Age-related reductions in appendicular skeletal muscle mass: association with habitual aerobic exercise status.

Appendicular skeletal muscle mass decreases with advancing age, and this is thought to be a key factor for reductions in functional independence in the elderly. We determined the potential modulatory influence of regular aerobic exercise on the age-related reductions in appendicular muscle mass. In the present cross-sectional study, we studied a total of 131 healthy men aged 20-79 years. For at least the previous 2 years subjects were either sedentary or endurance-trained. Appendicular skeletal muscle mass was measured using dual-energy X-ray absorptiometry. There were no significant group differences in height. Body mass and body surface area were lower in endurance-trained compared with sedentary men (P<0.05). In general, body fat increased with age in both groups, but was lower in endurance-trained compared with sedentary men at any age group (P<0.05). Lean body mass and maximal oxygen consumption decreased with age (P<0.05). Irrespective of expression (absolute, relative to body surface area, or relative to body mass), arm, leg, and total limb muscle mass generally decreased with age. Absolute appendicular muscle mass was not different between the two activity groups. When expressed relative to body mass or body surface area, appendicular muscle mass in the endurance-trained middle-aged and older men was significantly higher than their sedentary peers. The rate of decline in appendicular muscle mass with age was similar between the two activity groups. The results of the present cross-sectional study indicate that endurance-trained men had significantly higher appendicular skeletal muscle mass relative to body mass or body size compared with their sedentary peers. This may contribute, at least in part, to the lower incidence of functional disability observed in middle-aged and older men who exercise regularly.