Some recent news reports claim that cannabis can facilitate exercise by increasing our motivation, performance, and the simple pleasure of exercising. These anecdotal reports were usually focused on long-distance running. It’s not surprising that the main support for these claims is the belief that cannabis increases the pleasure of exercise while also alleviating after-exercise fatigue.

For example, following a long aerobic exercise, some people experience a feeling of euphoria, reduced anxiety, and diminished sensation of pain. The experience is due to the combined actions of both beta-endorphins and the production and release of an endogenous marijuana-like compound called anandamide. They are manufactured by the body to reduce the pain in the muscles and joints that was induced by extreme exercising. These morphine- and marijuana-like chemicals produced by the body are addictive. Yes, you can become addicted to molecules produced by your own body.

One important question to ask yourself: what did you just do that convinced your body that it was necessary to release these ancient molecules? The answer is obvious: you were injured by exercising. Essentially, extreme exercising produced so much injury that your body felt it necessary to self-administer its own pain relievers. Endurance athletes become addicted to their own endogenous opiate and marijuana-like chemicals. The addictive proclivities of these molecules, their ability to produce euphoria and mask pain, make it highly likely that your brain will insist that you run again as soon as possible. Can cannabis motivate us to run again and again with greater pleasure and performance?

Anandamide can cross the blood-brain barrier. In contrast, β-endorphin cannot cross the blood-brain barrier. Fortunately, the brain can produce its own β-endorphin. The pain reduction in the periphery depends on the stimulation of cannabinoid and beta-endorphin receptors scattered throughout the body and spinal cord, respectively. Inside the brain, the deceased pain perception, reduced anxiety, and profound euphoria are all due to the actions of β-endorphin and anandamide as well as the other marijuana-like molecules such as 2-arachidonoyl glycerol (2-AG). The brain evolved a cornucopia of psychoactive drugs to self-administer in response to the repeated injury that was associated with the risks and tasks of daily living.

Initial self-reports indicate that cannabis is used primarily to increase exercise pleasure, performance, motivation, and after-exercise recovery. However, now that so many states have legalized cannabis, a larger survey of people who reported using cannabis prior to both aerobic and anaerobic exercise discovered that cannabis improved exercise pleasure and after-exercise recovery but did little to increase exercise motivation or actual performance. This last point is not surprising, given that other studies have shown that cannabis negatively impacts exercise performance. Any positive effects of cannabis on exercise are likely indirect and largely accounted for by feelings of relaxation and well-being, as well as the proven analgesic actions of cannabis.

Animal studies have shown that selective activation of the type-1 cannabinoid receptor in the brain (the main one involved in the action of cannabis) by the main psychoactive ingredient, THC, has no effect on running performance or motivation. In contrast, THC increased the motivation to eat palatable food. Clearly, THC can stimulate motivation in a reinforcer-dependent manner, however this effect does not extend to exercising. Studies using drugs that enhance the endogenous cannabinoid system in other ways, such as blockade of inactivation or reuptake or more selective stimulators, have all failed to enhance the motivation to exercise. Taken together, these data suggest that cannabis administration does not boost the motivation to run or overall running performance. The current evidence indicates that evolution provided us with an endogenous cannabis system that is only beneficial after exercising to reduce the induced pain.