Simulations of motor unit number estimation techniques

Major, Lora A.; Jones, Kelvin E.

doi:10.1088/1741-2560/2/2/003

Cited by 37 publications

(21 citation statements)

References 54 publications

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“…At the level of the nerve trunk, recruitment of motor axons is random in relation to axon diameter and is likely superficial within the nerve trunk (Doherty and Brown 1993;Baker et al 2000;Major and Jones 2005) as depicted in Fig. 6b.…”

Section: Temporal Aspects Of Recruitmentmentioning

confidence: 99%

Neuromuscular electrical stimulation: implications of the electrically evoked sensory volley

et al. 2011

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Neuromuscular electrical stimulation (NMES) generates contractions by depolarising axons beneath the stimulating electrodes. The depolarisation of motor axons produces contractions by signals travelling from the stimulation location to the muscle (peripheral pathway), with no involvement of the central nervous system (CNS). The concomitant depolarisation of sensory axons sends a large volley into the CNS and this can contribute to contractions by signals travelling through the spinal cord (central pathway) which may have advantages when NMES is used to restore movement or reduce muscle atrophy. In addition, the electrically evoked sensory volley increases activity in CNS circuits that control movement and this can also enhance neuromuscular function after CNS damage. The first part of this review provides an overview of how peripheral and central pathways contribute to contractions evoked by NMES and describes how differences in NMES parameters affect the balance between transmission along these two pathways. The second part of this review describes how NMES location (i.e. over the nerve trunk or muscle belly) affects transmission along peripheral and central pathways and describes some implications for motor unit recruitment during NMES. The third part of this review summarises some of the effects that the electrically evoked sensory volley has on CNS circuits, and highlights the need to identify optimal stimulation parameters for eliciting plasticity in the CNS. A goal of this work is to identify the best way to utilize the electrically evoked sensory volley generated during NMES to exploit mechanisms inherent to the neuromuscular system and enhance neuromuscular function for rehabilitation.

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Section: Temporal Aspects Of Recruitmentmentioning

confidence: 99%

Neuromuscular electrical stimulation: implications of the electrically evoked sensory volley

et al. 2011

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“…Factors that might be more important are the amount and density of interposed tissues and the relative depth of the motor axons in the fascicle at each location. Using a stimulation model, it was shown that preferential activation of large diameter motor axons is unlikely in MPS (Major and Jones, 2005). Additional SMUPs were selectively recruited when altering the stimulus pulse width, most likely because myelinated nerve fibers of different sizes have different thresholds (Grill and Mortimer, 1996).…”

Section: Discussionmentioning

confidence: 99%

Test–retest reliability of a modified multiple point stimulation technique for motor unit number estimation

Porter

Alvarez

Jones

et al. 2008

Clinical Neurophysiology

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Objective-Multiple point stimulation (MPS) is a widely used technique to estimate the number of motor units in a muscle. Test-retest reliability must be high for the motor unit number estimates to be clinically useful. We hypothesized that the reliability of MPS can be improved by using a long stimulus pulse width (1 ms), in addition to the standard 0.05 ms pulse width.Methods-Median nerve innervated thenar muscles were examined in 11 young subjects, 27 ± 3 (mean ±SD) years old and in 5 elderly subjects, 71 ± 11 years old. The experimenter conducted the studies twice on each subject.Results-Test-retest reliability, using the modified MPS technique, was substantially higher (Cronbach's α of 0.88) than using the standard method (Cronbach's α of 0.80) in the young subjects. In contrast, for the elderly subjects the test-retest reliability of MUNE was high for both the modified technique (Cronbach's α of 0.96) and the standard technique (Cronbach's α of 0.99).Conclusions-Test-retest reliability of MPS can be significantly improved by using a long stimulus pulse width and the standard stimulus pulse width in younger subjects. However, this is not necessary in elderly subjects.Significance-The greater reliability of this modified MPS method should enhance its clinical utility.

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“…The problem of alternation (motor units recruited in numerous combinations by stimulation of a motor nerve) is overcome in this method by calculating the average of 10 randomly chosen motor unit forces associated with incremental force increases at different stimulus amplitudes instead of counting incremental increases in muscle twitch force [40][41][42] .…”

Section: Motor Unit Number Estimationmentioning

confidence: 99%

Characterization of Neuronal Death and Functional Deficits following Nerve Injury during the Early Postnatal Developmental Period in Rats

et al. 2015

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In contrast to adult rat nerve injury models, neonatal sciatic nerve crush leads to massive motor and sensory neuron death. Death of these neurons results from both the loss of functional contact between the nerve terminals and their targets, and the inability of immature Schwann cells in the distal stump of the injured nerve to sustain regeneration. However, current dogma holds that little to no motoneuron death occurs in response to nerve crush at postnatal day 5 (P5). The purpose of the current study was to fully characterize the extent of motor and sensory neuronal death and functional recovery following sciatic nerve crush at mid-thigh level in rats at postnatal days 3-30 (P3-P30), and then compare this to adult injured animals. Following nerve crush at P3, motoneuron numbers were reduced to 35% of that of naïve uninjured animals. Animals in the P5 and P7 group also displayed statistically fewer motoneurons than naïve animals. Animals that were injured at P30 or earlier displayed statistically lower sensory neuron counts in the dorsal root ganglion than naïve controls. Surprisingly, complete behavioral recovery was observed exclusively in the P30 and adult injured groups. Similar results were observed in muscle twitch/tetanic force analysis, motor unit number estimation and wet muscle weights. Rats in both the P5 and P7 injury groups displayed significant neuronal death and impaired functional recovery following injury, challenging current dogma and suggesting that severe deficits persist following nerve injury during this early postnatal developmental period. These findings have important implications concerning the timing of neonatal nerve injury in rats.

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Simulations of motor unit number estimation techniques

Cited by 37 publications

References 54 publications

Neuromuscular electrical stimulation: implications of the electrically evoked sensory volley

Neuromuscular electrical stimulation: implications of the electrically evoked sensory volley

Test–retest reliability of a modified multiple point stimulation technique for motor unit number estimation

Characterization of Neuronal Death and Functional Deficits following Nerve Injury during the Early Postnatal Developmental Period in Rats

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