Using Covid-19 Response Policy to Estimate Open Water Swim Drafting Effects in Triathlon

TL;DR

This paper uses a natural experiment from COVID-19 race restrictions to causally estimate open-water swim drafting effects in triathlon, revealing benefits only from the third trailing position onward.

Contribution

It provides the first large-scale causal estimate of swim drafting effects in real-world triathlon races using a natural experiment and advanced statistical methods.

Findings

Drafting benefits are statistically insignificant in 2020.

Drafting becomes advantageous from the third trailing position onward.

Drafting benefits decay inversely with trailing position.

Abstract

This study investigates the causal effects of open-water swim drafting by leveraging a natural experiment induced by staggered race starts during the COVID-19 pandemic. Before 2020, athletes started in groups, enabling drafting benefits, while pandemic-related restrictions significantly reduced these opportunities. Using agglomerative hierarchical clustering of swim-out times, I analyze optimal drafting positions and estimate their impact on Swim-Out performance. Our empirical findings reveal that swim drafting benefits were statistically insignificant in 2020 but persisted post-pandemic at slightly reduced levels. I find that drafting becomes advantageous only from the third trailing position onward, with earlier positions primarily serving to minimize fatigue. To mitigate endogeneity, I employ athlete and event fixed effects. The seemingly inverse decaying nature of drafting benefits partially addresses some concerns of simultaneous reverse causality and omitted variable bias. This study provides the first largescale causal estimate of drafting effects in real-world triathlon race settings.