Voluntary Cooling during Exercise Is Augmented in People with Multiple Sclerosis Who Experience Heat Sensitivity

Introduction: We tested the hypothesis that people with multiple sclerosis (MS) who experience heat sensitivity voluntarily engage in cool-seeking behavior during exercise to a greater extent than healthy controls. Methods: In a 27.0 degrees C +/- 0.2 degrees C, 41% +/- 2% RH environment, seven participants with relapsing-remitting MS who exhibited heat sensitivity and seven healthy controls completed two randomized trials cycling for 40 min (EX) at 3.5W.kg(-1) metabolic heat production, followed by 30 min recovery (REC). In one trial, participants were restricted from engaging in cooling (CON). In the other trial, participants voluntarily pressed a button to receive 2 min of similar to 2 degrees Cwater perfusing a top (COOL). Mean skin and core temperatures and mean skin wettedness were recorded continuously. Total time in cooling provided an index of cool-seeking behavior. RPE, total symptom scores (MS only), and subjective fatigue (MS only) were recorded every 10 min. Results: Core temperature (+0.5 degrees C +/- 0.1 degrees C) and skin wettedness (+0.53 +/- 0.02 a.u.) increased but were not different between groups or trials at end exercise (P = 0.196) or end recovery (P = 0.342). Mean skin temperature was reduced in COOL compared with CON at end exercise (P <= 0.002), with no differences between groups (P >= 0.532). MS spent more total time in cooling during EX (MS, 13 +/- 3 min; healthy, 7 +/- 4 min; P < 0.001) but not REC (MS, 2 +/- 1min; healthy, 0 +/- 1min; P = 0.496). RPE was greater at end exercise in MS(P = 0.001). Total symptom scores increased during exercise (P = 0.005) but was not different between trials (P = 0.321), whereas subjective fatigue was not attenuated in the cooling trial (P = 0.065). Conclusion: Voluntary cooling is augmented in MS but does not consistently mitigate perceptions of heat-related symptoms or subjective fatigue.