Alternate activity in the synergistic muscles during prolonged low-level contractions

1998 ◽  
Vol 84 (6) ◽  
pp. 1943-1951 ◽  
Author(s):  
H. Tamaki ◽  
K. Kitada ◽  
T. Akamine ◽  
F. Murata ◽  
T. Sakou ◽  
...  
Keyword(s):  
Time Course ◽  
Human Subjects ◽  
Plantar Flexion ◽  
Constant Load ◽  
Voluntary Contraction ◽  
Medial Gastrocnemius ◽  
Lateral Gastrocnemius ◽  
Low Level ◽  
Synergistic Muscles ◽  
Synergistic Muscle

The purpose of this study was to investigate the functional interrelationship between synergistic muscle activities during low-level fatiguing contractions. Six human subjects performed static and dynamic contractions at an ankle joint angle of 110° plantar flexion and within the range of 90–110° (anatomic position = 90°) under constant load (10% maximal voluntary contraction) for 210 min. Surface electromyogram records from lateral gastrocnemius (LG), medial gastrocnemius (MG), and soleus (Sol) muscles showed high and silent activities alternately in the three muscles and a complementary and alternate activity between muscles in the time course. In the second half of all exercise times, the number of changes in activity increased significantly ( P < 0.05) in each muscle. The ratios of active to silent periods of electromyogram activity were significantly higher ( P< 0.05) in MG (4.5 ± 2.2) and Sol (4.3 ± 2.8) than in the LG (0.4 ± 0.1), but no significant differences were observed between MG and Sol. These results suggest that the relative activation of synergistic motor pools are not constant during a low-level fatiguing task.

scholarly journals Quantifying Topographical Changes in Muscle Activation: A Statistical Parametric Mapping Approach

Proceedings ◽  
2020 ◽  
Vol 49 (1) ◽  
pp. 71
Author(s):  
Patricio A. Pincheira ◽  
Eduardo Martinez-Valdes ◽  
Carlos De la Fuente ◽  
Felipe Palma ◽  
Oscar Valencia ◽  
...  
Keyword(s):  
Repeated Measures ◽  
Muscle Activation ◽  
Plantar Flexion ◽  
Statistical Parametric Mapping ◽  
High Sensitivity ◽  
Voluntary Contraction ◽  
Medial Gastrocnemius ◽  
Isometric Contractions ◽  
Parametric Mapping ◽  
Repeated Measures Anova

Regional changes in muscle activation occur at different contraction intensities. These changes can be observed with activity maps created with high-density electromyography (HDEMG). When quantifying these changes, statistical parametric mapping (SPM) is a neuroimaging technique that may be used to perform statistical analyses with high sensitivity and spatial resolution. The aim of this study was to identify regional changes in muscle activation at different contraction intensities, comparing SPM and the HDEMG barycenter (centroid). Twelve participants performed plantar flexion isometric contractions at 20%, 40%, and 60% of the maximal voluntary contraction (MVC), while HDEMG was recorded from the medial gastrocnemius. An SPM repeated measures ANOVA design revealed specific mediolateral and cephalocaudal changes in muscle activation with increasing contraction intensities, which were not clearly detected by the variation in the barycenter coordinates. Only SPM revealed statistically significant nonuniform changes in EMG amplitude between all increasing levels of muscle activation.

Influences of premotoneuronal command statistics on the scaling of motor output variability during isometric plantar flexion

2013 ◽  
Vol 110 (11) ◽  
pp. 2592-2606 ◽  
Author(s):  
Renato N. Watanabe ◽  
Fernando H. Magalhães ◽  
Leonardo A. Elias ◽  
Vitor M. Chaud ◽  
Emanuele M. Mello ◽  
...  
Keyword(s):  
Point Processes ◽  
Plantar Flexion ◽  
Spike Trains ◽  
Triceps Surae ◽  
Medial Gastrocnemius ◽  
Lateral Gastrocnemius ◽  
Output Variability ◽  
Motor Output Variability ◽  
Wide Range ◽  
Gastrocnemius Muscles

