title: Incidence and predictors of exertional hyperthermia after a 15-km road race in cool environmental conditions.
abstract: OBJECTIVE
  Current knowledge about the incidence and risk factors for exertional hyperthermia (core body temperature ≥40°C) is predominantly based on military populations or small-sized studies in athletes. We assessed the incidence of exertional hyperthermia in 227 participants of a 15-km running race, and identified predictors for exertional hyperthermia.
  
  
  METHODS
  Observational study.
  
  
  METHODS
  We measured intestinal core body temperature before and immediately after the race. To identify predictive factors of maximum core body temperature, we entered sex, age, BMI, post-finish dehydration, number of training weeks, fluid intake before and during the race, finish time, and core body temperature change during warming-up into a backward linear regression analysis. Additionally, two subgroups of hyperthermic and non-hyperthermic participants were compared.
  
  
  RESULTS
  In a WBGT of 11°C, core body temperature increased from 37.6±0.4°C at baseline to 37.8±0.4°C after warming-up, and 39.2±0.7°C at the finish. A total of 15% of all participants had exertional hyperthermia at the finish. Age, BMI, fluid intake before the race and the core body temperature change during warming-up significantly predicted maximal core body temperature (p<0.001). Participants with hyperthermia at the finish line had a significantly greater core body temperature rise (p<0.01) during the warming-up compared to non-hyperthermic peers, but similar race times (p=0.46).
  
  
  CONCLUSIONS
  15% of the recreational runners developed exertional hyperthermia, whilst core body temperature change during the warming-up was identified as strongest predictor for core body temperature at the finish. This study emphasizes that exertional hyperthermia is a common phenomenon in recreational athletes, and can be partially predicted.
authors.affiliation: Department of Physiology, Radboud University Medical Centre, the Netherlands.
authors.forename: Matthijs T W
authors.initials: MT
authors.lastname: Veltmeijer
authors.affiliation: Department of Physiology, Radboud University Medical Centre, the Netherlands; Henry Low Heart Centre, Department of Cardiology, Hartford Hospital, USA.
authors.forename: Thijs M H
authors.initials: TM
authors.lastname: Eijsvogels
authors.affiliation: Department of Physiology, Radboud University Medical Centre, the Netherlands; Research Institute for Sport and Exercise Science, Liverpool John Moores University, United Kingdom.
authors.forename: Dick H J
authors.initials: DH
authors.lastname: Thijssen
authors.affiliation: Department of Physiology, Radboud University Medical Centre, the Netherlands. Electronic address: Maria.Hopman@Radboudumc.nl.
authors.forename: Maria T E
authors.initials: MT
authors.lastname: Hopman
mesh_terms: D000328:Adult; D000367:Age Factors; D015992:Body Mass Index; D001831:Body Temperature; D004326:Drinking; D005260:Female; D018882:Heat Stress Disorders / Q000453:epidemiology* / Q000209:etiology; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D005082:Physical Exertion / Q000502:physiology*; D012307:Risk Factors; D012420:Running / Q000502:physiology*; D013696:Temperature; D063996:Warm-Up Exercise / Q000502:physiology
keywords: Body temperature; Body temperature regulation; Exercise; Heat stress disorders; Heatstroke