The Effect of Endurance Training on Reproductive Function in Male Runners

Abstract

Investigations on reproductive function in male athletes are not as abundant in the literature as the research available on female athletes. The primary reason for this is the absence of an obvious clinical sign indicative of an alteration in reproductive function in male athletes. 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 not apparent. In male runners, an effect of endurance training on reproductive function related to a specific 'volume threshold' of training is proposed. Data are supportive of this 'volume threshold' effect, provided careful and consistent definitions of volume of training are applied. In fact, if volume of training is carefully defined endurance-trained male runners exhibit a rather consistent range of subclinical modifications in the gonadal hormones and semen profile, and clinical (oligospermia) alterations in reproductive function. The precise mechanism responsible for these observed alterations remains unknown, although several peripheral and central mechanisms have been suggested. Clearly, more research is necessary to confirm, and to elucidate, the nature of the 'volume threshold' hypothesis in male runners.

Findings on sperm alterations and DNA fragmentation, nutritional, hormonal and antioxidant status in an elite triathlete. Case report

“…Several studies have shown a potential relationship of exercise to hormonal and seminological alterations. [4][5][6][7] The characteristics observed in the present case seem to be in accordance with previously published observations, 4-7,12 the triathlete did not show any alterations for sperm number or velocity but showed significant alterations in sperm morphology and a great degree of sperm DNA fragmentation. Significant alterations in morphology and sperm DNA fragmentation have been correlated with longer times to conception and less chances of live birth.…”

“…Some authors have even established a theory of a volume-threshold. 4 Previous studies have related triathlon practice to semen alterations. 5,6 This relationship has been observed to be related to training volume.…”

Response of semen parameters to three training modalities

“…Moreover, Ironman triathletes have been shown to exhibit oxidative damage as a result of training and competition (39). We have mentioned the minimum running volume threshold (3,15); however, as we have mentioned already, volume is not the only training parameter to consider relative to reproductive function. All influential parameters must be studied carefully in the training context, and an increase in scrotal temperature and reactive oxygen species production, which are well known to adversely influence seminal plasma and spermatozoa, should be avoided or minimized.…”

“…Early investigations pointed to exercise volume as the variable most affecting reproduction, thus hypothesizing a volume threshold for reproductive disorders (14,15). Other authors have suggested that exercise intensity is equally deleterious to, or even more so than, volume on reproductive function (16,17).…”

Is There a Link between Exercise and Male Factor Infertility?

“…The authors remark that a particular level or degree of training must be surpassed before any clinical alterations become evident [41]. Other authors also supported this notion as they concluded from their findings that a volume threshold for the effect of training on sperm parameters and hormones does truly exist [13,42,43]. Such volume threshold has been observed both in running and in cycling.…”