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The kinematics, movement phasing and timing of a field hockey drive in response to varying conditions of uncertainty Weicker, Dianne Louise


This study was designed to provide a detailed analysis of the parameters which interact to produce a field hockey drive. The drive was performed by an elite performer under two conditions of uncertainty--BLOCKED and RANDOM order of ball speed presentation. In the former condition, ball speeds were directed toward the subject until she performed ten successful drives at a single speed. This continued over three successive speed blocks (20, 30 and 40 m.p.h.). Under the RANDOM condition, the same three ball speeds were delivered to the subject in a random and unpredictable order until ten successful drives were recorded at each speed. Cine analysis (50 f.p.s.) of the subject's successful responses under the two experimental conditions permitted conclusions to be drawn pertaining to the kinematics, phasing, and timing of the stroke. Measurements were recorded for each stroke segment. All movement phases of each stroke remained consistent over the recorded temporal variables of movement duration and peak velocity. The emphasis appeared to be placed upon varying the initial phases of the stroke (i.e., backswing, preparatory phases) in order to produce a temporally consistent ballistic downswing to ball contact. It seemed likely that the subject appraised the ball's changing retinal image size to determine which ball speed was being delivered and then incorporated additional stick movement to "mark time" before initiating temporally consistent movement phases (C1, C2). As spatial uncertainty increased, the subject delayed her response initiation, but then tended to respond in intervals of one reaction time for each stroke phase. Consistency was evident for displacement and initiation point values, but to a lesser extent than existed for the other variables. However, as a result of this adjustment in spatial location and displacement of the stickend during the preliminary phases of the response, the subject was able to produce a consistent and accurate ballistic downswing.

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