The impact of cannabis on exercise is rife with assumptions and contradictions. All at once, the plant is considered a performance-enhancing drug, banned by numerous sporting events, and a 'couch-lock', employed by the perennially lazy.

Emerging evidence suggests both perspectives are off the mark.

In US states that have legalized cannabis, several recent surveys have found those who use the drug actually get up and move more than non-users.

And while there is no direct evidence to suggest that recreational cannabis improves athletic performance in the moment, researchers at the University of Colorado Boulder (UCB) think it could make exercise more enjoyable.

In a recent experiment, 42 healthy adult runners from Colorado who identified as regular cannabis users ran on a treadmill at a moderate pace for 30 minutes. Before, during, and after the run, scientists monitored their physical and mental state. On another occasion, participants were given the choice to use either THC or CBD products before a similar 30-minute run.

THC, or tetrahydrocannabinol, is the compound in cannabis largely responsible for the plant's psychoactive effects. Whereas CBD, or cannabidiol, is a compound in the plant that offers muscle-relaxing, anti-inflammatory effects without producing the trippy mind-altering effects traditionally associated with marijuana.

"The bottom-line finding is that cannabis before exercise seems to increase positive mood and enjoyment during exercise, whether you use THC or CBD. But THC products specifically may make exercise feel more effortful," says psychologist Laurel Gibson from UCB.

Today, only a small number of studies have dug into the acute effects of cannabis on exercise, and most were conducted decades ago.

Recent legalization in states like Colorado has finally allowed scientists to conduct observational experiments on the drug, and researchers at the University of Colorado Boulder are particularly interested in those who say they like running high.

Ultrarunner Heather Mashhoudi was one of the participants included in the study. Anecdotally, she says that a natural 'runner's high' on a 30 kilometer (just under 20 mile) run feels very similar to getting high on cannabis and running for a much shorter time.

Interestingly, studies have linked intense exercise to the endocannabinoid system in the brain, which is what cannabis taps into.

In 2023, psychologists at UCB found that getting high before a run often resulted in a slower, yet more enjoyable bout of exercise for regular cannabis users.

The newest study from Gibson and her team supports those results. Compared to running sober, running high was more enjoyable for participants, even if the inclusion of THC did make the exercise feel slightly harder.

By comparison, participants who took only CBD in experiments still enjoyed the run more than they did without it, but they did not feel as though their run required more exertion.

To be clear, this does not mean that scientists are recommending that people use THC or CBD products before exercise, as there could still be potential harms.

In the recent experiments, those who took THC showed an increased heart rate while high before they started running. Even though this effect wasn't compounded by running, there is reason to remain cautious about the potential consequences to cardiovascular health.

Neuroscientist Angela Bryan, also on the UCB research team, warns that "it's too early to make broad recommendations", but she thinks "it's worth exploring" further.

Because of ethical considerations, the study was not double-blinded or randomized, and dosage among participants wasn't regulated. Furthermore, the group of participants was limited to include regular cannabis users who ran a lot, which means enrollment could very well be biased towards those with positive cannabis experiences while exercising.

Studies with more rigorous methodologies are now needed to test these initial observations, but Bryan says "it is pretty clear from our research that cannabis is not a performance-enhancing drug."

Whether the drug helps in recovery after exercise is another matter still up for debate.

The study was published in Sports Medicine.