Ask the Doctors by Eve Glazier, M.D. and Elizabeth Ko, M.D

High-Intensity Exercise Can Affect Men's Libido

Dear Doctor: A new study said that working out too much could ruin your sex life. I like to be in shape -- but not at that high a price. What's the deal?

Dear Reader: Exercise is unequivocally good for men's libido. Compared with sedentary individuals, men who exercise regularly have higher testosterone levels, greater libido and greater fertility. But extreme exercise is not without risks. Hormones are complex, and although the body is adept at regulating them through feedback mechanisms -- a finely tuned system known as the hormonal axis -- that feedback can be disrupted. In women, chronic endurance exercise training can lead to disruption of the hormonal axis, which can affect their menstrual cycle and fertility. It can similarly disrupt men's hormonal axis, leading to testosterone levels at the lower end of normal. The question is: What degree of exercise leads to this disruption, and does the disruption lead to decreased libido?

The study you mentioned, published earlier this year in Medicine and Science in Sports and Exercise, attempted to answer this question -- at least among men. Male subjects filled out online surveys about their level of exercise and their level of libido. Data were gathered from participants who were healthy, free of hormonal disorders, not taking prescription medications, older than 18 and involved in sporting activities. The researchers' primary focus was those men involved in organizations associated with endurance running, biking or triathlons.

Of the men who filled out online surveys, 1,077 men met the overall criteria, with respondents answering questions about the total number of hours exercised per week and the level of exercise intensity. The researchers also separated the men into two groups: low libido and normal-to-high libido. Notably, there were considerably fewer men in the low-libido group: only 60 compared to 1,017 in the normal-to-high libido group.

In men reporting normal-to-high libido, 33.1 percent exercised 4 to 6 hours per week; 35 percent exercised 7 to 10 hours per week; and 22.2 percent exercised more than 10 hours per week. Conversely, in the low-libido group, 10 percent exercised 4 to 6 hours per week; 23.3 percent exercised 7 to 10 hours per week; and 65 percent exercised more than 10 hours per week.

Researchers also assessed level of intensity and how many years the participant had been exercising at that intensity. In the low-libido group, there were three times as many intense/prolonged exercisers than there were moderate intensity/duration exercisers.

So, yes, this study shows that males who exercised at a high intensity for many years had a lower libido than those with a more moderate track record. But keep two things in mind. One, the low-libido group consisted of only 60 people, so the power of the data is not strong. Two, 22.2 percent of men in the normal-to-high libido group exercised more than 10 hours a week; 65 percent in the low-libido group exercised that much. Unless you exercise more than 10 hours per week, every week, I wouldn't be concerned.

That said, if you're finding that your libido is low and you're exercising more than 10 hours per week, you might want to reconsider your priorities.

(Send your questions to, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)