Effects of strength training on muscle power and serum hormones in middle-aged and older men

Effects of 16-wk strength training on maximal strength and power performanc e of the arm and leg muscles and serum concentrations [testosterone (T), fr ee testosterone (FT), and cortisol] were examined in 11 middle-aged (M46; 4 6 +/- 2 yr) and 11 older men (M64; 64 +/- 2 yr). During the 16-wk training, the relative increases in maximal strength and muscle power output of the arm and leg muscles were significant in both groups (P < 0.05-0.001), with no significant differences between the two groups. The absolute increases w ere higher (P < 0.01-0.05) in M46 than in M64 mainly during the last 8 wk o f training. No significant changes were observed for serum T and FT concent rations. Analysis of covariance showed that, during the 16-wk training peri od, serum FT concentrations tended to decrease in M64 and increase in M46 ( P < 0.05). However, significant correlations between the mean level of indi vidual serum T and FT concentrations and the individual changes in maximal strength were observed in a combined group during the 16-wk training (r = 0 .49 and 0.5, respectively; P < 0.05). These data indicate that a prolonged total strength-training program would lead to large gains in maximal streng th and power load characteristics of the upper and lower extremity muscles, but the pattern of maximal and power development seemed to differ between the upper and lower extremities in both groups, possibly limited in magnitu de because of neu romuscular and/or age-related endocrine impairments.