Despite increased participation in US long-distance running races, cardiac arrest incidence remains stable. Authors Jonathan Kim, MD, MSc, of Emory University, and Aaron Baggish, MD, of the University of Lausanne Switzerland, discuss the RACER 2 study and compare results with initial findings published in the RACER 1 study from 13 years ago, with JAMA Associate Editor Gregory Marcus, MD, MAS. Related Content:

• Cardiac Arrest During Long-Distance Running Races