Associations between Motor Unit Action Potential Parameters and Surface EMG Features
File(s)Del_Vecchio_et_al_JAP_2017.pdf (1002.63 KB)
Accepted version
Author(s)
Del Vecchio, A
Negro, F
Felici, F
Farina, D
Type
Journal Article
Abstract
The surface interference EMG signal provides some information on the neural drive to muscles. However, the association between neural drive to muscle and muscle activation has long been debated with controversial indications due to the unavailability of motor unit population data. In this study, we clarify the potential and limitations of interference EMG analysis to infer motor unit recruitment strategies with an experimental investigation of several concurrently active motor units and of the associated features of the surface EMG. For this purpose, we recorded high-density surface EMG signals during linearly increasing force contractions of the tibialis anterior muscle, up to 70% of maximal force. The recruitment threshold (RT), conduction velocity (MUCV), median frequency (MDFMU) and amplitude (RMSMU) of action potentials of 587 motor units from 13 individuals were assessed and associated to features of the interference EMG. MUCV was positively associated with RT (R2 = 0.64 ± 0.14) whereas MDFMU and RMSMU showed a weaker relation with RT (R2 = 0.11 ± 0.11; 0.39 ± 0.24, respectively). Moreover, the changes in average conduction velocity estimated from the interference EMG predicted well the changes in MUCV (R2 = 0.71), with a strong association to ankle dorsi-flexion force (R2 = 0.81 ± 0.12). Conversely, both the average EMG MDF and RMS were poorly associated to motor unit recruitment. These results clarify the limitations of EMG spectral and amplitude analysis in inferring the neural strategies of muscle control and indicate that, conversely, the average conduction velocity could provide relevant information on these strategies.
Date Issued
2017-07-27
Date Acceptance
2017-07-25
Citation
Journal of Applied Physiology, 2017, 123 (4), pp.835-843
ISSN
0021-8987
Publisher
American Physiological Society
Start Page
835
End Page
843
Journal / Book Title
Journal of Applied Physiology
Volume
123
Issue
4
Copyright Statement
Copyright © 2017 the American Physiological Society
Subjects
EMG features
conduction velocity
motor unit
recruitment
size principle
surface electromyography
06 Biological Sciences
11 Medical And Health Sciences
Physiology
Publication Status
Published