This exercise works the lower and upper sections of the abs.
Lie down into supine position on the ground with straight arms and legs; place the Fit-ball above your head with straight arms. In phase one lift your legs simultaneously and the ball with your straight arms while also your shoulder blades elevate from the ground then move the ball in an arch and place it between your ankles and then let your legs go down towards the ground. Pay attention that you should not lie down back to the ground, you should hold yourself slightly above the ground and the ball should not touch the ground either. Moving alongside the same arch you should pass the ball from your legs to your hands and approach the ground. Repeat the exercise several times.