If you’ve ever gone for a run and gotten into that pleasant state of motion meets relaxation, you know the feeling of a runner’s high. The pleasant feeling of having released stress and gotten the blood flowing can last long after you take off your running shoes. This alone is a great reason to become a runner!
Endorphins—those neuropeptides released by the brain during periods of exercise or stress— have long taken all the credit for producing the runner’s high.Turns out it may be another substance that deserves the credit for producing this natural high.
When researchers in the 1980s discovered that blood levels rise after exercise, the logical takeaway was that endorphins were released by the brain to stimulate that natural high feeling that a good run can produce. But endorphins are large molecules, which would make it unlikely that they could pass through the brain-blood barrier. Instead, a smaller molecule called endocannabinoids seems a more likely contender for bringing on that carefree feeling.
Endocannabinoids are essentially the body’s very own marijuana molecules. They’re small enough to pass from the brain to the bloodstream and attach to receptors there. Might these natural stimulants be the real reason for the runner’s high?
Researchers at the Central Institute of Mental Health at the University of Heidelberg medical school in Mannheim, Germany seem to think so. After conducting research on lab mice to study the effects of endocannabinoids vs. endorphins after bouts of exercise, they found that blocking the cannabis molecules prevented the post-run high. Blocking endorphins, however, did not have the same effect. Which means it couldn’t have been the endorphins bringing on that elevated feeling.
While this research is more suggestive than substantial, as it concerns mice and not necessarily humans, the implications are interesting. As a species, our biological makeup has always encouraged us to run, from potential predators and as hunters. Throughout evolution, our body has preserved this inner reward system for running. Even if science can’t fully explain the runner’s high yet, anyone who has ever experienced it knows that it’s a great feeling, and well worth running for.