Pacing and heat stress independently and differentially effect elite marathon performance

Purpose Pacing strategies and weather conditions can have a large influence on elite marathon race times. The purpose of this study is to evaluate the relationship between elite marathon running performance, heat stress, and pacing while controlling for sex, age, and previous personal best marathon time. We hypothesized slower race times would be evident with greater variations in pacing and higher heat stress.Methods A multilevel model with random effects was used to evaluate the predictability of individual and group level parameters across 12 elite international marathons (2001-2021) from the Olympic Games and the World Championships. The analysis focused on pacing, defined as the individual's standard deviation of five-kilometer splits throughout the marathon, and heat index, which is a product of temperature and humidity.Results While accounting for the effects of all other analyzed variables, a 1-min increase in the variation of pacing across five-kilometer splits significantly slowed race times by 6.75 min (standard error = 0.21 min, t value = 32.36) and a 1 ? increase in heat index significantly slowed race times by 0.35 min (standard error = 0.05 min, t value = 7.63).Conclusion There are large individual effects of pacing and smaller but meaningful effects of heat stress on elite marathon race times holding constant an individual's age, sex, and previous personal best time. Reduced pacing variations lowers the impact of heat stress to a small degree. Even pacing and tolerating varying levels of heat stress are key for the best elite marathon finish times.