Lie on your back with your knees bent and feet flat on the floor.
Place a slider under each heel.
Your knees and feet should be hips distance apart.
Flex your feet, and tighten your abdominal muscles.
Tighten your buttock muscles and lift your hips from the floor.
You should have a straight line from your chest to your knees.
Rapidly, alternately slide your heels in towards your buttock.
As one leg bends, straighten the other leg.
Continue this motion, ensuring your legs remain hips distance apart and your knees point directly up to the ceiling.