This study focuses on neuromuscular mechanisms behind ankle torque and EMG variability during a maintained isometric plantar flexion contraction. Experimentally obtained torque standard deviation (SD) and soleus, medial gastrocnemius, and lateral gastrocnemius EMG envelope mean and SD increased with mean torque for a wide range of torque levels. Computer simulations were performed on a biophysically-based neuromuscular model of the triceps surae consisting of premotoneuronal spike trains (the global input, GI) driving the motoneuron pools of the soleus, medial gastrocnemius, and lateral gastrocnemius muscles, which activate their respective muscle units. Two types of point processes were adopted to represent the statistics of the GI: Poisson and Gamma. Simulations showed a better agreement with experimental results when the GI was modeled by Gamma point processes having lower orders (higher variability) for higher target torques. At the same time, the simulations reproduced well the experimental data of EMG envelope mean and SD as a function of mean plantar flexion torque, for the three muscles. These results suggest that the experimentally found relations between torque-EMG variability as a function of mean plantar flexion torque level depend not only on the intrinsic properties of the motoneuron pools and the muscle units innervated, but also on the increasing variability of the premotoneuronal GI spike trains when their mean rates increase to command a higher plantar flexion torque level. The simulations also provided information on spike train statistics of several hundred motoneurons that compose the triceps surae, providing a wide picture of the associated mechanisms behind torque and EMG variability.

Reflex responses of human soleus muscle to small perturbations

1976 ◽  
Vol 39 (5) ◽  
pp. 1105-1116 ◽  
Author(s):  
R. B. Stein ◽  
P. Bawa
Keyword(s):  
Soleus Muscle ◽  
Time Course ◽  
Human Subjects ◽  
Voluntary Contraction ◽  
M Wave ◽  
Force Fluctuations ◽  
Twitch Contraction ◽  
Small Branch ◽  
Normal Human ◽  
Damped Oscillation

1. A small branch of the nerve to soleus muscle in normal human subjects was stimulated intramuscularly with a needle electrode while the subjects were maintaining a steady voluntary contraction. The EMG and force fluctuations produced by these stimuli were recorded and averaged. 2. In addition to the M-wave produced directly by stimulating motoneurons and the resultant twitch contraction, one or more EMG waves were seen with a latency greater than 100 ms. These later waves produced further contractions, and when there were several later waves, the EMG and force fluctuations appeared as a damped oscillation with a frequency between 5.5 and 8 Hz. 3. By varying the angle of the ankle and hence the time course of the twitch contraction, the timing of the latter waves was shown to be closely related to the contraction time. Thus, the later waves appeared to be produced reflexly by the tension fluctuations, rather than directly by the stimulus. 4. The frequency response function between the tension fluctuations and the reflux EMG responses was computed. The gain agreed with that of primary muscle spindle afferents, but the phase data showed extra lags consistent with a time delay which was too long to be spinal in origin. This reflex probably involves supraspinal centers.

scholarly journals Adaptations of motoneuron properties to chronic compensatory muscle overload

2015 ◽  
Vol 113 (7) ◽  
pp. 2769-2777 ◽  
Author(s):  
P. Krutki ◽  
A. Hałuszka ◽  
W. Mrówczyński ◽  
P. F. Gardiner ◽  
J. Celichowski
Keyword(s):  
Plantar Flexion ◽  
Input Resistance ◽  
Medial Gastrocnemius ◽  
Membrane Properties ◽  
Control Group ◽  
Lateral Gastrocnemius ◽  
Electrophysiological Properties ◽  
Slow Type ◽  
Rhythmic Firing ◽  
Firing Properties

The aim of the study was to determine whether chronic muscle overload has measurable effect on electrophysiological properties of motoneurons (MNs), and whether duration of this overload influences intensity of adaptations. The compensatory overload was induced in the rat medial gastrocnemius (MG) by bilateral tenotomy of its synergists (lateral gastrocnemius, soleus, and plantaris); as a result, only the MG was able to evoke the foot plantar flexion. To assure regular activation of the MG muscle, rats were placed in wheel-equipped cages and subjected to a low-level treadmill exercise. The intracellular recordings from MG motoneurons were made after 5 or 12 wk of the overload, and in a control group of intact rats. Some of the passive and threshold membrane properties as well as rhythmic firing properties were considerably modified in fast-type MNs, while remaining unaltered in slow-type MNs. The significant changes included a shortening of the spike duration and the spike rise time, an increase of the afterhyperpolarization amplitude, an increase of the input resistance, a decrease of the rheobase, and a decrease of the minimum current necessary to evoke steady-state firing. The data suggest higher excitability of fast-type MNs innervating the overloaded muscle, and a shift towards electrophysiological properties of slow-type MNs. All of the adaptations could be observed after 5 wk of the compensatory overload with no further changes occurring after 12 wk. This indicates that the response to an increased level of chronic activation of MNs is relatively quick and stable.

