The head should not bounce up and down during this drill.

在做这个训练的时候，头部不允许上下移动。

Medicine Patient: Why do you ask me to bounce up and down on my bed?

病人：为什么你让我在床上上下蹦跳呢？

As it starts to bounce up it will stretch in the direction it is going.

当小球弹跳起来后它要在它弹跳的方向上拉伸变形。

I rode him like a pro the other just stood and watched me bounce up and down on his stiff hard cock.

i骑上他像一个专业，其他只是站在，并观看了我反弹向上和向下对他的僵硬硬公鸡。

So if I release it all the way here, you would not expect that it will bounce up all the way to here.

如果我在这里释放，不可能,它会到达这点。

He then placed the second lift on the ledge and used it to bounce up even higher, landing on the top rim of the canyon.

然后他用第二个发射器把自己弹到更高的地方，站到了峡谷的顶端。