RESUMEN
Purpose: The ability to swim fast underwater is believed to be connected to lower limb strength and some somatic traits. The main purpose of the study was to evaluate strength and speed parameters based on the relationship between the strength of underwater dolphin kicks and the countermovement jump test (CMJ) among adolescent swimmers. Methods: 48 adolescent male swimmers (13.47 ± 0.84 years) were examined for muscle mass of arms (m m arms), trunk (m m trunk), and legs (m m legs), body height (BH), and biological age (BA). An underwater tethered dolphin kicking test was conducted in a pool; average force (5F ave) and impulse per single cycle (5I ave) in the 5-second period were measured. Force indices (20F ave - average force from 20 seconds and 20I ave - average impulse per single cycle from 20 seconds) were also measured in 20-second tethered front crawl swimming. During CMJ testing, general lower body muscle motor capabilities were evaluated by extracting the work (CMJw [J]) and height (CMJh [m]) of the jump. Results: The strongest correlations were observed between: (a) 5F ave and BH, m m arms and CMJw; (b) CMJw, m m arms, and 20F ave; (c) indices of swimming speed and 5I ave (BA control); (d) total swimming velocity and average tethered swimming force (BA control). Moderate partial correlations (BA control) were noted between speed indices of swimming race and CMJ. Conclusions: The underwater tethered dolphin kick test is a useful predictor test of 50-m front crawl performance in young male swimmers, with better specificity for swimmers than CMJ results themselves.
Asunto(s)
Rendimiento Atlético , Extremidad Inferior , Natación , Natación/fisiología , Humanos , Masculino , Adolescente , Extremidad Inferior/fisiología , Rendimiento Atlético/fisiología , Fuerza Muscular/fisiología , AguaRESUMEN
Objective To explore characteristics of flow field around the athletes, change of net flow force, and influences of hip flexion angles at the end of extension kick on the submerged dolphin kick stroke. Methods The body shape data of a swimmer were obtained by three-dimensional (3D) scanning, and the data were reversely reconstructed to obtain the swimmer model. The joints of the swimmer model were separated, and each segment of the athlete was divided into independent rigid body, and simulation of the submerged dolphin kick stroke was realized by controlling movement of each independent rigid body. The computational fluid dynamics (CFD) software package ANSYS Fluent was used as the solver for calculation and solution. Results The vortex structures were shed off from the surface of the swimmer’s body in the area with a large velocity gradient in flow field, and the shedding of vortex structures was different at the stage of extension kick and flexion kick. Propulsion was mainly generated during extension kick phase. At the end of extension kick, the drag decreased as the hip flexion angle increased from 20° to 30°. Conclusions To some extent, increasing flexion angle of the hip joint at the end of extension kick will reduce the drag force and increase the swimming speed in process of the submerged dolphin kick stroke.