Assessing the Relationship between In-Water Kinetic Asymmetries and Performance in Swimming.

The present study aimed to investigate the relationship among force, impulse and their asymmetries with swimming performance across different distances, and to explore whether the correlations were dependent on the presence of "real" asymmetries (i.e., higher than metric variability). Thirty-five male swimmers (age: 19.5 years ± 5.0, body mass: 75.4 ± 11.5 kg, body height: 181.7 ± 7.6 cm) performed a 15-s tethered-swimming test, in which peak force, mean force and impulse of each body side were measured. The absolute and relative asymmetries were subsequently obtained. The coefficient of variation was calculated and used to identify the presence of "real" asymmetries (i.e., asymmetries greater than the CV). The official times for 50-, 100-, and 200-m front-crawl swimming were obtained. Pearson's r correlations showed that peak and mean force presented moderate to strong associations (r = -0.51 to -0.84; p ≤ 0.001 to 0.013) with performance at all distances. Impulse only presented moderate associations with 50-m front crawl performance (r = -0.50 to -0.62; p ≤ 0.001 to 0.013). When considering the whole sample, no associations were seen between asymmetries and swimming performance, but when considering only athletes presenting "real" asymmetries, weak to moderate correlations were found between peak force asymmetries and 50/100-m performance (r = 0.47 and 0.59; p = 0.016 and 0.002). In conclusion, force and impulse are related to swimming performance, and individual asymmetries should be monitored in swimmers, as they might be present and related to performance depending on the approach adopted.