I am not medically trained . So do not undertake any of my suggestions without consulting your doctor or PD nurse.
As running and general fitness is the main reason for my always " looking for help and assistance" I came across Creatine. It's useful in maintaining muscle strength in sports and also has been trialed for PWP. The Parkinson's trial was non committal in its results and was closed down. But it is extensively used in sport. So I am giving it a try !! I am currently in training for an off road duathalon so I will let you know if it is beneficial . Mike