scholarly journals Neck muscle biomechanics and neural control

2018 ◽  
Vol 120 (1) ◽  
pp. 361-371 ◽  
Author(s):  
Jason B. Fice ◽  
Gunter P. Siegmund ◽  
Jean-Sébastien Blouin
Keyword(s):  
Neural Control ◽  
Muscle Activation ◽  
Maximum Voluntary Contraction ◽  
Neck Muscles ◽  
Voluntary Activation ◽  
Neck Muscle ◽  
Intrasubject Variability ◽  
Spatial Tuning ◽  
Muscle Biomechanics ◽  
The Moment

The mechanics, morphometry, and geometry of our joints, segments, and muscles are fundamental biomechanical properties intrinsic to human neural control. The goal of our study was to investigate whether the biomechanical actions of individual neck muscles predict their neural control. Specifically, we compared the moment direction and variability produced by electrical stimulation of a neck muscle (biomechanics) to the preferred activation direction and variability (neural control). Subjects sat upright with their head fixed to a six-axis load cell and their torso restrained. Indwelling wire electrodes were placed into the sternocleidomastoid (SCM), splenius capitis (SPL), and semispinalis capitis (SSC) muscles. The electrically stimulated direction was defined as the moment direction produced when a current (2–19 mA) was passed through each muscle’s electrodes. Preferred activation direction was defined as the vector sum of the spatial tuning curve built from root mean squared electromyogram when subjects produced isometric moments at 7.5% and 15% of their maximum voluntary contraction (MVC) in 26 three-dimensional directions. The spatial tuning curves at 15% MVC were well defined (unimodal, P < 0.05), and their preferred directions were 23°, 39°, and 21° different from their electrically stimulated directions for the SCM, SPL, and SSC, respectively ( P < 0.05). Intrasubject variability was smaller in electrically stimulated moment directions compared with voluntary preferred directions, and intrasubject variability decreased with increased activation levels. Our findings show that the neural control of neck muscles is not based solely on optimizing individual muscle biomechanics but, as activation increases, biomechanical constraints in part dictate the activation of synergistic neck muscles. NEW & NOTEWORTHY Biomechanics are an intrinsic part of human neural control. In this study, we found that the biomechanics of individual neck muscles cannot fully predict their neural control. Consequently, physiologically based computational neck muscle controllers cannot calculate muscle activation schemes based on the isolated biomechanics of muscles. Furthermore, by measuring biomechanics we showed that the intrasubject variability of the neural control was lower for electrical vs. voluntary activation of the neck muscles.

scholarly journals Motor planning perturbation: muscle activation and reaction time

2018 ◽  
Vol 120 (4) ◽  
pp. 2059-2065
Author(s):  
Stefan Delmas ◽  
Agostina Casamento-Moran ◽  
Seoung Hoon Park ◽  
Basma Yacoubi ◽  
Evangelos A. Christou
Keyword(s):  
Reaction Time ◽  
Muscle Activity ◽  
Muscle Activation ◽  
Maximum Voluntary Contraction ◽  
Motor Planning ◽  
Reaction Time Task ◽  
Voluntary Contraction ◽  
Voluntary Activation ◽  
Time Interval ◽  
Voluntary Activity

Reaction time (RT) is the time interval between the appearance of a stimulus and initiation of a motor response. Within RT, two processes occur, selection of motor goals and motor planning. An unresolved question is whether perturbation to the motor planning component of RT slows the response and alters the voluntary activation of muscle. The purpose of this study was to determine how the modulation of muscle activity during an RT response changes with motor plan perturbation. Twenty-four young adults (20.5 ±1.1 yr, 13 women) performed 15 trials of an isometric RT task with ankle dorsiflexion using a sinusoidal anticipatory strategy (10–20% maximum voluntary contraction). We compared the processing part of the RT and modulation of muscle activity from 10 to 60 Hz of the tibialis anterior (primary agonist) when the stimulus appeared at the trough or at the peak of the sinusoidal task. We found that RT ( P = 0.003) was longer when the stimulus occurred at the peak compared with the trough. During the time of the reaction, the electromyography (EMG) power from 10 to 35 Hz was less at the peak than the trough ( P = 0.019), whereas the EMG power from 35 to 60 Hz was similar between the peak and trough ( P = 0.92). These results suggest that perturbation to motor planning lengthens the processing part of RT and alters the voluntary activation of the muscle by decreasing the relative amount of power from 10 to 35 Hz. NEW & NOTEWORTHY We aimed to determine whether perturbation to motor planning would alter the speed and muscle activity of the response. We compared trials when a stimulus appeared at the peak or trough of an oscillatory reaction time task. When the stimulus occurred at the trough, participants responded faster, with greater force, and less EMG power from 10-35 Hz. We provide evidence that motor planning perturbation slows the response and alters the voluntary activity of the muscle.

