This seemingly simple exercise is a lot more challenging than it looks. "Shifting your weight back mere inches takes core strength and balance, and holding yourself in the position works your upper and lower body isometrically," says Tamilee Webb, who includes this move on her new DVD, Tight on Time: Body Blast ($14.99; To help you stay balanced, contract your core as you hold the position and find a focal point on the ground.

You'll Need: A yoga or exercise mat will help cushion your knees if you're doing this move on a hard surface.

Workout Details: Do 2 or 3 sets of 3 to 6 reps as part of your regular strength program. Beginners, do 1 or 2 sets.

Make It Harder: While both arms are extended, tilt your torso from side to side, as if your arms were airplane wings.