To the Editor We read with interest the recent article on the incidence and outcomes of cardiac arrest during long-distance running events in the US. However, we would like to highlight a methodological concern regarding the use of race finishers as a surrogate for race participants. While the authors acknowledged that this approach may have included some runners more than once—potentially underestimating the per-person incidence—it also introduced a second bias not addressed in the limitations section: exclusion of nonfinishers from the denominator, despite the inclusion of all cardiac arrests (including those occurring mid-race) in the numerator.