Physics . When you drop your body, it's in a "weightless" mode,就是失重状态, 就像你从楼上跳下来,身体也是失重状态一样。The gravity is used to accelerate your body while you drop. 这是牛顿第二定律 So during this very quick momentary "dropping", you can finish the edge switching. Because, not much pressure is on the board, you can roll your ankle 从一边的立刃立到另外一边。 The moment you body start stopping, when drop to the lowest point that you knees can go, that's when you body applied more than your body weight/gravity to the board, because the board is facing a momentum 冲量 created by your body dropping movement. 这个时候就会出现你说的加压。不过正好,你完成了换刃,也要开始转弯,并且是弯前到弯中弧度最大的地方(basically the point of changing direction in the traverse),弧度越大、离心力越大,你此时正需要对板子加大压力以应对这个离心力。所以down unweighted 其实是非常精巧完整和高效的换刃方式 When you stand on the board not moving at all, the pressure on the board equals to your weight/gravity. This is 牛顿第三定律 😂😂😂