The central nervous system modulates the neuromechanical delay in a broad range for the control of muscle force
File(s)Del_Vecchio_et_al_JAP_2018_NMD.pdf (1.05 MB)
Accepted version
Author(s)
Type
Journal Article
Abstract
Force is generated by muscle units according to the neural activation sent by motor neurons. The motor unit is therefore the interface between the neural coding of movement and the musculotendinous system. Here we propose a method to accurately measure the latency between an estimate of the neural drive to muscle and force. Further, we systematically investigate this latency, that we refer to as the neuromechanical delay (NMD), as a function of the rate of force generation. In two experimental sessions, eight men performed isometric finger abduction and ankle dorsiflexion sinusoidal contractions at three frequencies and peak-to-peak amplitudes [0.5,1,1.5 (Hz); 1,5,10 of maximal force (%MVC)], with a mean force of 10% MVC. The discharge timings of motor units of the first dorsal interosseous (FDI) and tibialis anterior (TA) muscle were identified by high-density surface EMG decomposition. The neural drive was estimated as the cumulative discharge timings of the identified motor units. The neural drive predicted 80 ± 0.4% of the force fluctuations and consistently anticipated force by 194.6 ± 55 ms (average across conditions and muscles). The NMD decreased non-linearly with the rate of force generation (R2 = 0.82 ± 0.07; exponential fitting) with a broad range of values (from 70 to 385 ms) and was 66 ± 0.01 ms shorter for the FDI than TA (P<0.001). In conclusion, we provided a method to estimate the delay between the neural control and force generation and we showed that this delay is muscle-dependent and is modulated within a wide range by the central nervous system.
Date Issued
2018-11-01
Date Acceptance
2018-07-03
Citation
Journal of Applied Physiology, 2018, 125 (5), pp.1404-1410
ISSN
8750-7587
Publisher
American Physiological Society
Start Page
1404
End Page
1410
Journal / Book Title
Journal of Applied Physiology
Volume
125
Issue
5
Copyright Statement
© 2018, Journal of Applied Physiology.
Identifier
https://www.ncbi.nlm.nih.gov/pubmed/29975604
Subjects
Electromechanical delay
Force Prediction
Motor unit
Neural Drive
Sinusoidal Contractions
Publication Status
Published
Coverage Spatial
United States
Date Publish Online
2018-11-08