What This Means
This research suggests that rising temperatures due to global warming will not affect all marathon runners equally. By analyzing data from 1938 male recreational runners across three marathon events held under different temperature conditions (cool, moderate, and hot), the researchers found that temperature alone accounted for about 11% of the variation in finishing times. More importantly, the study found that certain runner characteristics determined how much a runner's performance suffered in the heat.
Specifically, runners who were faster (based on their personal best times), older, less experienced, or had a higher body mass index (BMI) tended to slow down more in hotter conditions compared to their peers. Interestingly, training-related factors like weekly mileage, how often someone runs, and their longest training run did not seem to interact with temperature in the same way — meaning these factors predicted performance similarly regardless of how hot it was.
This research suggests that as marathon events get warmer due to climate change, race organizers, coaches, and runners themselves may want to pay particular attention to these four characteristics — running ability, age, experience level, and body composition — when developing strategies to cope with heat. Recreational runners who are older, newer to the sport, or carry more body weight may need targeted heat preparation strategies, as do surprisingly fast runners who may be more accustomed to pushing their limits and thus more vulnerable when conditions become challenging.