Yearlong physical activity and sarcopenia in older adults: the Nakanojo Study.

We tested the hypothesis that a low level of regular daily physical activity in elderly individuals would be associated with a clinically significant degree of sarcopenia. Subjects were 78 male and 97 female free-living Japanese, aged 65-84 years. A pedometer/accelerometer measured continuously the number of steps taken and the intensity of activity 24 h/day for 1 year. A whole-body dual X-ray absorptiometry scan assessed skeletal muscle mass in the upper and lower extremities at the end of the year. Sarcopenia was defined as a muscle mass/height(2) value >1 SD below the mean for healthy young Japanese. Linear and exponential regressions showed that after controlling data for age and/or sex, muscle mass was associated with physical activity, more closely for the legs than for the arms, and for duration of moderate activity (>3 METs) than for step count. Muscle mass increased progressively with daily activity, although when data were categorized into quartiles, muscle mass was not significantly greater in men and women who exceeded, respectively, 8,000 and 6,900 steps/day and/or 22 and 19 min/day at >3 METs. All participants meeting such criteria exceeded our sarcopenia threshold. Multivariate-adjusted logistic regressions predicted that individuals who walked <5,300 steps/day and/or spent <15 min/day at >3 METs were, respectively, 2.00-2.66 and/or 2.03-4.55 times more likely to show sarcopenia than those who walked >7,800 steps/day and/or spent >23 min/day at >3 METs. Our hypothesis was proven correct: seniors who walked at least 7,000-8,000 steps/day and/or spent 15-20 min/day at an intensity of >3 METs were likely to have a muscle mass above the sarcopenia threshold.