REPRODUCTIVE HORMONAL RESPONSES TO MAXIMAL EXERCISE IN ENDURANCE-TRAINED MEN WITH LOW RESTING TESTOSTERONE LEVELS

A cross-sectional study was conducted to compare the changes from rest and in response to a maximal exercise bout for select reproductive ho rmones between age matched groups of endurance trained (ET; distance r unners) men with low resting testosterone and untrained (UT) men. Both ET and UT men completed two evaluation sessions: (a) resting hormonal profiling, and (b) a maximal treadmill exercise test to exhaustion. S erial blood samples were taken for four hours at each of the evaluatio n sessions. Resting and exercise hormonal concentrations were plotted and the area under the response curve (AUG) measured. Percentage chang e in AUC values were also calculated and compared (exercise vs. restin g AUC values). Resting testosterone (16.6 +/- 2.4 vs. 23.9 +/- 3.1 nmo l . l(-1)) and prolactin (3.3 +/- 1.4 vs. 6.0 +/- 2.0 mu g . l(-1)) co ncentrations in the ET men were significantly lower (p < 0.05) than th ose in the UT men. All other resting hormonal levels did not differ be tween the groups (p > 0.05). Exercise produced a significant increase (p < 0.05) in the ET men for testosterone, LH, and prolactin AUC value s, when compared to resting values. In the UT men the only significant change was a reduction (p < 0.05) in the exercise LH AUC versus the r esting AUC value. AUC percentage change values showed between-group di fferences (p < 0.05) for testosterone, LH and prolactin. The level of change in each of these hormones was found to be greater in the ET tha n UT group (approximate to 20 to 75%). The hormonal changes of the UT men were viewed as ''control - reference'' responses within a function ing hypothalamo-pituitary-testicular regulatory axis; therefore, it wa s concluded that the ET men displayed an ''atypical'' response to exer cise to that of UT men relative to this axis.