The Fun Run
It turns out it’s not the endorphins that give you that feeling of runner’s high. As the NYT’s Gretchen Reynolds explains, it’s something closer to the other kind of high: “Endocannabinoids are, essentially, internally produced marijuana, or cannabis. Cannabis contains cannabinoid molecules, which are small enough to cross the blood-brain barrier and attach there to receptors, producing a floaty, hey-dude high.” (I would definitely run fifteen miles for that feeling. Unless I could find some other, easier way to achieve the same sensation…)