As aging is associated with the loss of strength and muscle mass and an increase in body fat, this study examined whether increased physical activity could prevent or even reverse these deleterious effects in older adults. Eleven men and 31 women ranging in age from 70 to 89 years were randomized to a physical activity (PA) group or successful aging health educational control (SA) group for 12 months. After the 12-month period, body weight and cross-sectional areas of skeletal muscle decreased in a similar manner in both groups. However, strength adjusted for muscle mass only decreased in the SA group (p<0.05). There was an increase in muscle fat infiltration in the SA group (18.4±6.0 %) that was greater than in the PA group (2.3±5.7 %). This study demonstrated the clear effects of moderate physical activity in order to prevent progressive loss of muscle strength in older adults and the age-associated increase in skeletal muscle fat infiltration.
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