Modelling stroking parameters in competitive sprint swimming: Understanding inter- and intra-lap variability to...

This study investigated the inter- and intra-lap variability in stroking parameters during sprint competition to gain insight into the race management of speed (S), stroke length (SL), stroke rate (SR) and stroke index (SI) in relation to gender. The stroking parameters of 32 male and 32 female finalists in the 2015 World Championships and French Championships were analysed during 50-m and 100-m freestyle events. Using a video-derived two-dimensional direct linear transformation system, the biological coefficients of variation (BCV) between cycles were computed for the 50-m and the two laps of the 100-m (L1₁₀₀, L2₁₀₀). Speed changes within each lap were modelled by linear, quadratic or cubic models. The 50-m showed higher S and SR but lower SL and SI than L1₁₀₀. The 50-m exhibited greater BCV S than L1₁₀₀, which showed higher S, SR, SL and SI than L2₁₀₀. BCV S and BCV SL were lower in L1₁₀₀ than L2₁₀₀ but BCV SR was higher in L1₁₀₀ than L2₁₀₀. Male swimmers showed greater BCV S than female swimmers in the 50-m and L1₁₀₀. For the whole population, the linear regression model was dominant in the 50-m (53.1%), L1₁₀₀ (53.1%) and L2₁₀₀ (43.8%). High mean speed often related to high intra-lap speed fluctuations and a linear speed decrease in the 50-m suggesting an 'all-out' pacing, while lower fluctuations occurred during the 100-m suggesting an 'economical' pacing.