Fatigue-related modulation of low-frequency common drive to motor units

2020 ◽  
Vol 120 (6) ◽  
pp. 1305-1317
Author(s):  
Ing-Shiou Hwang ◽  
Yen-Ting Lin ◽  
Chien-Chun Huang ◽  
Yi-Ching Chen
Keyword(s):  
Low Frequency ◽  
Motor Units ◽  
Common Drive

scholarly journals Reorganization of multidigit physiological tremors after repetitive contractions of a single finger

2009 ◽  
Vol 106 (3) ◽  
pp. 966-974 ◽  
Author(s):  
Ing-Shiou Hwang ◽  
Zong-Ru Yang ◽  
Chien-Ting Huang ◽  
Mei-Chun Guo
Keyword(s):  
Principal Component ◽  
Motor Units ◽  
Middle Finger ◽  
Neuromuscular Function ◽  
Transfer Effect ◽  
Position Tracking ◽  
Single Finger ◽  
Common Drive ◽  
Middle Ring ◽  
Flexor Digitorum

In light of the interplay among physiological finger tremors, this study was undertaken to investigate the transfer effect of fatigue on coordinative strategies of multiple fingers. Fourteen volunteers performed prolonged position tracking with a loaded middle finger while measures of neuromuscular function, including electromyographic activities of the extensor digitorum (ED)/flexor digitorum superficialis (FDS) and physiological tremors of the index, middle, ring, and little fingers, were monitored. The subjects exhibited inferior tracking congruence and an increase in ED activity at the end of the tracking. Fatigue spread was manifested in a remarkable increase in tremor across fingers, in association with enhanced involuntary tremor coupling among fingers that was topologically organized in relation to the distance of the digits from the middle finger. Principal component analysis suggested that an enhanced 8- to 12-Hz central rhythm contributed primarily to the tremor restructure following fatigue spread. The observed tremor reorganization validated the hypothesis that the effect of fatigue was not limited to the instructed finger and that fatigue functionally decreased independence of the digits. The spreading of fatigue weakens neural inputs that diverge to motor units acting on various digits because of fatigue-related enhancement of common drive at the supraspinal level.

Fast-to-Slow Conversion Following Chronic Low-Frequency Activation of Medial Gastrocnemius Muscle in Cats. II. Motoneuron Properties

1997 ◽  
Vol 77 (5) ◽  
pp. 2605-2615 ◽  
Author(s):  
John B. Munson ◽  
Robert C. Foehring ◽  
Lorne M. Mendell ◽  
Tessa Gordon
Keyword(s):  
Gastrocnemius Muscle ◽  
Low Frequency ◽  
Motor Units ◽  
Input Resistance ◽  
Medial Gastrocnemius ◽  
Excitatory Postsynaptic Potential ◽  
Chronic Stimulation ◽  
General Hypothesis ◽  
Slow Type ◽  
Medial Gastrocnemius Muscle

Munson, John B., Robert C. Foehring, Lorne M. Mendell, and Tessa Gordon. Fast-to-slow conversion following chronic low-frequency activation of medial gastrocnemius muscle in cats. II. Motoneuron properties. J. Neurophysiol. 77: 2605–2615, 1997. Chronic stimulation (for 2–3 mo) of the medial gastrocnemius (MG) muscle nerve by indwelling electrodes renders the normally heterogeneous MG muscle mechanically and histochemically slow (type SO). We tested the hypothesis that motoneurons of MG muscle thus made type SO by chronic stimulation would also convert to slow phenotype. Properties of all single muscle units became homogeneously type SO (slowly contracting, nonfatiguing, nonsagging contraction during tetanic activation). Motoneuron electrical properties were also modified in the direction of type S, fatigue-resistant motor units. Two separate populations were identified (on the basis of afterhyperpolarization, rheobase, and input resistance) that likely correspond to motoneurons that had been fast (type F) or type S before stimulation. Type F motoneurons, although modified by chronic stimulation, were not converted to the type S phenotype, despite apparent complete conversion of their muscle units to the slow oxidative type (type SO). Muscle units of the former type F motor units were faster and/or more powerful than those of the former type S motor units, indicating some intrinsic regulation of motor unit properties. Experiments in which chronic stimulation was applied to the MG nerve cross-regenerated into skin yielded changes in motoneuron properties similar to those above, suggesting that muscle was not essential for the effects observed. Modulation of group Ia excitatory postsynaptic potential (EPSP) amplitude during high-frequency trains, which in normal MG motoneurons can be either positive or negative, was negative in 48 of 49 chronically stimulated motoneurons. Negative modulation is characteristic of EPSPs in motoneurons of most fatigue-resistant motor units. The general hypothesis of a periphery-to-motoneuron retrograde mechanism was supported, although the degree of control exerted by the periphery may vary: natural type SO muscle appears especially competent to modify motoneuron properties. We speculate that activity-dependent regulation of the neurotrophin-(NT) 4/5 in muscle plays an important role in controlling muscle and motoneuron properties.

