Olympic medallist Jenny Simpson has announced she will never run again after suffering a cardiac arrest in June, saying "that chapter has ended" following her diagnosis with a rare inherited heart condition. The 39-year-old American, a former 1500m world champion, collapsed while pacing a mile group at a pop-up event in North Carolina and required CPR and a defibrillator before being taken to hospital, where she suffered a second cardiac arrest.

Doctors diagnosed Simpson with arrhythmogenic right ventricular cardiomyopathy (ARVC), a genetic condition that damages heart muscle cells and prevents the heart pumping blood properly, making a return to running dangerous. Simpson represented the USA at three Olympics, winning bronze at Rio 2016 and gold at the 2011 World Championships, plus silver medals in 1500m at the 2013 and 2017 Worlds, before retiring from competitive racing at the end of 2024.