The etiology of sarcopenia, the age-related loss of skeletal muscle mass, is multifactorial but still poorly unknown whether daily ambulatory activity can prevent the age-related loss of skeletal muscle mass.
PURPOSE: To evaluate the relationships between pedometer-determined ambulatory activity and age-related loss of skeletal muscle mass and distribution, and also caloric intake in healthy Japanese men aged 39 to 65 years.
METHODS: 40 healthy men (mean age, 50.8 [SD 7.7] yrs; standing height, 1.62 [SD 0.06] m; weight, 61.6 [SD 9.6] kg; BMI, 23.3 [SD 3.0] kg/m2) were recruited for this cross-sectional study. Selected anthropometric measures were obtained bilaterally from all participants: humerus length, femur length, tibial length, and hip and waist circumferences. B-mode ultrasound-measured skeletal muscle thickness (MTH) as well as subcutaneous fat thickness (FTH) was taken at 6 sites from the anterior and posterior aspects of the body: biceps, abdomen, quadriceps, hamstrings, tibialis anterior, and triceps surae, and the MTH was expressed in terms relative to limb length (MTH/L). Percent body fat was estimated from FTH using an ultrasound-derived prediction equation, and fat-free mass (FFM) was calculated. Ambulatory activity was measured 14 consecutive days after the orientation in which participants were familiarized with use of the pedometer (Omron). Three-day dietary questionnaires were recorded to monitor their caloric and nutritional intake.
RESULTS: Age was negatively correlated with quadriceps MTH/L (r = -0.368, P<0.05), abdomen MTH (r = -0.577, P<0.01) and FFM (r = -0.323, P<0.05) but not other measured MTH sites (i.e., triceps surae MTH/L, r = -0.096) or the ambulatory activity (r = -0.184), suggesting that sarcopenia was site-specific. Daily ambulatory activity was positively correlated with caloric intake per body weight (r = 0.397, P<0.05) and triceps surae MTH/L (r = 0.538, P<0.01) but not other MTH sites, and negatively correlated with % body fat (r = -0.555, P<0.01). There was no significant correlation between caloric intake and age-related change in MTH/L.
CONCLUSIONS: Our results indicated that sarcopenia is observed as being a site-specific loss of skeletal muscle mass, such as quadriceps MTH/L, in Japanese healthy middle-aged men and that daily ambulatory activity can prevent age-related muscle loss in the triceps surae.