1. Lie flat on floor with hands by side and knees bent.
Your feet should be placed around shoulder width as starting posititon.
2. Push with your heels, lift your hips off the floor while back straight.
Breathe out as your perform this part and hold at top for a second.
3. Slowly go back to starting position as your breathe in
This is an excellent exercise
for strengthening the bottom,
back of legs and also core.
It is an excellent exercise to perform
if you have any back injuries.
Article from here
*Don't overdo it*