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.

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.

scholarly journals Multi- and Single-Joint Resistance Exercises Promote Similar Plantar Flexor Activation in Resistance Trained Men

2020 ◽  
Vol 17 (24) ◽  
pp. 9487
Author(s):  
Paulo Gentil ◽  
Daniel Souza ◽  
Murillo Santana ◽  
Rafael Ribeiro Alves ◽  
Mário Hebling Campos ◽  
...  
Keyword(s):  
Muscle Activation ◽  
Negative Impact ◽  
Triceps Surae ◽  
Medial Gastrocnemius ◽  
Plantar Flexors ◽  
Lateral Gastrocnemius ◽  
Leg Press ◽  
Electromyographic Signal ◽  
Triceps Surae Muscles ◽  
Gastrocnemius Muscles

The present study aimed to compare soleus, lateral, and medial gastrocnemius muscles activation during leg press and calf raise exercises in trained men. The study involved 22 trained men (27.1 ± 3.6 years, 82.7 ± 6.6 kg, 177.5 ± 5.2 cm, 3.6 ± 1.4 experience years) who performed one set of each exercise using a 10-repetition maximum (10RM) load in a counterbalanced randomized order and separated by 10 min of rest. The electromyographic signal was measured for the three major plantar flexors: soleus, medial, and lateral gastrocnemius. A comparison between exercises showed that the mean adjusted by peak values during the leg press were 49.20% for the gastrocnemius lateralis, 51.31% for the gastrocnemius medialis, and 50.76% for the soleus. Values for calf raise were 50.70%, 52.19%, and 51.34% for the lateral, medial gastrocnemius, and soleus, respectively. There were no significant differences between exercises for any muscle (lateral gastrocnemius (p = 0.230), medial gastrocnemius (p = 0.668), and soleus (p = 0.535)). The present findings suggest that both leg press and calf raises can be used with the purpose to recruit triceps surae muscles. This bring the suggestion that one can chose between exercises based on personal preferences and practical aspects, without any negative impact on muscle activation.

scholarly journals Rightward shift of optimal fascicle length with decreasing voluntary activity level in the soleus and lateral gastrocnemius muscles

2020 ◽  
pp. jeb.235614
Author(s):  
Anthony L. Hessel ◽  
Brent J. Raiteri ◽  
Michael J. Marsh ◽  
Daniel Hahn
Keyword(s):  
Muscle Activity ◽  
Plantar Flexion ◽  
Voluntary Contraction ◽  
Activity Level ◽  
Triceps Surae ◽  
Activity Levels ◽  
Fascicle Length ◽  
Lateral Gastrocnemius ◽  
Ankle Angle ◽  
Gastrocnemius Muscles

Much of our understanding of in vivo skeletal muscle properties is based on studies performed under maximal activation, which is problematic because muscles are rarely activated maximally during movements such as walking. Currently, force-length properties of the human triceps surae at submaximal voluntary muscle activity levels are not characterized. We therefore evaluated plantar flexor torque/force-ankle angle and torque/force-fascicle length properties of the soleus and lateral gastrocnemius muscles during voluntary contractions at three activity levels: 100, 30, and 22% of maximal voluntary contraction. Soleus activity levels were controlled by participants via real-time electromyography feedback and contractions were performed at ankle angles ranging from 10° plantar flexion to 35° dorsiflexion. Using dynamometry and ultrasound imaging, torque-fascicle length curves of the soleus and lateral gastrocnemius muscles were constructed. The results indicate that small muscle activity reductions shift the torque/force-angle and torque/force-fascicle length curves of these muscles to more dorsiflexed ankle angles and longer fascicle lengths (from 3 to 20% optimal fascicle length, depending on ankle angle). The shift in the torque- and force-fascicle length curves during submaximal voluntary contraction have potential implications for human locomotion (e.g. walking) as the operating range of fascicles shifts to the ascending limb, where muscle force capacity is reduced by at least 15%. These data demonstrate the need to match activity levels during construction of the torque- and force-fascicle length curves to activity levels achieved during movement to better characterize the lengths that muscles operate at relative to their optimum during a specific task.

scholarly journals Absence of lateral gastrocnemius activity and differential motor unit behavior in soleus and medial gastrocnemius during standing balance

