Heart Rate and VO₂Kinetics in Patients with Parkinson’s Disease and Orthostatic Hypotension

During exercise, a lower heart rate (HR) has been identified in people with Parkinson’s disease (PD), which is referred to as “chronotropic incompetence” and is often attributed to disease-related impairments in autonomic function. This autonomic dysfunction is likely to slow HR and oxygen uptake (VO 2 ) during exercise initiation, which would result in utilization of anaerobic metabolism, muscle metabolite accumulation, and compromise resistance to neuromuscular fatigue which all negatively impact exercise tolerance. However, little is known about how HR and VO 2 are affected by more severe PD-related impairments in autonomic function, as observed in PD with orthostatic hypotension (PD+OH). Therefore, we quantified and compared the HR and VO 2 response to locomotor exercise in PD+OH and healthy, age-matched adults (CON) and hypothesized that the kinetics of both are slower in PD+OH. HR and VO 2 data were continuously collected during 6-minute bouts of semi-recumbent leg cycling exercise at 1) moderate (80% of gas exchange threshold) and 2) heavy (30% above gas exchange threshold) intensity work rates. Two trials at each intensity were ensemble averaged and fit with monoexponential curves, from which mean response time was calculated. HR kinetics analysis revealed a slower mean response time to the heavy intensity work rate in PD+OH compared to CON (106 ±41 s vs 75 ±40 s, p=0.032), while moderate intensity did not elicit differences between groups (59 ±20 s vs 49 ±29 s, p=0.155). Analysis of VO 2 data identified a slower mean response time for PD+OH compared to CON in both moderate (74 ±11 s vs 67 ±10 s, p=0.045) and heavy (76 ±22 s vs 61 ±10 s, p=0.021) intensity exercise. The results suggest that, in addition to previously identified chronotropic incompetence, PD+OH also exhibit a slower HR and VO 2 time-course response to exercise, particularly in the heavy intensity domain. Due to the metabolic demand of exercise requiring a prompt increase in oxygen delivery, slower kinetic responses may contribute to higher reliance on anaerobic metabolism and influence exercise tolerance or fatigue. This impairment may be a limiting factor the participation of PD+OH in exercise-based therapies or during repeated cardiovascular stresses during activities of daily living. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.