This paper studies the determinants (and economics) of free-riding in the swimming stage of massstart triathlon. The theoretical framework builds upon non-discriminatory Tullock contests, modeling triathlon as a simplified two-stage game with quadratic effort costs, and extends to n-player and asymmetric settings in which drafting multiplicatively reduces heterogeneous effective marginal costs.Empirically, I construct an event-study measure of free-riding based on relative rank changes across the two stages to capture free-riding propagation, centered on the exceptional 2020 season, during which non-drafting rules were enforced due to the COVID-19 pandemic.Causal identification combines pooled OLS (POLS) with athlete and event fixed effects (FE), as well as a regression discontinuity design (RDD) exploiting COVID-19 policy—induced rule changes—specifically, individually staggered starts—that mechanically reduced drafting potential and, consequently, its utilization. Additionally the economic analysis chapter uses elasticity, production frontier, and conditional quantile methods to primarily examine group-size effects.The results show that: (i) free-riding was substantially positive prior to 2020, collapsed during the 2020 season, and only partially recovered thereafter; (ii) the drafting effects are stronger for weaker swimmers and athletes in deeper drafting positions, with modest gender differences; and (iii) age heterogeneity is pronounced, with middle-aged and older cohorts benefiting the most, suggesting that athlete experience plays a vital role in efficiently utilizing free-riding gains. However, this latter finding may also be significantly confounded by compositional changes in athletes’ body characteristics over time.