Exercising in groups seems to increase the level of endorphin hormones naturally released during exertion, causing feelings of happiness, a study suggests. According to research from Oxford University, which looked at 12 rowers after a taxing workout on a rowing machine, those who trained alone had a lower tolerance for pain than those who worked out in groups (endorphins protect against pain). After 45 minutes of rowing either separately or in a team of six, researchers measured rowers’ pain thresholds by how long they could tolerate an inflated blood pressure cuff on the arm. Endorphin release might occur during a range of communal activities, from religion and dancing to laughing, the authors suggest. “The exact features of group activity that generate this effect are unknown, but this study contributes to a growing body of evidence suggesting that synchronised, coordinated physical activity may be responsible,” lead author Emma Cohen told the BBC.