初学蛙泳的学生 ,往往出现臀部下沉、身体倾斜较大 ,甚至出现“站着游”的毛病。分析其原因 ,除技术方面外 ,主要是重心和浮心的关系。当人平卧在水面时 ,由于人的体重而产生一个向下的重力 ,其合力点叫重心。又据阿基米德原理 ,人在水里就会自然产生一个向上的浮力 ,其合力点 Breaststroke beginners students often appear buttocks sink, body tilt larger, and even “standing tour” problems. Analysis of the reasons, in addition to technical aspects, the main center of gravity and buoyancy relationship. When a person is lying on the water, a downward gravity occurs due to the weight of the person, and the resultant force is the center of gravity. According to Archimedes’ principle, people in the water will naturally have a upward buoyancy, and its point of cooperation