turns out the runners high isn’t endorphins after all, it’s actually your endocannabinoid system at work.
Endorphins, aka the opiates our bodies produce, are actually caused by the endocannabinoid system. Specifically interaction on the CB1 receptor.
Interestingly, “A new study by researchers at the University of Heidelberg medical school in Germany found that mice showed elevated levels of both endorphins and endocannabinoids after running, an activity they engage in for fun. The researchers also observed that mice were less sensitive to pain, less anxious and more tranquil after running, shown by their willingness to spend time in lighted areas of their cages rather than retreating to dark corners.
When the team used drugs to block the animals' endocannabinoid receptors, the mice were no longer relaxed after running, proving to be just as anxious as before their runs and very sensitive to pain. Blocking opioid receptors, on the other hand, didn't affect the creatures' post-run tranquillity”