Three-dimensional spatial tuning of neck muscle activation in humans

2002 ◽  
Vol 147 (4) ◽  
pp. 437-448 ◽  
Author(s):  
Anita Vasavada ◽  
Barry Peterson ◽  
Scott Delp
Keyword(s):  
Muscle Activation ◽  
Three Dimensional ◽  
Neck Muscle ◽  
Spatial Tuning

Neural Control of Superficial and Deep Neck Muscles in Humans

2007 ◽  
Vol 98 (2) ◽  
pp. 920-928 ◽  
Author(s):  
Jean-Sébastien Blouin ◽  
Gunter P. Siegmund ◽  
Mark G. Carpenter ◽  
J. Timothy Inglis
Keyword(s):  
Neural Control ◽  
Muscle Contractions ◽  
Neck Muscles ◽  
Neck Muscle ◽  
Neural Signals ◽  
Tuning Curves ◽  
Layered Architecture ◽  
Force Direction ◽  
Neck Motoneurons ◽  
Isometric Forces

Human neck muscles have a complex multi-layered architecture. The role and neural control of these neck muscles were examined in nine seated subjects performing three series of isometric neck muscle contractions: 50-N contractions in eight fixed horizontal directions, 25-N contractions, and 50-N contractions, both with a continuously changing horizontal force direction. Activity in the left sternocleidomastoid, trapezius, levator scapulae, splenius capitis, semispinalis capitis, semispinalis cervicis, and multifidus muscles was measured with wire electrodes inserted at the C4/C5 level under ultrasound guidance. We hypothesized that deep and superficial neck muscles would function as postural and focal muscles, respectively, and would thus be controlled by different neural signals. To test these hypotheses, electromyographic (EMG) tuning curves and correlations in the temporal and frequency domains were computed. Three main results emerged from these analyses: EMG tuning curves from all muscles exhibited well-defined preferred directions of activation for the 50-N isometric forces, larger contractions (25 vs. 50 N) yielded more focused EMG tuning curves, and agonist neck muscles from all layers received a common neural drive in the range of 10–15 Hz. The current results demonstrate that all neck muscles can exhibit phasic activity during isometric neck muscle contractions. Similar oscillations in the EMG of neck muscles from different layers further suggest that neck motoneurons were activated by common neurons. The reticular formation appears a likely generator of the common drive to the neck motoneurons due to its widespread projections to different groups of neck motoneurons.

scholarly journals COMPARISON OF NECK MUSCLE ELECTROMYOGRAPHY ACTIVITY IN RESPONSE TO EXTERNAL FORCE BETWEEN STATIC AND DYNAMIC LOADING

2019 ◽  
Vol 19 (04) ◽  
pp. 1850034
Author(s):  
D. W. KAK ◽  
A. R. ANITA ◽  
N. M. NIZLAN ◽  
I. NORMALA ◽  
N. A. ABDUL JALIL ◽  
...  
Keyword(s):  
Dynamic Loading ◽  
Static Loading ◽  
Muscle Activation ◽  
Motor Vehicle ◽  
Neck Muscles ◽  
Motor Vehicle Crash ◽  
Neck Muscle ◽  
Activation Level ◽  
Static And Dynamic Loading ◽  
Head Neck

Understanding the behavior of neck muscles is essential to accurately simulate the human head-neck segment movement especially for low-speed motor vehicle crash situation. Some head-neck mathematical models were designed using neck muscle activation behavior in isometric contraction (static loading) as the properties of neck muscle activation. However, neck muscle activation pattern and strength capability may vary between static and dynamic loading. This study aimed to determine the differences between neck muscle activation level under static and dynamic loading. A neck strength test involving 22 human volunteers was conducted with two different tasks in extension and flexion direction with three different loads. The neck muscle activation level is determined through measuring the electromyography (EMG) responses of selected flexor and extensor muscles using surface bilateral electrode and recorded. The findings showed that neck muscle activation level was significantly greater in dynamic loading than static loading ([Formula: see text]). These implied that more efforts from neck muscles were required to resist against dynamic loading than static loading. Nonetheless, the differences in EMG activities between these two loading conditions progressively decreased when more loads were applied. This study has established an empirical model to describe the relationship between neck muscle activation level and force output for both loading condition in flexion and extension.

