There is a theory in quantum mechanics sometimes called Heisenbergs Uncertainty Principle. It states that it is impossible to measure the position and momentum of an atom without affecting the overall system.
I believe this theorem can be extended to Parkinson's patients who are tested by their professionals or participate in studies on effectiveness of medications. I find my symptoms magnify when put under pressure. I recently participated in a study and when asked to perform a series of activities within a minute my mind went blank and the shakes started. This affected subsequent tests and I feel distorts the results. I am interested whether other Parkinson's persons have had similar experiences.