Listen up maggot! You WILL exercise regularly for 10-15 minutes a day at a sensible pace, and you WILL like it!

RODALE NEWS, EMMAUS, PA—It's January. You're energized, motivated, and pumped to finally get fit and lose weight, preferably fast. Your enthusiasm is equally matched by a buff, confident trainer promising to whip your couch-potato behind into shape with a miracle, eight-week boot camp–style class. But before you reach for your credit card, it's important to understand that this type of intense exercise program is not the smartest way to ease back onto the workout scene. "The intensity is much too high for the average person," says Walter Thompson, PhD, regents' professor of kinesiology and health at Georgia State University.

In fact, boot camps—intense group workouts led by an instructor, often in a military, drill-sergeant style—can backfire. "Jumping into a workout routine that is too vigorous can be a fast track back to the couch," explains Michele Stanten, fitness director for Prevention magazine. "An injury or sore muscles can make it tough to work out consistently, which is the key to success. You'll be more likely to stick to a routine that you enjoy and feels good."

THE DETAILS: The latest IDEA Fitness Programs & Equipment Trends Report found that personal trainers are increasingly offering boot camp–style classes in addition to one-on-one fitness services, most likely the result of the economy (standard personal training is more expensive) and in response to popular boot camp–type fitness programs on TV shows depicting fast weight-loss results. But it's a trend that's not likely to lead to more fitness. "A lot of people are going to get hurt because the consumer right now is overzealous about physical activity," explains Thompson. "Everyone has resolutions, and most are to lose weight and exercise more."