2014 ◽  
Vol 116 (2) ◽  
pp. 140-148 ◽  
Author(s):  
Martin E. Héroux ◽  
Christopher J. Dakin ◽  
Billy L. Luu ◽  
John Timothy Inglis ◽  
Jean-Sébastien Blouin
Keyword(s):  
Firing Rate ◽  
Motor Unit ◽  
Standing Position ◽  
Standing Balance ◽  
Triceps Surae ◽  
Medial Gastrocnemius ◽  
Isometric Contractions ◽  
Functional Requirements ◽  
Vertical Projection ◽  
Lateral Gastrocnemius

In a standing position, the vertical projection of the center of mass passes in front of the ankle, which requires active plantar-flexor torque from the triceps surae to maintain balance. We recorded motor unit (MU) activity in the medial (MG) and lateral (LG) gastrocnemius muscle and the soleus (SOL) in standing balance and voluntary isometric contractions to understand the effect of functional requirements and descending drive from different neural sources on motoneuron behavior. Single MU activity was recorded in seven subjects with wire electrodes in the triceps surae. Two 3-min standing balance trials and several ramp-and-hold contractions were performed. Lateral gastrocnemius MU activity was rarely observed in standing. The lowest thresholds for LG MUs in ramp contractions were 20–35 times higher than SOL and MG MUs ( P < 0.001). Compared with MUs from the SOL, MG MUs were intermittently active ( P < 0.001), had higher recruitment thresholds ( P = 0.022), and greater firing rate variability ( P < 0.001); this difference in firing rate variability was present in standing balance and isometric contractions. In SOL and MG MUs, both recruitment of new MUs ( R2 = 0.59–0.79, P < 0.01) and MU firing rates ( R2 = 0.05–0.40, P < 0.05) were associated with anterior-posterior and medio-lateral torque in standing. Our results suggest that the two heads of the gastrocnemius may operate in different ankle ranges with the larger MG being of primary importance when standing, likely due to its fascicle orientation. These differences in MU discharge behavior were independent of the type of descending neural drive, which points to a muscle-specific optimization of triceps surae motoneurons.

scholarly journals Dry needling of the gastrocnemius muscle. Overlap between trigger point area and the presence of blood vessels

2019 ◽  
Vol 02 (02) ◽  
pp. 063-063
Author(s):  
Velasco Fernández P. ◽  
Valera Garrido F.
Keyword(s):  
Blood Vessels ◽  
Gastrocnemius Muscle ◽  
Trigger Point ◽  
Trigger Points ◽  
Medial Gastrocnemius ◽  
Dry Needling ◽  
Lateral Gastrocnemius ◽  
Myofascial Trigger Points ◽  
Gastrocnemius Muscles ◽  
Venous Pattern

Abstract Aims To evaluate the anatomic variability of the gastrocnemius venous system using ultrasound and the overlap of the same with myofascial trigger points (MTrPs 1 and 2) clinically located in this muscle. Material and Methods In total, 82 legs of 41 healthy adults were studied, belonging to 26 men and 15 women aged between 22 and 50 years. The blood vessels located below MTrP1 and MTrP2, described by Travell and Simons were observed, and each image was analyzed by sectors (medial, central and lateral) to quantify the number of blood vessels, their distribution and overlap with the MTrPs described at this level. Results Examination of the 164 heads of 82 gastrocnemius muscles revealed that at least one vessel exists for each section analyzed. The number of veins per head varied between 1 and 8. The most common pattern in the medial gastrocnemius was three vessels (41.5%) and two vessels (49%) in the lateral gastrocnemius. In 100% of the cases the localization of the veins coincided with the clinical localization of the MTrPs. Conclusions The venous pattern of the proximal gastrocnemius is highly variable among subjects regarding the number of blood vessels and their distribution. There is a complete overlap between the clinical localization of the gastrocnemius MTrPs and the presence of blood vessels.

