Most Saturday mornings for the last two decades, I’ve met up with a group of friends to perform this ritual. They put Oxford’s rowers through a hard workout on a rowing machine, testing their pain threshold before and after. As expected, exercise boosted pain threshold, presumably thanks to the pain-blocking effect of endorphins. But when the rowers repeated exactly the same workout alongside their teammates rather than alone in the room, their pain threshold increased twice as much. The social energetics hypothesis and its associated neurochemistry helps explain why my tempo runs feel so much easier in a group.