This is a variation on the pelvic lift for your buttocks. Lie down. Keep your arms neutral to your sides. Use your lower abdominal muscles to keep your lower back to the floor.This works out these muscles. Now lift your hips off the floor. At this position, "close" your legs so that your knees touch. This is one repetitions. Do five sets of ten repetitions.
Disclaimer: None of the above information can be taken as a substitute for advice from a medical professional such as a physician.
My third book, Pocket Guide to Fitness, is available on www.louizapatsis.com, http://www.authorhouse.com, www.bn.com and http://www.amazon.com. If you look up my name on those Web sites, you will find my other books The Boy in a Wheelchair and Life, Work and Play: Poems and Short Stories.