Determining patterns of motor recruitment during locomotion

2002 ◽  
Vol 205 (3) ◽  
pp. 359-369 ◽  
Author(s):  
James M. Wakeling ◽  
Motoshi Kaya ◽  
Genevieve K. Temple ◽  
Ian A. Johnston ◽  
Walter Herzog
Keyword(s):  
Motor Unit ◽  
Frequency Band ◽  
Fibre Type ◽  
Low Frequency ◽  
Motor Units ◽  
Motor Unit Recruitment ◽  
Medial Gastrocnemius ◽  
Fibre Types ◽  
Myoelectric Signals ◽  
Frequency Bands

SUMMARY Motor units are the functional units of muscle contraction in vertebrates. Each motor unit comprises muscle fibres of a particular fibre type and can be considered as fast or slow depending on its fibre-type composition. Motor units are typically recruited in a set order, from slow to fast, in response to the force requirements from the muscle. The anatomical separation of fast and slow muscle in fish permits direct recordings from these two fibre types. The frequency spectra from different slow and fast myotomal muscles were measured in the rainbow trout Oncorhynchus mykiss. These two muscle fibre types generated distinct low and high myoelectric frequency bands. The cat paw-shake is an activity that recruits mainly fast muscle. This study showed that the myoelectric signal from the medial gastrocnemius of the cat was concentrated in a high frequency band during paw-shake behaviour. During slow walking, the slow motor units of the medial gastrocnemius are also recruited, and this appeared as increased muscle activity within a low frequency band. Therefore, high and low frequency bands could be distinguished in the myoelectric signals from the cat medial gastrocnemius and probably corresponded, respectively, to fast and slow motor unit recruitment. Myoelectric signals are resolved into time/frequency space using wavelets to demonstrate how patterns of motor unit recruitment can be determined for a range of locomotor activities.

scholarly journals Common Synaptic Input to the Human Hypoglossal Motor Nucleus

2011 ◽  
Vol 105 (1) ◽  
pp. 380-387 ◽  
Author(s):  
Christopher M. Laine ◽  
E. Fiona Bailey
Keyword(s):  
Firing Rate ◽  
Motor Unit ◽  
Synaptic Input ◽  
Motor Units ◽  
Motor Nucleus ◽  
Tongue Protrusion ◽  
Ongoing Research ◽  
Airway Patency ◽  
Significant Difference ◽  
Common Drive

The tongue plays a key role in various volitional and automatic functions such as swallowing, maintenance of airway patency, and speech. Precisely how hypoglossal motor neurons, which control the tongue, receive and process their often concurrent input drives is a subject of ongoing research. We investigated common synaptic input to the hypoglossal motor nucleus by measuring the coordination of spike timing, firing rate, and oscillatory activity across motor units recorded from unilateral (i.e., within a belly) or bilateral (i.e., across both bellies) locations within the genioglossus (GG), the primary protruder muscle of the tongue. Simultaneously recorded pairs of motor units were obtained from 14 healthy adult volunteers using tungsten microelectrodes inserted percutaneously into the GG while the subjects were engaged in volitional tongue protrusion or rest breathing. Bilateral motor unit pairs showed concurrent low frequency alterations in firing rate (common drive) with no significant difference between tasks. Unilateral motor unit pairs showed significantly stronger common drive in the protrusion task compared with rest breathing, as well as higher indices of synchronous spiking (short-term synchrony). Common oscillatory input was assessed using coherence analysis and was observed in all conditions for frequencies up to ∼5 Hz. Coherence at frequencies up to ∼10 Hz was strongest in motor unit pairs recorded from the same GG belly in tongue protrusion. Taken together, our results suggest that cortical drive increases motor unit coordination within but not across GG bellies, while input drive during rest breathing is distributed uniformly to both bellies of the muscle.

