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Aging, regularity and variability in maximum isometric moments.

John H Challis1

  • 1Biomechanics Laboratory, 29 Recreation Building, Department of Kinesiology, The Pennsylvania State University, University Park, PA 16802, USA. jhc10@psu.edu

Journal of Biomechanics
|June 11, 2005
PubMed
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Older adults exhibit more regular muscle force production in plantar flexion compared to younger adults, likely due to fewer motor units. This study investigated age-related differences in maximal isometric plantar flexion moments.

Area of Science:

  • Biomechanics
  • Motor Control
  • Gerontology

Background:

  • Aging is associated with changes in neuromuscular function, including potential alterations in motor unit number and muscle force regulation.
  • Understanding age-related differences in muscle strength and control is crucial for maintaining functional independence in older adults.

Purpose of the Study:

  • To compare the variability and regularity of maximum isometric plantar flexion moments between young and elderly individuals.
  • To test the hypothesis that older adults exhibit greater regularity in moment production due to a reduced number of motor units.

Main Methods:

  • Maximal isometric plantar flexion moments were measured in two groups: young (n=11, mean age 23.8 years) and elderly (n=13, mean age 74.0 years).
  • Three maximal voluntary contractions were performed by each subject.

Related Experiment Videos

  • Peak moments, coefficients of variation, and approximate entropy (to assess signal regularity) of the moment-time curve plateau were analyzed.

    • Main Results:

    • Younger subjects produced significantly greater peak plantar flexion moments than elderly subjects.
    • No significant difference was found in the coefficients of variation between the age groups.
    • Elderly subjects demonstrated significantly greater regularity (lower approximate entropy) in their moment profiles compared to young subjects.

    Conclusions:

    • The hypothesis was supported: older adults exhibit more regular isometric plantar flexion moment profiles than younger adults.
    • Reduced motor unit number in elderly individuals may underlie the observed increase in signal regularity.
    • These findings contribute to understanding age-related changes in motor control and muscle force generation.