Sit on a mat and place a stability ball between your legs (at your calves/ankles). Squeezing the ball in place, lie backonto the floor, and extend legs straight up into the air. Keep knees slightly bent and arms out to the sides for support.
Keeping upper body and glutes stationary, lower your legs down to the right, as close to the ground as possible. Return to start and repeat to the left side to complete one rep.
Make sure your back stays firmly planted and that your legs swing in line with your hips (not above or below them).
Muscles Worked: Abs, Obliques, Hips