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The aging neuromuscular system and motor performance.

Sandra K Hunter1, Hugo M Pereira2, Kevin G Keenan3

  • 1Exercise Science Program, Department of Physical Therapy, Marquette University, Milwaukee, Wisconsin; and sandra.hunter@marquette.edu.

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Aging significantly impairs motor function by altering motor units, leading to reduced strength and increased performance variability. Physical activity may help mitigate these age-related changes.

Keywords:
agingcontractile velocitymotor unitmuscle fatiguepowersteadinessstrengthvoluntary activation

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Area of Science:

  • Neuromuscular Physiology
  • Gerontology
  • Motor Control

Background:

  • Motor units, the fundamental components of the neuromuscular system, undergo significant age-related alterations.
  • These changes profoundly impact motor function, particularly in older and very old adult populations.

Purpose of the Study:

  • To review evidence on how age-related changes in motor unit morphology and properties affect motor performance.
  • To explore the contributing factors to increased motor performance variability with aging.
  • To identify research opportunities, including the role of physical activity in mitigating age-related motor decline.

Main Methods:

  • This is a review article, synthesizing existing research on aging and motor units.
  • Analysis of studies examining motor unit properties, neural inputs, and functional performance in older adults.

Main Results:

  • Age-related changes lead to reduced maximal strength, power, contractile velocity, and increased fatigability.
  • Increased variability in motor tasks, including decreased force steadiness and inconsistent contraction velocities, is observed.
  • Factors contributing to variability include altered synaptic inputs, fewer/larger motor units, unstable neuromuscular junctions, and changes in muscle fiber characteristics.

Conclusions:

  • Age-related motor unit changes impair motor performance and increase variability.
  • Further longitudinal studies are needed to understand the causes of variability and the potential benefits of physical activity.
  • Interventions aimed at reducing age-related motor variability are crucial for the growing elderly population.