Runners have long noted that euphoria and sense of well-being are often felt during and after a hard run. Indeed, this mental and physical reward is the reason many runners exercise. The ability to run quickly and for long distance is obviously an important evolutionary advantage, as in the capability to catch food or not.
The “high” experienced by runners and others exercising vigorously has long been explained by endorphins and the opioid receptor system. But since this explanation came the discovery of the endocannabinoid (eCB) regulatory system consisting of receptors on nerve and other cells and natural cannabinoids (CBs) that activate these receptors,. For nearly a decade many have thought that this system better explains the mental lift and euphoria people often feel during and after robust exercise.
Now a study in the Journal of Experimental Biology, “Wired to run: exercise-induced endocannabinoid signaling in humans and cursorial mammals with implications for the ‘runner’s high“, expands on the evolutionary importance of this pleasurable signalling. The term “cursorial” means well adapted to running. Human being and dogs are cursorial, ferrets, not so much. In this research, intense exercise dramatically raised the levels of endocannabinoids in humans and dogs, in ferrets, not so much. The researchers concluded, “Thus, a neurobiological reward for endurance exercise may explain why humans and other cursorial mammals habitually engage in aerobic exercise despite the higher associated energy costs and injury risks, and why non-cursorial mammals avoid such locomotor behaviors.”
This “neurobiological reward” occurs when your body’s own eCB, anandamide, activates cannabinoid receptors CB1 on nerve cells in brain and body. Anandamide (AEA) and similar 2-AG, activate these nerve receptors in much the same way as does the plant cannabinoid THC, from the plant cannabis sativa. Activation of CB1 receptors by any of these cannabinoids provides a euphoric effect. As the release of anandamide is stimulated by intensive exercise such as running, your body provides a rewarding euphoria for a hard run or workout.
Regrettably perhaps, achieving this runner’s high requires fairly robust levels of exercise. Seemingly we must “pay for” the experience with quite hard physical labor; walking did not increase CB levels in this study. But don’t let that discourage you from walking; it offers dozens of other rewards, even health itself.