Abstract des Autors

The effects of a 16-wk strength-training program on total and regional body composition were assessed by dual-energy X-ray absorptiometry (DEXA), magnetic resonance imaging (MRI), and hydrodensitometry in 13 untrained healthy men (60+/-4 yr). Nine additional men (62+/-6 yr) served as inactive controls. The strength-training program resulted in substantial increases in both upper (39+/-8%; P<0.001) and lower (42+/-14%; P<0.001) body strength. Total fat-free mass (FFM) increased by 2 kg, and total fat mass decreased by the same amount when measured by DEXA. When measured by hydrodensitometry, similar increases in FFM and decreases in fat mass were observed. When measured by DEXA, FFM was increased in the arms, legs, and trunk, whereas fat mass was reduced in the arms, legs, and trunk as a result of training. MRI analysis revealed significant increases in midthigh muscle cross-sectional area and significant reductions in midthigh subcutaneous fat. These changes in body composition were not associated with changes in serum concentration of growth hormone, insulin-like growth factor I, or testosterone. None of the measured variables changed significantly in the control subjects. Thus, strength training increases regional and total lean mass and decreases regional and total fat mass in middle-aged and older men. The mechanisms for these changes will require further study. Verf.-Referat