Neuromechanical adaptation to hopping with an elastic ankle-foot orthosis

2006 ◽  
Vol 100 (1) ◽  
pp. 163-170 ◽  
Author(s):  
Daniel P. Ferris ◽  
Zaineb A. Bohra ◽  
Jamie R. Lukos ◽  
Catherine R. Kinnaird
Keyword(s):  
Muscle Activation ◽  
Human Subjects ◽  
Medial Gastrocnemius ◽  
Lateral Gastrocnemius ◽  
Ankle Foot Orthosis ◽  
Ankle Stiffness ◽  
Surface Stiffness ◽  
Stiffness Constant ◽  
Leg Stiffness ◽  
Foot Orthosis

When humans hop or run on different surfaces, they adjust their effective leg stiffness to offset changes in surface stiffness. As a result, the overall stiffness of the leg-surface series combination remains independent of surface stiffness. The purpose of this study was to determine whether humans make a similar adjustment when springs are placed in parallel with the leg via a lower limb orthosis. We studied seven human subjects hopping in place on one leg while wearing an ankle-foot orthosis. We used an ankle-foot orthosis because the ankle joint is primarily responsible for leg stiffness during hopping. A spring was added to the ankle-foot orthosis so that it increased orthosis stiffness by providing plantar flexor torque during ankle dorsiflexion. We hypothesized that subjects would decrease their biological ankle stiffness when the spring was added to the orthosis, keeping total ankle stiffness constant. We collected kinematic, kinetic, and electromyographic data during hopping with and without the spring on the orthosis. We found that total ankle stiffness and leg stiffness did not change across the two orthosis conditions (ANOVA, P > 0.05). This was possible because subjects decreased their biological ankle stiffness to offset the orthosis spring stiffness ( P < 0.0001). The reduction in biological ankle stiffness was accompanied by decreases in soleus, medial gastrocnemius, and lateral gastrocnemius muscle activation ( P < 0.0002). These results suggest that an elastic exoskeleton might improve human running performance by reducing muscle recruitment.

scholarly journals Influence of static stretching on viscoelastic properties of human tendon structures in vivo

2001 ◽  
Vol 90 (2) ◽  
pp. 520-527 ◽  
Author(s):  
Keitaro Kubo ◽  
Hiroaki Kanehisa ◽  
Yasuo Kawakami ◽  
Tetsuo Fukunaga
Keyword(s):  
Viscoelastic Properties ◽  
Plantar Flexion ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Medial Gastrocnemius ◽  
Static Stretching ◽  
Tendon Elongation ◽  
Before And After ◽  
Human Tendon

The purpose of this study was to investigate the influences of static stretching on the viscoelastic properties of human tendon structures in vivo. Seven male subjects performed static stretching in which the ankle was passively flexed to 35° of dorsiflexion and remained stationary for 10 min. Before and after the stretching, the elongation of the tendon and aponeurosis of medial gastrocnemius muscle (MG) was directly measured by ultrasonography while the subjects performed ramp isometric plantar flexion up to the maximum voluntary contraction (MVC), followed by a ramp relaxation. The relationship between the estimated muscle force (Fm) of MG and tendon elongation ( L) during the ascending phase was fitted to a linear regression, the slope of which was defined as stiffness of the tendon structures. The percentage of the area within the Fm- L loop to the area beneath the curve during the ascending phase was calculated as an index representing hysteresis. Stretching produced no significant change in MVC but significantly decreased stiffness and hysteresis from 22.9 ± 5.8 to 20.6 ± 4.6 N/mm and from 20.6 ± 8.8 to 13.5 ± 7.6%, respectively. The present results suggest that stretching decreased the viscosity of tendon structures but increased the elasticity.

