LOWER LIMB KINEMATICS AND FLOW CHARACTERISTICS OF THE WATER POLO 'EGGBEATER' KICK
AbstractINTRODUCTION The water polo 'eggbeater kick' involves a cyclical action of the lower limbs producing upward forces to support players in an elevated position to pass, receive a pass, shoot for goal, or block those of an opponent. Since the pioneering work of Clarys (1 974) very little analysis has been conducted on the water polo eggbeater kick. The purpose of this study was to investigate the lower limb kinematics and flow characteristics of the water polo eggbeater kick and to identlfy variables associated with height sustained over several kick cycles. METHOD 'helve male competitive water polo players varying in ability from novice to elite at national level were videotaped from above and below the water while each performed an eggbeater kick to 'hold' their elevated position for a period of 30 seconds. The analysis period consisted of at least 1.5 complete cycles of each foot corresponding to the middle of the 30 second period. Standard three-dimensional videotaping and analysis techniques were employed to determine the co-ordinates of the above-water and below-water anatomical ) landmarks. The planes of the right and left feet were defined by black spherical craft beads attached inferiorly to the calcaneous and medial and lateral metatarsal phalangeal joints. This enabled calculation of pitch and sweepback angles of the foot with respect to the direction of flow. These angles were defined in a similar manner to that commonly used in studies of the hand in swimming (Schleihauf, 1979). RESULT The height of the vertex of the head that could be sustained by the players ranged from 0.22 m to 0.42 m. Three foot velocity variables were significantly related to height (p < 0.05) and together accounted for 89 percent of the variance in height achieved. These were the mean of the squared foot velocity (r = 0.85). and the percent contribution of the vertical and antero-posterior components of foot velocity (r = -0.72 and r = 0.72 respectively). Although there was a considerable contribution by the medio-lateral component to resultant foot velocity, the magnitude of this component was not related to height. Pitch angles were small throughout the kick. The mean maximum pitch angle was 28 degrees (SDk 9 degrees) and the mean minimum pitch angle was 13 degrees (SD f 8 degrees). CONCLUSION The results indicated that foot speed is the most important factor contributing to performance in the eggbeater kick. It is also desirable to rnaximise the relative contribution' of the antero-posterior motions and to rninimise vertical motions. The fact that players used small angles of pitch and have large horizontal components of foot velocity indicated that Lift forces contributed greatly to forces in the upward direction. REFERENCES Clarys, J.P. (1974). Analysis of the eggbeater and breaststroke kicks in water polo. In Proceedings of the International Symposium on Biomechanics in Swimming, pp 241-246. Baltimore, University Park Press. Schleihauf, R.E. (1979). A Hydrodynamic analysis of swimming propulsion. In Swimming III (Edited by Terauds, J. and Bedingfield, E.W.), pp. 70-109. Baltimore, University Park Press.