scholarly journals Common drive to the upper airway muscle genioglossus during inspiratory loading

2015 ◽  
Vol 114 (5) ◽  
pp. 2883-2892 ◽  
Author(s):  
Michael J. Woods ◽  
Christian L. Nicholas ◽  
John G. Semmler ◽  
Julia K. M. Chan ◽  
Amy S. Jordan ◽  
...  
Keyword(s):  
Upper Airway ◽  
Motor Units ◽  
Quadratic Functions ◽  
Emg Activity ◽  
Respiratory Drive ◽  
Activation Effect ◽  
Single Motor Unit ◽  
Common Drive ◽  
Load Discharge ◽  
Inspiratory Load

Common drive is thought to constitute a central mechanism by which the efficiency of a motor neuron pool is increased. This study tested the hypothesis that common drive to the upper airway muscle genioglossus (GG) would increase with increased respiratory drive in response to an inspiratory load. Respiration, GG electromyographic (EMG) activity, single-motor unit activity, and coherence in the 0–5 Hz range between pairs of GG motor units were assessed for the 30 s before an inspiratory load, the first and second 30 s of the load, and the 30 s after the load. Twelve of twenty young, healthy male subjects provided usable data, yielding 77 pairs of motor units: 2 Inspiratory Phasic, 39 Inspiratory Tonic, 15 Expiratory Tonic, and 21 Tonic. Respiratory and GG inspiratory activity significantly increased during the loads and returned to preload levels during the postload periods (all showed significant quadratic functions over load trials, P < 0.05). As hypothesized, common drive increased during the load in inspiratory modulated motor units to a greater extent than in expiratory/tonic motor units (significant load × discharge pattern interaction, P < 0.05). Furthermore, this effect persisted during the postload period. In conclusion, common drive to inspiratory modulated motor units was elevated in response to increased respiratory drive. The postload elevation in common drive was suggestive of a poststimulus activation effect.

Voluntary control of motor units in human antagonist muscles: coactivation and reciprocal activation

1987 ◽  
Vol 58 (3) ◽  
pp. 525-542 ◽  
Author(s):  
C. J. De Luca ◽  
B. Mambrito
Keyword(s):  
Firing Rate ◽  
Motor Units ◽  
Interphalangeal Joint ◽  
Time Shift ◽  
Extensor Pollicis Longus ◽  
Firing Rates ◽  
Antagonist Muscles ◽  
Control Scheme ◽  
Common Drive ◽  
Flexion And Extension

1. Myoelectric (ME) activity of several motor units was detected simultaneously from the human flexor pollicis longus and extensor pollicis longus muscles, the only two muscles that control the interphalangeal joint of the thumb. The ME signals were detected while the subjects produced isometric force outputs to track three different paradigms: triangular trajectories, random-force trajectories requiring both flexion and extension contractions, and net zero force resulting from stiffening the joint by voluntarily coactivating both muscles. 2. The ME signals were decomposed into their constituent motor-unit action potential trains. The firing rate behavior of the concurrently active motor units was studied using cross-correlation techniques. 3. During isometric contractions, the firing rates of motor units within a muscle were greatly cross-correlated with essentially zero time shift with respect to each other. This observation confirms our previous report of this behavior, which has been called common drive. Common drive was also found among the motor units of the agonist and antagonist muscles during voluntary coactivation to stiffen the interphalangeal joint. This observation suggests two interesting points: 1) that the common drive mechanism has a component of central origin, and 2) that the central nervous system may control the motoneuron pools of an agonist-antagonist muscle pair as if they were one pool when both are performing the same task. 4. During force reversals, the firing rates of motor units reverse in an orderly manner: earlier recruited motor units decrease their firing rate before later recruited motor units. This orderly reversal of firing rates is consistent with the concept of orderly recruitment and derecruitment. 5. A control scheme is suggested to explain the behavior of the motor units in both muscles during force reversal. It consists of centrally mediated reciprocally organized flexion and extension commands along with a common coactivation command to both muscles. This control scheme allows for coactivation and reciprocal activation of an agonist-antagonist set. 6. The agonist-antagonist pair was observed to generate a net force in two control modalities: proportional activation and reciprocal activation. In proportional activation, the agonist-antagonist set is coactivated during either of two states: when uncertainty exists in the required task or when a compensatory force contraction is perceived to be required.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Muscles from the same muscle group do not necessarily share common drive: evidence from the human triceps surae

