A comparison of motor unit behaviour in young and aged subjects.
Abstract
We evaluated motor unit behaviour in young and aged subjects during ramped tension development and release to 10% maximum voluntary contraction requiring 10 seconds to complete. Six young and six elderly adults performed isometric abductor digiti minimi muscle contractions while motor units were recorded with implanted fine wire electrodes. Computer interactive programs yielded interspike interval (ISI) data for 16 units from the young and for 15 units from the aged subjects. Mean ISIs for young were 88.4 ms for shortening and 96.5 ms for lengthening contractions. Units from the aged had ISIs of 110.5 ms and 117.1 ms for shortening and lengthening contractions. Some evidence for between-group differences in firing pattern during ascending and descending ramps was also found.
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Motor unit firing properties are markedly affected by aging.
“some previous studies reported that motor unit firing properties, which are one of indicators of age-related dysfunctions in the central nervous system, are markedly affected by aging (Soderberg et al., 1991; Kamen et al., 1995; Erim et al., 1999; Roos et al., 1999; Watanabe et al., 2016).”
From Effect of resistance training and fish protein intake on motor unit firing pattern and motor function of elderly (2018) · cites this paper as Soderberg et al., 1991
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“Consistent with these differences are the results of a number of studies that have reported decreases in MU firing rates with ageing in both proximal and distal muscles (Borg, 198 1 ; Howard et al., 1988; Nelson et al., 1984; Soderberg et al., 1991).”
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Connelly, D. M., Rice, C. L., Roos, M. R., & Vandervoort, A. A. (1999) · Journal of Applied Physiology · doi:10.1152/jappl.1999.87.2.843 · Cited by 340 · see citing works
“For example, MU discharge rates at forces ,20% maximum voluntary contraction (MVC) were studied in biceps brachii, triceps brachii, TA (26), and abductor digiti minimi (33, 41).”
MethodMotor unit discharge behavior in older adults during maximal-effort contractions.
Kamen, G., Sison, S. V., Du, C. C., & Patten, C. (1995) · Journal of Applied Physiology · doi:10.1152/jappl.1995.79.6.1908 · Cited by 323 · see citing works
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“Other investigators have reported either no difference or a trend toward lower firing rates in older adults at lower force levels (4,17,18).”
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MethodEffects of aging on motor-unit control properties.
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“reported reductions in MU firing rates with aging in both proximal and distal muscles (2, 22, 35, 40).”
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“Age-related changes in motor unit behavior have been investigated mainly for the small hand muscles (Erim et al. 1999; Kamen et al. 1995; Knight and Kamen 2007; Nelson et al. 1983, 1984; Patten et al. 2001; Soderberg et al. 1991).”
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“At low levels of force, firing rates are similar among young and older adults [24,29,57].”
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“However, Soderberg et al. (1991) reported a trend for different firing rates in young and older adults at 10% MVC. Connelly et al. (1999) measured firing rates in the tibialis anterior during dorsiflexion and found lower firing rates in older adults than in young adults.”
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Hibino, H., & Gorniak, S. L. (2024) · PLoS ONE · doi:10.1371/journal.pone.0312468
Vila-Chã, C. J. F., Andreis, F. R., Kristoffersen, S. S., Vaz, C., Negro, F., & Oliveira, A. S. (2026) · Journal of Neurophysiology · doi:10.1152/jn.00334.2025
- Authors
- SODERBERG, G. L., MINOR, S. D., & NELSON, R. M.
- Affiliations
- University of Iowa (US)
- Washington University in St. Louis (US)
- Thomas Jefferson University (US)
- Venue
- Age and Ageing
- Publisher
- Oxford University Press (OUP)
- Published
- 1991
- Volume
- 20
- Issue
- 1
- Pages
- 8-15
- ISSN
- 0002-0729 (ISSN-L)
- 1468-2834
- OpenAlex
- W2135483153
- Cited by
- 36
- References
- 0
- Citations by year
- 2026: 1 · 2025: 1 · 2024: 1 · 2022: 1 · 2020: 1 · 2019: 2 · 2018: 2 · 2016: 2 · 2012: 2
- FWCI
- 0.86
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- Age and Ageing (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
- Health Sciences › Medicine › Physiology › Nutrition and Health in Aging
- Keywords
- aging, interspike intervals, motor unit firing patterns, isometric contraction, abductor digiti minimi, fine-wire electrodes, muscle fatigue, older adults
- MeSH terms
- Adult, Aged, Aged, 80 and over, Aging, Electromyography, Female, Humans, Male, Middle Aged, Motor Neurons, Muscle Contraction, Muscles, Neuromuscular Junction, Reference Values, Signal Processing, Computer-Assisted
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