle activity and facial morphology in children with lip and/or tongue dysfunction. The sample consisted of 7 girls and 2 boys, 7 to 12 years old. EMG recordings with and without the shield in situ were obtained when the shield was placed, and 3, 6, and 12 months later. Lateral cephalograms were obtained at the initial and 1-year stages. The lip muscles showed dominant activity when the subjects were sucking on an empty straw and during swallowing; this was strongest during the first 3 months. The mentalis, buccinator, and digastric muscles generally showed weaker activity. The anterior temporal muscle showed dominant activity during maximal clench, but after the 3-month stage a significant decrease was noted. After 1 year of treatment, no significant changes in overjet or overbite were observed. Most of the craniofacial growth changes were normal for the age group. The results indicate that treatment with an oral shield caused a decrease in orofacial muscle activity during oral functions. Although there was a slight average retraction of the maxillary incisors, the change in position was not statistically significant.

  17. Does breathing type influence electromyographic activity of obligatory and accessory respiratory muscles?

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    Gutiérrez, M F; Valenzuela, S; Miralles, R; Portus, C; Santander, H; Fuentes, A D; Celhay, I

    2014-11-01

    Craniomandibular electromyographic (EMG) studies frequently include several parameters, e.g. resting, chewing and tooth-clenching. EMG activity during these parameters has been recorded in the elevator muscles, but little is known about the respiratory muscles. The aim of this study was to compare EMG activity in obligatory and accessory respiratory muscles between subjects with different breathing types. Forty male subjects were classified according to their breathing type into two groups of 20 each: costo-diaphragmatic breathing type and upper costal breathing type. Bipolar surface electrodes were placed on the sternocleidomastoid, diaphragm, external intercostal and latissimus dorsi muscles. EMG activity was recorded during the following tasks: (i) normal quiet breathing, (ii) maximal voluntary clenching in intercuspal position, (iii) natural rate chewing until swallowing threshold, (iv) short-time chewing. Diaphragm EMG activity was significantly higher in the upper costal breathing type than in the costo-diaphragmatic breathing type in all tasks (P breathing type than in the costo-diaphragmatic breathing type in tasks 3 and 4 (P breathing types in the tasks studied (P > 0·05). The significantly higher EMG activity observed in subjects with upper costal breathing than in the costo-diaphragmatic breathing type suggests that there could be differences in motor unit recruitment strategies depending on the breathing type. This may be an expression of the adaptive capability of muscle chains in subjects who clinically have a different thoraco-abdominal expansion during inspiration at rest.

  18. A comparison of muscle activity in concentric and counter movement maximum bench press.

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    van den Tillaar, Roland; Ettema, Gertjan

    2013-01-01

    The purpose of this study was to compare the kinematics and muscle activation patterns of regular free-weight bench press (counter movement) with pure concentric lifts in the ascending phase of a successful one repetition maximum (1-RM) attempt in the bench press. Our aim was to evaluate if diminishing potentiation could be the cause of the sticking region. Since diminishing potentiation cannot occur in pure concentric lifts, the occurrence of a sticking region in this type of muscle actions would support the hypothesis that the sticking region is due to a poor mechanical position. Eleven male participants (age 21.9 ± 1.7 yrs, body mass 80.7 ± 10.9 kg, body height 1.79 ± 0.07 m) conducted 1-RM lifts in counter movement and in pure concentric bench presses in which kinematics and EMG activity were measured. In both conditions, a sticking region occurred. However, the start of the sticking region was different between the two bench presses. In addition, in four of six muscles, the muscle activity was higher in the counter movement bench press compared to the concentric one. Considering the findings of the muscle activity of six muscles during the maximal lifts it was concluded that the diminishing effect of force potentiation, which occurs in the counter movement bench press, in combination with a delayed muscle activation unlikely explains the existence of the sticking region in a 1-RM bench press. Most likely, the sticking region is the result of a poor mechanical force position.

  19. Application of histamine or serotonin to the hypoglossal nucleus increases genioglossus muscle activity across the wake-sleep cycle.

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    Neuzeret, Pierre-Charles; Sakai, Kazuya; Gormand, Frédéric; Petitjean, Thierry; Buda, Colette; Sastre, Jean-Pierre; Parrot, Sandrine; Guidon, Gérard; Lin, Jian-Sheng

    2009-03-01

    The decrease in genioglossus (GG) muscle activity during sleep, especially rapid eye movement (REM) or paradoxical sleep, can lead to airway occlusion and obstructive sleep apnoea (OSA). The hypoglossal nucleus innervating the GG muscle is under the control of serotonergic, noradrenergic and histaminergic neurons that cease firing during paradoxical sleep. The objectives of this study were to determine the effect on GG muscle activity during different wake-sleep states of the microdialysis application of serotonin, histamine (HA) or noradrenaline (NE) to the hypoglossal nucleus in freely moving cats. Six adult cats were implanted with electroencephalogram, electro-oculogram and neck electromyogram electrodes to record wake-sleep states and with GG muscle and diaphragm electrodes to record respiratory muscle activity. Microdialysis probes were inserted into the hypoglossal nucleus for monoamine application. Changes in GG muscle activity were assessed by power spectrum analysis. In the baseline conditions, tonic GG muscle activity decreased progressively and significantly from wakefulness to slow-wave sleep and even further during slow-wave sleep with ponto-geniculo-occipital waves and paradoxical sleep. Application of serotonin or HA significantly increased GG muscle activity during the wake-sleep states when compared with controls. By contrast, NE had no excitatory effect. Our results indicate that both serotonin and HA have a potent excitatory action on GG muscle activity, suggesting multiple aminergic control of upper airway muscle activity during the wake-sleep cycle. These data might help in the development of pharmacological approaches for the treatment of OSA.

