Lie down on your belly. Relax the upper half of your body. Do what's comfortable with your arms. Just keep your skull and spine aligned.
Keep your legs straight. Turn them so that the soles of your feet face each other. Point your feet. Lift your legs. Flex your feet. Slowly let down your legs. Repeat for five sets of ten repetitions, with each repetition including the pointed and flexed positions.
Advanced level: When you let your legs down, do so until they are about an inch off the floor, not all the way to the floor. Then raise them again.
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.