Many experts recommend working out with friends to increase motivation, but it can backfire.

"People end up talking more than exercising or slowing their speeds or [lowering] intensity levels to chat," says Stacey Rosenfeld, Ph.D., a psychologist at Columbia University Medical Center in New York City. Plus, walking or running with friends can

prevent you from following your body's cues.

If you want to speed up or slow down, for instance, you may not be able to coordinate that with someone else. Arrive at the gym with friends to increase motivation, but save the bonding for later.