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The purpose of the study was to compare the anthropometric, functional and sport-specific skill characteristics and goal orientations of male youth soccer players at the extremes of height and skeletal maturity in two competitive age groups, 11–12 and 13–14 years. The shortest and tallest players, and least and most skeletally mature players (n = 8 per group) within each age group were compared on chronological age; skeletal age (Fels method); pubertal status (pubic hair); size, proportions and adiposity; four functional capacities; four soccer-specific skills; and task and ego orientation. The tallest players were older chronologically, advanced in maturity (skeletal, pubertal) and heavier, and had relatively longer legs than the shortest players in each age group. At 11–12 years, the most mature players were chronologically younger but advanced in pubertal status, taller and heavier with more adiposity. At 13–14 years, the most mature players were taller, heavier and advanced in pubertal status but did not differ in chronological age compared with the least mature players. Players at the extremes of height and skeletal maturity differed in speed and power (tallest > shortest; most mature > lest mature), but did not differ consistently in aerobic endurance and in soccer-specific skills. Results suggested that size and strength discrepancies among youth players were not a major advantage or disadvantage to performance. By inference, coaches and sport administrators may need to provide opportunities for or perhaps protect smaller, skilled players during the adolescent years.

The aim was to develop a path-flow analysis model for young swimmers’ performance based on biomechanical and energetic parameters, using structural equation modeling. Thirty-eight male young swimmers served as subjects. Performance was assessed by the 200-m freestyle event. For biomechanical assessment the stroke length, the stroke frequency and the swimming velocity were analyzed. Energetics assessment included the critical velocity, the stroke index and the propulsive efficiency. The confirmatory model explained 79% of swimming performance after deleting the stroke index-performance path, which was nonsignificant (SRMR = 0.06). As a conclusion, the model is appropriate to explain performance in young swimmers.

The aim of the current study was to analyze the hydrodynamics of three kayaks: 97-kg-class, single-rower, flatwater sports competition, full-scale design evolution models (Nelo K1 Vanquish LI, LII, and LIII) of M.A.R. Kayaks Lda., Portugal, which are among the fastest frontline kayaks. The effect of kayak design transformation on kayak hydrodynamics performance was studied by the application of computational fluid dynamics (CFD). The steady-state CFD simulations where performed by application of the k-omega turbulent model and the volume-of-fluid method to obtain two-phase flow around the kayaks. The numerical result of viscous, pressure drag, and coefficients along with wave drag at individual average race velocities was obtained. At an average velocity of 4.5 m/s, the reduction in drag was 29.4% for the design change from LI to LII and 15.4% for the change from LII to LIII, thus demonstrating and reaffirming a progressive evolution in design. In addition, the knowledge of drag hydrodynamics presented in the current study facilitates the estimation of the paddling effort required from the athlete during progression at different race velocities. This study finds an application during selection and training, where a coach can select the kayak with better hydrodynamics.

The aim of the article is to determine the hydrodynamic characteristics of a swimmer’s scanned hand model for various possible combinations of both the angle of attack and the sweepback angle, simulating separate underwater arm stroke phases of front crawl swimming. An actual swimmer’s hand with thumb adducted was scanned using an Artec L 3D scanner. ANSYS Fluent code was applied for carrying out steady-state computational fluid dynamics (CFD) analysis. The hand model was positioned in nine different positions corresponding to the swimmer’s hand orientations (angle of attack and sweepback angle) and velocities observed during the underwater hand stroke of front crawl. Hydrodynamic forces and coefficients were calculated. Results showed significantly higher drag coefficient values in the pull phase, when compared with previous studies under a steady-state flow condition. The mean value of the ratio of drag and lift coefficients was 2.67 ± 2.3 in underwater phases. The mean value of the ratio of drag and lift forces was 2.73 ± 2.4 in underwater phases. Moreover, hydrodynamic coefficients were not almost constant throughout different flow velocities, and variation was observed for different hand positions corresponding to different stroke phases. The current study suggests that the realistic variation of both the orientation angles influenced higher values of drag, lift and resultant coefficients and forces.

