Key points are not available for this paper at this time.
In brief Exhaustive endurance training may suppress testicular function. This tentative conclusion was drawn from a study of six endurance athletes who underwent 2 weeks of prolonged running and cycling. No significant changes were noted for strength, weight, or body fat. However, persistent fatigue developed in all subjects. Their plasma testosterone decreased 17% (from 673 to 558 ng/dl, p <.05), and sperm count decreased, though not significantly. All reported a decline in sexual activity and sex drive, which may be related to the development of general fatigue and could be an early sign of overtraining stress.
Griffith et al. (Tue,) studied this question.