I am 61 years old in good health and very athletic: water skiing, swimming, bikeriding. I have been diagnosed with moderate to sever spinal stenosis and degenerative disc disease. The Orthopededic surgion says I am a candidate for a 4 level lumbar fusion which would turn me into a post. How much flexibility would I lose and what are the permanent possible negative outcomes. currently I am exercising resulting in OK days and not so good days.