We tested the hypothesis that compromised postural balance in older subjects is associated with changes in calf muscle-tendon physiological and mechanical properties. Trial duration and center of pressure (COP) displacements were measured in 24 younger (aged 24 ± 1 yr), 10 middle-aged (aged 46 ± 1 yr), and 36 older (aged 68 ± 1 yr) healthy subjects under varying levels of postural difficulty. Muscle-tendon characteristics were assessed by dynamometry, twitch superimposition, and ultrasonography. In tandem and single-leg stances, trial duration decreased (≤65% lower, P < 0.001) and COP displacements increased (≤90% higher, P < 0.05) with age. Muscle strength, size, activation capacity, and tendon mechanical properties decreased with age by 55, 13, 13, and 36-48%, respectively (P < 0.05). Regressions with these parameters and balance indexes were significant (P < 0.05) for single-leg and tandem (0.69 < r2 < 0.90) postures only, indicating that the age-related changes in muscle-tendon characteristics may explain the majority of the variance in balance performance during tasks more difficult than habitual bipedal stance. Copyright © 2006 the American Physiological Society.
Calf muscle-tendon properties and postural balance in old age
Narici, M.Conceptualization
;
2006
Abstract
We tested the hypothesis that compromised postural balance in older subjects is associated with changes in calf muscle-tendon physiological and mechanical properties. Trial duration and center of pressure (COP) displacements were measured in 24 younger (aged 24 ± 1 yr), 10 middle-aged (aged 46 ± 1 yr), and 36 older (aged 68 ± 1 yr) healthy subjects under varying levels of postural difficulty. Muscle-tendon characteristics were assessed by dynamometry, twitch superimposition, and ultrasonography. In tandem and single-leg stances, trial duration decreased (≤65% lower, P < 0.001) and COP displacements increased (≤90% higher, P < 0.05) with age. Muscle strength, size, activation capacity, and tendon mechanical properties decreased with age by 55, 13, 13, and 36-48%, respectively (P < 0.05). Regressions with these parameters and balance indexes were significant (P < 0.05) for single-leg and tandem (0.69 < r2 < 0.90) postures only, indicating that the age-related changes in muscle-tendon characteristics may explain the majority of the variance in balance performance during tasks more difficult than habitual bipedal stance. Copyright © 2006 the American Physiological Society.Pubblicazioni consigliate
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