runner's high is also like smoking dope + endorphins

ACS | After a nice long bout of aerobic exercise, some people experience what’s known as a “runner’s high”: a feeling of euphoria coupled with reduced anxiety and a lessened ability to feel pain. For decades, scientists have associated this phenomenon with an increased level in the blood of β-endorphins, opioid peptides thought to elevate mood.

Now, German researchers have shown the brain’s endocannabinoid system—the same one affected by marijuana’s Δ9-tetrahydrocannabinol (THC)—may also play a role in producing runner’s high, at least in mice