Trunk Side Bend On Ball
Lie on your side on the ball with your arms up and your hands by your head. Cross your legs to create a stable base with both feet on the floor and your legs straight. The top leg will be in front of your body and the bottom leg behind it.
Tighten your abs and slowly lift your body upward to form a straight line. Hold for 3 seconds and slowly let yourself back down. Repeat 10 times on each side.