PLASMA-CATECHOLAMINE AND SERUM TESTOSTERONE RESPONSES TO 4 UNITS OF RESISTANCE EXERCISE IN YOUNG AND ADULT MALE-ATHLETES

The plasma noradrenaline (NA) and adrenaline (A) concentration respons es of seven young male athletes [15 (SD 1) years] and seven adult male athletes [25 (SD 6) years] were investigated together with the serum testosterone (Tes) concentration responses in four different half-squa tting exercises. The loads, number of repetitions, exercise intensity and recovery between the sets were manipulated such that different typ es of metabolic demand could be expected. However, the amount of work done was kept equal in each kind of exercise. After the most exhaustin g unit of exercise (E3; two sets of 30 repetitions with 50% of 1 repet ition maximum and with 2-min recovery between the sets) the plasma NA concentration was significantly lower in the younger than in the adult subjects [15.7 (SD 7.8) vs 32.7 (SD 13.2) nmol . l(-1), P < 0.05], wh ile the A concentrations were similar. In the other three exercises no differences in the plasma catecholamine concentration responses among the groups were observed. The postexercise Tes concentrations, howeve r, were significantly lower in the younger than in the adult subjects in every exercise unit. No correlations between the plasma catecholami ne and serum Tes concentration responses were observed in any of the e xercise units in either group. The results of the present study may su ggest reduced sympathetic nervous activity in the younger subjects com pared to the adults in response to exhausting resistance exercise. The results may also suggest that the catecholamines were less involved i n eliciting an increase in Tes secretion in these resistance exercises .