THE EFFECT OF ENDURANCE TRAINING ON REPRODUCTIVE FUNCTION IN MALE RUNNERS - A VOLUME THRESHOLD HYPOTHESIS

Investigations on reproductive function in male athletes are not as ab undant in the literature as the research available on female athletes. The primary reason for this is the absence of an obvious clinical sig n indicative of an alteration in reproductive function in male athlete s, While alterations in the reproductive status of female athletes may be easily detected by the loss of menstrual regularity, a distinctive clinical sign reflective of reproductive dysfunction in the male is n ot apparent. In male runners, an effect of endurance training on repro ductive function related to a specific 'volume threshold' of training is proposed, Data are supportive of this 'volume threshold' effect, pr ovided careful and consistent definitions of volume of training are ap plied, In fact, if volume of training is carefully defined endurance-t rained male runners exhibit a rather consistent range of subclinical m odifications in the gonadal hormones and semen profile. and clinical ( oligospermia) alterations in reproductive function. The precise mechan ism responsible for these observed alterations remains unknown, althou gh several peripheral and central mechanisms have been suggested. Clea rly, more research is necessary to confirm, and to elucidate, the natu re of the 'volume threshold' hypothesis in male runners.