Engineering Elite Swimming Start Performance: Key Kinetic and Kinematic Variables with Reference Values

To provide deeper insights into the complex and multidimensional nature of swimming start performance, the present study aimed to determine its key performance indicators (KPIs) and provide percentile-based reference values for elite junior and adult swimmers. Hence, routine performance analysis data of Swiss junior and senior national team members were analyzed, including multiple European champions, World champions, Olympic medalists and a World record holder (n = 136, age: 18.3 ± 3.6 [13-32] years, World Aquatics swimming points: 761 ± 73 [609-1061]). All kinetic and kinematic variables measured by the instrumented starting block were analyzed, and variables with pairwise correlation > 0.80 were clustered using principal component analysis with orthogonal Varimax rotation, retaining components with Eigenvalue > 1.0 and factor loadings > 0.6. The highest loaded variables of each component were used as independent variables, alongside the variables with low co-variance, to determine KPIs with multiple linear regression analysis. As such, peak and average power (<i>p</i> ≤ 0.05), front horizontal and total vertical peak forces (<i>p</i> ≤ 0.04), timing of peak power and rear horizontal forces (<i>p</i> ≤ 0.02), resultant grab forces and their timing (<i>p</i> ≤ 0.05), center-of-gravity height at take-off (<i>p</i> = 0.03), take-off horizontal and vertical velocity (<i>p</i> = 0.02), resultant entry velocity (<i>p</i> = 0.01), entry time (<i>p</i> < 0.01), distance before the first kick (<i>p</i> < 0.01), maximal swimming depth (<i>p</i> = 0.02) and distance before breaking through the water surface (<i>p</i> < 0.01) showed a significant effect on the dependent variables (15 m start time). In conclusion, swimmers should maximize power and force production peaking earlier and grab forces peaking later during the block phase. They should increase take-off and entry velocities, distance before the first undulating kick, maximal swimming depth and underwater distance.