This exercise requires upper-body strength and core stability. It activates the abs and hip muscles when bringing the ball toward the body.
Shout out to my son Ryan for producing the video clip for me.
Place your abdomen on top of the ball. Roll forward until your hands reach the floor in front of the ball. Walk your hands out until only your feet remain on top of the ball (if that is too difficult leave the entire shin on the ball for more balance). Contract the core and hold good, strong form; your body should be in a straight line from feet to head.
From the push-up position, bend at the knees and move the ball toward your chest and then back to the start position.
After you can complete 15-20 reps, move on to the next progression.
From the prone push-up position, bend at the waist so the hips elevate and the knees move closer to the torso, moving the ball toward your hands.
Extend your legs to move the ball back to the start position.
Once you can perform 15-20 consistent reps of the jackknife (phase 2), add the twist:
Lift one foot off of the ball, bend the leg at 90 degrees. Keep your abdominal contracted and slowly roll your trunk over to one side. You will roll to the point where all your weight will be on one leg.