Get a medium-sized Swiss ball and place the small of your back on it. Your feet are on the floor, legs at a smaller than 90-degree angle. Relax your arms and upper body. Lift your thighs by straightening your legs. Your back will move back over the Swiss ball. Balance and keep it behind you back. You will notice that you are using your hamstrings. Your knee angle is now over 90 degrees. Do five sets of ten repetitions. Get some water. you may be dizzy. ;)
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.