Background: Swimming stroke asymmetry represents a potential determinant of the generation of propulsive forces that affect the maintenance of swimming speed. Tethered-swimming has been a reliable test, which is highly correlated to the freestyle swimming speed. Tethered swimming can assess the propulsive forces generated in front crawl (i. e., left and right stroke), and it can be a helpful tool to measure freestyle stroke asymmetries. Aim: This study aimed to examine whether the influence of stroke asymmetry parameters (dominant and non-dominant arm peak force, mean force and asymmetry index) on performance differs across 50, 100, and 200 m freestyle swimming events (official results). Methods: Twenty international male swimmers (age, 15 ± 2 years; height, 1.72 ± 0.18 m; body mass, 61.23 ± 4.68 kg, 601 ± 63.3 World Aquatics points) volunteered to take part in this study. Swimming stroke asymmetry was tested by the method of tethered swimming (30 s maximal effort tethered front crawl swim; force-time data were sampled at 1*kHz). Results: Backward regression analysis shows a statistically significant influence of stroke asymmetry parameters on 50, 100, and 200 m freestyle swimming events (50 m: F = 25.99, p < .001; 100 m: F = 25.68, p <.001; 200 m: F = 15.04, p <.001) with high explanatory power (R² = 0.83-0.84). Mean peak force of the non-dominant arm was the strongest predictor across all distances (* = *0.79; * = *0.80; * = *1.15; p < 0.01) indicating that greater force was associated with better performance, as well as asymmetry index (* = .36, p = .003; * = .33, p = .006; * = .36, p = .010) indicating that greater asymmetry was associated to lower performance. Conclusions: We can conclude that greater stroke asymmetry is associated with slower results, as well as higher values of mean peak force of non-dominant arm stroke emerge as a key predictor across all distances
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