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How Much Gym Is Too Much to Gym as Far as Boners Are Concerned?

Probably a lot more than you’re doing.
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In the past 36 hours, sites covered the crap out of a study suggesting that gym rats have lower sex drives than men who don't work out that much. The headlines either imparted concern for men's libidos or mocked muscleheads. But neither is really warranted: The study mostly looked at endurance athletes, not weight-lifters, and the general public doesn't spend nearly as much time working out as the men in the study. Here's the deal.


Studies have suggested that moderate physical activity could increase men's production of testosterone, which would theoretically increase sex drive, while others have hinted that long and grueling endurance workouts could blunt testosterone and even lead to abnormal sperm, bad news for people trying to make babies. (Intense exercise can similarly affect women's libidos and even halt their periods, which is known as "athletic amenorrhea.") But existing studies about men only measured testosterone levels and didn't ask men about their sex lives. So for a new study in Medicine & Science in Sports & Exercise, researchers at the University of North Carolina created an online questionnaire and had active men fill it out.

The survey was based on pre-existing, validated questionnaires from psychology studies and asked men how often they thought about or had sex, how often and how intensely they worked out each week, and other questions about their general health. The researchers recruited men via running and cycling groups, college athletic departments, and publications targeted at endurance athletes. Only healthy men who said they don't take prescription drugs could take the survey and nearly 1,100 men completed it.

This study targeted endurance athletes, since endurance exercise has been associated with reductions in testosterone. Unsurprisingly, the majority of the men said running was their primary form of exercise (80 percent), followed by 9 percent who mostly cycled, and 5 percent who did strength training. A little more than 55 percent of them had run at least one marathon and 25 percent had done a triathlon. They work out a LOT: 59 percent spent a minimum of 7 hours a week exercising.


The researchers divided men into groups based on workout duration and intensity: either short, moderate, or long, and light, moderate, or very intense. They also categorized men based on their answers about sex-having or sex -thinking, grouping them into segments of high, moderate/normal, or low libidos based on standard scoring. Finally, they compared men's exercise habits to their libido scores.

Overall, 60 men out of the 1,077 respondents (or 5.6 percent) scored "low" on the libido survey. They found that men who said their weekly workout routines were light or moderate in either intensity or duration were more likely to score normal or high on the libido survey than men whose workouts were really long and intense. (And, yes, they controlled for age to factor in that libido does decrease as people get older.) Strenuous exercise was, in effect, associated with lower libido and the longer men worked out each week, the worse it was.

Of the 60 men with low sex drive, 39 of them trained more than ten hours per week and 14 trained for seven to ten hours. There were 226 and 356 men who said they trained that long, respectively, and had normal/high libidos, so working out like it's your (part-time) job doesn't automatically mean low sex drive, but the risk is higher.

The study wasn't designed to explain why these connections might exist, but the lead author told the New York Times that men who are workout beasts may be physically more tired in addition to having lower testosterone levels. The authors said that if a guy is concerned about his libido he should try working out a little less to see if that helps.


Some people really enjoyed a conclusion that favored working out less.

But, of course, the inevitable query was posed:

Doing nothing will do your sex life no favors. Working out has been shown to boost testosterone and libido in men who are sedentary or do very little physical activity; this study just suggests there's diminishing returns in men who are already active. So, no, this does not mean that sitting around playing video games will make you hornier than your friend who does CrossFit.

As with most studies, there are some limitations. This study relies on self-reported data so it's impossible to know how much the guys were really exercising and having or thinking about sex. (But if we had to guess, we'd say humans are prone to overestimating both.) And it also relied on a group of men who like endurance sports and who chose to complete the survey—it's not a representative sample of men. The researchers want to do more studies that track exercise, testosterone levels, AND libidos, and figure out whether intensity or duration has a bigger impact on libido, but it will be years until those are finished.