Heat Stress Challenges in Marathon vs. Ultra-Endurance Running

Abstract

Several studies have investigated the effect of hot and humid ambient conditions on running exercise up to the marathon. However, studies on exercise longer than marathon are sparse. Events exceeding 6 hours can be defined as ultra-marathons and have variable characteristics (e.g. distance, elevation profile, technicity of the terrain, altitude, night running) making hazardous the transposition of the current knowledge obtained in marathon to ultra-marathon. Thus, the aim of this manuscript was to discuss the potential differences between marathon and ultra-marathon in terms of thermoregulatory challenges. The high running intensity (especially for the fastest runners), the urban context with high albedo effect materials, and the hot microclimate self-generated in mass-participation events (especially for the average to slow runners) are specific risk factors associated with marathon running in hot environments. Uphill running/walking (sometimes with poles), exotic destination with long-haul travel, desert environment and the necessity to sustain a thermoregulatory and sweating responses for several days are risk factors more specific to ultra-marathon. These differences called for specific research on the effect of hot ambient conditions in ultra-endurance disciplines to create appropriated recommendations.