Anecdotal reports regarding the 2013 Fédération Internationale de Natation World Swimming Championships held in Barcelona suggested that swimming performances were biased, presumably because of a current.
Purpose: The purpose of this study was to analyze the swimmers’ performance data to determine the merit of these rumors.
Methods: The mean time difference between odd and even 50-m lengths for each lane in the 1500-m freestyle was compared. For each 50-m event, a percent change in performance from the preliminaries to semifinals and semifinals to finals was calculated for all qualifying swimmers. Observations were grouped according to the swimmers’ lane assignments.
Results: For the 1500-m freestyle, lane assignment significantly affected the time difference between odd and even 50-m lengths (P < 0.001). The change in performance for the 50-m events was also affected by lane assignment (P < 0.001). When swimmers transitioned from lanes 1–4 for their first swim (preliminaries or semifinals) to lanes 5–8 for their second (semifinals or finals), their performance time improved by 1.11% (95% confidence interval, 0.82%–1.41%), which was significantly greater than any other lane change scenario. When swimmers were in lanes 5–8 for their first swim and lanes 1–4 for their second, their performance time was slower by 0.59% (95% confidence interval, 0.39%–0.80%), which was significantly worse than any other lane change combination.
Conclusions: Swimmers were advantaged or disadvantaged depending on the direction and lane in which they swam. The existence of a current is the only cause that we can propose to explain these findings. Because one of Fédération Internationale de Natation’s primary stated objectives is to provide fairness in competition, new policies are needed to prevent similar biases from occurring in the future.