Science always brings us new facts that challenge us and challenge our perceptions of the world. For example, over the past five years, we have begun to see research into a type of compound, produced by the body, that is probably responsible for what we know as the ‘runner’s high’.  Most of us know that the ‘runner’s high’ is the euphoric feeling that occurs when you run, but it also occurs when you do any task that is physiologically difficult.  Linked with the runner’s high are a wide assortment of related biological properties such as a reduced pain sensation, relaxation, and a sense of well-being.

For many years, it was thought that a type of substance made by your body – called endogenous opioids – were what caused runner’s high.  These naturally occurring opioids work through the same receptors that morphine, heroin, and a variety of other drugs work through to produce their effects.  However, while it has been shown without doubt that our bodies do make these opioids, it doesn’t appear that they are responsible for the runner’s high. 

Interestingly, studies now suggest that the compounds that trigger and sustain runner’s high are compounds called ‘cannabinoids’.   You may recognize that term, especially if you are familiar with some of the synonyms for marijuana.  In fact, these internal produced cannabinoids (also called ‘endocannabinoids’) – of which there are two – actually bind and work through the same receptors in the brain that the active ingredient in marijuana works through.  Yes, you read that correctly:  you may have never inhaled marijuana, but just the same, your body produces similar substances that produce similar physiological responses as marijuana.  These findings may actually pave the way for a whole new class of pharmacological drugs that work through the endocannabinoid system to help with pain.

This is one of the underappreciated aspects of science:  often we find applications for what we learn that surprise us.  In both the cases of the opioids and the cannabinoids, it was research on how externally taken illicit drugs affected physiology (the best treatments for those drugs) that provided the foundation for us to understand processes that actually already exist and are active in all of us.   The lesson here is that often what we find out through science provides not only unexpected results, but also unexpected applications.

So, why are we interested – especially in a sports medicine context?  Surprisingly, it appears that only species that evolved to run such as humans, horses, and dogs get increases in endocannabinoids during intense activity (sorry, no endocannabinoids during walking!).  So some scientists are suggesting that people who produce more endocannabinoids during exercise are more likely to be active and thus, less like to suffer from many of the chronic diseases that come from physical inactivity.  This is another suggestion that our levels of activity are not necessarily voluntary, but may be regulated by another in a developing list of biological factors that control activity. 

So, go enjoy your run or your heavy work out.  You may be getting a shot of endocannabinoids that’ll make the rest of your day very pleasant without you having to inhale or break any laws!

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To read more, start with this article by David A. Raichlen in The Journal of Experimental Biology