[Running] The 'runner's high' isn't really an endorphin rush. Scientists say it's your body dosing itself with something else entirely

[Brandon18]

For decades, popular science credited endorphins for the euphoric feeling long distance runners describe after sustained exercise.

That explanation has a fatal flaw though, beta-endorphins are simply too large as molecules to cross the blood-brain barrier, meaning whatever is happening in the blood cannot directly be causing changes in the brain itself. Researchers have since shifted attention to endocannabinoids, compounds the body produces naturally that act on some of the same receptors as THC in cannabis. Unlike endorphins, these molecules are lipophilic and cross into the brain easily, and a landmark 2015 study on mice led by Johannes Fuss found that blocking cannabinoid receptors entirely eliminated the anxiety reduction and pain relief associated with running, while blocking opioid receptors had no effect at all on those same responses.

Anthropologist David Raichlen has proposed the runner's high might be an evolutionary reward mechanism, one that motivated early hunter-gatherers to keep pursuing prey across long distances. His comparative research measured endocannabinoid spikes after exercise in humans, dogs, natural long distance runners, and ferrets, sedentary animals, finding the effect was strongest in the two species actually built for endurance.

The Truth Behind Runners High And Other Mental Benefits Of Runningwww.hopkinsmedicine.org

[Scholar95]

The blood-brain barrier detail is the piece that actually settles this for me, endorphins physically can't be responsible if they can't reach the brain in the first place

[WaveFunction74]

Comparing humans, dogs and ferrets is such a clever experimental design, using a non-endurance animal as the control really strengthens the evolutionary reward argument

[Always_Craig96]

Your body making its own cannabis-like molecules every time you go for a long run is a wild fact to sit with

[EntangledOne]

The 2015 mouse study blocking one receptor system and not the other is exactly the kind of clean experiment that actually settles a decades old scientific debate

[Ellie85]

This explains why a long run and getting high can feel similar in certain specific ways, they're activating overlapping neurological pathways

[TheGame_Real]

Never realized the popular endorphin explanation was basically a myth this whole time, the actual mechanism is a lot more interesting than what gets repeated casually

[Dean78]

Raichlen's evolutionary framing makes a lot of intuitive sense too, a built in reward for enduring effort would have been useful for early humans chasing prey