The Number of Active Motor Units and Their Firing Rates in Voluntary Contraction of Human Brachialis Muscle

Kanosue, Kazuyuki; Yoshida, Masaki; Akazawa, Kenzo; Fujii, Katsuhuiko

doi:10.2170/jjphysiol.29.427

Cited by 107 publications

(55 citation statements)

References 14 publications

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“…Baldissera, Gustafsson & Parmiggiani (1978) have accounted for this effect (the so-called secondary range of motoneurone firing) by a model based on the time course of motoneuronal after-hyperpolarization, indicating that it may well be a passive response to high levels of synaptic current injection. This effect may also account for the extremely rapid firing-rate bursts (60-120/sec) seen by Desmedt & Godaux (1977) (Kanosue et al 1979) has demonstrated behaviour similar to that seen here in the deltoid, but with an increased reliance on rate coding above 70 % m.v.c. Our study did not investigate the force range between 80 and 100 % m.v.c.…”

Section: Motor Unit Beha Viour In Different Musclessupporting

confidence: 73%

Behaviour of human motor units in different muscles during linearly varying contractions

Luca

Lefever

McCue

et al. 1982

The Journal of Physiology

620

367

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contraction (m.v.c.). Experiments were performed on four normal subjects and three groups of highly trained performers (long-distance swimmers, powerlifters and pianists).3. Results revealed a highly ordered recruitment and decruitment scheme, based on motoneurone excitability, in both muscles and in all subject groups.4. Differenceswereobservedbetweentheinitial (recruitment)andfinal (decruitment) firing rates in each muscle. These parameters were invariant with respect to the force rates studied, although some differences were observed among subject groups.5. In general, firing rates of f.

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Section: Motor Unit Beha Viour In Different Musclessupporting

confidence: 73%

Behaviour of human motor units in different muscles during linearly varying contractions

Luca

Lefever

McCue

et al. 1982

The Journal of Physiology

620

367

View full text Add to dashboard Cite

show abstract

“…However, entry into the primary range following subprimary range discharge should be considered as an alternative explanation for ratelimiting discharge patterns. Particularly at low forces, a subprimary-primary range pattern of activation would achieve efficient modulation of motor-unit force while reserving secondary range modulation for more intense efforts, as suggested by some studies of motor-unit activity (Kanosue et al 1979).…”

Section: Subprimary Range In Rat Hindlimb Motoneuronsmentioning

confidence: 99%

Characteristics and Organization of Discharge Properties in Rat Hindlimb Motoneurons

Turkin

O'Neill

Jung

et al. 2010

Journal of Neurophysiology

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Turkin VV, O'Neill D, Jung R, Iarkov A, Hamm TM. Characteristics and organization of discharge properties in rat hindlimb motoneurons. J Neurophysiol 104: 1549 -1565, 2010. First published June 30, 2010 doi:10.1152/jn.00379.2010. The discharge properties of hindlimb motoneurons in ketamine-xylazine anesthetized rats were measured to assess contributions of persistent intrinsic currents to these characteristics and to determine their distribution in motoneuron pools. Most motoneurons (30/37) responded to ramp current injections with adapting patterns of discharge and the frequency-current (f-I) relations of nearly all motoneurons included a steep subprimary range of discharge. Despite the prevalence of adapting f-I relations, responses included indications that persistent inward currents (PICs) were activated, including increased membrane noise and prepotentials before discharge, as well as counterclockwise hysteresis and secondary ranges in f-I relations. Examination of spike thresholds and afterhyperpolarization (AHP) trajectories during repetitive discharge revealed systematic changes in threshold and trajectory within the subprimary, primary, and secondary f-I ranges. These changes in the primary and secondary ranges were qualitatively similar to those described previously for cat motoneurons. Within the subprimary range, AHP trajectories often included shallow approaches to threshold following recruitment and slope of the AHP ramp consistently increased until the subprimary range was reached. We suggest that PICs activated near recruitment contributed to these slope changes and formation of the subprimary range. Discharge characteristics were strongly correlated with motoneuron size, using input conductance as an indicator of size. Discharge adaptation, recruitment current, and frequency increased with input conductance, whereas both subprimary and primary f-I gains decreased. These results are discussed with respect to potential mechanisms and their functional implications.

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“…The central nervous system achieves a precise and task-specific control of skeletal muscle forces by controlling the number of activated motor units (recruitment) and the firing frequency of the activated motor units (rate-coding) (Kamen and Du, 1999;Kanosue et al, 1979). In individuals with paralysis due to upper motor neuron dysfunction, electrical stimulation is used to substitute for the loss of voluntary motor control to enable patients to stand, walk, and grasp objects (Kralj et al, 1988;Liberson et al, 1961).…”

Section: Introductionmentioning

confidence: 99%

Effects of stimulation frequency versus pulse duration modulation on muscle fatigue

Kesar

Chou

Binder‐Macleod

2008

Journal of Electromyography and Kinesiology

109

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During functional electrical stimulation (FES), both the frequency and intensity can be increased to increase muscle force output and counteract the effects of muscle fatigue. Most current FES systems, however, deliver a constant frequency and only vary the stimulation intensity to control muscle force. This study compared muscle performance and fatigue produced during repetitive electrical stimulation using three different strategies: (1) constant pulse-duration and stepwise increases in frequency (frequency-modulation); (2) constant frequency and stepwise increases in pulse-duration (pulse-duration-modulation); and (3) constant frequency and pulse-duration (no-modulation). Surface electrical stimulation was delivered to the quadriceps femoris muscles of 12 healthy individuals and isometric forces were recorded. Muscle performance was assessed by measuring the percent changes in the peak forces and force-time integrals between the first and the last fatiguing trains. Muscle fatigue was assessed by measuring percent declines in peak force between the 60 Hz pre-and post-fatigue testing trains. The results showed that frequency-modulation showed better performance for both peak forces and force-time integrals in response to the fatiguing trains than pulse-duration-modulation, while producing similar levels of muscle fatigue. Although frequencymodulation is not commonly used during FES, clinicians should consider this strategy to improve muscle performance.

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The Number of Active Motor Units and Their Firing Rates in Voluntary Contraction of Human Brachialis Muscle

Cited by 107 publications

References 14 publications

Behaviour of human motor units in different muscles during linearly varying contractions

Behaviour of human motor units in different muscles during linearly varying contractions

Characteristics and Organization of Discharge Properties in Rat Hindlimb Motoneurons

Effects of stimulation frequency versus pulse duration modulation on muscle fatigue

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