This exercise is intended to increase the pelvis stability challenge of the bridge as well as increase the requirements for hamstring strength.
To do this exercise you will need a mat. Start by lying on your back with your knees bent and your feet planted in the ground. Then inhale as you rock your pelvis towards your tailbone and exhale as you rock your pelvis towards your belly button and begin lifting the pelvis into the air one vertebra at a time. At the top, inhale into your chest and then exhale as you let all of the air out of your lungs let one leg float up into the air to a tabletop position. Inhale place the leg back on the ground and then exhale as you lift the other foot. Repeat these leg lifts three to five times on each side and then exhale as you lower your spine to the ground one vertebra at a time.
Things to think about
This exercise is a hamstring strengthener. If your hamstring cramps simply lower your spine to the ground straighten your leg to the ceiling with a flexed foot to stretch the hamstring.
As always maintain open hips at the top of the bridge. Be sure that as you exhale you are getting all of the air out of your lungs and that the front of the pelvis makes an even plane with the thighs.