Lie on your back with your knees bent and heels 12 inches from your body.
1. Place a small piece of foam at least 3 inches thick between your knees. Draw your navel in toward your spine and squeeze the foam tightly between your knees as you raise your hips off the floor. Make sure your butt muscle is contracted and hold for a three count. Do 10-25 repetitions.
2. The same movement can be performed with a resistance band. This is an elastic band that makes the muscle work harder, tied just above your knees. Start with your knees hip distance apart and press into the band as you raise your hips and push the knees away from your midline for 10-25 repetitions.
3. Now try it on one leg. Shift the weight to your right leg as you raise the left foot off the ground. Do 10 reps on one side, repeat for the other leg.
(Text by Bruce Cohn, Globe staff graphic/Joan McLaughlin)