Monosynaptic EPSPs in primate lumbar motoneurons

1993 ◽  
Vol 70 (4) ◽  
pp. 1585-1592 ◽  
Author(s):  
J. S. Carp
Keyword(s):  
Input Resistance ◽  
Triceps Surae ◽  
Medial Gastrocnemius ◽  
Macaca Nemestrina ◽  
Synaptic Connectivity ◽  
Lateral Gastrocnemius ◽  
Mean Values ◽  
Epsp Amplitude ◽  
The Mean ◽  
Stimulation Of

1. Homonymous and heteronymous monosynaptic composite excitatory postsynaptic potentials (EPSPs) were evaluated by intracellular recordings from 89 motoneurons innervating triceps surae (n = 59) and more distal (n = 30) muscles in 14 pentobarbital-anesthetized monkeys (Macaca nemestrina). 2. Homonymous EPSPs were found in all motoneurons tested. The mean values +/- SD for maximum EPSP amplitude of triceps surae motoneurons were 2.5 +/- 1.3, 1.8 +/- 1.3 and 4.5 +/- 2.0 mV for medial gastrocnemius, lateral gastrocnemius, and soleus motoneurons, respectively. Heteronymous EPSPs were almost always smaller than their corresponding homonymous EPSPs. 3. Triceps surae EPSP amplitude was larger in motoneurons with higher input resistance. However, this relationship was weak, suggesting that factors related to input resistance play a limited role in determining the magnitude of the EPSP. 4. The mean ratio +/- SD of the amplitude of the EPSP elicited by combined stimulation of all triceps surae nerves to the amplitude of the algebraic sum of the three individual EPSPs was 0.95 +/- 0.05. This ratio was greater in motoneurons with lower rheobase. 5. Some patterns of synaptic connectivity in the macaque are consistent with previously reported differences between primates and cat (e.g., heteronymous EPSPs elicited by medial gastrocnemius nerve stimulation in soleus motoneurons are small in macaque and other primates but large in cat). However, no overall pattern emerges from a comparison of the similarities and differences in EPSPs among species in which they have been studied (i.e., macaque, baboon, and cat). That is, there are no two species in which EPSP properties are consistently similar to each other, but different from those of the third species.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Increases in corticospinal responsiveness during a sustained submaximal plantar flexion

2009 ◽  
Vol 107 (1) ◽  
pp. 112-120 ◽  
Author(s):  
B. W. Hoffman ◽  
T. Oya ◽  
T. J. Carroll ◽  
A. G. Cresswell
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Evoked Potentials ◽  
Magnetic Stimulation ◽  
Motor Evoked Potentials ◽  
Plantar Flexion ◽  
Triceps Surae ◽  
Medial Gastrocnemius ◽  
Task Failure ◽  
Submaximal Contraction

Studying the responsiveness of specific central nervous system pathways to electrical or magnetic stimulation can provide important information regarding fatigue processes in the central nervous system. We investigated the changes in corticospinal responsiveness during a sustained submaximal contraction of the triceps surae. Comparisons were made between the size of motor-evoked potentials (MEPs) elicited by motor cortical stimulation and cervicomedullary motor-evoked potentials (CMEPs) elicited by magnetic stimulation of the descending tracts to determine the site of any change in corticospinal responsiveness. Participants maintained an isometric contraction of triceps surae at 30% of maximal voluntary contraction (MVC) for as long as possible on two occasions. Stimulation was applied to the motor cortex or the cervicomedullary junction at 1-min intervals during contraction until task failure. Peripheral nerve stimulation was also applied to evoke maximal M waves (Mmax) and a superimposed twitch. Additionally, MEPs and CMEPs were evoked during brief contractions at 80%, 90%, and 100% of MVC as a nonfatigue control. During the sustained contractions, MEP amplitude increased significantly in soleus (113%) and medial gastrocnemius (108%) muscles and, at task failure, matched MEP amplitude in the prefatigue MVC (∼20–25% Mmax). In contrast, CMEP amplitude increased significantly in medial gastrocnemius (51%), but not in soleus (63%) muscle and, at task failure, was significantly smaller than during prefatigue MVC (5–6% Mmax vs. 11–13% Mmax). The data indicate that cortical processes contribute substantially to the increase in corticospinal responsiveness during sustained submaximal contraction of triceps surae.

