Lying Hamstring Curl: Lie back flat with a exercise ball under the heels. Bridge the hips and hold this position during the whole exercise. Flex feet and dig the heels into the ball and then place the arms to the side for support. Slowly roll the ball inwards as you curl the heels all the while do not bring the hips to the floor. Return slowly to the position you started in. Do 3 X 10 or 15 sets.