Training-induced increment in maximal oxygen consumption (V̇O₂max) derives from central and peripheral cardiovascular adaptations in healthy individuals. Whether such a response is altered in Parkinson’s disease (PD), a condition that may cause cardiovascular autonomic dysfunction, remains unclear. This study investigated changes in V̇O₂max and lower-limb muscle oxygen (O2) extraction capacity following moderate-intensity continuous training (MICT) in PD patients. Seven male PD patients (age 70.4 ± 7.0 years, Hoehn and Yahr stage 2) participated in a 4-month, bi-weekly MICT. Before and after the intervention, resting heart rate (RHR) was assessed, and a cardiopulmonary exercise test (CPET) was performed to determine V̇O₂max, maximal power output (POmax), and maximal heart rate (HRmax). During the CPET, peak concentration changes of deoxygenated haemoglobin (Hb) and myoglobin (Mb) Δ[deoxy(Hb + Mb)]peak in the vastus lateralis, and taken as an index of O2 extraction, were assessed with a functional near-infrared spectroscopy (fNIRS). Comparisons with the Paired Samples T-Test or the corresponding non-parametric Wilcoxon Test were performed to assess changes in outcomes from pre- to post-MICT, while Pearson correlation was computed between Δ[deoxy(Hb + Mb)]peak and V̇O2max. V̇O₂max (p = 0.006), HRmax (p = 0.03), and POmax (p = 0.005) were significantly increased following MICT, while RHR (p = 0.66) and Δ[deoxy(Hb + Mb)]peak (p = 0.114) were not. Pearson correlational analysis between Δ[deoxy(Hb + Mb)]peak and V̇O₂max was significant pre- (r = 0.78, p textless 0.05), but not post-MICT (r = −0.11, p textgreater 0.05). The significant improvement in V̇O₂max and HRmax, along with POmax, would suggest that central, rather than peripheral adaptations, contributed to V̇O₂max amelioration. Future studies involving a larger cohort, a physical exercise intervention aligned with cardiovascular health guidelines, additional NIRS-derived parameters to minimise variability related to exercise-induced blood flow, and CPET familiarisation will be necessary to confirm or refute these preliminary findings.