Circulatory responses at the onset of handgrip exercise in patients with Parkinson's disease.

Abstract

What is the central question of this study? The initial circulatory response to isometric exercise in young healthy subjects is thought to be cholinergically mediated. Do patients with Parkinson's disease, a specific population known to present cholinergic dysfunction, present impairment in these initial circulatory responses? What is the main finding and its importance? The initial reduction in total peripheral resistance was absent in patients with Parkinson's disease and in older subjects, which augmented the pressor response at the onset of isometric handgrip exercise. Given that cholinergic mechanisms play an important role in the circulatory responses at the onset of isometric exercise in humans, our data suggest that cholinergic mechanisms might be compromised with ageing. Physical exercise has been used as coping strategy for Parkinson's disease (PD). Thus, a better understanding of circulatory responses to exercise in this population is warranted. During the onset of isometric handgrip (IHG) exercise there is an increase in blood pressure (BP) and a reduction in the total peripheral resistance (TPR) in young subjects. This immediate reduction of TPR is thought to be mediated by a cholinergic mechanism. Given that PD also affects cholinergic neurons, we hypothesized that patients with PD would present blunted circulatory responses at the onset of IHG exercise. Mean BP, stroke volume, heart rate, cardiac output and TPR were measured during performance of 20s of IHG at 40% maximal voluntary contraction in 12 patients with PD (66±2years old, 171±7cm, 74±7kg), 11 older subjects (65±9years old, 171±7cm, 74±10kg) and 10 young subjects (21±1years old, 178±6cm, 79±9kg). Isometric handgrip elicited an augmented BP increase in patients with PD and older subjects at 10 and 20s compared with young subjects. However, the BP augmentation was lower at 20s in patients with PD. The IHG-induced reduction in TPR was attenuated in patients with PD and older subjects compared with young subjects. Our results show that the circulatory responses at the onset of IHG are impaired in patients with PD and older subjects. Overall, these findings suggest that the cholinergic mechanism might be compromised with ageing.