When performing this exercise, you'll want to keep your abdominals pulled in.
Begin lying on your back with your knees and hands up.
Initiate the exercise by extending one leg, straightening the knee and hip to bring the leg towards the ground. Only go as far as you can to maintain your back against the ground.
Your lumbar position must be maintained against the towel/floor throughout the exercise.
Keep your abdominals drawn in and tight, and return the moving leg and arm to the starting position
