So much for the personal touch. Folks in extra-large aerobics classes—those with 70 to 90 participants—show up more often and are more fond of their classmates than exercisers in sessions of 18 to 26 people, report researchers at the University of Arizona. And individuals in extra-large classes even work out a bit harder, so they get more cardiovascular bang for their buck.
"We're conditioned to think that smaller is better," notes Arizona sports psychologist Jean Williams, Ph.D. "And that may be true if you're taking a golf class, where you need a lot of correction on your technique."
But in an activity where energy is more important than hair-trigger precision, a key motivator may be sheer excitement. And that rises with the number of participants, says Williams. "When you have so many people present, you tend to pick up their enthusiasm."
The one exception to the big-is-better rule may be very small aerobics classes—fewer than 10 participants, say. They may not provide the sheer visceral thrill of large classes, but the lack of anonymity may force you to work out hard anyway.