Background: Exercise associated collapse (EAC) is a common medical encounter at distance running events. Risk factors associated with EAC are not well documented. The objective is to determine the overall incidence of EAC and identify risk factors associated with EAC in 21.1-km and 56-km runners.
Methods: A cross-sectional analysis of 153,208 race starters from the Two Oceans Marathon races (2008-2015). All EACs on race day were documented by medical staff. Risk factors associated with EAC investigated included demographics, race distance (21.1 km vs. 56-km), running speed, race experience and race day environmental data (wet-bulb globe temperature [WBGT], humidity, wind speed). Incidence (per 1000 starters; 95% CIs) and incidence ratios (95%CIs) were calculated.
Results: The overall incidence of EAC was 1.50 (95% CI: 1.31-1.71). Longer race distance (IR: 2.1; 1.6-2.7; P<0.0001) and slower running speed (IR: 1.3; 1.1-1.5; P=0.0017) were significant risk factors associated with EAC. The incidence of EAC was higher in female vs. male 21.1-km race starters (IR=2.25; 1.47-3.46; P=0.0229). Age and environmental conditions were not associated with EAC (P>0.05) in a cool and temperate environment.
Conclusions: About 1 in 667 race starters (21.1 km and 56-km) develop EAC. Longer race distance, slower running speed and female sex (in 21.1-km starters) are significant risk factors associated with EAC. Race medical directors can identify race entrants that may be at risk of developing EAC, develop prevention strategies and better prepare medical care at these events.