Author + information
- Johannes Scherr, MD∗ ( and )
- Martin Halle, MD
- ↵∗Department of Prevention and Sports Medicine, Klinikum rechts der Isar, Technische Universitaet Muenchen, Georg-Brauchle-Ring 56 (Campus C), D–80992 Munich, Germany
We read with interest the recent article by Yankelson et al. (1) that examined the percent of life-threatening events during endurance races with a special focus on serious cardiac events and heat stroke. They concluded that the amount of serious events related to heat stroke is 10 times higher than the serious events that are cardiac in nature. In our opinion, 2 limiting aspects of the study warrant special attention.
First, the races examined in the study were all conducted in a warm climate. Median start-time temperature at these races (obtained from international meteorological offices, measured according to the standards of the World Meteorological Organization, Geneva, Switzerland) was 12°C higher (ambient temperatureStart [median (interquartile range)]: 23.8°C [16.9°C to 26.9°C] corresponding to 74.8°F [62.4°F to 80.4°F]) than the start-time temperature at the 20 largest endurance races (half and full marathon races from 2000 to 2013) worldwide (approximately 790,000 runners) (temperature: 11.8°C [8.1°C to 15.4°C] corresponding to 53.2°F [46.6°F to 59.7°F]; p < 0.001). Importantly, a ‘‘Do Not Start’’ temperature threshold of >21°C for marathon races has been recommended to reduce heat-related health risks during running events (2). Beyond this temperature limit, an increase in the amount of marathoners unable to finish and a proportionally high rate of exercise-induced heat strokes are more likely to occur. This maximum temperature threshold was exceeded in approximately 67% of the races in the study by Yankelson et al. (1) (compared with only 5% in the 20 largest races). Neglecting the ambient temperature, which is a relevant biasing factor, limits the ability of the conclusions of the study to be generalized to all other endurance activities in different climates.
Second, almost all of the investigated races (all of the Tel Aviv Night Run events and also some of the daytime Tel Aviv Races) were only 10 km. Certainly, the exercise intensity during these events was higher than that in half or full marathon races, resulting in higher core body temperature. It is known in marathon running that serious cardiac events occur most often during the last quarter (marathon: 32 to 42 km, half marathon: 16 to 21 km) of the race (3). Therefore, it is very likely that most of the participants within the study were not at high risk of experiencing a cardiac event simply on the basis of the duration of the races.
Therefore, we believe that the conclusions drawn from these results cannot and should not be generalized to running events performed at lower temperatures (i.e., <21°C) or to running events of longer duration (e.g., marathon running).
- 2015 American College of Cardiology Foundation