Single Leg Bend
How to do it: Stand barefoot next to a chair with your left hand on its back and your right arm extending out to the side, palm down. Lift your right thigh till the knee is bent at nearly 90 degrees; point your toes. Bend your left leg and slowly sink down, keeping your back straight. Push up, slowly straightening the left leg to the starting position. Repeat five times, then switch legs.
What it does: As you work to stay balanced throughout the up-and-down bending motion, you also strengthen your core, rear end, and thighs.
Make it harder: After you bend your knee and sink down, extend your right leg forward, straight, keeping your toes pointed and your foot a few inches off the floor. Pause, then return to the starting position.