Effects of 12-wk eccentric calf muscle training on muscle-tendon glucose uptake and SEMG in patients with chronic Achilles tendon pain

2014 ◽  
Vol 117 (2) ◽  
pp. 105-111 ◽  
Author(s):  
Tahir Masood ◽  
Kari Kalliokoski ◽  
S. Peter Magnusson ◽  
Jens Bojsen-Møller ◽  
Taija Finni
Keyword(s):  
Achilles Tendon ◽  
Glucose Uptake ◽  
Plantar Flexion ◽  
Achilles Tendinopathy ◽  
Triceps Surae ◽  
Medial Gastrocnemius ◽  
Flexor Hallucis Longus ◽  
Myoelectric Activity ◽  
Plantar Flexors ◽  
Lateral Gastrocnemius

High-load eccentric exercises have been a key component in the conservative management of chronic Achilles tendinopathy. This study investigated the effects of a 12-wk progressive, home-based eccentric rehabilitation program on ankle plantar flexors' glucose uptake (GU) and myoelectric activity and Achilles tendon GU. A longitudinal study design with control ( n = 10) and patient ( n = 10) groups was used. Surface electromyography (SEMG) from four ankle plantar flexors and GU from the same muscles and the Achilles tendon were measured during submaximal intermittent isometric plantar flexion task. The results indicated that the symptomatic leg was weaker ( P < 0.05) than the asymptomatic leg at baseline, but improved ( P < 0.001) with eccentric rehabilitation. Additionally, the rehabilitation resulted in greater GU in both soleus ( P < 0.01) and lateral gastrocnemius ( P < 0.001) in the symptomatic leg, while the asymptomatic leg displayed higher uptake for medial gastrocnemius and flexor hallucis longus ( P < 0.05). While both patient legs had higher tendon GU than the controls ( P < 0.05), there was no rehabilitation effect on the tendon GU. Concerning SEMG, at baseline, soleus showed more relative activity in the symptomatic leg compared with both the asymptomatic and control legs ( P < 0.05), probably reflecting an effort to compensate for the decreased force potential. The rehabilitation resulted in greater SEMG activity in the lateral gastrocnemius ( P < 0.01) of the symptomatic leg with no other within- or between-group differences. Eccentric rehabilitation was effective in decreasing subjective severity of Achilles tendinopathy. It also resulted in redistribution of relative electrical activity, but not metabolic activity, within the triceps surae muscle.

Ultrasound reveals negligible cocontraction during isometric plantar flexion and dorsiflexion despite the presence of antagonist electromyographic activity

2015 ◽  
Vol 118 (10) ◽  
pp. 1193-1199 ◽  
Author(s):  
Brent J. Raiteri ◽  
Andrew G. Cresswell ◽  
Glen A. Lichtwark
Keyword(s):  
Cross Talk ◽  
Muscle Activity ◽  
Plantar Flexion ◽  
Medial Gastrocnemius ◽  
Electromyographic Activity ◽  
Plantar Flexors ◽  
Fascicle Length ◽  
Lateral Gastrocnemius ◽  
Muscle Fascicle

Because of the approximate linear relationship between muscle force and muscle activity, muscle forces are often estimated during maximal voluntary isometric contractions (MVICs) from torque and surface electromyography (sEMG) measurements. However, sEMG recordings from a target muscle may contain cross-talk originating from nearby muscles, which could lead to erroneous force estimates. Here we used ultrasound imaging to measure in vivo muscle fascicle length ( Lf) changes and sEMG to measure muscle activity of the tibialis anterior, medial gastrocnemius, lateral gastrocnemius, and soleus muscles during ramp MVICs in plantar and dorsiflexion directions ( n = 8). After correcting longitudinal Lfchanges for ankle rotation, the antagonist Lfat peak antagonist root-mean-square (RMS) amplitude were significantly longer than the agonist Lfat this sEMG-matched level. On average, Lfshortened from resting length by 1.29 to 2.90 mm when muscles acted as agonists and lengthened from resting length by 0.43 to 1.16 mm when muscles acted as antagonists (depending on the muscle of interest). The lack of fascicle shortening when muscles acted as antagonists indicates that cocontraction was likely to be negligible, despite cocontraction as determined by sEMG of between 7 and 23% MVIC across all muscles. Different interelectrode distances (IEDs) over the plantar flexors revealed significantly higher antagonist RMS amplitudes for the 4-cm IEDs compared with the 2-cm IEDs, which further indicates that cross-talk was present. Consequently, investigators should be wary about performing agonist torque corrections for isometric plantar flexion and dorsiflexion based on the antagonist sEMG trace and predicted antagonist moment.

