TESTOSTERONE, GROWTH-HORMONE AND IGF-I RESPONSES TO ACUTE AND CHRONICRESISTIVE EXERCISE IN MEN AGED 55-70 YEARS

We investigated the responses of serum testosterone (T) and human grow th hormone (hGH) concentrations to a bout of heavy resistive exercise and the responses of T, hGH, and insulinlike growth factor I (IGF-I) t o a 16 wk progressive resistive training program in 13 men (60 +/- 4 y rs). Body composition via hydrostatic weighing and muscle strength usi ng a 3 repetition maximum (3RM) test on 6 variable resistance exercise machines were assessed before and after the training program. Fasting blood samples were drawn on 2 consecutive days prior to training and again on 2 consecutive days after the last day of exercise. Blood was also drawn immediately before and similar to 10 min after a single exe rcise session during the first wk of training, and after an exercise s ession of the same relative resistance during the last wk of training. The training program resulted in a 37 % increase in upper body streng th and a 39 % increase in lower body strength (both p < 0.01). Lean bo dy mass increased significantly (61.8 +/- 2.1 vs 63.7 +/- 7.8 kg; p < 0.001) while % fat decreased (26.5 +/- 1.5 vs 24.9 +/- 6.0 %; p < 0.01 ) as a result of training. Serum T concentration was unchanged, but GH increased similar to 18-fold in response to a sing le bout of resisti ve exercise before (0.24 +/- 0.08 vs 4.60 +/- 1.35 mg/l) and after (0. 26 +/- 0.06 vs 4.66 +/- 1.46 mg/l; p < 0.01) training. Baseline serum concentrations of T, hGH, and ICF-I were unaffected by the training pr ogram. We conclude that an acute bout of resistive exercise causes a s ubstantial hGH response in older men, but 16 wks of progressive resist ive training does not affect baseline concentrations of the anabolic h ormones.