Abstract des Autors

In this paper, the volleyball serve is used as an exemplar of self-paced, extrinsic timing tasks and a constraints-led approach to the acquisition of coordination is advocated. From this perspective, a neo-Darwinian approach to the study of biological systems is invoked to understand how interacting constraints influence the emergence of coodination within the movement system. The implications for the organisation of practice in volleyball, particularly with respect to task decomposition, are discussed. To this end, recent proposals have suggested that examining how coordination is achieved in skilled perfomers can be used to structure practice for learners. Our analysis of the volleyball serve showed a highly consistent placement of the ball in the left-right and forward-backward dimensions was not essential for successful serving. Whilst performers tended to compensate for variances in the y and x directions, they stabilised the vertical position of the ball at it's zenith and contact, despite a range of initial conditions and ball flight trajectories. On the basis of these results, it seems that practice of the serve should emphasise the acquisition of an invariant peak height of ball toss rather than consistency in the left-right and forward-backward directions. Further, when ball-placement was practised by skilled athletes, with and without striking, greater amplitude and variability in ball zenith was observed in the former condition. The interpretation is that decoupling informational and physical constraints in practice is less conducive to successful performance. Moreover, the evidence suggests that the strategy of studying skilled athletes can aid understanding of how to decompose tasks during sport skill acquisition. Verf.-Referat