While it is impossible to prove, it is my opinion that cycling has kept me out of a wheelchair. I have M.H.E. (a hereditary bone disorder) and when I was 8 or 9 years old, the docs told me I would be in a wheelchair before I was 30. I will be 55 this year, and still am not in that dang chair.
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"Whenever I see an adult riding a bicycle, I know there is hope for mankind." (H. G. Wells)