You may have seen wedges at a gym. See my prior two posts. Lie down on a wedge with your head on the lower level of a "wedge". You may want to use a towel so you won't be on the floor. Use a medicine ball or bar at a weight that works you out, yet you are able to do. With your head, neck and back aligned in a straight fashion, holding the medicine ball or bar with arms straight over your head, come up for a sit up until your chest is about half a foot from your knees. Repeat for four sets of ten repetitions. If you are a beginner with this exercise, hold the medicine ball or bar with bent arms between your ribcage and your belly button.
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.