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Previous planar models of the downswing in golf have suggested that upper limb segments (left shoulder girdle and left arm) move in a consistent fixed plane and that the clubhead also moves only in this plane. This study sought to examine these assumptions. Three-dimensional kinematic analysis of seven right-handed golfers of various abilities (handicap 0?–?15) was used to define a plane (named the left-arm plane) containing the 7th cervical vertebra, left shoulder and left wrist. We found that the angles of this plane to the reference horizontal z axis and target line axis (parallel to the reference x axis) were not consistent. The angle to the horizontal z axis varied from a mean of 133° (s = 1°) at the start of the downswing to 102° (s = 4°) at impact, suggesting a “steepening” of the left-arm plane. The angle of the plane to the target line changed from ??9° (s = 16°) to 5° (s = 15°) during the same period, showing anticlockwise (from above) rotation, although there was large inter-individual variation. The distance of the clubhead from the left-arm plane was 0.019?m (s = 0.280?m) at the start at the downswing and 0.291?m (s = 0.077?m) at impact, showing that the clubhead did not lie in the same plane as the body segments. We conclude that the left arm and shoulder girdle do not move in a consistent plane throughout the downswing, and that the clubhead does not move in this plane. Previous models of the downswing in golf may therefore be incorrect, and more complex (but realistic) simulations should be performed. 相似文献
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John Sherblom Lisa Ker nen Lesley Withers 《Journal of Applied Communication Research》2002,30(2):143-162
Independence and competence define the traditional characteristics of a game warden. External pressure to transform the game warden service into a more culturally and ethnically diverse state law enforcement agency, however, creates tensions surrounding these characteristics in the organization's structurationally defined agency and reflexivity of law enforcement; duality of structure in office memos and citation counts; social integration and institutional reproduction of law enforcement training, use of decoys, and search and seizure procedures; and time-space distanciation of working a 40-hour week or having complete responsibility for a territory. The present study examined how these tensions interact with the traditional assumptions of independence and competence to transform the meaning of these characteristics, and of the game warden service itself. 相似文献