RESUMO
Objective To determine the effects of javelin release parameters related to aerodynamics on aerodynamic distance and results in javelin throwing in actual competition environments. MethodsKinematic data from javelin throwing of 22 Chinese and American elite women javelin throwers were obtained using three-dimensional videographic method. The trial with the longest aerodynamic distance and the trial with the shortest aerodynamic distance for each thrower in the same competition were included in this study. Aerodynamics-related techinical parameters in long and short aerodynamic distance trials were compared. Results Compared with short aerodynamicdistance trials, the vacuum flight distances of long aerodynamic distance trials were significantly shorter, but the official distances were significantly longer. The release velocities of long aerodynamic distance trials were significantly lower, the attack angles and bending angles were significantly smaller. The horizontal direction angles at release of the long aerodynamic distance trials were more to the right side. The elevation angles and horizontal pointing angles during right/left foot landing in long aerodynamic distance trials were not significantly different from those in short aerodynamic distance trials. Conclusions Throwing javelin with submaximal effort beneficiates the control of aerodynamics-related release parameters and thus increased chances to obtain long aerodynamic distance and better result in women javelin throwing. Reducing attack angle and releasing javelin about 5°to the right will assist women javelin throwers to obtain longer aerodynamic distance.
RESUMO
Introdução. No kitesurfing, os velejadores deslocam-se alterando o ângulo de ataque do kite de duas formas: mudando o kite na janela de vento e movimentando a barra de controle. Objetivo. Descrever o comportamento da força do kite em relação ao seu posicionamento e à distância percorrida pela barra de controle. Métodos. Foram utilizados sistemas de videogrametria e dinamometria. Duas situações foram testadas: movimentando o kite na janela de vento e deslocando a barra. Resultados. A força aumentou quando a barra foi abaixada. Movimentando o kite, a zona de força foi definida pela combinação de ângulos verticais menores que 60° com ângulos horizontais menores que 20°. Conclusão. A força aumenta quando a barra é abaixada. O ângulo vertical pode exercer maior influência na força.
Introduction. During kitesurfing, the sailors propel themselves changing the kite´s attack angle in two ways: moving the kite in the wind window and moving the control bar. Objective. To describe the behavior of the kite's forces in relation to its position in the wind window and the distance traveled by the control bar. Methods. Videogrammetry and dynamometry were used. Two tests were performed: moving the control bar and moving the kite in the wind window. Results. The force increased while the bar was moved down. Moving the kite, the power zone was defined as the combination of vertical angles smaller than 60° with horizontal angles smaller than 20°. Conclusion. The force increases when the bar goes down. The vertical angle seems to be more important to the force values.
Introducción. Nel kitesurfing, lo deportista navega cambiando el ángulo de ataque del kite de dos formas: moviendo el kite en la ventana de viento y moviendo la barra de control. Objetivo. Describir el comportamiento de la fuerza del kite en relación a su posicionamiento en la ventana de viento y al desplazamiento de la barra de control. Métodos. Fueron utilizados sistemas de videogrametría y dinamometría, en dos situaciones: moviendo el kite y moviendo la barra. Resultados. La fuerza aumento cuando la barra fue bajada. Moviendo el kite, la área de fuerza fue definida por la combinación de ángulos verticales menores que 60° con ángulos horizontales menores que 20°. Conclusión. La fuerza aumenta cuando la barra baja. El ángulo vertical puede ejercer más influencia en la fuerza.