  20. Mitochondrial superoxide flashes: metabolic biomarkers of skeletal muscle activity and disease.

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    Wei, Lan; Salahura, Gheorghe; Boncompagni, Simona; Kasischke, Karl A; Protasi, Feliciano; Sheu, Shey-Shing; Dirksen, Robert T

    2011-09-01

    Mitochondrial superoxide flashes (mSOFs) are stochastic events of quantal mitochondrial superoxide generation. Here, we used flexor digitorum brevis muscle fibers from transgenic mice with muscle-specific expression of a novel mitochondrial-targeted superoxide biosensor (mt-cpYFP) to characterize mSOF activity in skeletal muscle at rest, following intense activity, and under pathological conditions. Results demonstrate that mSOF activity in muscle depended on electron transport chain and adenine nucleotide translocase functionality, but it was independent of cyclophilin-D-mediated mitochondrial permeability transition pore activity. The diverse spatial dimensions of individual mSOF events were found to reflect a complex underlying morphology of the mitochondrial network, as examined by electron microscopy. Muscle activity regulated mSOF activity in a biphasic manner. Specifically, mSOF frequency was significantly increased following brief tetanic stimulation (18.1 ± 1.6 to 22.3 ± 2.0 flashes/1000 μm²·100 s before and after 5 tetani) and markedly decreased (to 7.7 ± 1.6 flashes/1000 μm²·100 s) following prolonged tetanic stimulation (40 tetani). A significant temperature-dependent increase in mSOF frequency (11.9 ± 0.8 and 19.8 ± 2.6 flashes/1000 μm²·100 s at 23°C and 37°C) was observed in fibers from RYR1(Y522S/WT) mice, a mouse model of malignant hyperthermia and heat-induced hypermetabolism. Together, these results demonstrate that mSOF activity is a highly sensitive biomarker of mitochondrial respiration and the cellular metabolic state of muscle during physiological activity and pathological oxidative stress

  1. Cytoskeleton, L-type Ca2+ and stretch activated channels in injured skeletal muscle

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    Fabio Francini

    2013-07-01

    Full Text Available The extra-sarcomeric cytoskeleton (actin microfilaments and anchoring proteins is involved in maintaining the sarco-membrane stiffness and integrity and in turn the mechanical stability and function of the intra- and sub-sarcoplasmic proteins. Accordingly, it regulates Ca2+ entry through the L-type Ca2+ channels and the mechano-sensitivity of the stretch activated channels (SACs. Moreover, being intra-sarcomeric cytoskeleton bound to costameric proteins and other proteins of the sarcoplasma by intermediate filaments, as desmin, it integrates the properties of the sarcolemma with the skeletal muscle fibres contraction. The aim of this research was to compare the cytoskeleton, SACs and the ECC alterations in two different types of injured skeletal muscle fibres: by muscle denervation and mechanical overload (eccentric contraction. Experiments on denervation were made in isolated Soleus muscle of male Wistar rats; forced eccentric-contraction (EC injury was achieved in Extensor Digitorum Longus muscles of Swiss mice. The method employed conventional intracellular recording with microelectrodes inserted in a single fibre of an isolated skeletal muscle bundle. The state of cytoskeleton was evaluated by recording SAC currents and by evaluating the resting membrane potential (RMP value determined in current-clamp mode. The results demonstrated that in both injured skeletal muscle conditions the functionality of L-type Ca2+ current, ICa, was affected. In parallel, muscle fibres showed an increase of the resting membrane permeability and of the SAC current. These issues, together with a more depolarized RMP are an index of altered cytoskeleton. In conclusion, we found a symilar alteration of ICa, SAC and cytoskeleton in both injured skeletal muscle conditions.

  2. Genetic model for the chronic activation of skeletal muscle AMP-activated protein kinase leads to glycogen accumulation.

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    Barré, Laura; Richardson, Christine; Hirshman, Michael F; Brozinick, Joseph; Fiering, Steven; Kemp, Bruce E; Goodyear, Laurie J; Witters, Lee A

    2007-03-01

    The AMP-activated protein kinase (AMPK) is an important metabolic sensor/effector that coordinates many of the changes in mammalian tissues during variations in energy availability. We have sought to create an in vivo genetic model of chronic AMPK activation, selecting murine skeletal muscle as a representative tissue where AMPK plays important roles. Muscle-selective expression of a mutant noncatalytic gamma1 subunit (R70Qgamma) of AMPK activates AMPK and increases muscle glycogen content. The increase in glycogen content requires the presence of the endogenous AMPK catalytic alpha-subunit, since the offspring of cross-breeding of these mice with mice expressing a dominant negative AMPKalpha subunit have normal glycogen content. In R70Qgamma1-expressing mice, there is a small, but significant, increase in muscle glycogen synthase (GSY) activity associated with an increase in the muscle expression of the liver isoform GSY2. The increase in glycogen content is accompanied, as might be expected, by an increase in exercise capacity. Transgene expression of this mutant AMPKgamma1 subunit may provide a useful model for the chronic activation of AMPK in other tissues to clarify its multiple roles in the regulation of metabolism and other physiological processes.