Objective: To investigate the effect of marathon training on hormonal and semen profiles in male athletes.
Design: Prospective longitudinal study over 1 year.
Setting: Department of Obstetrics and Gynaecology, University of Cape Town, South Africa.
Participants: Twenty-four healthy male marathon runners, 25 to 54 years of age.
Main outcome measures: Hormonal evaluation included determination of plasma concentrations of total T, LH, FSH, PRL, E2, and P. Semen analyses included an evaluation of count, motility, morphology, and volume. These profiles were correlated with training intensity.
Results: The intensity of training increased significantly in the first 5 months of the study. This was accompanied by a significant rise in serum PRL levels and a fall in P levels. No other significant hormonal changes were identified. The semen volume and sperm motility and morphology fell significantly during training, but there was no significant alteration in the sperm count.
Conclusion: This longitudinal study demonstrates that endurance training can modify significantly hormonal profiles and semen parameters in long-distance runners.