The purpose of this study was to assess the effects of jumping distance on the landing mechanics after a volleyball spike, to help in injury prevention and training for safer landing. Ground reaction forces and three-dimensional kinematic data were collected from six male university right-handed volleyball players under "Normal" and "Long" jumping distance conditions of landing after a spike. The results revealed that the landings under the Long jumping distance condition produced significantly greater centre of gravity velocities and larger mean loading rates. Although data were collected for bilateral landings with the two feet contacting the force platform at the same time, landing motion was asymmetric and the left leg was considered to play a more critical role in the absorption of the landing impact. The trunk and hip positions at the initial contact with the floor and the range of motions of the knee and ankle were key kinematic parameters for reducing the vertical peak ground reaction forces and extending the time from the initial contact to the occurrence of this peak force, which consequently reduced the mean loading rate upon landing.

The purpose of this study was to investigate the motions during the airborne phase and their relations with single-legged landing position in elite male volleyball players during o‹cial games, and gain insights into techniques for safe landing. The spike-landing motions of four male world-level right-handed volleyball players were recorded with two high-speed video cameras during o‹cial games for a three-dimensional analysis. The results indicated a large trunk twist and a trunk left lean during the airborne phase of single-legged landings. The lower limbs reacted to the upper body motion diŠerently for the left and right legs. The left hip extended during the last portion of the airborne phase to prepare for landing while the right hip continuously ‰exed and abducted, elevating the right leg, which resulted in left-legged landings. The results of one double-legged landing of a skilled player indicated that a compact trunk twist with a small left lean may have been why a straight body conˆguration was maintained and the right leg did not elevate as in the single-legged landings.

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-The aim of this study was to compare the birth-date distribution of youth athletes of a high-level Brazilian soccer club with the general population of the same age group. In a cross-sectional study, the birth date of 341 youth athletes (under 10-20) was compared with a reference population (live births that occurred in São Paulo state in the same age group; n = 5,480,868). The subjects were divided into quarters of birth: 1 st = January-March; 2 nd = April-June; 3 rd = July-September; 4 th = October-December. The chisquare test (χ 2 ) was used to compare the expected (reference population) and observed (athletes) distributions. It was detected a significant difference between the expected distribution and observed distribution (χ 2 = 29.53; p<0.0001), with a higher percentage of athletes born in the 1 st quarter (47.5%) and a lower percentage in the 4 th quarter (8.8%). The present results confirm the occurrence of the relative age effect (RAE) during the player selection process in a top-level Brazilian soccer club. The occurrence of this phenomenon during the selection and development of young athletes needs to be taken into account and should be analyzed carefully in order to minimize the loss of potential youth soccer talent. Further studies are required to identify the determinants of RAE and to establish preventive strategies that ensure a more efficient selection process of young soccer players. Key words: Athlete; Maturation; Relative age effect; Soccer; Talent identification; Youth. Resumo -O objetivo do presente estudo foi comparar a distribuição das datas de nascimento dos atletas das categorias de base de um clube da elite do futebol brasileiro com a população do estado de São Paulo da mesma faixa etária. Por meio de estudo transversal, as datas de nascimento de 341 atletas das categorias de base de um clube de São Paulo (sub 10-20) foram comparadas com uma população de referência (nascidos vivos do Estado de São Paulo da mesma faixa etária; n = 5.480.868). Os indivíduos foram distribuídos 400The relative age effect in soccer Massa et al.

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