Not Too Hot to Run: Adaptation to Extreme Heat in Competitive Runners

This paper examines how adaptation shapes the impact of extreme heat on labor productivity. We use global data on competitive runners, combined with highresolution weather information, to estimate how race-day heat affects running speed. Consistent with adaptation, we find that runners from hotter countries are significantly less affected by extreme temperatures. The performance gap is most pronounced in endurance events and narrows in high-stakes races, suggesting that both physiological factors and incentives may play a role. Our findings contribute to the literature on climate adaptation by providing evidence that prior exposure reduces sensitivity to heat.