Neck Muscles in the Rhesus Monkey. II. Electromyographic Patterns of Activation Underlying Postures and Movements

2001 ◽  
Vol 86 (4) ◽  
pp. 1729-1749 ◽  
Author(s):  
Brian D. Corneil ◽  
Etienne Olivier ◽  
Frances J. R. Richmond ◽  
Gerald E. Loeb ◽  
Douglas P. Munoz
Keyword(s):  
Muscle Activation ◽  
Neck Muscles ◽  
Head Movements ◽  
Emg Activity ◽  
Neck Muscle ◽  
Spatial And Temporal Patterns ◽  
Gaze Shifts ◽  
Antagonist Muscles ◽  
Agonist And Antagonist ◽  
Head Positions

Electromyographic (EMG) activity was recorded in ≤12 neck muscles in four alert monkeys whose heads were unrestrained to describe the spatial and temporal patterns of neck muscle activation accompanying a large range of head postures and movements. Some head postures and movements were elicited by training animals to generate gaze shifts to visual targets. Other spontaneous head movements were made during orienting, tracking, feeding, expressive, and head-shaking behaviors. These latter movements exhibited a wider range of kinematic patterns. Stable postures and small head movements of only a few degrees were associated with activation of a small number of muscles in a reproducible synergy. Additional muscles were recruited for more eccentric postures and larger movements. For head movements during trained gaze shifts, movement amplitude, velocity, and acceleration were correlated linearly and agonist muscles were recruited without antagonist muscles. Complex sequences of reciprocal bursts in agonist and antagonist muscles were observed during very brisk movements. Turning movements of similar amplitudes that began from different initial head positions were associated with systematic variations in the activities of different muscles and in the relative timings of these activities. Unique recruitment synergies were observed during feeding and head-shaking behaviors. Our results emphasize that the recruitment of a given muscle was generally ordered and consistent but that strategies for coordination among various neck muscles were often complex and appeared to depend on the specifics of musculoskeletal architecture, posture, and movement kinematics that differ substantially among species.

Effect of neck posture on the activation of feline neck muscles during voluntary head turns

1994 ◽  
Vol 72 (4) ◽  
pp. 2004-2014 ◽  
Author(s):  
D. B. Thomson ◽  
G. E. Loeb ◽  
F. J. Richmond
Keyword(s):  
Muscle Activation ◽  
Motor Task ◽  
Motor Program ◽  
Neck Muscles ◽  
Head Movements ◽  
Neck Muscle ◽  
Head Turning ◽  
Activation Patterns ◽  
Levator Scapulae ◽  
Horizontal Head

1. To determine whether neck posture affects the usage of neck muscles during a specific motor task, we recorded the electromyographic (EMG) patterns of neck muscles in four cats, which made horizontal, head-turning movements to fixate eccentrically placed targets. In some trials, the cervical column was oriented vertically whereas in other trials, the cervical column was oriented more horizontally. 2. During horizontal head movements, five muscles (obliquus capitis inferior, splenius, levator scapulae, complexus, and biventer cervicis) displayed activation patterns that were consistent from cat to cat and did not change when the cats adopted a different neck posture. Most of these muscles are large, superficial muscles that attach to the skull and span many cervical joints. 3. Posturally dependent patterns of activation were observed in five other neck muscles (semispinalis cervicis, longissimus capitis, levator scapulae ventralis, scalenus anterior, and obliquus capitis superior). Most of these muscles lie deeper and more laterally within the neck musculature and generally span fewer cervical joints than the muscles that displayed invariant patterns of activation. 4. These results suggest that the set of invariantly activated muscles may compose part of a basic motor program that is triggered during head movements in the horizontal plane. This motor program appears to be modified by the selective activation of ancillary muscles, which are recruited in a manner related to the neck posture. The deep positioning of the ancillary muscles may permit them to regulate the mobility of the cervical column and to adjust the net muscular force applied across the neck to the skull. Organizing the motor output in this manner might simplify the task of computing the appropriate patterns of neck-muscle activation.

scholarly journals Electrically and hybrid-induced muscle activations: effects of muscle size and fiber type

