https://blogs.scientificamerican.com/observations/reclaiming-control-in-the-face-of-parkinsons/

The first time I met Joe was in an empty chapel in Palo Alto, Calif. I’d come there because one of his students, a friend of mine, told me he was a medical mystery. A 77-year-old Parkinson’s patient who’d had the disease for at least 11 years but, with only a small dose of medication (carbidopa-levidopa), was able to drastically improve his motor skills and quality of life beyond what even his physicians could believe. He was now teaching Qigong and Tai Chi in the community on Wednesday afternoons in a spacious, wooden room in a church on Cowper Street.

The chapel had no pews, only a single carpet in the center. Joe, the only other person in the room, stood on the border between concrete and carpet, with a walker. Today, no other students showed up; it would just be Joe and me. Joe had been diagnosed with Parkinson’s disease (or as his neurologist Helen Brontë-Stewart calls it, PD), a neurodegenerative disorder that correlates with depletion of dopaminergic neurons in the central nervous system, resulting in slow movement, rigidity, tremors and postural instability.