Lie on your back with your body straight and your calf muscles resting on a stability ball.
Keeping your body straight and stable, lift your hips off the ground by pressing your calves and heels into the ball.
Once in this position, bend your knee joints pulling the ball in towards your hips, then extend your knee joints pushing the ball away from your hips.
Throughout this movement, keep your hips off the ground and your trunk stable.
Repeat for the required number of repetitions and then return to the starting position.