2016 ◽  
Vol 26 (3) ◽  
Author(s):  
Kelly Stratton ◽  
Pouran D. Faghri
Keyword(s):  
Electrical Activity ◽  
Muscle Activation ◽  
Fiber Type ◽  
Vastus Lateralis ◽  
Maximum Voluntary Contraction ◽  
Voluntary Activation ◽  
Muscle Size ◽  
Muscle Coordination ◽  
Abductor Pollicis Brevis ◽  
Informed Consent Form

The effect of three electrical stimulation (ES) frequencies (10, 35, and 50 Hz) on two muscle groups with different proportions of fast and slow twitch fibers (abductor pollicis brevis (APB) and vastus lateralis (VL)) was explored. We evaluated the acute muscles’ responses individually and during hybrid activations (ES superimposed by voluntary activations). Surface electromyography (sEMG) and force measurements were evaluated as outcomes. Ten healthy adults (mean age: 24.4 ± 2.5 years) participated after signing an informed consent form approved by the university Institutional Review Board. Protocols were developed to: 1) compare EMG activities during each frequency for each muscle when generating 25% Maximum Voluntary Contraction (MVC) force, and 2) compare EMG activities during each frequency when additional voluntary activation was superimposed over ES-induced 25% MVC to reach 50% and 75% MVC. Empirical mode decomposition (EMD) was utilized to separate ES artifacts from voluntary muscle activation. For both muscles, higher stimulation frequency (35 and 50Hz) induced higher electrical output detected at 25% of MVC, suggesting more recruitment with higher frequencies. Hybrid activation generated proportionally less electrical activity than ES alone. ES and voluntary activations appear to generate two different modes of muscle recruitment. ES may provoke muscle strength by activating more fatiguing fast acting fibers, but voluntary activation elicits more muscle coordination. Therefore, during the hybrid activation, less electrical activity may be detected due to recruitment of more fatigue-resistant deeper muscle fibers, not reachable by surface EMG.

scholarly journals The effects of 12 weeks of static stretch training on the functional, mechanical, and architectural characteristics of the triceps surae muscle–tendon complex

2021 ◽  
Author(s):  
Stefano Longo ◽  
Emiliano Cè ◽  
Angela Valentina Bisconti ◽  
Susanna Rampichini ◽  
Christian Doria ◽  
...  
Keyword(s):  
Muscle Activation ◽  
Maximum Voluntary Contraction ◽  
Muscle Stiffness ◽  
Triceps Surae ◽  
Maximum Force ◽  
Passive Stiffness ◽  
Electromechanical Delay ◽  
Fascicle Length ◽  
Generating Capacity ◽  
Plantarflexor Muscles

Abstract Purpose We investigated the effects of 12 weeks of passive static stretching training (PST) on force-generating capacity, passive stiffness, muscle architecture of plantarflexor muscles. Methods Thirty healthy adults participated in the study. Fifteen participants (STR, 6 women, 9 men) underwent 12-week plantarflexor muscles PST [(5 × 45 s-on/15 s-off) × 2exercises] × 5times/week (duration: 2250 s/week), while 15 participants (CTRL, 6 women, 9 men) served as control (no PST). Range of motion (ROM), maximum passive resistive torque (PRTmax), triceps surae architecture [fascicle length, fascicle angle, and thickness], passive stiffness [muscle–tendon complex (MTC) and muscle stiffness], and plantarflexors maximun force-generating capacity variables (maximum voluntary contraction, maximum muscle activation, rate of torque development, electromechanical delay) were calculated Pre, at the 6th (Wk6), and the 12th week (Wk12) of the protocol in both groups. Results Compared to Pre, STR ROM increased (P < 0.05) at Wk6 (8%) and Wk12 (23%). PRTmax increased at Wk12 (30%, P < 0.05), while MTC stiffness decreased (16%, P < 0.05). Muscle stiffness decreased (P < 0.05) at Wk6 (11%) and Wk12 (16%). No changes in triceps surae architecture and plantarflexors maximum force-generating capacity variables were found in STR (P > 0.05). Percentage changes in ROM correlated with percentage changes in PRTmax (ρ = 0.62, P = 0.01) and MTC stiffness (ρ = − 0.78, P = 0.001). In CTRL, no changes (P > 0.05) occurred in any variables at any time point. Conclusion The expected long-term PST-induced changes in ROM were associated with modifications in the whole passive mechanical properties of the ankle joint, while maximum force-generating capacity characteristics were preserved. 12 weeks of PST do not seem a sufficient stimulus to induce triceps surae architectural changes.

