This exercise builds strength in your core, particularly emphasizing your lower abdominals. This exercise will also improve strength in the lower back and hip flexors.
Sit on the floor with your knees bent and feet flat on the floor. Lean back slightly with your hands on the floor just behind your hips.
Lift your feet off the floor but keep your knees bent. Bend your elbows and lean back more as you straighten your legs slightly. Trace the letter U with your bent knees. Try to lean back and touch your elbows to the floor at the bottom of your U.
Keep your back flat to avoid injury.
Keep your legs pulled up, off the ground, and as close to your torso as possible.