PRE-SEASON KINEMATICS OF INTERCOLLEGIATE HIGH JUMPERS
AbstractThe purpose of this study was to compare three-dimensional kinematic variables among intercollegiate high jumpers during the pre-season at increasing heights, Five Division I college high jumpers were video taped during a preseason indoor practice session. The jumpers were filmed from the penultimate step to contact with the jumping mat. The film setting included two 60 Hz SVHS camcorders set at a shutter speed of 11250 second. One camera was positioned along the axis of the high jump bar, with the second camera positioned at a 45 degree angle relative to the optical axis of the first. Each successful jump was digitized and analyzed using the Ariel Performance Analysis System (APAS). The views were synchronized using the initial foot contact of the penultimate step as a temporal reference point. The views were transformed to three-dimensional coordinates using a Direct Linear Transformation (DLT). Each joint center location was smoothed individually. The cutoff frequency of a double-pass recursive Butterworth filter was determined by an inspection of the power spectrum. Variables for analysis included: (1) horizontal velocity of the center of mass at the start of the takeoff phase and at takeoff, (2) vertical velocity of the center of mass at the end of the approach run and at the point of bar clearance, (4) joint angles of the ankle, knee, hip and shoulder at the point of takeoff, and (5) the horizontal distance between the center of mass of the body and the lateral malleolus of the ankle (body lean) at the point of takeoff. Results of the kinematic comparison revealed that jumpers adjust to increasing heights by increasing the vertical velocity of the center of mass at the point of takeoff and by adjusting the orientation of the shoulders (leaning) later in the jump in order to allow for a longer propulsion phase to attain a higher center of mass.
Coaching and Sports Activities
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