Next to complex motor deficits, people with Parkinson's disease and Multiple Sclerosis experience highly disabling non-motor symptoms; for example, anxiety and depression, cognitive decline, fatigue, and sleep problems. Physical training is increasingly recognized as an assisting and, importantly, safe therapy for these patients to alleviate disease burden. However, the optimal dose (i.e., type, frequency, intensity, duration) of exercise has not yet been established. This study aims to investigate differences in response patterns of motor and non-motor symptoms, blood-based biomarkers of neuroplasticity and neurodegeneration, as well as functional brain connectivity to eight weeks of high intensity interval training \[2x/week, \~30 min/session\], continuous aerobic training \[2x/week, \~50 min/session\], or movement advice \[+3000 steps/day for 5 days/week monitored with an activity tracker\]. Frequently repeated assessment of outcomes measures will be conducted.
