Mind Your Body: Strength in Numbers

Working out in the company of other people confers a variety of benefits. Here are just a few.

Make love, not war

Couples who exercise in tandem resolve conflicts faster and communicate better. "The boosts in mood-elevating endorphins, serotonin and dopamine spark creativity, which is associated with problem solving," says Linda Vanderbleek, a researcher at Troy University.

Copycat

We adapt to the workout ethic of those around us. If someone next to you on the treadmill is running hard, he'll inspire you to take it up a notch. But if he's dogging it, that may slow you down. The reason? Social comparison. "It's human nature to make judgments about ourselves based on the dress, skill sets, and performance of those around us," says Thomas Plante, a psychology professor at Santa Clara University. "This takes place even among strangers."

A heightened state of bliss

Working out with others delivers extra euphoria. When a team from Oxford University carried out tests on 12 rowers after a vigorous workout in a virtual boat, the group had increased endorphin levels compared to solo exercisers. The surge may be due to the synchronization of physical activity. The coordinated effort can also create more intimacy between couples. "When people are in sync bodily, they feel a deeper connection," says Helen Fisher, a biological anthropologist.

Jumping for joy

Exercising with pals affects your motor function—learned movements that allow you to run, catch, and jump. In fact, the more you're engaged with others, the slower your motor skills decline as you age. "Neurons are activated by the seemingly unrelated acts ofsocial interaction and movement," says Aron Buchman, a neurosurgeon at Rush University Medical Center in Chicago.

Dish network

The desire for social contact motivates people to hit the gym even when they feel too tired to work out, according to a study at a fitness club in England."They might have been following an exercise buddy's romantic or work saga," says Nick Crossley, the sociologist at the University of Manchester who conducted the study. "It's like following stories in a book or soap opera."

Going It Alone

When to exercise solo

• To relax. Exercising with friends is more emotionally draining, especially for introverts, finds Thomas Plante, a psychologist at Santa Clara University. Sweating companionless is calming because you don't have to navigate conversations and weigh others' feelings.
• To be on. A solitary cardio stint can improve memory, mental clarity, focus, and alertness, says Plante—useful on those days when you have a job interview or an elaborately prepared apology to make to your best friend.
• To avoid feeling self-conscious. If fear of being judged too fat, too slow, or too sweaty is keeping you from the gym, sidestep your worries and go solo.