时差N小时 路时为什么要甩胳膊?(上)（在线收听）

Have you ever wondered why we swing our arms while walking? It’s a curious phenomenon, since arms don’t play an obvious role in locomotion. You can still walk normally when your arms are full of groceries or with your hands in your pockets, so why do we do it? Isn’t it a waste of energy? Two independent studies, both published in 2009, may provide some answers to this mystery. The Answer… Using a combination of mechanical models, computer simulations and tests with human walkers and runners, the studies concluded that arm swinging just sort of…happens. In other words, you don’t need muscles for your arms to start swinging, although you can use muscles to swing your arms higher or more forcefully. If you’re walking and your arms are hanging relaxed by your sides, they will normally swing in sync with the opposite leg. That is, your right arm swings forward when your left leg steps forward and vice versa.

你想过为什么走路时我们要甩胳膊吗？这是很有趣的现象，因为胳膊在走路时并没有明显的作用。当你手上拎着东西或将手插进口袋里，你仍然可以正常走路。那我们为什么要甩胳膊呢？是在浪费体力？两项发布在2009年的独立研究也许能为此提供答案。答案……利用机器模型，电脑模拟和对走路的人和跑步的人测验，研究得出：走路时甩胳膊只是一种自然而然的动作。换句话说，你不需要胳膊上的肌肉来甩胳膊，尽管你可以用肌肉来甩胳膊甩得更高些或有力些。走路时如果你的胳膊垂在身体侧面，无事可做，那胳膊就会朝腿运动的相反方向甩动。