scholarly journals Importance of Maximal Strength and Muscle-Tendon Mechanics for Improving Force Steadiness in Persons with Parkinson’s Disease

2020 ◽  
Vol 10 (8) ◽  
pp. 471
Author(s):  
Rowan R. Smart ◽  
Cydney M. Richardson ◽  
Daryl J. Wile ◽  
Brian H. Dalton ◽  
Jennifer M. Jakobi
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Plantar Flexion ◽  
Voluntary Contraction ◽  
Medial Gastrocnemius ◽  
Force Steadiness ◽  
Tracking Tasks ◽  
Tendon Mechanics ◽  
Tendon Elongation ◽  
Underlying Causes

Although plantar flexion force steadiness (FS) is reduced in persons with Parkinson’s disease (PD), the underlying causes are unknown. The aim of this exploratory design study was to ascertain the influence of maximal voluntary contraction (MVC) force and gastrocnemius-Achilles muscle-tendon unit behaviour on FS in persons with PD. Nine persons with PD and nine age- and sex-matched non-PD controls (~70 years, 6 females per group) performed plantar flexion MVCs and sub-maximal tracking tasks at 5, 10, 25, 50 and 75% MVC. Achilles tendon elongation and medial gastrocnemius fascicle lengths were recorded via ultrasound during contraction. FS was quantified using the coefficient of variation (CV) of force. Contributions of MVC and tendon mechanics to FS were determined using multiple regression analyses. Persons with PD were 35% weaker during MVC (p = 0.04) and had 97% greater CV (p = 0.01) with 47% less fascicle shortening (p = 0.004) and 38% less tendon elongation (p = 0.002) than controls. Reduced strength was a direct contributor to lower FS in PD (ß = 0.631), and an indirect factor through limiting optimal muscle-tendon unit interaction. Interestingly, our findings indicate an uncoupling between fascicle shortening and tendon elongation in persons with PD. To better understand limitations in FS and muscle-tendon unit behavior, it is imperative to identify the origins of MVC decrements in persons with PD.

Soleus aponeurosis strain distribution following chronic unloading in humans: an in vivo MR phase-contrast study

2006 ◽  
Vol 100 (6) ◽  
pp. 2004-2011 ◽  
Author(s):  
Hae-Dong Lee ◽  
Taija Finni ◽  
John A. Hodgson ◽  
Alex M. Lai ◽  
V. Reggie Edgerton ◽  
...  
Keyword(s):  
Achilles Tendon ◽  
Strain Distribution ◽  
Phase Contrast ◽  
Plantar Flexion ◽  
Voluntary Contraction ◽  
Triceps Surae ◽  
Medial Gastrocnemius ◽  
Contrast Study ◽  
Ankle Plantar Flexion

The in vivo strain properties of human skeletal muscle-tendon complexes are poorly understood, particularly following chronic periods of reduced load bearing. We studied eight healthy volunteers who underwent 4 wk of unilateral lower limb suspension (ULLS) to induce chronic unloading. Before and after the ULLS, maximum isometric ankle plantar flexion torque was determined by using a magnetic resonance (MR)-compatible dynamometry. Volumes of the triceps surae muscles and strain distribution of the soleus aponeurosis and the Achilles tendon at a constant submaximal plantar flexion (20% pre-maximal voluntary contraction) were measured by using MRI and velocity-encoded, phase-contrast MRI techniques. Following ULLS, volumes of the soleus and the medial gastrocnemius and the maximum isometric ankle plantar flexion (maximum voluntary contraction) decreased by 5.5 ± 1.9, 7.5 ± 2.7, and 48.1 ± 6.1%, respectively. The strain of the aponeurosis along the length of the muscle before the ULLS was 0.3 ± 0.3%, ranging from −1.5 to 2.7% in different locations of the aponeurosis. Following ULLS, the mean strain was −6.4 ± 0.3%, ranging from −1.6 to 1.3%. The strain distribution of the midregion of the aponeurosis was significantly influenced by the ULLS, whereas the more distal component showed no consistent changes. Achilles tendon strain was not affected by the ULLS. These results raise the issue as to whether these changes in strain distribution affect the functional properties of the triceps surae and whether the probability of strain injuries within the triceps surae increases following chronic unloading in those regions of this muscle complex in which unusual strains occur.

Sign in / Sign up

Export Citation Format

Share Document