If your friends are happy—turns out you’re more likely to be happy too. If your friends are overweight, that too ups the odds you’ll pack on pounds. Those effects have been shown in studies. And now researchers have identified another seemingly contagious quality: exercise.

　　如果你的朋友很快乐，那你也快乐的可能性很大。如果你的朋友体重超重，那你体重增加的几率也会上升。这些效应已经被研究证明。现在研究人员证实了另一个似乎具传染性的东西：锻炼。

　　The investigators analyzed the running activity of more than a million individuals worldwide who used an exercise tracking device for five years. And they used weather patterns as a way to randomly examine different parts of that global network.

　　研究人员分析了全球100多万人的跑步活动，这些人5年来一直在使用运动追踪装置。研究人员运用天气模式对全球不同地区进行随机检测。

　　"If it happens to be a really nice day out, sunny and not too hot, not too cool, that will induce people to run more.” Sinan Aral, a computational social scientist at MIT. “If it’s a rainy day and cold, that will induce people to stay in more on average."

　　“如果赶上好天气，阳光明媚，温度适中，那外出跑步的人会更多。”麻省理工学院的计算社会科学家希南?阿拉尔表示。“但是如果是下雨天，而且很阴冷，那人们更愿意呆在家里。”

　　And since cities have different weather patterns, he says, this natural experiment allowed them to ask: Does a rainy day in New York affect running in San Diego? "If the weather in New York causes changes in the running behavior in San Diego, it can really only be happening thru peer influences of the friends who live between New York and San Diego."

　　阿拉尔表示，由于不同的城市有不同的天气模式，自然实验使研究人员产生这样的问题：纽约下雨会影响圣地亚哥的跑步活动吗?“如果纽约的天气可以改变圣地亚哥的跑步行为，这只能通过居住在纽约和圣地亚哥的朋友之间的同伴影响产生。”

　　And that is exactly what he and his colleague saw: that the behavior of one city’s runners could indeed affect the behavior of runners in another socially connected city. The study is in the journal Nature Communications.

　　这就是阿拉尔和同事们得出的结论：一个城市跑步者的行为可能的确会影响与其有社交联系的另一个城市跑步者的行为。这项研究结果发表在《自然通讯》期刊上。

　　A few caveats: women tended to be influenced more by the female runners in their networks. And less active runners tended to influence more active runners to run more, but not so much the other way around. Still, this could be valuable intel for health professionals. "We have to start thinking about consumers and citizens as networked consumers and networked citizens. Where they are influenced by and influence their social network in very strong and dynamic ways, that will change the way a particular intervention succeeds or fails."

　　几点说明：女性更容易受其社交圈中的女性跑步者的影响。活跃度低的跑步者会令活跃度高的跑步者增加跑步距离，但后者对前者的影响却不太多。不过，这对健康专家来说可能仍是个有价值的情报。“我们要开始将用户和市民看作网络化的用户和市民。因为他们会以非常强烈又动态的方式影响其社交网络，或被社交网络影响，而这会改变特殊干涉的成败。”

　　In other words—if your prescription is more exercise? The doctors might want to write a prescription for your friends and family, too.

　　换言之，如果医生给你开的处方是增加锻炼，那医生或许想让你的朋友和家人也多运动运动。