Reproductive hormonal responses to maximal exercise in endurance-trained men with low resting testosterone levels

Summary

A cross-sectional study was conducted to com- pare the changes from rest and in response to a maximal exercise bout for select reproductive hormones between age matched groups of endurance trained (ET; distance runners) 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. Serial blood samples were taken for four hours at each of the evaluation sessions. Resting and exercise hormonal concentrations were plotted and the area under the response curve (AUC) measured. Percentage change in AUC values were also calculated and compared (exercise vs. resting AUC values). Resting testoserone (16.6 ± 2.4 vs. 23.9 ± 3.1 nmol • 1⁻¹) and prolactin (3.3 ± 1.4 vs. 6.0 ± 2.0 μg • 1⁻¹) concentrations in the ET men were significantly lower (p < 0.05) than those in the UT men. All other resting hormonal levels did not differ between the groups (p > 0.05). Exercise produced a significant increase (p < 0.05) in the ET men for testosterone, LH, and prolactin AUC values, 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 re- sting AUC value. AUC percentage change values showed between-group differences (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 than UT group (≈20 to 75%). The hormonal changes of the UT men were viewed as “control – reference” responses within a functioning hypothalamo-pituitary-testicular regulatory axis; therefore, it was concluded that the ET men displayed an “atypical” response to exercise to that of UT men relative to this axis.

Key words

Exercise - hormones - men