Comparing swimming starts of flat and deep trajectory underwater movements performed by adolescent male swimmers

Biomechanical analyses of the swimming start performed by the best swimmers indicates the occurrence of a few effective start types. This issue has only been described to a small degree among adolescent swimmers. The objective is to determine kinematic differences in various parts of the swimming start to the front crawl among adolescent swimmers performing a start with flat (FT) or deep underwater trajectory (DT). Methods: The study comprised 32 male swimmers aged 16–19 (average World Aquatics score = 556 ± 88 points). The trials were recorded using two cameras (above- and underwater). A kinematic analysis of the time from start to attain 5 m was performed. Results: The maximum submersion depth was 0.94 ± 0.09 m (FT) and 1.21 ± 0.11 m (DT). Between-group differences were observed for FT and DT, respectively, in: attack angle at the submersion (38.37 ± 6.85° and 44.90 ± 6.08°), the distance of maximum submersion depth (5.24 ± 0.36 m and 5.58 ± 0.50 m) and underwater angles of attack during submersion (angle of the shoulders at the of submersion: 29.40 ± 3.90° and 34.30 ± 4.14°, angle of the hips at the submersion: 21.70 ± 4.52° and 26.49 ± 5.05°). Conclusions: It was found that swimmers can successfully use different start variants. The underwater trajectory is primarily influenced by the body position at the moment the fingers contact with the water and during submersion, and not only by the manner of performing the push-off. The authors conclude that the characteristics of the start should not be based on one variable or its selected start phase – the description of the technique should comprise a set of kinematic indices from its different parts.