THE USE OF ACTIVE LANDINGS IN THE HORIZONTAL JUMPS
AbstractINTRODUCTION Coaching and scientific literature on the horizontal jumps has often cited the importance of using an active landing, or "pawing" action, as a means of reducing braking impulses, thus reducing losses in the horizontal velocity of the total-body centre of mass (CM) during ground contact. However, this concept has not been extensively researched. Koh and Hay (1990) investigated the kinematics of the long jump (LJ) and triple jump (TJ), with particular emphasis on the relationship between the horizontal foot velocity and changes in the horizontal velocity of the CM during ground contact. While they were able to identify the use of active landings in both the LJ and the TJ, no statistically significant relationship between pre-touchdown foot velocity and changes in CM velocity during contact could be found. They suggested that this may have been due to the homogeneous nature of their elite subjects. PURPOSE AND METHODS The purpose of this study was to examine the takeoff kinematics of non-elite long and triple jumpers, and attempt to determine the relationship between pre-touchdown horizontal foot velocity and changes in the horizontal CM velocity during ground contact. Subjects were senior male jumpers competing in the long and triple jump competitions at the 1995 Atlantic Track and Field Championships, in Saint John, NB. Video data of the LJ takeoff and the TJ hop-to-step contact was collected in the sagittal plane with the best two trials of each subject being digitised. RESULTS - Kinematic analysis found that all subjects had negative horizontal foot velocity relative to the CM (i.e., they used active landings). Results showed a potential relationship between horizontal foot velocity and several other variables, including changes in CM velocity and ground contact time. CONCLUSIONS The present study sewed as a preliminary investigation for a more in-depth analysis of the kinetics and kinematics of the horizontal jumps, which involved the collection of ground reaction force data along with video data to examine the relationship of pre-contact horizontal foot velocity on the horizontal and vertical impulses encountered at ground contact as well as changes in CM velocity. Preliminary results from this analysis will be discussed.
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