Lay on top of exercise ball with legs and hands slightly apart. Place chest down so torso is wrapped over ball.
Raise arm and torso upward beside head while raising leg on opposite side up out behind body. Lower arm, torso, and leg to original position and repeat. Perform movement with opposite arm and leg.
Lift leg and arm deliberately with no jerking. Also see Alternating Bird Dog (one exercise ball).
Movement can be made easier by positioning body a bit lower on ball.
Exercise can be made more challenging by positioning ball lower toward hips or place supporting arm further away from ball.