I just watched a remarkable video on Youtube. The title is Cycling for Freezing Gait in Parkinson`s Disease. A man in his late 50s has advanced Parkinson`s disease. He has constant tremors in his arms, and can only walk a few steps before falling over. He spends much of his life in a wheel chair. And yet he demonstrates that he can still ride a bicycle , perfectly, without any problem. Perhaps some kind person can provide a link?