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Motor Unit Firing Properties During Force Control Task and Associations With Neurological Tests in Children

Masamichi Okudaira1,2, Ryosuke Takeda1, Tetsuya Hirono1,3

  • 1Laboratory of Neuromuscular Biomechanics, School of Health and Sport Sciences, Chukyo University, Toyota,Japan.

Pediatric Exercise Science
|August 8, 2023
PubMed

Insights

Motor unit firing rate variability is crucial for precise force control in children, but it does not develop naturally with age. This neural property significantly impacts force steadiness in developing individuals.

Area of Science:

  • Neuromuscular Physiology
  • Developmental Motor Control
  • Pediatric Exercise Science

Background:

  • Understanding the development of motor control in children is essential for identifying factors influencing motor performance.
  • Motor unit (MU) properties, such as firing rate and variability, are fundamental to force production and steadiness.
  • Previous research has not fully elucidated the relationship between MU firing characteristics and force steadiness during childhood development.

Purpose of the Study:

  • To investigate the developmental trajectory of motor unit firing properties in children aged 6-12 years.
  • To examine the association between neural properties (MU firing) and force steadiness (FS) in this age group.
  • To explore the relationship between MU firing characteristics and standard neurological tests.

Main Methods:

  • High-density surface electromyography was used to record vastus lateralis muscle activity during force steadiness tests in 38 children (aged 6-12).
  • Participants performed maximal voluntary knee extension, a submaximal FS test, a reaction time test, and a single-leg standing test.
  • Motor unit firing rate (MUFR) and MUFR variability were analyzed in relation to age and force steadiness.

Main Results:

  • Force steadiness significantly improved with increasing age (r = -.540, P < .001).
  • Motor unit firing rate (MUFR) significantly decreased with age (r = -.343, P = .035), while MUFR variability showed no age association.
  • Force steadiness was significantly correlated with MUFR variability, independent of age (r = .551, P = .002), but not directly with MUFR.

Conclusions:

  • Motor unit firing rate variability plays a critical role in achieving precise force control in children.
  • Unlike force steadiness and MUFR, MUFR variability does not appear to develop systematically with age during childhood.
  • Neurological tests (reaction time, single-leg standing) were not found to correlate with MU firing properties in this cohort.

Keywords:
decompositionhierarchical multiple regressionhigh-density surface electromyographyneural developmentquadriceps

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