2020 ◽  
Author(s):  
François Hug ◽  
Alessandro Del Vecchio ◽  
Simon Avrillon ◽  
Dario Farina ◽  
Kylie J. Tucker
Keyword(s):  
Motor Units ◽  
Muscle Group ◽  
Triceps Surae ◽  
Neural Drive ◽  
Flexible Control ◽  
Neural Origin ◽  
Density Surface ◽  
Motor Unit Action ◽  
Common Drive ◽  
Human Participants

It has been proposed that movements are produced through groups of muscles, or motor modules, activated by common neural commands. However, the neural origin of motor modules is still debated. Here, we used complementary approaches to determine: i) whether three muscles of the same muscle group (soleus, gastrocnemius medialis [GM] and lateralis [GL]) are activated by a common neural drive ; and ii) whether the neural drive to GM and GL could be differentially modified by altering the mechanical requirements of the task. Eighteen human participants performed an isometric standing heel raise and submaximal isometric plantarflexions (10%, 30%, 50% of maximal effort). High-density surface electromyography recordings were decomposed into motor unit action potentials and coherence analysis was applied on the motor units spike trains. We identified strong common drive to each muscle, but minimal common drive between the muscles. Further, large between-muscle differences were observed during the isometric plantarflexions, such as a delayed recruitment time of GL compared to GM and soleus motor units and opposite time-dependent changes in the estimates of neural drive to muscles during the torque plateau. Finally, the feet position adopted during the heel raise task (neutral vs internally rotated) affected only the GL neural drive with no change for GM. These results provide conclusive that not all anatomically defined synergist muscles are controlled by strong common neural drive. Independent drive to some muscles from the same muscle group may allow for more flexible control to comply with secondary goals such as joint stabilization.

Common Drive in Motor Units of a Synergistic Muscle Pair

2002 ◽  
Vol 87 (4) ◽  
pp. 2200-2204 ◽  
Author(s):  
Carlo J. De Luca ◽  
Zeynep Erim
Keyword(s):  
Motor Units ◽  
Motor Unit Action Potential ◽  
Time Varying ◽  
Firing Rates ◽  
Muscle Pair ◽  
Synergistic Muscles ◽  
Motor Unit Action ◽  
Common Drive ◽  
The Individual ◽  
Extensor Carpi Radialis

The interaction among the motor units of the extensor carpi radialis longus (ECRL) and the extensor carpi ulnaris (ECU) muscles in man was studied during wrist extensions in which the two muscles acted as synergists. Intramuscular recordings were obtained using special quadrifilar needle electrodes. Isometric wrist extensions at 20–30% of the maximal effort were studied. The electromyographic (EMG) signals were decomposed into the individual motor-unit action potential trains comprising the signal. The interaction among motor units were characterized by the estimated time-varying mean firing rate and the cross-correlation between the time-varying mean firing rates of pairs of motor units. Pairs of motor units within each muscle as well as pairs of motor units across the muscles were considered. In-phase common fluctuations, termed common drive, were observed in the mean firing rates of motor units within each muscle, consistent with earlier work on other muscles. Common fluctuations were also observed between the firing rates of ECU and ECRL motor units albeit with a variable phase shift. The existence of common drive across synergistic muscles was interpreted as implying that the CNS considers the muscles as a functional unit when they act as synergists.

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