Effects of aging on human skeletal muscle after immobilization and retraining

Aug 8, 2009Journal of applied physiology (Bethesda, Md. : 1985)

How aging changes muscle loss and recovery after immobilization and retraining

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Abstract

Aging affects neuromuscular response to immobilization, with greater neuronal motor function impact in older individuals.

Both young and old men experienced significant decreases in muscle strength and contractile properties after 2 weeks of immobilization.
Older individuals showed a smaller decline in quadriceps muscle volume and pennation angle compared to younger individuals.
Only older men experienced a decrease in quadriceps activation during immobilization.
After 4 weeks of retraining, both age groups regained initial muscle strength, but older individuals had smaller increases in quadriceps volume.
Young individuals showed an increase in pennation angle during retraining, while older individuals did not.

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Inactivity is a recognized compounding factor in sarcopenia and muscle weakness in old age. However, while the negative effects of unloading on skeletal muscle in young individuals are well elucidated, only little is known about the consequence of immobilization and the regenerative capacity in elderly individuals. Thus the aim of this study was to examine the effect of aging on changes in muscle contractile properties, specific force, and muscle mass characteristics in 9 old (61-74 yr) and 11 young men (21-27 yr) after 2 wk of immobilization and 4 wk of retraining. Both young and old experienced decreases in maximal muscle strength, resting twitch peak torque and twitch rate of force development, quadriceps muscle volume, pennation angle, and specific force after 2 wk of immobilization (P < 0.05). The decline in quadriceps volume and pennation angle was smaller in old compared with young (P < 0.05). In contrast, only old men experienced a decrease in quadriceps activation. After retraining, both young and old regained their initial muscle strength, but old had smaller gains in quadriceps volume compared with young, and pennation angle increased in young only (P < 0.05). The present study is the first to demonstrate that aging alters the neuromuscular response to short-term disuse and recovery in humans. Notably, immobilization had a greater impact on neuronal motor function in old individuals, while young individuals were more affected at the muscle level. In addition, old individuals showed an attenuated response to retraining after immobilization compared with young individuals.

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Effects of aging on human skeletal muscle after immobilization and retraining

Abstract

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