BDNF and Parkinson disease: Based on animal studies, several mechanisms are believed to explain the effects of physical activity as an adjuvant therapy against PD: increased synthesis and release of neurotrophins (17–20), restoration of the equilibrium between the level and interactions of neurotransmitters (21, 22), increased resistance to oxidative stress (23), reduced inflammatory process in the brain (21, 24, 25), and enhanced synaptogenesis (26), angiogenesis (27), and neurogenesis (28, 29) (Figure 1).