Too tired for love? It turns out that how hard you go in the gym may have very little to do with your libido after all…

Worried your Valentine’s Day gym session will impact your performance later on? Or maybe you swear by a solid weights session to help get you in the mood?

It turns out that the science linking exercise and sex drive is shaky, with no hard and fast rules for men or women.

With a whole host of chemicals, bodily processes, and lifestyle factors to take into account, it unfortunately isn’t as simple as “run 5k, have great sex.”

Sometimes something as simple as a good nap might be the best thing to help get you in the mood.

Here’s everything you need to know.

What is sexual desire?

We all remember those awkward sex-ed classes at school. But, at a nuts and bolts level, what causes sexual desire?

A study published in the Journal of Sexual Medicine looked at the brain systems involved in arousal, and the causes of low sex drive (hypoactive sexual desire disorder or HSDD).

By narrowing in on studies in which drugs were used to incite sexual desire in rats, the study authors found that “brain dopamine systems that link the hypothalamus and limbic system appear to form the core of the excitatory system.

"This system also includes melanocortins, oxytocin, and norepinephrine. Brain opioid, endocannabinoid, and serotonin systems are activated during periods of sexual inhibition, and blunt the ability of excitatory systems to be activated.”

In other words, there’s a whole host of chemicals flying about, and we still aren’t quite sure how important each aspect is, or even which part of the brain plays the biggest role, as Dr Amy Wells, senior lecturer in exercise physiology at the University of Hertfordshire explains: “Among the androgen [male sex hormone] receptors in the male brain, the most important [in terms of sexual desire] include the temporal, preoptic, hypothalamus, amygdala, midbrain, frontal, and prefrontal areas and cingulate gyrus.”

Complex stuff, right? Let’s look at what we do know.

Does testosterone play a role?

In men, testosterone is crucial for building muscle, with studies proving that increasing testosterone levels in the body can help build leaner body mass and help fight age-related muscle deterioration. But, as Wells explains, around 40% of men over 45 suffer from low levels of testosterone, which can lead to decreased libido.

In a study of 105 men and 91 women, published in the Archives of Sexual Behavior, researchers investigated links between testosterone and sexual desire in healthy adults.

After asking participants to complete surveys, and testing saliva samples for cortisol and testosterone levels, they found that testosterone was associated with women wanting to engage in sex with themselves, but not with a partner. However, the study found “no significant correlations between T and desire in men”.

In other words, it isn’t as simple as more testosterone equals higher sex drive. “It should be recognised that low sexual desire is often associated with several other determinants, including relational and intrapsychic ones, which are at least as important as T deficiency,” says Wells. “Also, not all men with T deficiency show low libido.”

Does exercise have a direct impact on sex drive?

As to whether exercise directly impacts sex drive, the jury is out. “There is conflicting research around exercise, hormones and sex drive for both men and women,” Tracey Sainsbury, fertility expert at Femme Health explains. “Some studies suggest that moderate-intensity exercise may boost testosterone levels, potentially improving sex drive. But it also might have the opposite effect.”

Wells takes a deeper look: “Hackney et al., 2017 used an online questionnaire to examine the exercise habits and sex drives of men and found that ‘exposure to higher levels of chronic intense and greater durations of endurance training on a regular basis are significantly associated with a decreased libido scores in men,’” she explains.

“What’s more, another study found that men who participate in lots of endurance exercise training (like marathon running) can have suppressed testosterone and libido.”

In other words, overdoing it could flatline your desire to get it on. But, again, testosterone isn’t the only factor. “One of the other main hormones linked with male sexual desire is prolactin (PRL),” explains Wells. “Prolactin plays a major role in regulating male sexual desire, and high-intensity exercise is likely to increase PRL levels. Oestrogen has also been shown to be important for sexual desire in men, but the effects of exercise on oestrogen levels are limited.”

Is it different for women?

“Oestrogen and progesterone are the main sex hormones in women,” Sainsbury explains. “Testosterone is also present in females and together the sex hormones play a huge role in mood, including sex drive.”

Wells says that female sex drive is highest before ovulation, when oestrogen is at its peak in the female body. “Regarding exercise, there is conflicting evidence of the effect on oestrogen, but there have been some studies that showed exercise increased circulating oestrogen in postmenopausal women, and that a 12-week weight training programme also showed positive results,” she says. “However, there are other conflicting studies, so more research is required before strongly promoting exercise as medicine in this population.”

How else might exercise impact our sex drive?

As we’ve seen, evidence that exercise can boost sex hormones in men and women is up for debate. But there are other ways that exercise can increase sex drive.

Wells points to several studies correlating body image with sexual well-being: Woertman & van den Brink, 2012 found that positive body image is associated with greater sexual satisfaction in women; McNulty, Wenner and Fisher, 2016 found that poor body image leads to a decreased desire to engage in sexual activity; and, in a study of over 350 undergraduate students, La Rocque & Cioe, 2011 also found a significant relationship between negative body image and sexual avoidance.

The reverse seems to be true too. “Correlational research has shown that women who engage in frequent exercise have lower levels of body dissatisfaction than those who exercise less often,” says Wells. “Therefore, exercise is likely to increase body confidence in some women, and this could impact sexual desire. I’m sure this is also true for men to some extent.”

What other lifestyle factors play a role?

Getting in the mood depends on a whole host of factors, not just whether you’ve hit the treadmill today…

Stress is a key inhibitor, according to Dr Emily Nagoski author Come As You Are. This is one area where exercise can help. “Physical activity is the single most efficient strategy for completing the stress response cycle and recalibrating your central nervous system into a calm state,” Wells explains. “Nagoski stresses the importance of exercise to deal with stress and ultimately improve sexual desire by releasing our sexual brakes.”

Sainsbury agrees, pointing to a study in the journal Frontiers of Psychology which found that exercise can help alleviate the symptoms of depression and assist in the management of stress.

Sleep also plays a role, with chronic sleep deprivation linked with lower sex drive in men and women, as well as erectile dysfunction – yet another reason to prioritise recovery post-workout.

Ultimately, while exercise can help us feel better about ourselves, and calmer, the link between exercise and chemical drivers of arousal is harder to prove. When it comes to getting more nookie, Wells recommends open, and ongoing communication with your partner as the best course of action.

“Obviously, in relationships, lots of issues are likely to impact sexual desire, so individuals may need to consider relationship counselling and communication with their partner to solve the issue,” she says. “In all, sexual desire is likely to be very multi-faceted and goes beyond biology and hormones, but exercise can play a key part in healthy sexual function.”

Words: Tom Ward