The importance of keeping cool: Reply regarding the Wilderness Medical Society practice guidelines for the prevention and treatment of heat-related illness.

water retention from the overconsumption of fluids or sustained consumption beyond the capacity for urinary free water excretion. EAH is not uncommon with considerable weight loss in some environments, but symptomatic cases are generally associated with weight gain and weight loss of less than 3% of body weight. As noted in the WMS Practice Guidelines for EAH, athletes should be encouraged to drink to thirst, and strive for a weight loss of 2% to 4% during prolonged exercise. Recommendations to avoid more than 2% weight loss serve to promote the overconsumption of fluids. The issues we raise are not trivial, as the failure to prevent and appropriately manage EAH can mean the difference between life and death. We hope that by highlighting the potential dangers of overhydration and use of intravenous isotonic or hypotonic saline in those with EAH, your readers will be better prepared to appropriately advise endurance athletes about hydration and make better medical decisions when faced with a potential case of EAH.