Strength Training Increases Conduction Velocity of High-Threshold Motor Units
Casolo A, Farina D, Falla D, Bazzucchi I, Felici F, Del Vecchio A (2020)
Publication Type: Journal article
Publication year: 2020
Journal
Book Volume: 52
Pages Range: 955-967
Journal Issue: 4
DOI: 10.1249/MSS.0000000000002196
Abstract
Purpose Motor unit conduction velocity (MUCV) represents the propagation velocity of action potentials along the muscle fibers innervated by individual motor neurons and indirectly reflects the electrophysiological properties of the sarcolemma. In this study, we investigated the effect of a 4-wk strength training intervention on the peripheral properties (MUCV and motor unit action potential amplitude, RMSMU) of populations of longitudinally tracked motor units (MU). Methods The adjustments exhibited by 12 individuals who participated in the training (INT) were compared with 12 controls (CON). Strength training involved ballistic (4 × 10) and sustained (3 × 10) isometric ankle dorsiflexions. Measurement sessions involved the recordings of maximal voluntary isometric force and submaximal isometric ramp contractions, whereas high-density surface EMG was recorded from the tibialis anterior. High-density surface EMG signals were decomposed into individual MU discharge timings, and MU was tracked across the intervention. Results Maximal voluntary isometric force (+14.1%, P = 0.003) and average MUCV (+3.0%, P = 0.028) increased in the INT group, whereas normalized MU recruitment threshold (RT) decreased (-14.9%, P = 0.001). The slope (rate of change) of the regression between MUCV and MU RT increased only in the INT group (+32.6%, P = 0.028), indicating a progressive greater increase in MUCV for higher-threshold MU. The intercept (initial value) of MUCV did not change after the intervention (P = 0.568). The association between RMSMU and MU RT was not altered by the training. Conclusion The increase in the rate of change in MUCV as a function of MU RT, but not the initial value of MUCV, suggests that short-term strength training elicits specific adaptations in the electrophysiological properties of the muscle fiber membrane in high-threshold MU.
Authors with CRIS profile
Involved external institutions
Università degli Studi di Roma "Foro Italico"
Italy (IT)
Imperial College London / The Imperial College of Science, Technology and Medicine
United Kingdom (GB)
University of Birmingham
United Kingdom (GB)
Italy (IT)
Imperial College London / The Imperial College of Science, Technology and Medicine
United Kingdom (GB)
University of Birmingham
United Kingdom (GB)
How to cite
APA:
Casolo, A., Farina, D., Falla, D., Bazzucchi, I., Felici, F., & Del Vecchio, A. (2020). Strength Training Increases Conduction Velocity of High-Threshold Motor Units. Medicine and science in sports and exercise , 52(4), 955-967. https://doi.org/10.1249/MSS.0000000000002196
MLA:
Casolo, Andrea, et al. "Strength Training Increases Conduction Velocity of High-Threshold Motor Units." Medicine and science in sports and exercise 52.4 (2020): 955-967.
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