EFFECTS OF STRENGTH TRAINING ON TOTAL AND REGIONAL BODY-COMPOSITION IN OLDER MEN

The effects of a 16-wk strength-training program on total and regional body composition were assessed by dual-energy X-ray absorptiometry (D EXA), magnetic resonance imaging (MRI), and hydrodensitometry in 13 un trained healthy men [60 +/- 4 (SD) yr]. Nine additional men (62 +/- 6 yr) served as inactive controls. The strength-training program resulte d in substantial increases in both upper (39 +/- 8%; P < 0.001) and lo wer (42 +/- 14%; P < 0.001) body strength. Total fat-free mass (FFM) i ncreased by 2 kg (62.0 +/- 7.1 to 64.0 +/- 7.2 kg; P < 0.001), and tot al fat mass decreased by the same amount (23.8 +/- 6.7 to 21.8 +/- 6.0 kg; P < 0.001) when measured by DEXA. When measured by hydrodensitome try, similar increases in FFM (61.3 +/- 7.8 to 63.0 +/- 7.6 kg, P < 0. 01) and decreases in fat mass (23.8 +/- 7.9 to 22.1 +/- 7.7 kg; P < 0. 001) were observed. When measured by DEXA, FFM was increased in the ar ms (6.045 +/- 0.860 to 6.418 +/- 0.803 kg; P < 0.01), legs (19.416 +/- 2.228 to 20.131 +/- 2.303 kg; P < 0.001), and trunk (29.229 +/- 4.108 to 30.134 +/- 4.184 kg; P < 0.01), whereas fat mass was reduced in th e arms (2.383 +/- 0.830 to 2.128 +/- 0.714 kg; P < 0.01), legs (7.583 +/- 1.675 to 6.945 +/- 1.551 kg; P < 0.001), and trunk (12.216 +/- 4.1 43 to 11.281 +/- 3.653 kg; P < 0.01) as a result of training. MRI anal ysis revealed significant increases in midthigh muscle cross-sectional area (161 +/- 19 to 172 +/- 18 cm(2); P < 0.01) and significant reduc tions in midthigh subcutaneous fat (65 +/- 19 to 59 +/- 17 cm(2); P < 0.05). These changes in body composition were not associated with chan ges in serum concentration of growth hormone, insulin-like growth fact or I, or testosterone. None of the measured variables changed signific antly in the control subjects. Thus, strength training increases regio nal and total lean mass and decreases regional and total fat mass in m iddle-aged and older men. The mechanisms for these changes will requir e further study.