Testosterone is often referred to as the “male sex hormone” because although women have a small amount of testosterone in their bodies, men’s levels are far greater. Its primary function is to ignite the male sex drive and to produce sperm.

Compromised testosterone levels can cause lack of energy, low libido, poor sexual performance and even erectile dysfunction. Although certain types of exercise can boost testosterone, research shows that an overzealous exercise habit can actually lower your testosterone levels, thus affecting a man’s sex drive.

Both men and women can suffer the adverse effects of too much exercise. When a woman’s hormones levels are compromised by excessive exertion, she usually will experience amenorrhea, or absent periods. When a man experiences similarly compromised hormone levels, the effects may not be immediately apparent, making men more prone to over-exercising without even realizing it. According to a study done at the University of British Columbia and published in the British Journal of Sports Medicine, men who ran more than 40 miles per week had testosterone levels that were one-fifth lower than men who ran shorter distances. Another study at the University of Melbourne showed that running for less than two hours increased testosterone levels, however running for two hours or more suppressed testosterone. This essentially shows an inverse relationship between running and testosterone. It’s crucial to strike a balance between getting the training results you want, and avoiding overexertion and the negative side effects that come with it. Yet another study, carried out in Brazil at the Federal University of São Paulo, examined testosterone levels of twenty men before and after running a marathon. After the marathon, the men’s testosterone levels were approximately 50 percent lower than their normal baseline levels—a huge decrease. This could have severe repercussions for those who run marathons on a regular basis, especially if they train long-distance in preparation for those marathons. Other forms of exercise may increase your testosterone levels more than moderate running. Consider implementing weight training, as lifting weights is proven to trigger testosterone release. In general, large compound movement exercises are best for increasing testosterone. As with long-distance running, too much weightlifting can harm your hormone levels, so keep your sessions under 60 minutes.