News and notes about science
Men who exercise strenuously may have a lower libido than those whose workouts are lighter, according to one of the first studies to scientifically delve into the relationship between men’s workouts and their sex lives.
For years, scientists and active people have debated whether and how exercise affects sexual desire and human reproduction.
But most past studies have centered on women. Typically, this research has found that when some female athletes, such as marathon runners, train intensely for many hours a week, they can develop menstrual dysfunctions. These problems seem caused by hormonal imbalances related to physical stress and frequently affect a woman’s interest in sex and her ability to conceive.
Less is known about the effects of exercise, especially heavy exercise, on men’s libidos and fertility. There have been hints that, in moderate amounts, physical activity increases the male body’s production of the hormone testosterone, which theoretically should ramp up sex drive. Other small studies, on the other hand, have suggested that lengthy and grueling training may blunt the levels of testosterone in a man’s bloodstream both immediately and over the long term.
But those studies examined only hormone changes related to exercise, which can be measured easily, and not differences in sexual emotions and behavior, which are tougher to quantify.
So for the new study, which was published this month in Medicine & Science in Sports & Exercise, researchers at the University of North Carolina in Chapel Hill decided to ask active men about their sex lives.
They began by developing a questionnaire based on earlier psychological research into men’s sexual behavior. The scientists also created a separate questionnaire with detailed queries about exercise habits, including how often and intensely the men worked out each week. A final set of questions asked about general health and medical histories.
Almost 1,100 physically active adult men completed all of the questions. Most were experienced athletes who had participated for years in training and competitions.
The scientists used their responses to stratify the men based on the extent and intensity of their workouts. They wound up with groups whose weekly exercise was short, moderately lengthy or quite prolonged, and separately whose weekly exercise was light, moderate or extremely intense.
They also categorized the men according to their answers about their sex lives, creating groups with relatively high, moderate or low libidos. Finally, they compared the men’s exercise habits to their reported interest and engagement in sex.
And there were clear patterns. The men whose exercise routines were moderate or light in intensity or duration were far more likely to report moderate or high libidos than were the men whose workouts were especially prolonged or intense, even after the researchers controlled for age.
This type of study also cannot tell us whether too much exercise causes low libido, only that the two are linked. And it did not examine why strenuous exercise might dampen libidos.
But Anthony Hackney, a professor of exercise physiology and nutrition at the University of North Carolina who led the study, speculates that physical fatigue and lower testosterone levels after exhausting exercise likely play a role.