Primary Muscle Group: Abdominals
Muscle groups worked in this exercise: Abdominus Rectus, Internal and External Obliques and Transversalis.
Preparation: Lying on your back, place both heels on the ball with your knees slightly bent. Arms are at your sides.
Breathing: Exhale while lifting shoulders up; inhale as you lower back down to the floor.
Execution: Extend your arms toward your knees. This action makes the ball shift slightly and force you to use your leg muscles to keep it steady!
Comments: If you're a beginner, this is a great way to increase your strength and reach the goal of the traditional crunch on top of the ball.