Myoelectric activity along human gastrocnemius medialis : Different spatial distributions of postural and electrically elicited surface potentials

Abstract It has recently been shown that motor units in human medial gastrocnemius (MG), activated during standing, occupy relatively small territories along the muscle’s longitudinal axis. Such organisation provides potential for different motor tasks to produce differing regional patterns of activ...

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Bibliographic Details
Published in:Journal of electromyography and kinesiology 2013-02, Vol.23 (1), p.43-50
Main Authors: Hodson-Tole, Emma F, Loram, Ian D, Vieira, Taian M.M
Format: Article
Language:English
Subjects:
Action Potentials - physiology
Electric Stimulation
Electrical stimulation
Electrode array
Electromyography - methods
Female
Humans
Male
Motor Neurons - physiology
Motor units
Muscle Contraction - physiology
Muscle, Skeletal - physiology
Neural Conduction - physiology
Neuromuscular Junction - physiology
Physical Medicine and Rehabilitation
Postural control
Posture - physiology
Regional distribution
Surface electromyograms
Young Adult
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Summary:Abstract It has recently been shown that motor units in human medial gastrocnemius (MG), activated during standing, occupy relatively small territories along the muscle’s longitudinal axis. Such organisation provides potential for different motor tasks to produce differing regional patterns of activity. Here, we investigate whether postural control and nerve electrical stimulation produce equal longitudinal activation patterns in MG. Myoelectric activity, at different proximal–distal locations of MG, was recorded using a linear electrode array. To ensure differences in signal amplitude between channels did not result from local, morphological factors two experimental protocols were completed: (i) quiet standing; (ii) electrical stimulation of the tibial nerve. Averaged, rectified values (ARVs) were calculated for each channel in each condition. The distribution of signals along electrode channels was described using linear regression and differences between protocols at each channel determined as the ratio between mean ARV from standing: stimulation protocols. Ratio values changed systematically across electrode channels in seven (of eight) participants, with larger values in distal channels. The distribution of ARV along MG therefore differed between experimental conditions. Compared to fibres of units activated during MG nerve stimulation, units activated during standing may have a tendency to be more highly represented in the distal muscle portion.
ISSN:1050-6411
1873-5711
DOI:10.1016/j.jelekin.2012.08.003