scholarly journals Locomotor exercise induces long-lasting impairments in the capacity of the human motor cortex to voluntarily activate knee extensor muscles

2009 ◽  
Vol 106 (2) ◽  
pp. 556-565 ◽  
Author(s):  
Simranjit K. Sidhu ◽  
David J. Bentley ◽  
Timothy J. Carroll
Keyword(s):  
Motor Cortex ◽  
Motor Nerve ◽  
Maximum Voluntary Contraction ◽  
Voluntary Activation ◽  
Exercise Session ◽  
Knee Extensors ◽  
Central Component ◽  
Control Session ◽  
Cycling Exercise ◽  
Human Motor Cortex

Muscle fatigue is a reduction in the capacity to exert force and may involve a “central” component originating in the brain and/or spinal cord. Here we examined whether supraspinal factors contribute to impaired central drive after locomotor endurance exercise. On 2 separate days, 10 moderately active individuals completed a locomotor cycling exercise session or a control session. Brief (2 s) and sustained (30 s) isometric knee extension contractions were completed before and after locomotor exercise consisting of eight, 5-min bouts of cycling at 80% of maximum workload. In the control session, subjects completed the isometric contractions in a rested state. Twitch responses to supramaximal motor nerve stimulation and transcranial magnetic stimulation were obtained to assess peripheral force-generating capacity and voluntary activation. Maximum voluntary contraction (MVC) force during brief contractions decreased by 23 ± 6.3% after cycling exercise and remained 12 ± 2.8% below baseline 45 min later ( F1,9 > 15.5; P < 0.01). Resting twitch amplitudes declined by ∼45% ( F1,9 = 28.3; P < 0.001). Cortical voluntary activation declined from 90.6 ± 1.6% at baseline to 80.6 ± 2.1% after exercise ( F1,9 = 28.0; P < 0.001) and remained significantly reduced relative to control 30–45 min later (80.6 ± 3.4%; F1,9 = 10.7; P < 0.01). Thus locomotor exercise caused a long-lasting impairment in the capacity of the motor cortex to drive the knee extensors. Force was reduced more during sustained MVC after locomotor exercise than in the control session. Peripheral mechanisms contributed relatively more to this force reduction in the control session, whereas supraspinal fatigue played a greater role in sustained MVC reduction after locomotor exercise.

scholarly journals Central excitability does not limit postfatigue voluntary activation of quadriceps femoris

2006 ◽  
Vol 100 (6) ◽  
pp. 1757-1764 ◽  
Author(s):  
J. M. Kalmar ◽  
E. Cafarelli
Keyword(s):  
Evoked Potentials ◽  
Repeated Measures ◽  
Muscle Activation ◽  
Motor Evoked Potentials ◽  
Vastus Lateralis ◽  
Central Fatigue ◽  
Knee Extension ◽  
Voluntary Activation ◽  
Fatigue Protocol ◽  
Central Excitability

After fatigue, motor evoked potentials (MEP) elicited by transcranial magnetic stimulation and cervicomedullary evoked potentials elicited by stimulation of the corticospinal tract are depressed. These reductions in corticomotor excitability and corticospinal transmission are accompanied by voluntary activation failure, but this may not reflect a causal relationship. Our purpose was to determine whether a decline in central excitability contributes to central fatigue. We hypothesized that, if central excitability limits voluntary activation, then a caffeine-induced increase in central excitability should offset voluntary activation failure. In this repeated-measures study, eight men each attended two sessions. Baseline measures of knee extension torque, maximal voluntary activation, peripheral transmission, contractile properties, and central excitability were made before administration of caffeine (6 mg/kg) or placebo. The amplitude of vastus lateralis MEPs elicited during minimal muscle activation provided a measure of central excitability. After a 1-h rest, baseline measures were repeated before, during, and after a fatigue protocol that ended when maximal voluntary torque declined by 35% (Tlim). Increased prefatigue MEP amplitude ( P = 0.055) and cortically evoked twitch ( P < 0.05) in the caffeine trial indicate that the drug increased central excitability. In the caffeine trial, increased MEP amplitude was correlated with time to task failure ( r = 0.74, P < 0.05). Caffeine potentiated the MEP early in the fatigue protocol ( P < 0.05) and offset the 40% decline in placebo MEP ( P < 0.05) at Tlim. However, this was not associated with enhanced maximal voluntary activation during fatigue or recovery, demonstrating that voluntary activation is not limited by central excitability.

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