The expression “citius, fortius, altius” (Latin for “faster, higher, stronger”) is the Olympic motto indicating what is required to achieve athletic excellence. Which of these skills is most important to reach an optimal personal performance was not specified by its creator, Pierre de Coubertin, but a combination is presumably optimal. Similar issues are at play when trying to understand the beneficial outcomes of physical activity on general health and motor functioning in people with neurological disorders such as Parkinson disease (PD). One component of physical activity, namely its intensity, has thus far been studied best. For persons with PD, intense physical activity (also referred to as aerobic exercise) has positive associations with aerobic capacity and motor signs.1 Intense physical activity may also improve nonmotor symptoms, such as cognitive functioning and sleep.1 In addition to these symptomatic outcomes, there is some early but converging evidence that intense physical activity may also exert disease-modifying effects in PD. Specifically, phase 2 exercise trials have shown stabilization of motor symptoms following 6 months of aerobic exercise.2,3 A higher intensity was more effective than a moderate intensity.3 The precise working mechanisms of aerobic exercise in PD remain unknown, although several modes of action have been suggested.4-6 Specifically, preliminary neuroimaging evidence from a phase 2 trial suggests that engaging in regular high-intensity aerobic exercise may induce preservation of basal ganglia networks.7 Similar protective effects of aerobic exercise on the basal ganglia network have been observed in rodents with experimental parkinsonism.8