Effects of acute whole-body and lower limb heating on hemodynamic responses to walking in patients with peripheral artery disease
Authors: Hamaoka Takuto , Leuenberger Urs , Blaha Cheryl , Luck Jonathan , Dalton Paul , Hamaoka Mami , Aziz Faisal 
Published: May 2024

Background: The exercise pressor reflex is exaggerated in patients with peripheral artery disease (PAD). There has been speculation regarding cardiovascular benefits of heating therapy for patients with PAD. The impact of acute leg heating and whole-body heating on hemodynamic responses during walking remains incompletely understood. The purpose of this study was to evaluate the effects of acute whole-body and lower leg heating on hemodynamic responses to walking in both patients with PAD and healthy control subjects. Hypothesis: We hypothesized that both acute whole-body and lower leg heating would attenuate the pressor response to walking in patients with PAD. Methods: 10 PAD patients (68 ± 7 yrs; Male/Female, N = 7/3) and 8 age-matched healthy control subjects (64 ± 5 yrs, Male/Female, N = 5/3) participated in this study. The treadmill walking test followed the Gardner protocol, involving a constant speed of 2 mph with a 2%-grade increment every 2 minutes. The study encompassed 3 trials/visits: 1) non-heating (control), 2) post leg heating, and 3) post whole-body heating. The order of these visits was randomized. During the leg heating visit, the subjects' lower limbs (below the knees) were immersed in warm water (40-42℃) for 30 minutes. Whole-body heating was administered by outfitting the subjects in a tube-lined heating suit until their internal temperature increased by 0.3℃ (~ 45 min). Hemodynamic responses were assessed by comparing the average systolic blood pressure (SBP) and heart rate (HR) during the last 3 stages of treadmill walking with baseline values. Results: Resting SBP and HR did not exhibit significant differences between groups (all P > 0.05). During the control visit, the increase in SBP due to treadmill walking was significantly (P = 0.04) higher in patients with PAD than in healthy subjects. No group differences were observed in the increase in HR by treadmill walking. The responses in SBP and HR to treadmill walking, following leg heating, were comparable to those observed in the control visit for both groups (all P > 0.05). Compared to the control visit, whole-body heating significantly attenuated the SBP (ΔSBP%, 32.9 ± 13.5 vs. 21.3 ± 9.5 %, P = 0.02) and HR responses (ΔHR%, 61.6 ± 24.3 vs. 42.7 ± 15.6 %, P = 0.03) to treadmill walking in PAD. However, in healthy subjects after whole-body heating, these responses were not different from the control visit (both P > 0.05). Neither whole-body nor leg heating had any impact on the walking distance in patients with PAD. Discussion and Conclusion: Acute whole-body heating significantly attenuated the pressor response to walking in patients with PAD, while lower leg heating exhibited no such impact. These findings suggest potential benefits of acute whole-body heating for patients with PAD. We speculate that the comprehensive systemic adjustments by whole-body heat exposure play a pivotal role in improving the exaggerated pressor response to exercise in PAD. Conversely, local lower leg heating, as observed in our study, seems insuffcient to change the hemodynamic response to exercise in patients with PAD. This study was supported by NIH R01 HL141198 and R01 HL144781. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.