When performing a Pilates Criss Cross, hold a light pair of toning balls in the hands near the side of the head instead of clasping the hands behind the head. Lie down on the floor, legs bent and lifted above your hips. Tuck in the abdominal muscles and lift the head and shoulders off the floor. Extend one leg out while the other pulls in toward your chest. Switch legs, pushing the opposite leg outward while bringing the other knee toward your chest.