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INTRODUCTION: Marathon races faced with unexpectedly hot conditions must make a decision to start or not to start. The current race cancellation parameters may not reflect the safety profile of an individual race, and a universal temperature may not work an individual race. METHODS: A retrospective review of the number of starters, finishers, and finish line medical encounters was used to calculate the rate of 'unsuccessful' marathon starters from race records, where unsuccessful is defined as medical encounters seen for any reason in the finish medical area plus marathon starters who did not finish. Unsuccessful marathon starters were plotted against the race start wet bulb globe temperature (WBGT), and the WBGT level at which a mass casualty incident (MCI) occurred was used to calculate a 'do not start' WBGT. RESULTS: A start WBGT of >21°C resulted in MCI or midrace cancellation in several races. Twin Cities Marathon data show a rapid increase in the rate of unsuccessful marathoner starters above a start WBGT of 13°C. The event experienced an area-wide MCI at a start WBGT of 22°C with an unsuccessful starter rate of 160 per 1000 finishers. CONCLUSIONS: Marathons in northern latitudes (>40°) held in 'unexpectedly' hot conditions when the participants are not acclimatized and the start WBGT is >21°C often end in either race cancellation or an MCI. It would seem prudent not to start these races in similar conditions. The rate of unsuccessful marathon starters per 1000 marathon finishers plotted against start WBGT generates a curve that can be used to estimate a do not start level. The do not start WBGT for Twin Cities Marathon is 20.5°C on the basis of this model. [ABSTRACT FROM AUTHOR]

The medical work load seems to increase both with heat and humidity, and with cold and rainy conditions. Heat tolerance during exercise is variable and heat intolerance may contribute to collapse and increase medical encounters. Exposure to cold, wet conditions results in increasing incidence of hypothermia in exhausted marathon runners. Finish-line encounters and course dropouts increase as conditions cool and warm away from the most advantageous conditions in the 4.4-15 C (40-59 F) wet bulb globe temperature (WBGT) range. The risk of requiring medical attention and not finishing rises considerably when the WBGT is >15.5 C (60 F). Comparing the correlation coefficients of the Boston Marathon and Twin Cities Marathon data suggests that the risks of medical problems and not finishing are associated with the warmest temperature of the race and not the start temperature. The community consequences of races conducted in hot and humid conditions can be significant, particularly when the WBGT is >15.5 C. The emergency medical systems can be overwhelmed with a surge of patients, some very ill, and the emergency call response times drop to unacceptable levels blocking access for the citizens of the community. With respect to marathon encounters, heat stress increases both the finish-line medical encounter rate and the on course drop-out rate, and seems to increase the incidence of hyponatraemia and heat stroke. Cold conditions increase the drop-out rate along the course and, if associated with wet conditions, also increase the encounter rate. [ABSTRACT FROM AUTHOR]

INTRODUCTION:: Exertional heat stroke is a cause of collapse in marathon runners. Rectal temperature (Trectal) measurement is the usual method of estimating core temperature in collapsed runners, and temporal artery thermometer (TAT) measurement is untested for field use in marathon runners and other athletes. The objective of this study is to compare TAT measurement with Trectal measurement in collapsed marathon runners. METHODS:: TAT-500i (Exergen Corp, Wellesley, MA) temperature measurements were obtained using the manufacturer's instruction manual on 60 collapsed marathon runners who had Trectal measurements in the finish area medical tent during two consecutive annual races. RESULTS:: The TAT temperatures identified only 2 of 17 hyperthermic runners (Trectal > 39.4 degrees C (103 degrees F)), a sensitivity of only 0.12, and a Pearson' correlation coefficient of 0.374 (r = 0.14). Among the 17 hyperthermic runners, the correlation of Trectal to TAT temperatures was 0.526 (r = 0.28) with a mean +/- SD Trectal of 40.7 +/- 0.94 degrees C (105.1 +/- 1.7 degrees F) and a mean +/- SD TAT temperature of 37.4+/- 1.3 degrees C (99.4 +/- 2.4 degrees F). Among the 43 collapsed normothermic runners, there was no correlation between the rectal and the TAT measurements (r = -0.142, P = 0.37). CONCLUSIONS:: These findings indicate that there is little association between the temperatures obtained by temporal artery measurement and Trectal measurement in collapsed marathon runners and that TAT temperature is unable to identify hyperthermic runners. Based on these findings, TAT measurement should not be used to assess core body temperature or make treatment decisions for marathon runners with potential exertional heat stroke. [ABSTRACT FROM AUTHOR]