THE RUNNER’S HIGH

Are you familiar with the term “runner’s high?” It’s the sensation of inner peace milers in particular receive after prolonged running. It’s also sometimes called a second wind. In high school I was involved in track and cross-country sports. I can testify to the incredible feeling I would occasionally, but not always, receive while running. Usually it would happen after many miles of pounding the pavement. Then, unexpectedly, it would hit with considerable force producing a momentous euphoria, and an increase in strength and inner peace. That’s technically what we call the runner’s high. In addition, no other form of exercise seems as reliable in generating this wonderful mental state. Recently, exciting research from the UK has identified the endocannabinoid system as the primary contender for this unusual phenomenon.

Here’s a definition of the runner’s high from Pargman:

Traditionally, the runner’s high has been operationally defined as a “euphoric sensation experienced during running, usually unexpected, in which the runner feels a heightened sense of well being, enhanced appreciation of nature, and transcendence of barriers of time and space”(Pargman et al p.342)[ref]2004; Br J Sports Med 2004;38:536-541[/ref].

THE EXERCISE-INDUCED HIGH

One could also call the sedated, calm, sense of well-being after a typical workout in the gym a type of “runner’s high.” Here it’s simply the nice feeling of peace and relaxation that we get after intense exercise of any type, including running.

Together we can call them exercise-induced highs with the runner’s experience being more powerful, and possibly unique.

RESEARCH

Initially investigators theorized that this phenomenon was due to the release of adrenalin, a “fight or flight” hormone. Then, several decades ago Dr Candice Pert and Dr Solomon Snyder isolated the opiate peptide receptor system. This revelation shocked the world while just missing the Nobel Prize for their efforts. After that everyone claimed that the runner’s high was due to exercise-induced release of “endogenous morphine.” These are opiate-like molecules called endorphins located within regions of the brain involved in cognition and pain relief among others. It seemed the perfect candidate for inducing a “high.” In the decades that followed we also saw human growth hormone (HGH) added to the list. Then came dopamine as it stimulated the reward center in our runner’s brain. Another feel-good contender was serotonin.

However, even though the theory of endorphins dominated as the source for the runner’s high, it has not been able to maintain its elite status. The endogenous opiate system has endured criticism over the years for several reasons. For example, in addition to inducing euphoria, opiates cause respiratory depression, pinpoint pupils and constipation but runners never get those symptoms. In fact, it’s quite the opposite. Running is a sure cure for constipation as any miler will contend. Finally, the scientific community weighed in with some major heavyweights like world authority on opiate peptides Dr Snyder:

Dr Huda Akil and Dr Solomon Snyder—have publicly criticised the hypothesis as being “overly simplistic”, being “poorly supported by scientific evidence”, and a “myth perpetrated by pop culture[ref]IBID[/ref].”

In fact, compelling evidence suggests that an exercise-induced high may be a combination of many endogenous molecules released during and after exercise: namely dopamine, HGH, testosterone, cortisol, serotonin, endorphins and now cannabinoids.

THE ENDOCANNABINOIDS

Recently, with the isolation of the endocannabinoid receptors CB1 and CB2 scientists are able to see this phenomenon in a new light. Maybe the blissful runner’s high is really due to the activation of our endocannabinoids?

Why not? After all, we are seeing an endless stream of research showing how cannabinoids play a role in rewarding pleasurable activities in such diverse systems as alcohol and opiate addiction; pleasure in eating sweet and savory foods; nicotine addiction and so forth. Why not add exercise-induced euphoria to the list?

The proof lies just over the horizon. Recently authorities have revealed with certainty that endocannabinoids play a critical role in exercise:

However, recent data in our laboratory showed that endurance exercise activates the endocannabinoid system, suggesting a new mechanism underlying exercise induced alterations of mental status…we found that exercise of moderate intensity dramatically increased concentrations of anandamide [a THC-like endocannabinoid] in blood plasma[ref]IBID [2004; Br J Sports Med 2004;38:536-541][/ref].

In part two we’ll finish our discussion on the role of exercise and endocannabinoid activation. It appears as if the runner’s high may indeed be an event triggered by our own heady cannabinoids while other forms of exercise induced tranquillity may have their origins in yet other biomolecules hidden within our central nervous systems.