Different discrete motor-unit activation patterns in the flexor carpi radialis in boys and men
Author
Woods, StaceyMcKiel, Andrew
Herda, Trent
Klentrou, Panagiota
Holmes, Michael W. R.
Gabriel, David A.
Falk, Bareket
Journal title
European Journal of Applied PhysiologyPublication Volume
124Publication Issue
6Publication Begin page
1933Publication End page
1942
Metadata
Show full item recordAbstract
Background Lower activation of higher threshold (type-II) motor units (MUs) has been suggested in children compared with adults. We examined child–adult differences in discrete MU activation of the flexor carpi radialis (FCR). Methods Fifteen boys (10.2 ± 1.4 years), and 17 men (25.0 ± 2.7 years) completed 2 laboratory sessions. Following a habitu-ation session, maximal voluntary isometric wrist flexion torque (MVIC) was determined before completing trapezoidal isometric contractions at 70%MVIC. Surface electromyography was captured by Delsys Trigno Galileo sensors and decom-posed into individual MU action potential trains. Recruitment threshold (RT), and MU firing rates (MUFR) were calculated. Results MVIC was significantly greater in men (10.19 ± 1.92 Nm) than in boys (4.33 ± 1.47 Nm) (p < 0.05), but not statisti-cally different after accounting for differences in body size. Mean MUFR was not different between boys (17.41 ± 7.83 pps) and men (17.47 ± 7.64 pps). However, the MUFR–RT slope was significantly (p < 0.05) steeper (more negative) in boys, reflecting a progressively greater decrease in MUFR with increasing RT. Additionally, boys recruited more of their MUs early in the ramped contraction. Conclusion Compared with men, boys tended to recruit their MUs earlier and at a lower percentage of MVIC. This difference in MU recruitment may explain the greater decrease in MUFR with increasing RT in boys compared with men. Overall, these findings suggest an age-related difference in the neural strategy used to develop moderate–high torque in wrist flexors, where boys recruit more of their MUs earlier in the force gradation process, possibly resulting in a narrower recruitment range.ae974a485f413a2113503eed53cd6c53
10.1007/s00421-024-05417-2