ABS AND CORE
Lie on your back and pull your right knee up to your chest whilst holding your left leg straight out six inches off the ground.
The higher you pull your knee up to your chest, the least pressure you will exert on your lower back.
Place your finger tips on the side of your head. Place your left elbow on your right knee (or as close as you can get it) and your right elbow on the ground.
As you draw your left leg in and straighten your right leg, twist your upper body so your elbows switch places and you right elbow ends on your left leg, whilst your left elbow ends on the ground.
Breath all the time, keep your abs tight throughout the exercise and keep your head off the ground.