????但是凱娜里克說最有意思的發現是，身材走樣的人都會被認為比經常鍛煉的人老5歲?！拔蚁?，那是一種年輕有活力的感覺，”凱娜里克說，而這同樣也有助于延年益壽。

????她的研究還有另一個發現，那就是將持續保持鍛煉的老鼠強制停止運動后，出現的癥狀如同強制停止注射嗎啡的老鼠一樣。所以，富于進取心的人開始可能只會參加半程馬拉松，然后就覺得可以再多跑一段，于是就是全程馬拉松，接下來就是超級馬拉松，最后就可以完成鐵人三項了。

????“身體到達一定極限之后就會有一種上癮的感覺，”凱娜里克說?！叭绻麄兠爸笱┡懿?，或是連跑100英里穿越死亡峽谷時，你會發現，一定有某些其他的東西在發揮作用?！?/p>

????布朗說，要看一個人對耐力運動是不是發自內心的熱愛，就問問他“除了運動員，你在生活中還有其他身份嗎？”這個問題至關重要。雖然“躺在功勞薄”上是個貶義詞，但在一個大多數人都身材走樣的社會中，倘若你既能跑完10公里還能賺到六位數薪水，絕對是件了不起的事。

????譯者：唐昕昕

????But Kanarek says what she found most interesting was that the less fit were deemed about five years older than the intense exercisers. "I think there's that desire to feel younger," says Kanarek, to perhaps stave off mortality.

????Couple that with another of her research findings -- namely that rats weaned off of intense exercise go through classic symptoms of withdrawal very similar to the kind experienced by rats given morphine -- and you can start to see how an achievement-oriented sort might start with a half-marathon, but then decide she needs to do more. A marathon. An ultra-marathon. An Ironman.

????"When people become really extreme, they do get into this addictive pattern," says Kanarek. "If they're running when it's snowing, or doing ultras -- running 100 miles through Death Valley -- there's something else going on there."

????The key to recognizing if one's attitude toward endurance events is healthy or not, says Brown, is to ask "Do you have an identity in your life other than that as a performer? That's essential." While "resting on your laurels" has a negative connotation, in a society where many people are out-of-shape, being able to run a 10K -- and earn six figures -- is pretty good too.