Stability Ball Hamstring Curl
1) Lay flat on the floor and rest your legs on the top on the ball. Place your hands either side.
2) Lift your hips up slightly and engage the core.
1) Curl your legs and bring the ball closer towards your body. The endpoint should be your lower back raised from the floor with your heels still on the ball. Your knees should be bent.
2) Pause for a second - you should be crunching the abs at this point. Slowly extend your legs and push the ball away from you to the starting position.