Acute hormone responses to heavy resistance lower and upper extremity exercise in young versus old men

Acute hormone responses of growth hormone (GH), total and free testosterone (TT and FT) and cortisol (C) to heavy resistance isometric exercise were examined in ten young men [YM 26.5 (SD 4.8) years] and ten old men [OM 70.0 (SD 3.7) years]. Loading conditions of the same relative intensity were created for the lower and upper extremity actions separately as well as for both of them together - lower extremity exercise (LE; knee extension), upper extremity exercise (UE; bench press extension), and lower and upper extremity exercise (LUE) performed simultaneously in a seated position. Single voluntary maximal isometric actions lasting for 5 s were performed repeatedly for ten repetitions (with a recovery of 5 s) for a total of four sets. The recovery time between the sets was 1 min. Each exercise led to large acute decreases in maximal isometric force in both YM (P < 0.001) and OM (P < 0.001) ranging from 41% to 26% with no significant differences between the groups. Serum GH concentrations increased in both YM (P < 0.05-0.01) and OM (P < 0.05) but the postexercise value in YM during LE was greater (P < 0.05) than for OM. The TT increased (P < 0.01-0.001) in YM in all three exercises, while in OM the increase occurred only during LE (P < 0.01). The exercises led to increases in FT in YM (P < 0.05 for LE and LUE), while in OM the increase occurred only during LUE (P < 0.05). The pre and postexercise FT were greater in YM (P < 0.001) than in OM. No significant changes occurred in C either in YM or in OM. The blood lactate concentrations increased during the exercises in both YM (P < 0.001) and OM (P < 0.05-0.001) but the postexercise values during LE and LUE in YM were greater (P < 0.05) than in OM. The present data would indicate that the responses of GH, TT and FT to heavy resistance isometric exercise are lowered with increasing age. The reduced acute hormone response together with the lowered basal values in FT in the older men compared to the young men may indicate decreased anabolic effects on muscles and may explain in part the loss of muscle mass and strength associated with aging.