Swiss ball crunch

Instructions

Lie your back on a Swiss ball. The bottom of your back should be at the top of the ball. Your feet are flat on the ground. Your arms are on your chest. This is the starting position.
Raise your upper body until you feel a good contraction of your abs. The bottom of your back should stay in contact with the ball.
Hold the position for one second and slowly return to the starting position.

Muscles