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Cited by 256Muscle activation and electromyography studiesMuscle Physiology and DisordersMotor Control and Adaptation

Effects of aging on motor-unit control properties.

Erim, Zeynep, Beg, M. Faisal, Burke, David T., de Luca, Carlo J.·1999·Journal of Neurophysiology
DOI 10.1152/jn.1999.82.5.2081
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Abstract

It was hypothesized that the age-related alterations in the morphological properties of a motor unit would be accompanied by modifications in the control aspects of the motor unit, as either an adaptive or compensatory mechanism to preserve smooth force production. In specific, the objective of the study was to investigate the age-related alterations in the concurrent firing behavior of multiple motor units in the first dorsal interosseous (FDI) muscle in isometric contractions at 20 and 50% of the subject's voluntary contraction level. Analysis of the data collected from 10 young (24-37 yr of age) and 10 elderly (65-88 yr of age) subjects led to three novel observations regarding the firing behavior of aged motor units. 1) Among elderly subjects, there is a decrease in the common fluctuations that are observed among the firing rates of motor units in the young. 2) The relationship observed between the firing rate and recruitment threshold of young subjects is disturbed in the elderly. Although in young subjects, at any point in a given submaximal contraction, earlier recruited motor units have higher firing rates than later-recruited units; in aged subjects this dependency of firing rate on recruitment rank is compromised. 3) The progressive decrease observed in the firing rates of concurrently active motor units in constant-force contractions in the young is not seen in the aged. In addition to these original findings, this study provided support for earlier reports of 1) decreased average firing rates probably reflecting the slowing of the muscle, 2) a shift in recruitment thresholds toward lower force levels in line with the shift toward type I fibers, and 3) multiphasic action potential shapes indicative of the reinnervation process that takes place during aging. Taken as a whole, these findings indicate significant age-related modifications in the control properties of human motor units.

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Authors
Erim, Z., Beg, M. F., Burke, D. T., & de Luca, C. J.
Affiliations
  • NeuroMuscular Research Center and
  • Boston University (US)
  • Harvard University (US)
ORCID
Beg, M. Faisal
Venue
Journal of Neurophysiology
Publisher
American Physiological Society
Published
1999-11-01
Volume
82
Issue
5
Pages
2081-2091
ISSN
  • 0022-3077 (ISSN-L)
  • 1522-1598
DOI
10.1152/jn.1999.82.5.2081
OpenAlex
W1907176958
Cited by
256
References
61
Citations by year
2026: 5 · 2025: 8 · 2024: 1 · 2023: 10 · 2022: 8 · 2021: 7 · 2020: 8 · 2019: 12 · 2018: 13 · 2017: 11 · 2016: 10 · 2015: 15 · 2014: 6 · 2013: 10 · 2012: 14
FWCI
8.21
Type
journal article
Language
en
Open access
closed
Locations
  • Journal of Neurophysiology (publishedVersion)
  • PubMed (publishedVersion)
Topics
  • Physical Sciences › Engineering › Biomedical Engineering › Muscle activation and electromyography studies
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Muscle Physiology and Disorders
  • Life Sciences › Neuroscience › Cognitive Neuroscience › Motor Control and Adaptation
Keywords
motor unit control, aging, motor unit firing rate, motor unit recruitment, first dorsal interosseous muscle, isometric contraction, recruitment threshold, muscle fiber type shift, older adults
MeSH terms
Adult, Aged, Aged, 80 and over, Aging, Electromyography, Fingers, Humans, Isometric Contraction, Motor Neurons, Reaction Time, Regression Analysis, Muscle, Skeletal

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