Crunch on Swiss Ball
Lie on a Swiss ball with your lower back pressed against the surface of the ball. Your legs should be bent at the knee and your feet should be pressed firmly against the floor. The upper torso should be hanging off the top of the ball. Your hands should be behind the back of your head. Lower your torso into a stretch position keeping the neck stationary at all times.
With the hips stationary, flex the waist by contracting the abdominals and curl the shoulders and trunk upward until you feel a nice contraction on your abdominals. The lower back should always stay in contact with the ball. Hold the contraction for a second.
Go back to the starting position and repeat the exercise according to the training plan.