For years, it was believed that the euphoric feeling experienced during endurance exercise, also known as the "runner's high," was due to the release of endorphins. However, a 2021 study challenged this belief, pointing instead to endocannabinoids. The study followed up on previous findings in mice that demonstrated the importance of the endocannabinoid system in producing the "runner's high" sensation. By attempting to replicate these findings in humans, the study aimed to confirm the importance of endocannabinoids in producing the euphoric feelings associated with endurance exercise.
The study conducted a randomized, double-blind, placebo-controlled experiment with 63 participants. The participants were asked to walk or run on a treadmill at a moderate intensity range for 45 minutes while receiving either a placebo or an opioid receptor antagonist. The study aimed to investigate whether the development of two core features of the "runner's high," euphoria, and reduced anxiety levels, depended on opioid signaling.
The results showed that endocannabinoids, not endorphins, are the key drivers of a runner's high in humans. Acute endurance exercise leads to an increase in plasma levels of the endocannabinoids anandamide and 2-arachidonoglycerol, which are associated with reduced anxiety and increased euphoria. The findings demonstrate that opioid blockade did not prevent the development of a runner's high, indicating that the effect is not dependent on opioid signaling in humans.
This study provides an exciting avenue for future research on the endocannabinoid system and its role in regulating the emotional and psychological effects of exercise. The discovery sheds new light on the biological mechanisms that drive the positive effects of exercise and could have significant implications for athletes, exercise enthusiasts, and health professionals alike.
Study Title: Exercise-induced euphoria and anxiolysis do not depend on endogenous opioids in humans
Study Link: https://pubmed.ncbi.nlm.nih.gov/33582575