Hamstring rolls on the ball

( Ben Torres, For the Chicago Tribune / December 20, 2012 )

Find an exercise ball and lay on your back. If you don't have a ball, you may use a stool or a chair — but you should skip the rolling portion of the exercise.

Place the ball underneath your heels so that your legs are lifted in the air. Place your arms to your sides and press down into the ground until you can lift your pelvis off the floor. At this point all of your leg muscles should be fired up and your feet should be flexed. Keep pressing into the floor and try to keep your hips lifting high as you bring your heels closer to your bottom and back out again. If done successfully, your ball should be rolling along the floor.