TY - JOUR

T1 - Effects of aging on muscle mechanical function and muscle fiber morphology during short-term immobilization and subsequent retraining

AU - Hvid, Lars

AU - Aagaard, Per

AU - Justesen, Lene

AU - Bayer, Monika L

AU - Andersen, Jesper L

AU - Ørtenblad, Niels

AU - Kjaer, Michael

AU - Suetta, Charlotte

PY - 2010

Y1 - 2010

N2 - Very little attention has been given to the combined effects of aging and disuse as separate factors causing deterioration in muscle mechanical function. Thus the purpose of this study was to investigate the effects of 2 wk of immobilization followed by 4 wk of retraining on knee extensor muscle mechanical function (e.g., maximal strength and rapid force capacity) and muscle fiber morphology in 9 old (OM: 67.3 ± 1.3 yr) and 11 young healthy men (YM: 24.4 ± 0.5 yr) with comparable levels of physical activity. Following immobilization, OM demonstrated markedly larger decreases in rapid force capacity (i.e., rate of force development, impulse) than YM (~ 20-37 vs. ~ 13-16%; P <0.05). In contrast, muscle fiber area decreased in YM for type I, IIA, and IIx fibers (~ 15-30%; P <0.05), whereas only type IIa area decreased in OM (13.2%; P <0.05). Subsequent retraining fully restored muscle mechanical function and muscle fiber area in YM, whereas OM showed an attenuated recovery in muscle fiber area and rapid force capacity (tendency). Changes in maximal isometric and dynamic muscle strength were similar between OM and YM. In conclusion, the present data reveal that OM may be more susceptible to the deleterious effects of short-term muscle disuse on muscle fiber size and rapid force capacity than YM. Furthermore, OM seems to require longer time to recover and regain rapid muscle force capacity, which may lead to a larger risk of falling in aged individuals after periods of short-term disuse.

AB - Very little attention has been given to the combined effects of aging and disuse as separate factors causing deterioration in muscle mechanical function. Thus the purpose of this study was to investigate the effects of 2 wk of immobilization followed by 4 wk of retraining on knee extensor muscle mechanical function (e.g., maximal strength and rapid force capacity) and muscle fiber morphology in 9 old (OM: 67.3 ± 1.3 yr) and 11 young healthy men (YM: 24.4 ± 0.5 yr) with comparable levels of physical activity. Following immobilization, OM demonstrated markedly larger decreases in rapid force capacity (i.e., rate of force development, impulse) than YM (~ 20-37 vs. ~ 13-16%; P <0.05). In contrast, muscle fiber area decreased in YM for type I, IIA, and IIx fibers (~ 15-30%; P <0.05), whereas only type IIa area decreased in OM (13.2%; P <0.05). Subsequent retraining fully restored muscle mechanical function and muscle fiber area in YM, whereas OM showed an attenuated recovery in muscle fiber area and rapid force capacity (tendency). Changes in maximal isometric and dynamic muscle strength were similar between OM and YM. In conclusion, the present data reveal that OM may be more susceptible to the deleterious effects of short-term muscle disuse on muscle fiber size and rapid force capacity than YM. Furthermore, OM seems to require longer time to recover and regain rapid muscle force capacity, which may lead to a larger risk of falling in aged individuals after periods of short-term disuse.

U2 - 10.1152/japplphysiol.00637.2010

DO - 10.1152/japplphysiol.00637.2010

M3 - Journal article

VL - 109

SP - 1628

EP - 1634

JO - Journal of Applied Physiology

JF - Journal of Applied Physiology

SN - 8750-7587

IS - 6

ER -