To examine acute endogenous hormonal responses to heavy resistance exercise eight young women (YW) and eight young men (YM) in the 30-year age group, seven middle-aged women (MW) and eight middle-aged men (MM) in the 50-year age group as well as eight elderly women (EW) and eight elderly men (EM) in the 70-year age group performed a heavy resistance exercise session with three different exercises (bench press, sit-up exercise and bilateral leg press). The relative loading intensity and volume of the exercise session were kept the same for each subject so that they performed each of the 5 sets of each exercise with the maximal load possible for 10 repetitions per set (10 repetition maximum). The recovery time between the sets was 3 minutes. The loading led to acute significant decreases in maximal isometric leg extension force by 19 +/- 7% (p < 0.001), 31 +/- 15% (p < 0.01) and by 14 +/- 12% (p < 0.01) in YW, MW and EW, respectively, and by 24 +/- 16% (p < 0.01), 34 +/- 9% (p < 0.001) and by 20 +/- 12% (p < 0.001) for YM, MM and EM, respectively. The mean concentrations of serum testosterone and cortisol remained statistically unchanged for all female groups. Significant increases took place in testosterone concentrations in YM (p < 0.05) and in MM (p < 0.01) and in cortisol in MM (p < 0.01), while EM demonstrated no change at all. Serum growth hormone (GH) increased in women both in YW from 3.6 +/- 3.4 to 11.7 +/- 8.2 micrograms x l-1 (p < 0.01) and in MW from 0.3 +/- 0.1 to 6.5 +/- 5.6 micrograms x l-1 (p < 0.05), while EW demonstrated no change. In men GH concentrations increased in YM from 0.1 +/- 0.1 to 21.2 +/- 18.1 micrograms x l-1 (p < 0.05) and in MM from 0.3 +/- 0.2 to 6.0 +/- 5.4 micrograms x l-1 (p < 0.05), while EM demonstrated no change. The primary results indicate that the response of GH concentrations to the same relative heavy resistance work load is greatly lowered with increasing age both in men and women, while acute responses in testosterone levels are minor.