托福阅读练习：Why Walking Weakens Wee Ones托福考试(TOEFL)

文章作者 100test 发表时间 2011:03:01 00:56:42
来源 100Test.Com百考试题网

很多人都认为，体型大的动物消耗更多的能量。但一项研究表明事实并非如此。来看看今天的托福阅读材料。

　　If you’ve ever had to pick up and carry a tired child through the mall, you know that walking sometimes tuckers out the toddlers. Now scientists think they know why. The results appear in the Journal of Experimental Biology. [P. Weyand et al., "The mass-specific energy cost of human walking is set by stature," J. Exp. Biol., link to come]
　　Larger animals tend to use less energy per gram of body mass than smaller ones do, even at rest. But what happens when they’re in motion? Researchers recruited walkers of different ages and sizes, from a three-foot-tall kindergartner to a six-foot adult. While the subjects logged miles on the treadmill, the scientists measured their stride and metabolism.
　　And they found that people pretty much walk the same way, regardless of their stature. If you scaled a five-year-old up to be six-and-a-half feet tall, the giant child would lope along just like a similarly sized adult.
　　What’s more, walkers of all heights use the same amount of energy per step. That means that big people don’t conserve energy by strolling in a more economical style. They expend less energy because—just as you may have always suspected—they simply need fewer strides to cover the same ground. Which means that for some people a walk in the park ain’t necessarily a walk in the park.