Hyperthermia and Exertional Heatstroke During Running, Cycling, Open Water Swimming, and Triathlon Events

Lawrence E Armstrong,1,2 Evan C Johnson,3 William M Adams,4– 7 John F Jardine2 1Human Performance Laboratory, Department of Kinesiology, University of Connecticut, Storrs, CT, USA; 2Korey Stringer Institute, Department of Kinesiology, University of Connecticut, Storrs, CT, USA; 3Division of Kinesiology & Health, University of Wyoming, Laramie, WY, USA; 4Department of Sports Medicine, United States Olympic & Paralympic Committee, Colorado Springs, CO, USA; 5United States Coalition for the Prevention of Illness and Injury in Sport, Colorado Springs, CO, USA; 6Department of Kinesiology, University of North Carolina at Greensboro, Greensboro, NC, USA; 7School of Sport, Exercise and Health Sciences, Loughborough University, National Centre for Sport and Exercise Medicine (NCSEM), Loughborough, UKCorrespondence: Lawrence E Armstrong, University of Connecticut, Department of Kinesiology, Human Performance Laboratory, 2095 Hillside Road, Unit 1110, Storrs, CT, 06269, USA, Email [email protected]: Few previous epidemiological studies, sports medicine position statements, and expert panel consensus reports have evaluated the similarities and differences of hyperthermia and exertional heatstroke (EHS) during endurance running, cycling, open water swimming, and triathlon competitions. Accordingly, we conducted manual online searches of the PubMed and Google Scholar databases using pre-defined inclusion criteria. The initial manual screenings of 1192 article titles and abstracts, and subsequent reviews of full-length pdf versions identified 80 articles that were acceptable for inclusion. These articles indicated that event medical teams recognized hyperthermia and EHS in the majority of running and triathlon field studies (range, 58.8 to 85.7%), whereas few reports of hyperthermia and EHS appeared in cycling and open water swimming field studies (range, 0 to 20%). Sports medicine position statements and consensus reports also exhibited these event-specific differences. Thus, we proposed mechanisms that involved physiological effector responses (sweating, increased skin blood flow) and biophysical heat transfer to the environment (evaporation, convection, radiation, and conduction). We anticipate that the above information will help race directors to distribute pre-race safety advice to athletes and will assist medical directors to better allocate medical resources (eg, staff number and skill sets, medical equipment) and optimize the management of hyperthermia and EHS.Keywords: heat illness, epidemiology, pathophysiology, thermoregulation, athlete