THE RELATION BETWEEN ENVIRONMENTAL CONDITIONS AND THE OCCURRENCE OF EXERTIONAL HEAT DISORDERS DURING PHYSICAL ACTIVITY

Abstract

Deaths and morbidity due to heat disorders during physical activity were gleaned from newspaper reports between 1970 and 1990. The environmental temperatures (dry-bulb temperature and relative humidity) recorded at the closest meteorological observatory at the time of occurrence were used to calculate the wet-bulb temperature and WBGT (wet-bulb globe temperature), and the relationship between heat disorders and environmental temperature was analyzed.
During the 21-year period, 108 cases of heat disorders (91 deaths and 477 casualties) were reported in newspapers. Of the 91 deaths, 9 were in females and 82 were in males, and mean ages were 23.3 years, females and 19.0 years, males.
It was possible to record the environmental conditions at the time of the heat disorder in 99 cases. The results indicated that almost all disorders occurred at ranges higher than 25.5°C, dry-bulb temperature, and 20.0°C, wet-bulb temperature, 40% relative humidity, and 24.0°C, WBGT. The mean WBGT was 28°C at physiological intensities less than 12-RMR (Relative Metabolic Rate) and 25.8°C at RMR higher than 15.
The seasonal distribution was from April to November. In cases observed in April, May and November, abrupt rises in WBGT in the 1.2-3.4°C range were observed on the day of occurrence in comparison with the previous day, suggesting that the degree of heat acclimatization is olso an important factor in preventing heat disorders.