Primary Muscle Group: Core Muscles
Muscle groups worked in this exercise: Rectus Abdominus, Internal and External Obliques.
Preparation: Start by sitting on the ball with your knees bent and feet flat on the floor. Slowly walk your feet forward as you slide your torso down the ball. Your trunk should be parallel to the floor. Just let your hips clear the ball and let your lower back press into the ball; cross your arms over your chest.
Breathing: Exhale as you lift. Inhale as you relax back to starting point.
Execution: Because this is an oblique torso lift, you'll need to place your right palm behind your head, taking care that your right elbow is out to the side. Place your left hand on your belly and just feel those abs contract as they work to stabilize you! Tuck in your tailbone and make the torso lift come from your hips. Slowly lift your upper body to the left and release back to neutral. Remember to switch sides.
Here are a few suggested alternative exercises:Ab CrunchAb Crunch - MachineAb Crunch ObliquesBall Crunch TraditionalDouble CrunchDumbbell Side BendsKneeling Cable CrunchKneeling Oblique TwistLateral Bend with Barbell