BIOMECHANICAL CONSIDERATIONS ON JUMPING IN SPORTS AN APPROACH TO A FUNDAMENTAL UNDERSTANDING
AbstractIn the introduction to the seventh edition of ,,The Mechanics of Athletics" Geoffrey Dyson mentioned the importance of increased knowledge of mechanical principles in the development of track and field athletics coaching. Dyson focussed on the knowledge of mechanics as an essential tool with which to distinguish between important and unimportant, correct and incorrect, cause and effect, possible and impossible (Dyson. 1978, 12). From his principal concept Dyson was ahead of most biomechanists of his time, who often reduced the human body to the simple CM-model dealing with sport skills, because he added to the mechanical laws other ones (e. g. biological laws) which also play an important part in the analysis and optimization f human motion . This paper, as a tribute to the applied research of Geoffrey Dyson and the general concept of applied research in sports biomechanics. will discuss biomechanical concepts to identify and explain limiting factors of jumping in different sports on the background of their usefulness for coaching and performance optimization. Before dealing with the different approaches the great variety of jumps in sports will be structured and organized. As criteria for this purpose the different surfaces (non-elastics vs elastic) the different initial mechanical conditions (with or without angular momentum. large or small amount of CM's velocity), and the geometry of take-off (one-leg take-off or double support take-off) are chosen. From the biomechanical concepts concerning jumping events the CM-strategy, the segmental contribution of linear and angular momenta concept, and the energy transfer through segments purpose are controversially discussed and applied to the different categories of jumping. As far as the practical validation of such models and concepts is concerned this should be explained by the example of a longitudinal study of the take-off for a double backward somersault in floor gymnastics. In this project it could be shown that the prognosed influence of initial angular and linear momenta prior to take-off is finally confirmed. Thus the used model proved valid, and could help to understand the importance of pre-take-off activity, but it can not explain the general take-off mechanism. For this purpose the energy transfer concept seems to be the state of the art and will be explained in the different jumping categories. Distinct differences of strategy for take-off from rigid and from elastic surfaces could be discovered. The energy transfer concept can contribute to a fundamental understanding of lower extremity function and the influence of the arms and the lead leg in jumping. The major advantage of this segmental procedure in comparison e. g. to a CM's-concept is considerable, and it provides a chance of bridging the gap between the theoretical sciences and the application of their results to the practical training process. And this has always been one of the principal objectives of the late Geoffrey Dyson.
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