This makes more sense to me than anything I've read or experienced. Reprinted with her permission.

Why the Italian Man Can Ride a Bicycle
(Cycling for Freezing Gait in Parkinson's Disease - YouTube)
by
Pamela G. Quinn

When I am “off”my legs feel almost hollow. They exist half way between sensation and paralysis. They lack full sensory input and output. It’s a very strange feeling and hard to describe; it’s unlike anything I felt in my pre-Parkinson years. And yet it makes sense to lose sense when you have a neurological disorder. You would think that the ability to feel the spectrum of sensation-- not just the act of touching -- would be one of the five traditional senses.

When you see a person with Parkinson’s disease standing alone, there is something crumpled about the whole body; the knees are slightly bent, the upper back is slightly curved, everything is held but not extended. This whole body slump is due to the fact that we’ve lost the ability to lengthen and extend by pushing against something, (actually, there is passive curvature – when we’re unable to feel resistance- and there is active curvature, when the shortening of the abdominal muscles pull the front down,)

I know about how to achieve good posture from my 20 years as a professional dancer: dancers elongate and strengthen their spines and cultivate strong posture because they know how to push against and connect to the floor. - it’s sort of like an ongoing isometric.

We see a kind of crumpled posture in the Italian man who freezes repeatedly before he gets on the bike, (we all know who I’m referring to: Cycling for Freezing Gait in Parkinson's Disease - YouTube) But when he rides the bike, it’s not just the legs that change; his whole body changes. His legs move, his torso extends, he can even turn his head while riding, Why such total transformation? Because the bike both allows and forces him to
push with his legs; the very mechanism provides the extra stimulus his legs need to function properly. The rotation of the pedals gives him a reason to push – a cue if you will-and the push-away action reverberates through his spine. Having something to push against reactivates his sensorial system through a kinesthetic demand from the pedals in a way the floor cannot.

It also makes sense that activating the legs is key to helping PD. Our legs are our motor system, and the festination that occurs with our freezing and walking is due to the fact that our upper body is ready to move before our lower body, so we initiate movement by leaning forward and those little steps that ensue are an attempt to prevent us from falling, The lower half of the body is slow, the upper less so.. When the body operates with these different tempos, we have problems.

We see the Italian man before the bike but not after his ride..... my suspicion is that after his ride, his gait and posture revert back to their former state without the impetus of the pressure cue from the pedals.

Last month my son called me from the subway entrance saying he had forgotten his wallet and had no metro card or money to get him to school. I was in my PJ’s and hadn’t taken my medication yet, But I knew how to get to him. I got dressed, hopped on my bike and pedaled eight minutes to the subway. On my way home I was smiling, thankful for the wonderful Italian man who showed me how to help my son.

My work remains unfinished, however,. We know from Jay Albert’s studies at the Cleveland Clinic that prolonged biking at certain rpms can have lasting effects - that we can carry our head high and walk well even after we get off the bike, having stored our ability to extend our bodies by repeatedly having something to push against, which in turn activates our sensorial capacity.

My training has just begun.