mood-improving neuromodulators

Exercise increases the levels of endocannabinoids in the bloodstream, Linden explains. Unlike endorphins, endocannabinoids can move easily through the cellular barrier separating the bloodstream from the brain, where these mood-improving neuromodulators promote short-term psychoactive effects such as reduced anxiety and feelings of calm.

https://www.hopkinsmedicine.org/health/wellness-and-prevention/the-truth-behind-runners-high-and-other-mental-benefits-of-running