The aim of this study was to evaluate the determinants of front crawl sprint performance of young swimmers using a cluster analysis. 103 swimmers, aged 11- to 13-years old, performed 25-m front crawl swimming at 50-m pace, recorded by two underwater cameras. Swimmers analysis included biomechanics, energetics, coordinative, and anthropometric characteristics. The organization of subjects in meaningful clusters, originated three groups (1.52 ± 0.16, 1.47 ± 0.17 and 1.40 ± 0.15 m/s, for Clusters 1, 2 and 3, respectively) with differences in velocity between Cluster 1 and 2 compared with Cluster 3 (p = .003). Anthropometric variables were the most determinants for clusters solution. Stroke length and stroke index were also considered relevant. In addition, differences between Cluster 1 and the others were also found for critical velocity, stroke rate and intracycle velocity variation (p < .05). It can be concluded that anthropometrics, technique and energetics (swimming efficiency) are determinant domains to young swimmers sprint performance.

The aim of this research was to numerically clarify the effect of finger spreading and thumb abduction on the hydrodynamic force generated by the hand and forearm during swimming. A computational fluid dynamics (CFD) analysis of a realistic hand and forearm model obtained using a computer tomography scanner was conducted. A mean flow speed of 2 m·s⁻¹ was used to analyze the possible combinations of three finger positions (grouped, partially spread, totally spread), three thumb positions (adducted, partially abducted, totally abducted), three angles of attack (a = 0°, 45°, 90°), and four sweepback angles (y = 0°, 90°, 180°, 270°) to yield a total of 108 simulated situations. The values of the drag coefficient were observed to increase with the angle of attack for all sweepback angles and finger and thumb positions. For y = 0° and 180°, the model with the thumb adducted and with the little finger spread presented higher drag coefficient values for a = 45° and 90°. Lift coefficient values were observed to be very low at a = 0° and 90° for all of the sweepback angles and finger and thumb positions studied, although very similar values are obtained at a = 45°. For y = 0° and 180°, the effect of finger and thumb positions appears to be much most distinct, indicating that having the thumb slightly abducted and the fingers grouped is a preferable position at y = 180°, whereas at y = 0°, having the thumb adducted and fingers slightly spread yielded higher lift values. Results show that finger and thumb positioning in swimming is a determinant of the propulsive force produced during swimming; indeed, this force is dependent on the direction of the flow over the hand and forearm, which changes across the arm’s stroke.

The purpose of the current study was to assess and to compare the hydrodynamics of the first and second gliding positions of the breaststroke underwater stroke used after starts and turns, considering drag force (D), drag coefficient (C_D ) and cross-sectional area (S). Twelve national-level swimmers were tested (6 males and 6 females, respectively 18.2 ± 4.0 and 17.3 ± 3.0 years old). Hydrodynamic parameters were assessed through inverse dynamics from the velocity to time curve characteristic of the underwater armstroke of the breaststroke technique. The results allow us to conclude that, for the same gliding velocities (1.37 ± 0.124 m/s), D and the swimmers’ S and C_D values obtained for the first gliding position are significantly lower than the corresponding values obtained for the second gliding position of the breaststroke underwater stroke (31.67 ± 6.44 N vs. 46.25 ± 7.22 N; 740.42 ± 101.89 cm² vs. 784.25 ± 99.62 cm² and 0.458 ± 0.076 vs. 0.664 ± 0.234, respectively). These differences observed for the total sample were not evident for each one of the gender’s subgroups.

This study evaluates the contributions of age, growth, skeletal maturation, playing position and training to longitudinal changes in functional and skill performance in male youth soccer. Players were annually followed over 5 years (n = 83, 4.4 measurements per player). Composite scores for functional and skill domains were calculated to provide an overall estimate of performance. Players were also classified by maturity status and playing position at baseline. After testing for multicollinearity, two-level multilevel (longitudinal) regression models were obtained for functional and skill composite scores. The scores improved with age and training. Body mass was an additional predictor in both models [functional (late maturing): 13.48 + 1.05 × centered on chronological age (CA)—0.01 × centered CA²—0.19 × fat mass (FM) + 0.004 × annual volume training—1.04 × dribbling speed; skills (defenders): 7.62 + 0.62 × centered CA—0.06 × centered CA² + 0.04 × fat-free mass—0.03 × FM + 0.005 × annual volume training—0.19 × repeated-sprint ability + 0.02 × aerobic endurance]. Skeletal maturity status was a significant predictor of functional capacities and playing position of skill performance. Sound accuracy of each multilevel model was demonstrated on an independent cross-sectional sample (n = 52).