Today’s must-read for runners from the New York Times:
We can stop crediting endorphins, the natural opioid painkillers produced by our bodies, for the floaty euphoria we often feel during aerobic exercise, according to a nifty new study of men, women and treadmills. In the study, runners developed a gentle intoxication, known as a runner’s high, even if researchers had blocked their bodies’ ability to respond to endorphins, suggesting that those substances could not be behind the buzz. Instead, the study suggests, a different set of biochemicals resembling internally homegrown versions of cannabis, better known as marijuana, are likely to be responsible.
https://www.nytimes.com/2021/03/10/well/move/running-exercise-mental-effects.html
(And I have to admit an inordinate fondness for the phrase “a nifty new study of men, women, and treadmills.” So many places to go from those words… 
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