Τετάρτη 24 Οκτωβρίου 2018

Impaired Thermoregulatory Function during Dynamic Exercise in Multiple Sclerosis

Introduction Impairments in sudomotor function during passive whole-body heating have been reported in multiple sclerosis (MS), a demyelinating disease of the CNS that disrupts autonomic function. However, the capability of the thermoregulatory system to control body temperature during exercise has never been assessed in MS. Thus, the aim of the present study was to test the hypothesis that thermoregulatory function is impaired in MS patients compared to healthy controls (CON) exercising at similar rates of metabolic heat production. Methods Sweating and skin blood flow responses were compared between 12 individuals diagnosed with relapsing-remitting MS (9 females, 3 males) and 12 sex-, age-, mass- and BSA-matched healthy controls during a single bout of cycling exercise (rate of metabolic heat production: ~4.5 W/kg) for 60 min in a climate-controlled room (25 °C, 30% RH). Results Individuals with MS exhibited an attenuated increase in cumulative whole-body sweat loss after 30 min (MS: 72 ± 51; CON: 104 ± 37 g, p=0.04) and 60 min (MS: 209 ± 94; CON: 285 ± 62 g, p=0.02), as well as lower sweating thermosensitivity (MS: 0.49 ± 0.26; CON: 0.86 ± 0.30 mg/cm2/min/°C, p=0.049). Despite evidence for thermoregulatory dysfunction, there were no differences between MS and CON in esophageal or rectal temperatures at 30 or 60 min time points (p>0.05). Cutaneous vasculature responses were also not different in MS compared to CON (p>0.05). Conclusion Taken together, MS blunts sweating responses during exercise while cutaneous vasculature responses are preserved. Altered mechanisms of body temperature regulation in persons with MS may lead to temporary worsening of disease symptoms and limit exercise tolerance under more thermally challenging conditions. Corresponding Author: Scott L. Davis, PhD, Associate Professor, Department of Applied Physiology & Wellness, Southern Methodist University, 3101 University Blvd., Suite 163, Dallas, TX 75205. Phone: (214) 768-1028. Fax: (214) 768-4990. Email: sldavis@smu.edu This study was supported by National Heart, Lung, and Blood Institute grant R15-HL-117224 (S. L. Davis); National Multiple Sclerosis Society grants RG4043A1/1 and RG4696A3/2 (S. L. Davis); MS Research Australia Incubator grant 14-009 (O. Jay and S. L. Davis); MS Research Australia Postgraduate Fellowship 15-087 (G. K. Chaseling); and the Kuzell Institute (S. L. Davis and O. Jay). Conflicts of Interest: No conflicts of interest, financial or otherwise, are declared by the authors. The results of this study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. The results and conclusions of the study do not constitute endorsement by the American College of Sports Medicine. Accepted for publication September 2018. © 2018 American College of Sports Medicine

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