KINEMATIC ANALYSES OF THE DISCUS THROWING COMPETITIONS AT THE WORLD ATHLETICS CHAMPIONSHIPS 1993
AbstractPurpose of the paper This paper wants to discus possibilities and limitations of applied kinematic performance diagnostics of discus throwing as an example for other athletic disciplines. On the basis of kinematic analyses of the finalists at the WAC 94 added to a data base including 260 throws of world class athletes the applicability of traditional kinematic approaches is called into question. &f&& Analyses were performed with a PEAK PERFORMANCE motion analysis system. The video fields were digitized manually. 17 body landmarks were taken to define the locations of 12 body segments. Timing Parameters The analysis of phase durations is a good indicator for the stability of individual movement rhythm and timing. Highest importance is usually awarded to the last three phases of the throw. 11 is true that the often formulated demand for a possibly short airborne phase can be supported by mechanical considerations but individual variations (see table 2) avoid a significant correlation between this parameter and throwing distance (r= -.0076, p= ,919) as well as release velocity (I= ,0193, p= ,891) . The same comes true for transition and delivery phase. No significant correlation to release parameters could be identified. These variations occur interindividually with astonishing uniform individual timing patterns. If we compare the men's medallists we find a high constancy in individual movement patterns as far as timing is concerned. Release Characteristics Of all release parameters velocity oi release appears to be the most important. The assumption of a direct linear relation between release velocity and throwing distance cannot be maintained. Quadratic regressions indicate an area for release velocities and not as expected for maximum velocities. If we summarize all data available on release velocity and throwing distance the correlation turns out to be r=.55. Correcting throwing distance for the influence of wind by calculating ballistic distance increases the correlation to I= .90. The negative coefficient for velocity and the difference between ballistic and official distance (r=-64) indicates a decreasing influence of the wind conditions with increasing release velocities. Thus increasing throwing distance by increasing release velocity is primarily an intraindividual problem of movement coordination on a high speed level. This result comes true not only for discus throwing but can also be observed in other throwing events and even athletic jumping events as well. Nevertheless individual styles profed to be rather repeatable and typical for a specific athlete. Discussion The present kinematic analysis of discus throwing increased the existing data base of the discipline. Timing Characteristics how extreme interindividual variabilities but high intraindividual constancy without significant relations to throwing distance. None of the timing variations can be recommended as the best solution. Release parameters revealed no further insights into throwing techniques. As release velocity contributes about 80% to the variance-of the ballistic distance it is the most important release parameter. The influence of the wind conditions appears to decrease statistically with increasing release velocity on the one hand but on the other hand avoids a higher correlation between release velocity and the official distance. Regression analysis revealed that release velocity must rather be optimized than maximized. This might be due to the individual athletes' ability to control the discus release at high velocities. History of the discus' acceleration described as change of discus velocity during the crucial phases of the turn again revealed interindividual variations without showing a common tendency or even a solution to be called the best. It must be questioned whether a kinematic analysis of top level athletes' techniques leads to further insights into the discipline itself. The kinematic data are nothing else than a descriptions of the athletes' movements in a more objective way. Those analyses did not yet identify the ideal technique. This means a dilemma for any trainer as he has no criteria to separate between mistakes and individual variations of movement technique.
Coaching and Sports Activities
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