What Factors Put Runners at Risk for Exertional Heat Stroke During a Marathon?

Exertional heat stroke (EHS) can develop in participants at running events. A runner with EHS overheats beyond their capacity to cool and can suffer organ damage, and even death, if not rapidly cooled. Understanding the factors that may lead to EHS can help race organizers and medical teams plan care. This is especially important for large-scale events involving high numbers of runners, which challenge both participant and community safety. In this study, investigators examined all EHS cases at the Boston Marathon from 2015 to 2019. They found that younger runners and faster runners had a higher incidence of EHS. Though all cases occurred during races held in warm and humid conditions, a greater increase in heat stress from start to peak during a race worsened EHS risk. Runners with EHS were only a small percentage of all runners presenting for medical care, and many were discharged directly from the race medical facilities without needing further care. None of the runners died, though their treatment was both labor- and time-intensive. Putting measures in place to predict and reduce EHS risk, thus minimizing strain on race and community resources, should be encouraged at large running events.