While seated on the floor raise both legs, about a foot off of the ground. Alternate your legs up and down as if kicking in water, and at the same time pass the medicine ball through your legs as they are moving. As one leg drops, the ball will pass over the leg that is raised, then repeat with the alternate leg. Think dribbling a basketball through your legs without actually bouncing it.
Depending upon how high or low your back is raised off the ground, you will feel pressure in different areas. Find the position where you feel your abs are totally engaged, so that your back isn't taking all of the work.
Primary Muscle
