For a long time, scientists have thought that people feel a rush of euphoria after a long run because their bodies release endorphins, hormones that block pain and trigger the brain’s reward system. However, endorphins may have been taking too much credit for the “runner’s high”.
According to new research using lab mice as models, the euphoric exercise rush may be the product of the body’s own endocannabinoids. Endocannabinoids are internally produced cannabis, which contains cannabinoid molecules that are tiny enough to cross the blood-brain barrier and attach to receptors to create that runner’s high sensation.
To be sure that endocannabinoids are at play and not endorphins, the researchers with the Central Institute of Mental Health at the University of Heidelberg Medical School tested their theory with a group of lab mice. They tested the mice’s anxiety levels and then allowed them to run. After running on their wheels for three miles, the mice appeared more chilled and less sensitive to pain.
Next the research team gave the mice two sets of drugs. One set blocked the effects of endorphins, whereas the other blocked endocannabinoids. When endorphins were blocked, the mice still showed all of the signs of experiencing the runner’s high. On the other hand, when endocannabinoids were blocked, the mice showed none of the signs of the post-workout euphoria.
The findings aren’t definitive because the study used mice as models. However, it does bring us closer to answering a basic question about our biology. This research can also help develop new treatments for chronic pain or anxiety conditions.