The downhills are already maxed out by the laws of physics and safety .

下山路由于物理原理和安全的考虑，已经是最快成绩了。

Interesting business lesson learned on a bicycle : it 's very difficult to improve your performance on the downhills .

从自行车比赛中学到一节有趣的商业课：你很难提高下坡时的成绩。