Working out with weed

Scientists investigate the counter-intuitive connections between exercise and cannabis.

The stereotypical image of a cannabis smoker is someone who sprawls on the sofa for hours surrounded by a haze of smoke and half-eaten snacks. The scene is played up for laughs in films, but social psychologist Angela Bryan thought it could be cause for concern. After all, cannabis is known to increase appetite and aid relaxation, which might put people at risk of health conditions such as obesity, says Bryan, who is at the University of Colorado Boulder.

But digging into health trends revealed the opposite. Nationwide US studies report that, compared to non-users, cannabis users actually have a lower prevalence of obesity.

A survey says

In Bryan’s survey, about 70% of respondents who used cannabis before working out said doing so made exercising more enjoyable. People who use cannabis might say that taking the drug makes any activity more fun, but Bryan suggests that in the case of exercise there are specific chemical interactions at play.

Consider a runner’s high, the feeling of euphoria that kicks in when some people reach a sweet spot in their workout. The experience has been attributed to the release of chemicals in the brain called endorphins, but solid evidence of this is wanting. For instance, endorphins are thought to give a pleasurable feeling because they activate opioid receptors. But researchers have found that people who take opioid-blocking drugs before exercising can still achieve states of bliss during a workout.

An alternative suggestion is that exercise-induced euphoria originates in the endocannabinoid system. A 2003 study found elevated levels of the endocannabinoid molecule anandamide in the blood of volunteers after they ran or cycled in a lab. Because cannabis targets these same endocannabinoid receptors, Bryan speculates that the drug might allow users to “jumpstart” those pleasurable feelings.

She stresses that direct evidence connecting cannabis to runner’s high remains to be found. But nevertheless, she says, people say they enjoy exercise with cannabis, which could create a positive feedback loop that motivates them to go back to the gym. “If something feels good,” she says, “you’re going to want to do it again.”

Another way in which cannabis could encourage exercise is by aiding recovery, Bryan says. In her survey, 77% of people who use cannabis alongside exercise said that it helps with recovery. Again, researchers haven’t done controlled studies looking at cannabis and recovery. So, for now, Bryan says, “we have to kind of guess based on the mechanisms that we know.”

What researchers do know is that intense physical activity puts stress on the body. It triggers a flood of chemicals known as cytokines, some of which inflame muscles, that manifests as soreness the next day. Cannabis might modulate this inflammation — but potentially in multiple conflicting ways. Bryan explains that although cannabidiol (CBD), a non-psychoactive component of cannabis, has been shown to suppress pro-inflammatory cytokines, the psychoactive part, tetrahydrocannabinol (THC), stimulates both pro- and anti-inflammatory cytokines. In other words, CBD could limit the feeling of sore muscles, whereas THC could help to both prevent and trigger the discomfort. Some studies suggest that THC can also help to manage pain, which might also boost recovery, she says.

Bryan’s team found that the survey respondents who used cannabis alongside exercise tended to be younger and male. Meanwhile, a survey, the results of which are unpublished, conducted on social media by Humboldt State University in Arcata, California, which targeted people who use cannabis with exercise, had roughly an equal number of male and female participants.

Led by Whitney Ogle, a physical therapist and cannabis researcher at Humboldt, the survey of 126 people uncovered cannabis use before all sorts of physical activity — 55 activities in total, ranging from archery to waterskiing. Aside from sheer enjoyment, people in the Humboldt survey reported numerous other benefits of combining cannabis with exercise. They thought that cannabis increased their focus, concentration and mind–body awareness — something that elite athletes have also reported⁶, although scientists have yet to come up with possible mechanisms for these effects.

Ogle’s survey also asked participants something the Colorado team’s survey did not: did people have negative experiences after combining cannabis and exercise? About 40% of respondents reported adverse effects, which included elevated heart rate and being too high to continue with their workout, Ogle says.

The biggest limitation of the survey by the Colorado team, Bryan says, is that it didn’t include a non-user control group. The researchers polled people from states such as Colorado, California and Washington, which already have higher levels of physical activity than does the country as a whole, so it’s hard to tell whether cannabis motivated people to exercise more than is typical in those states. Soon, researchers could have access to populations with a wider range of activity levels. “The good news for researchers is that states are legalizing like crazy,” Bryan says. Eleven US states and the District of Columbia have approved recreational marijuana use, and 33 states allow medical marijuana.