Effects of sustained stimulation on the excitability  of motoneurons innervating paralyzed and control muscles

Butler, Jane E.; Thomas, Christine K.

doi:10.1152/japplphysiol.01176.2001

Cited by 30 publications

(33 citation statements)

References 43 publications

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“…The high incidence of orderly motor unit recruitment in human skeletal muscles that, due to spinal trauma, are under no voluntary control from higher centers suggests that spinal systems also dominate the stereotyped excitation of human motoneurons during clonus. Thus any changes in spinal neuron excitability, synaptic inputs, or muscle properties due to injury (5,6,9,31) were appropriate to preserve an orderly pattern of motor unit recruitment, as found during voluntary contractions of muscles innervated from the level of injury (44).…”

Section: Discussionmentioning

confidence: 99%

Motor unit behavior during clonus

Wallace¹,

Ross²,

Thomas³

2005

Journal of Applied Physiology

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Medial gastrocnemius surface electromyographic activity and intramuscular electromyographic activity were recorded from six individuals with chronic cervical spinal cord injury to document the recruitment order of motor units during clonus. Four subjects induced clonus that lasted up to 30 s while two subjects induced clonus that they actively stopped after 1 min. Mean clonus frequency in different subjects ranged from 4.7 to 7.0 Hz. Most of the 166 motor units recorded during clonus (98%) fired once during each contraction but at slightly different times during each cycle. Other motor units fired during some clonus cycles (1%) or in bursts (1%). When 59 pairs of units were monitored over consecutive clonus cycles (n = 5-89 cycles), only 8 pairs of units altered their recruitment order in some cycles. Recruitment reversals only occurred in units that fired close together in the clonus cycle. These data demonstrate that orderly motor unit recruitment occurs during involuntary contractions of muscles paralyzed chronically by cervical spinal cord injury, providing further support for the importance of spinal mechanisms in the control of human motor unit behavior.

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Section: Discussionmentioning

confidence: 99%

Motor unit behavior during clonus

Wallace¹,

Ross²,

Thomas³

2005

Journal of Applied Physiology

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“…20 As mentioned above, the observation of preserved H max /M max did not exclude modifications taking place at the spinal level. Indeed, Butler and Thomas 15 assessed motoneuron excitability in SCI using F-waves and demonstrated a reduction in their persistence and amplitude during stimulation of the median nerve, giving evidence of alterations in motoneuron excitability for paralyzed thenar muscles. Therefore, the preservation of the H max /M max ratio in the present study can reflect overlapped depressed motoneuron excitability by modulating mechanisms mediating spinal excitability not assessed by the F-wave analysis.…”

Section: Electrically Induced Fatigue In Scimentioning

confidence: 99%

“…13,14 The only study to our knowledge examining neural implications in electrically induced fatigue in persons with SCI reported decreased motoneuron excitability, as assessed by analysis of F-waves, during a supramaximal fatiguing protocol. 15 It is thus evident that spinal activity can be modified under fatigue conditions and this may affect muscle response to NMES. For a given electrical input at the spinal level, force output can vary according to the state of spinal excitability.…”

Section: Introductionmentioning

confidence: 99%

“…For a given electrical input at the spinal level, force output can vary according to the state of spinal excitability. Unfortunately, although presenting results on muscular parameters, this study 15 did not focus on interpretation of peripheral fatigue components responsible for the decreased force. As a consequence, it is still impossible to know which processes are mainly involved in NMES-induced fatigue.…”

Section: Introductionmentioning

confidence: 99%

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Neural and muscular mechanisms of electrically induced fatigue in patients with spinal cord injury

et al. 2014

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Study design: Intervention study. Objectives: The present study aimed at examining whether spinal and/or peripheral alterations are in the origin of neuromuscular fatigue development induced by intermittent neuromuscular electrical stimulation (NMES) in subjects with complete spinal cord injury (SCI). Setting: Neurological Rehabilitation Center CMN Propara, Montpellier, France. Methods: Thirteen volunteers with complete SCI participated in the study. The right triceps surae muscle was fatigued using a 30-Hz NMES protocol (2 s ON-2 s OFF) composed of three series of five trains. Spinal excitability (assessed by the H-reflex), muscle excitability (assessed by the M-wave), muscle contractile properties (assessed by mechanical response parameters) and torque evoked by NMES were tested before and after each five-train series. Results: NMES-evoked torque significantly decreased throughout the protocol (Po0.001). This decrease was accompanied by a significant increase in M-wave amplitude (Po0.001), whereas H-reflex and the H max /M max ratio were not significantly modified. The amplitude of the mechanical response was significantly decreased at the end of the protocol (Po0.05). Conclusion:The results indicate significant fatigue development, which was attributed to impaired cross-bridge force-generating capacity, without modification of spinal excitability nor muscle excitability.

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“…A higher incidence of F-waves and F-waves of greater magnitude relative to the maximal motor response from a muscle are considered to be a reflection of greater motoneuron excitability [83][84][85]. Although F-wave studies at the single motor unit or muscle fiber level [86][87][88][89] are more difficult to perform, these data can be used to estimate the conduction velocity of the proximal segment of the peripheral axon, a particularly useful feature when ventral root damage is suspected.…”

Section: How Can Integration Of Different Input Systems At the Spinalmentioning

confidence: 99%

Physiological methods to measure motor function in humans and animals with spinal cord injury

Thomas

Noga

2003

JRRD

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Abstract-This article compares some physiological methods commonly used to measure the functional capability of the motor system in humans and animals after spinal cord injury. Some of the differences between animal and human experimentation are considered first. Then we discuss how to measure the effectiveness of conduction through the motor system. We describe ways to assess the integration of different inputs at the spinal cord and to measure the responsiveness of the neuromuscular system. We conclude that comparisons across species are invaluable to understand the control of movement, both before and after injury.

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Effects of sustained stimulation on the excitability of motoneurons innervating paralyzed and control muscles

Abstract: Butler, Jane E., and Christine K. Thomas. Effects of sustained stimulation on the excitability of motoneurons innervating paralyzed and control muscles.

Cited by 30 publications

References 43 publications

Motor unit behavior during clonus

Motor unit behavior during clonus

Neural and muscular mechanisms of electrically induced fatigue in patients with spinal cord injury

Physiological methods to measure motor function in humans and animals with spinal cord injury

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