You woke up four hours before you had to get to work. You hit your fitness routine fast and hard—cranking out set after set of lifts, or maybe churning around the track in a nasty high-intensity interval workout. You cooled down, cleaned up, and crushed your workday.

But when you got home to your (presumably foxy) significant other? Nothing. And despite your obvious attraction, there was...not much. No spark, no energy, nothing but the overwhelming desire to sleep.

Sound familiar? A new study is offering a clue why—and your workout may be to blame.

Does training hard make you soft?

In a new study, researchers at the University of North Carolina investigated the link between training intensity, training duration, and libido in men. Their findings: Men who participated in high-volume endurance training or ultra-high intensity workouts were more likely to report a low libido, according to their published study results.

For the purposes of the study, high volume training was defined as greater than ten sessions per week and more than ten hours per week. Additionally, men who train at very high intensities may experience less interest in sex.

There was good news, however, for men who train moderately: In the study, survey respondents who reported training at "low to moderate intensities" or for fewer hours per week were more likely to report a "normal or high libido."

The researchers asked survey respondents a variety of questions to establish whether their interest in sex was normal. "The questions we asked focused on desire for intimacy, seeking sexual partners, and other personal questions relative to sex," study author Anthony Hackney, Ph.D., D.Sc., explains. "These answers were then scored to come up with a composite index value of overall libido. So, in other words, we did far more than just ask them whether they thought they had high or low libido."

It's important to note, however, that the study merely established correlation, not causation. It's not like the study found biological markers indicating that training hard reduced sex drive; it simply established that men who did high-volume endurance training were more likely to say they had a reduced libido.

What exactly is a 'normal' libido?

First, a step back: If you’re experiencing a lackluster libido, you're not alone. Anywhere from 10% to 30% of men experience a chronic and troubling decreased interest in sex at some point in their lives, according to several academic estimates.

Technically, libido is simply defined as the drive to pursue sexual activity, either solo or with a partner. But the definition of low libido is subjective, says Yonah Krakowsky, M.D., a sexual medicine expert who treats men with libido issues at Men’s Health Boston. There are no numbers or markers that establish a clear "low libido" diagnosis—and sexual interest varies greatly from one man to another.

"Men have different expectations for sexual activity," Krakowsky says. "They come in for help with low libido when they don’t have the same drive as they used to, and they want to get it back."

So say the North Carolina study is starting to ring some alarm bells in your head, and you're wondering if your fiery gym routine is extinguishing your bedroom spark. The next step is to figure out why you're in the gym so often, and balance that against your expected sex drive, Hackney suggests. “First, ask whether a higher libido is something you need or desire in your life,” he says. "If you and your partner are trying to conceive a child, then yes, you may want to reduce your training load."

How to boost your libido

Even if you’ve noticed less interest in sex after a huge jump in your training, your gym routine may not necessarily be to blame. Issues like a recent job loss, death in the family, or a move can cause your sex drive to change, Krakowsky points out. There are also medical and psychological issues that can interfere with your interest in sex.

So a first step, try to reduce stress in your life, Krakowsky says. “You must have relaxation in your life to experience libido,” he says. He also suggests that you address and manage relationship problems and even try to increase mindfulness to see if you can solve the problem on your own.

Another suggestion: Get creative in the bedroom—and yes, that includes sex toys, says Dr. Ian Kerner, Ph.D., L.M.F.T., a licensed psychotherapist and nationally recognized sexuality counselor. “Knowing you can consistently pleasure your partner with intercourse-enhanced assistance in the form of a sex toy maintains your interest in sex and inspires you want to have more of it," Kerner says. He suggests TOR 2 by Lelo, a vibrating ring that enhances pleasure for both you and your partner.

If your own efforts don’t produce results, however, don’t hesitate to get help, even if you're not exactly stoked about discussing your sex life with a doctor. "It's completely normal to be hesitant about coming to your healthcare provider with these issues," Krakowsky says. "The minute you tell someone your concerns about low libido, it becomes very real. It's a hard point to get to, but it's also a good point to get to, because you open up possibilities. You tell yourself and your partner that this is something you want to address.” He suggests finding a health care provider that is specifically trained in men’s sexual health to address the problem and help provide a solution.