The Reverse Lunge
What it does: Strengthens the buttocks, thighs, and calves; stretches the hips; improves balance.
How to do it: Stand on a step stool or the bottom step of a staircase. Take a large step back with your right leg, landing on the ball of your foot; bring both fists near your waist, elbows back. Bend both knees as much as 90 degrees, with your left knee over your left foot. Step back up to the stool. Switch legs.