TY - JOUR

T1 - Effects of aging on human skeletal muscle after immobilization and retraining

AU - Suetta, C

AU - Hvid, L G

AU - Justesen, L

AU - Christensen, U

AU - Neergaard, K

AU - Simonsen, L

AU - Ortenblad, N

AU - Magnusson, S P

AU - Kjaer, M

AU - Aagaard, P

N1 - Keywords: Adult; Age Factors; Aged; Aging; Electric Stimulation; Humans; Immobilization; Male; Middle Aged; Motor Neurons; Muscle Contraction; Muscle Strength; Muscle Weakness; Neuromuscular Junction; Organ Size; Physical Therapy Modalities; Quadriceps Muscle; Recovery of Function; Sarcopenia; Time Factors; Torque; Young Adult

PY - 2009

Y1 - 2009

N2 - 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.

AB - 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.

U2 - 10.1152/japplphysiol.00290.2009

DO - 10.1152/japplphysiol.00290.2009

M3 - Journal article

C2 - 19661454

VL - 107

SP - 1172

EP - 1180

JO - Journal of Applied Physiology

JF - Journal of Applied Physiology

SN - 8750-7587

IS - 4

ER -