Heat illness in athletes: the dangerous combination of heat, humidity and exercise

Sports Med. 2004;34(1):9-16. doi: 10.2165/00007256-200434010-00002.


In 1980, 1700 people died during a prolonged heat wave in a region under-prepared for heat illness prevention. Dramatically underreported, heat-related pathology contributes to significant morbidity as well as occasional mortality in athletic, elderly, paediatric and disabled populations. Among US high school athletes, heat illness is the third leading cause of death. Significant risk factors for heat illness include dehydration, hot and humid climate, obesity, low physical fitness, lack of acclimatisation, previous history of heat stroke, sleep deprivation, medications (especially diuretics or antidepressants), sweat gland dysfunction, and upper respiratory or gastrointestinal illness. Many of these risk factors can be addressed with education and awareness of patients at risk. Dehydration, with fluid loss occasionally as high as 6-10% of bodyweight, appears to be one of the most common risk factors for heat illness in patients exercising in the heat. Core body temperature has been shown to rise an additional 0.15-0.2 degrees C for every 1% of bodyweight lost to dehydration during exercise. Identifying athletes at risk, limiting environmental exposure, and monitoring closely for signs and symptoms are all important components of preventing heat illness. However, monitoring hydration status and early intervention may be the most important factors in preventing severe heat illness.

Publication types

  • Review

MeSH terms

  • Adaptation, Physiological
  • Dehydration
  • Exercise / physiology*
  • Heat Stress Disorders / classification
  • Heat Stress Disorders / etiology*
  • Hot Temperature / adverse effects*
  • Humans
  • Humidity / adverse effects
  • Risk Factors
  • Sports / physiology*