Runner's high

The runner's high is a transient state of euphoria coupled with lessened feelings of anxiety and a higher pain threshold, which can come either from continuous moderate physical exertion over time or from short bursts of high-intensity exercise.

The exact prevalence is unknown, but it seems to be a relatively rare phenomenon that not every athlete experiences.

[1] The name comes from distance running, and it is alternatively called "rower's high" in rowing.

[2][3][4][5] Current medical reviews indicate that several endogenous euphoriants are responsible for producing exercise-related pleasurable feelings, specifically phenethylamine (an endogenous psychostimulant), β-endorphin (an endogenous opioid), and anandamide (an endogenous cannabinoid).

[6][7][8][9][10] However, more recent studies suggest that endorphins have a limited role in the feelings of euphoria specifically related to the runner's high due to their inability to cross the blood-brain barrier, placing more importance in the endocannabinoids instead, which can cross this barrier.