Contractile abilities of normal and “mini” triceps surae muscles from mice (Mus domesticus) selectively bred for high voluntary wheel running

2005 ◽  
Vol 99 (4) ◽  
pp. 1308-1316 ◽  
Author(s):  
Douglas A. Syme ◽  
Kristin Evashuk ◽  
Benjamin Grintuch ◽  
Enrico L. Rezende ◽  
Theodore Garland
Keyword(s):  
Wheel Running ◽  
Fold Increase ◽  
Triceps Surae ◽  
Medial Gastrocnemius ◽  
Selected Lines ◽  
Voluntary Wheel Running ◽  
Running Activity ◽  
Gastrocnemius Muscles ◽  
Contractile Characteristics ◽  
Voluntary Wheel

As reported previously, artificial selection of house mice caused a 2.7-fold increase in voluntary wheel running of four replicate selected lines compared with four random-bred control lines. Two of the selected lines developed a high incidence of a small-muscle phenotype (“mini muscles”) in the plantar flexor group of the hindlimb, which apparently results from a simple Mendelian recessive allele. At generations 36–38, we measured wheel running and key contractile characteristics of soleus and medial gastrocnemius muscles from normal and mini muscles in mice from these selected lines. Mice with mini muscles ran faster and a greater distance per day than normal individuals but not longer. As expected, in mini-muscle mice the medial and lateral gastrocnemius muscles were ∼54 and 45% the mass of normal muscles, respectively, but the plantaris muscles were not different in mass and soleus muscles were actually 30% larger. In spite of the increased mass, contractile characteristics of the soleus were unchanged in any notable way between mini and normal mice. However, medial gastrocnemius muscles in mini mice were changed markedly toward a slower phenotype, having slower twitches; demonstrated a more curved force-velocity relationship; produced about half the mass-specific isotonic power, 20–50% of the mass-specific cyclic work and power (only 10–25% the absolute power if the loss in mass is considered); and fatigued at about half the rate of normal muscles. These changes would promote increased, aerobically supported running activity but may compromise activities that require high power, such as sprinting.

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.

Differential displacement of the human soleus and medial gastrocnemius aponeuroses during isometric plantar flexor contractions in vivo

2004 ◽  
Vol 97 (5) ◽  
pp. 1908-1914 ◽  
Author(s):  
Jens Bojsen-Møller ◽  
Philip Hansen ◽  
Per Aagaard ◽  
Ulla Svantesson ◽  
Michael Kjaer ◽  
...  
Keyword(s):  
Knee Joint ◽  
Achilles Tendon ◽  
Plantar Flexion ◽  
Human Locomotion ◽  
Muscular Contraction ◽  
Triceps Surae ◽  
Medial Gastrocnemius ◽  
Plantar Flexor ◽  
Flexion Moment

The human triceps surae muscle-tendon complex is a unique structure with three separate muscle compartments that merge via their aponeuroses into the Achilles tendon. The mechanical function and properties of these structures during muscular contraction are not well understood. The purpose of the study was to investigate the extent to which differential displacement occurs between the aponeuroses of the medial gastrocnemius (MG) and soleus (Sol) muscles during plantar flexion. Eight subjects (mean ± SD; age 30 ± 7 yr, body mass 76.8 ± 5.5 kg, height 1.83 ± 0.06 m) performed maximal isometric ramp contractions with the plantar flexor muscles. The experiment was performed in two positions: position 1, in which the knee joint was maximally extended, and position 2, in which the knee joint was maximally flexed (125°). Plantarflexion moment was assessed with a strain gauge load cell, and the corresponding displacement of the MG and Sol aponeuroses was measured by ultrasonography. Differential shear displacement of the aponeurosis was quantified by subtracting displacement of Sol from that of MG. Maximal plantar flexion moment was 36% greater in position 1 than in position 2 (132 ± 20 vs. 97 ± 11 N·m). In position 1, the displacement of the MG aponeurosis at maximal force exceeded that of the Sol (12.6 ± 1.7 vs. 8.9 ± 1.5 mm), whereas in position 2 displacement of the Sol was greater than displacement of the MG (9.6 ± 1.0 vs. 7.9 ± 1.2 mm). The amount and “direction” of shear between the aponeuroses differed significantly between the two positions across the entire range of contraction, indicating that the Achilles tendon may be exposed to intratendinous shear and stress gradients during human locomotion.

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