Patients with Parkinson's disease (PD) have a reduced physical activity level, although exercise is especially recommended in this population [1] . Besides, motor and non-motor symptoms may also interfere with the ability to produce strenuous efforts. Yet, their baseline performances and the response to physical reconditioning have not been thoroughly investigated. The cross-sectional part of this study investigates different aspects of physical fitness of patients suffering from mild-to-moderate PD. The second part investigates the response to physical reconditioning. Sixty PD patients and 47 healthy controls (HC) matched for demographic features were tested for aerobic performances and muscle strength. Peak work load (PWL) and peak oxygen consumption (VO 2 peak) were assessed in both groups during an incremental cycle exercise test. Isokinetic knee muscle strength (IKMS) was also tested for the extensor and flexor muscles at 60° and 180°.s −1 . Subgroups of PD patients were also allocated to 12 weeks of strength training (ST, n = 17), aerobic training (AE, n = 20) or standard care control intervention ( n = 15). In comparison to HC, PD patients showed reduced PWL and VO 2 peak (respectively −19% and −14%, P ≤ 0.003). PD patients showed reduced IKMS of flexor muscles (from −17 to −24%, P ≤ 0.001), and reduced IKMS only for the most affected side of extensor muscles (−13%, P ≤ 0.015). Eighty-eight percent and 80% of the trained patients respectively completed the ST and the AE interventions. No major complication occurred during the interventions. The AE group improved PWL (+18%, P = 0.001) and VO 2 peak (+12%, P = 0.033). The ST group improved IKMS of flexors (+22–25%, P ≤ 0.02), IKMS of extensors only for the most affected side (+10–17%, P < 0.05), and PWL (+16%, P < 0.001). Aerobic and strength performances are both affected by PD. However, physical reconditioning is feasible and improves fitness of PD patients.