Therefore, the preliminary results of the pilot METEX-PD clinical trial will represent the prerequisite for the development of a rigorous multicenter randomized controlled trial with an appropriate sample size to investigate the molecular mechanisms of selected NFs, such as BDNF, IGF-1, or irisin, driving the disease-modifying effects in people with PD performing a defined dosage of structured exercise. Here, BDNF is linked to Parkinson disease.