Cold-Water Ingestion Improves Exercise Tolerance of Heat-Sensitive People with MS.

Purpose: Heat intolerance commonly affects the exercise capacity of people with multiple sclerosis (MS) during bouts of hot weather. Cold-water ingestion is a simple cooling strategy but its efficacy for prolonging exercise capacity with MS remains undetermined. We sought to identify whether cold-water ingestion blunts exercise-induced rises in body temperature and improves exercise tolerance in heat-sensitive individuals with MS. Methods: On two separate occasions, 20 participants (10 relapsing-remitting MS (EDSS: 1-5); 10 age-matched healthy controls (CON)) cycled at ~40% VO2max at 30[degrees]C, 30%RH until volitional exhaustion (or a maximum of 60 min). Every 15 minutes, participants ingested 3.2 mL[middle dot]kg-1 of either 1.5[degrees]C (CLD) or 37[degrees]C (NEU) water. Rectal (Tre) temperature, mean skin (Tsk) temperature, and heart rate (HR) were measured throughout. Results: All 10 CON, but only 3 of 10 MS participants completed 60 minutes of exercise in NEU trial. The remaining 7 MS participants all cycled longer (P=0.006) in CLD (46.4+/-14.2 min) compared to NEU (32.7+/-11.5 min), despite a similar absolute Tre (NEU: 37.32+/-0.34[degrees]C; CLD: 37.28+/-0.26[degrees]C; P=0.44), change in Tre (NEU: 0.38+/-0.21[degrees]C; CLD: 0.34+/-0.24[degrees]C), absolute Tsk (NEU: 34.48+/-0.47[degrees]C; CLD: 34.44+/-0.54[degrees]C; P=0.82) and HR (NEU: 114+/-20 beats[middle dot]min-1; CLD: 113+/-18 beats[middle dot]min-1; P=0.38) for the same exercise volume. Conclusions: Cold-water ingestion enhanced exercise tolerance of MS participants in the heat by ~30% despite no differences in core and mean skin temperatures or heart rate. These findings support the use of a simple cooling strategy for mitigating heat intolerance with MS, and lend insight into the potential role of cold-afferent thermoreceptors that reside in the abdomen and oral cavity in the modulation of exercise tolerance with MS in the heat. (C) 2017 American College of Sports Medicine

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