Despite the increasing importance of the underwater segment of start and turns in competition and its positive influence on the subsequent surface swimming, there is no evidence on how the transition from underwater to surface swimming should be performed. Therefore, the aim of the present study was to examine the role of segmental, kinematic and coordinative parameters on the swimming velocity during the pre-transition and transition phases. A total of 30 national male swimmers performed 4 × 25 m (one each stroke) from a push start at maximum velocity while recorded from a lateral view by two sequential cameras (50 Hz), and their kinematic and coordinative swimming parameters were calculated by means of two-dimensional direct linear transformation (DLT) algorithms. Unlike pre-transition, backward regression analysis of transition significantly predicted swimming velocity in all strokes except breaststroke (R² ranging from 0.263 in front crawl to 0.364 in butterfly). The inter-limb coordination was a predictor in butterfly stroke (p = 0.006), whereas the body depth and inclination were predictors in the alternate strokes (front crawl (p = 0.05) and backstroke (p = 0.04)). These results suggest that the body position and coordinative swimming parameters (apart from kicking or stroking rate and length) have an important influence on the transition performance, which depends on the swimming strokes.

There is a great heterogeneity in the starting techniques used by international-level swimmers in relay events. The aim of the present study was to analyse and compare the two most commonly used relay start techniques by male and female competitive swimmers. Thirteen males and seven females national and international-level swimmers performed several 25-m trials with their preferred relay start (n = 91, short-step; n = 54, long-step technique). Linear mixed models examined the effects of gender and start technique, with 5-m start times as a covariate. Swimmers performing long-step showed faster 5-m (0.09 s, d = 1.10) and 10-m (0.09 s, d = 0.39) times than those performing short-step starts, regardless of gender (all p < 0.001). This was the result of i) longer block times, ii) faster horizontal velocities with lower peak forces during the leg step and iii) faster velocities with higher peak forces when driving-off the block in the long-step technique. In both relay techniques, females showed 0.11 s (d = 1.38) longer 5-m and 0.69 s (d = 2.99) longer 10-m (both p < 0.001) times compared to males with longer block times and slower velocities in all key events. Swimmers should take advantage of the new starting platforms to apply long-step start techniques that increase horizontal displacement but also forward velocity before leaving the block.