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Different discrete motor-unit activation patterns in the flexor carpi radialis in boys and men

Stacey Woods1,2, Andrew McKiel1,2, Trent Herda3

  • 1Department of Kinesiology, Faculty of Applied Health Sciences, Brock University, St. Catharines, ON, L2S 3A1, Canada.

European Journal of Applied Physiology
|January 29, 2024
PubMed

Insights

Boys recruit motor units (MUs) earlier and at lower force levels than men during wrist flexion. This difference in neural strategy may explain age-related variations in muscle force control.

Area of Science:

  • Neuromuscular Physiology
  • Developmental Motor Control

Background:

  • Children may exhibit lower activation of higher-threshold motor units (MUs) compared to adults.
  • Investigating age-related differences in discrete MU activation is crucial for understanding motor development.

Purpose of the Study:

  • To compare discrete motor unit (MU) activation in the flexor carpi radialis (FCR) muscle between boys and men.
  • To elucidate age-specific neural strategies for force production.

Main Methods:

  • Surface electromyography (EMG) was used to record MU action potential trains in 15 boys and 17 men during isometric wrist flexion.
  • Motor unit recruitment threshold (RT) and motor unit firing rates (MUFR) were analyzed during trapezoidal contractions.
  • Maximal voluntary isometric wrist flexion torque (MVIC) was measured.

Main Results:

  • While MVIC was not different between groups after accounting for body size, boys exhibited a steeper MUFR-RT slope, indicating a greater decrease in MUFR with increasing RT.
  • Boys recruited a larger proportion of their MUs earlier in the contraction compared to men.
  • Mean MUFR was similar between boys and men.

Conclusions:

  • Boys tend to recruit MUs earlier and at a lower percentage of MVIC than men.
  • This difference in MU recruitment strategy may contribute to the observed steeper MUFR-RT slope in boys.
  • Findings suggest distinct age-related neural strategies for moderate-to-high force production in wrist flexors.
Abstract

Keywords:
ChildrenEMG decompositionExerciseMaturityMuscleStrength

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