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　　People, it seems, have evolved to be addicted to exercise

　　人类似乎在进化过程中对锻炼上瘾了

　　AS THE legions of gym bunnies and jogging enthusiasts who race out into the spring sunshine every year clearly demonstrate, running can be fun.

　　那一大批在春日和煦的阳光中奔跑着的健身爱好者无不向我们展示着奔跑的乐趣。

　　More specifically, running triggers the release of brain chemicals called endocannabinoids that create a potent feeling of pleasure.

　　更确切地讲，在奔跑时人体内有一种化学物质被释放，从而使人产生一种强烈的愉悦感。

　　As their name suggests, these endocannabinoids work in the same way as the active inGREdient of marijuana.

　　正如其名字的含义一般，这些endocannabinoids有着跟大麻中的有效成分一样的效果。

　　From an evolutionary standpoint this surge of endocannabinoids, and the runner's high it creates, make sense.

　　从进化论的观点来看，人体内endocannabinoids水平的上升及由此而生的赛跑者的亢奋对人类的发展是有意义的。

　　For ancient humans, remaining fit enough to run after game and away from predators and enemies was vital for survival.

　　那些远古时代的人类，为了能够顺利追捕到猎物并从其他猎食者的追击中逃脱，必须将身体状态始终维持在一个良好的水平。

　　Yet whether other mammals are also driven to exercise by endocannabinoids has remained a mystery.

　　既然人类如此，那么其他哺乳动物是否也会在endocannabinoids的内在驱动下而进行锻炼呢?

　　Now a study led by David Raichlen of the University of Arizona has revealed that the runner's high does exist in other species, but not in all.

　　这仍是个未解之谜。现在一项由Arizona大学的David Raichlen博士领衔的研究已经在其他哺乳动物体内-并非全部都有-发现了endocannabinoids的存在。

　　【每日晨读】经济学人GRE双语阅读 揭秘奔跑锻炼上瘾的秘密图2

　　You expect me to what?!

　　你想要我干什么?!

　　Dr Raichlen hypothesised that endocannabinoid-driven exercise highs would be found in those mammals that gain an evolutionary benefit from being fast on their feet: antelopes, horses and wolves, for example.

　　Raichlen先提出了一个假设：像羚羊，马和狼这样一些因拥有飞毛腿而在进化过程中受益的哺乳动物中也存在着锻炼产生的兴奋现象;

　　However, he also thought that they would not be present in those which are known for being quick and agile, but not for running, like ferrets.

　　而那些以灵动著称，却非凭奔跑文明的动物，如雪貂，则不会出现此现象。

　　To test these ideas, he and a team of colleagues devised an experiment that monitored the endocannabinoid levels of different species after they had been walking or running on a treadmill.

　　为了检验这些猜想，Raichlen和由其同事所组成的团队设计了一个实验-对在跑步机上行走，奔跑过后的动物体内的endocannabinoids水平进行监控。

　　The experimental animals in question were ten people, eight dogs and eight ferrets.

　　被考虑用来进行实验的动物有以下三种：十个人，八条狗和八只雪貂。

　　Dr Raichlen had them run or walk on the treadmill for 30 minutes.

　　Raichlen博士先让他们在跑步机上行走或奔跑30分钟。

　　Since running and walking speeds differ from species to species, the speed at which the treadmill moved was varied so that it raised the heart rates of the different participants to the same level.

　　由于不同的动物速度不一，所以跑步机的传送带速度设置是以使不同动物的心率达到同一水平为依据。