Racket stage non-professional players racket last moments elbow slightly open have apparent backward swivel action force is not very concentrated Racket last moments knee Angle to force too large stirrup decreases . 3 .

引拍阶段非专业运动员引拍最后时刻肘关节略有打开，有明显的向后 转体动作，用力不是很集中；引拍最后时刻膝关节角度过大， 蹬地力量减小。