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Bilateral and unilateral neuromuscular function and muscle cross-sectional area in middle-aged and elderly men and women.
J Gerontol A Biol Sci Med Sci. 1996 Jan; 51(1):B21-9.JG

Abstract

Forty-eight healthy men (M) and women (W), divided into two different age groups, i.e., M50 yrs (range 44-57; n = 12), W50 yrs (range 43-57; n = 12), M70 yrs (range 59-75; n = 12), and W70 yrs (range 62-75; n = 12), volunteered as subjects for examination of muscle cross-sectional area (CSA), maximal voluntary forces, force-time curves, and electromyographic activity of the knee extensor muscles during bilateral and unilateral isometric contractions. The maximal bilateral knee extension force and the average CSA values in M50 were greater (p < .05) than in M70 and in W50 were greater (p < .05-.001) than those recorded for W70. The early forces in the force-time curve were greater (p < .05) for M50 than for M70 and in W50 were greater (p < .05) than in W70. The individual values of the CSA of the left and right quadriceps femoris (QF) correlated (p < .05-.001) with the individual values of maximal unilateral knee extension forces in M50 (r = .87 and r = .87), M70 (r = .61 and r = .80), W50 (r = .79 and r = .58), and W70 (r = .56 and r = .54). When the force values were related to the CSA of the muscle, W70 demonstrated a lower (p < .05) value than the other three groups. Maximal voluntary bilateral forces didn't differ from those of the summed unilateral forces, and the maximal integrated EMG values during the bilateral and unilateral contractions of the same leg were also the same. The results suggest that the decline in maximal strength with increasing age could be related to the decline in the CSA of the muscle, but in older people, especially women, strength decreases seemed to be multifactorial, including possibly a decrease in voluntary neural drive or changes in "qualitative" characteristics of the muscle tissue. Explosive strength may decrease with aging even more than maximal strength, suggesting that atrophying effects of aging may be greater on fast-twitch muscle fibers than on slow-twitch fibers and/or that the rate of neural activation of the muscles may also be influenced by aging. On the other hand, the central nervous system in a simple single joint isometric force production of the knee extensors seems to be capable of activation of the two bilateral QF muscle groups to the same degree in comparison to that of the unilateral activation only.

Authors+Show Affiliations

Department of Biology of Physical Activity, University of Jyväskylä, Finland.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Comparative Study
Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

8548495

Citation

Häkkinen, K, et al. "Bilateral and Unilateral Neuromuscular Function and Muscle Cross-sectional Area in Middle-aged and Elderly Men and Women." The Journals of Gerontology. Series A, Biological Sciences and Medical Sciences, vol. 51, no. 1, 1996, pp. B21-9.
Häkkinen K, Kraemer WJ, Kallinen M, et al. Bilateral and unilateral neuromuscular function and muscle cross-sectional area in middle-aged and elderly men and women. J Gerontol A Biol Sci Med Sci. 1996;51(1):B21-9.
Häkkinen, K., Kraemer, W. J., Kallinen, M., Linnamo, V., Pastinen, U. M., & Newton, R. U. (1996). Bilateral and unilateral neuromuscular function and muscle cross-sectional area in middle-aged and elderly men and women. The Journals of Gerontology. Series A, Biological Sciences and Medical Sciences, 51(1), B21-9.
Häkkinen K, et al. Bilateral and Unilateral Neuromuscular Function and Muscle Cross-sectional Area in Middle-aged and Elderly Men and Women. J Gerontol A Biol Sci Med Sci. 1996;51(1):B21-9. PubMed PMID: 8548495.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Bilateral and unilateral neuromuscular function and muscle cross-sectional area in middle-aged and elderly men and women. AU - Häkkinen,K, AU - Kraemer,W J, AU - Kallinen,M, AU - Linnamo,V, AU - Pastinen,U M, AU - Newton,R U, PY - 1996/1/1/pubmed PY - 1996/1/1/medline PY - 1996/1/1/entrez SP - B21 EP - 9 JF - The journals of gerontology. Series A, Biological sciences and medical sciences JO - J. Gerontol. A Biol. Sci. Med. Sci. VL - 51 IS - 1 N2 - Forty-eight healthy men (M) and women (W), divided into two different age groups, i.e., M50 yrs (range 44-57; n = 12), W50 yrs (range 43-57; n = 12), M70 yrs (range 59-75; n = 12), and W70 yrs (range 62-75; n = 12), volunteered as subjects for examination of muscle cross-sectional area (CSA), maximal voluntary forces, force-time curves, and electromyographic activity of the knee extensor muscles during bilateral and unilateral isometric contractions. The maximal bilateral knee extension force and the average CSA values in M50 were greater (p < .05) than in M70 and in W50 were greater (p < .05-.001) than those recorded for W70. The early forces in the force-time curve were greater (p < .05) for M50 than for M70 and in W50 were greater (p < .05) than in W70. The individual values of the CSA of the left and right quadriceps femoris (QF) correlated (p < .05-.001) with the individual values of maximal unilateral knee extension forces in M50 (r = .87 and r = .87), M70 (r = .61 and r = .80), W50 (r = .79 and r = .58), and W70 (r = .56 and r = .54). When the force values were related to the CSA of the muscle, W70 demonstrated a lower (p < .05) value than the other three groups. Maximal voluntary bilateral forces didn't differ from those of the summed unilateral forces, and the maximal integrated EMG values during the bilateral and unilateral contractions of the same leg were also the same. The results suggest that the decline in maximal strength with increasing age could be related to the decline in the CSA of the muscle, but in older people, especially women, strength decreases seemed to be multifactorial, including possibly a decrease in voluntary neural drive or changes in "qualitative" characteristics of the muscle tissue. Explosive strength may decrease with aging even more than maximal strength, suggesting that atrophying effects of aging may be greater on fast-twitch muscle fibers than on slow-twitch fibers and/or that the rate of neural activation of the muscles may also be influenced by aging. On the other hand, the central nervous system in a simple single joint isometric force production of the knee extensors seems to be capable of activation of the two bilateral QF muscle groups to the same degree in comparison to that of the unilateral activation only. SN - 1079-5006 UR - https://www.unboundmedicine.com/medline/citation/8548495/Bilateral_and_unilateral_neuromuscular_function_and_muscle_cross_sectional_area_in_middle_aged_and_elderly_men_and_women_ L2 - https://academic.oup.com/biomedgerontology/article-lookup/doi/10.1093/gerona/51a.1.b21 DB - PRIME DP - Unbound Medicine ER -