Exercise at high intensity (between 60 and 80% of maximal heart rate) in people with PD seems to promote an endogenous increase of neurotrophic factors such as brain-derived neurotrophic factor (BDNF), glial derived neurotrophic factor (GDNF), insulin-like growth factor-3 (IGF3) and neurotransmitters such as dopamine and serotonin. The gene discussed is GDNF; the disease is Parkinson disease.