The New Fitness Rules

Classic Exercises Get a Modern Makeover

Squat

Old school: Don't bend your knees past 90 degrees.

New rule: It's OK to go over.

If you've sampled the barre workout craze, you know that your booty brushes the floor during endless squat variations. Why is it suddenly cool to get way down? There has been a debate among experts, but the consensus seems to be that it is a natural human movement. "Research found that if you do a squat and force yourself to keep your knees behind your toes, as in a 90-degree bend, you increase the stress on your hips by more than 1,000 percent," explains Michele Olson, PhD, a FITNESS advisory board member. "But if you allow your knees to come forward, you have only a bit more stress on your knees -- just 20 percent or so -- and significantly less pressure on the hip joint."