Can Exercise Be Bad for You?

Yesterday I had the opportunity to attend a brief but fascinating talk on the effects of exercise on male reproductive hormones. While that may not sound like good entertainment to most, it opened my eyes to issues related to endurance exercise of which I was previously unaware. In the late 1970s studies came out showing that female athletes, especially those who participated in endurance sports (such as running marathons) had an increased chance of irregular or absent menstrual cycles, referred to as Exercise-induced Amenorrhea. Spurred on by this information, scientists began looking at men who performed a variety of sports to see if effects were similar. What they found was that male endurance athletes indeed showed similar decreases in the production of sex hormones (testosterone), as well as the hormones that regulate testosterone production. For athletes that had trained this way for many years, the changes happened on the brain level, meaning that their behavior altered the function of the hypothalamus and pituitary. This resulted in decreased production of testosterone, which in turn, caused to a decreased production of sperm, a greater number of defective sperm and reduced motility in the sperm that existed. As with women, there was also a slight reduction in bone density (though less severe than that which occurred in women). Similar effects were not experienced by men who performed other types of sports, like wrestling or weighlifting. The implications, as the presenter noted, may be important for couples trying to have children. If one of the partners is an endurance athlete, it may behoove them to reduce their exercise routine to improve their chances of conception. Who knew?