Exercising together appears to increase the level of the feel-good endorphin hormones naturally released during physical exertion, a study suggests.
They may feel happier than if they were on their own
A team from Oxford University carried out tests on 12 rowers after a vigorous workout in a virtual boat.
Those who trained alone withstood less pain - a key measure of endorphins - than those who exercised together.
Writing in Biology Letters, the authors speculate these hormones may underpin an array of communal activities.
Row your boat
It has long been known that physical exertion releases endorphins and that these are responsible for the sometimes euphoric sensations experienced after exercising.
They have a protective effect against pain.
But researchers from Oxford University's Institute of Cognitive and Evolutionary Anthropology found this response was heightened by the synergistic effect of rowing together.
After 45 minutes of either rowing separately or in a team of six, the researchers measured their pain threshold by how long they could tolerate an inflated blood pressure cuff on the arm.
Exercise increased both groups' ability to tolerate pain, but the difference was significantly more pronounced among the team rowers.
This, they said, was a measure of an increased endorphin release.
As well as potentially improving performance in sport, the researchers speculated that this endorphin release may be the mechanism that underpins the sense of communal belonging that emerges from activities such as religious rituals, dancing or laughing.
"The results suggest that endorphin release is significantly greater in group training than in individual training even when power output, or physical exertion, remains constant," said lead author Emma Cohen.
"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."
Carole Seheult, a sport and exercise psychologist from the British Psychological Society, said the findings were entirely credible.
"Rowing is a sport which requires real team work and endorphins could well foster that process.
"But more generally we know from experience that exercising in groups is good for people at many levels, it's motivational, it's social. Groups sessions really do work."