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

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.