你天生享受運動樂趣嗎？

你天生享受運動樂趣嗎?

It’s possible that some of us are born not to run. According to an eye-opening new genetics study of lab rats, published in The Journal of Physiology, the motivation to exercise — or not — may be at least partly inherited.

很可能，我們中的一些人不擅長跑步純屬“自然災(zāi)害”。最近在《生理學雜志》(The Journal of Physiology)上發(fā)表的一項研究令人大開眼界：這項在實驗室大鼠身上進行的新型遺傳學研究表明，鍛煉(或不鍛煉)的動機至少有一部分是由遺傳決定的。

For years, scientists have been bedeviled by the question of why so few people regularly exercise when we know that we should. There are obvious reasons, including poor health and jammed schedules. But researchers have begun to speculate that genetics might also play a role, as some recent experiments suggest. In one, published last year, sets of fraternal and identical adult twins wore activity monitors to track their movements. The results indicated that the twins were more alike in their exercise habits than a shared upbringing alone would explain. Their willingness to work out or sit all day depended to a large extent on genetics, the researchers concluded.

多年來，有個問題一直困擾著科學家們：為什么人人都知道應(yīng)該經(jīng)常鍛煉，但真正能做到的卻寥寥無幾?有一些原因顯而易見，譬如健康狀況不佳，以及忙得抽不出時間來等。但是，最近的一些實驗結(jié)果促使研究人員猜測遺傳是否也在其中發(fā)揮了一定的作用。一項發(fā)表于去年的實驗招募了若干組異卵和同卵雙生的成年雙胞胎，并要求他們佩戴活動監(jiān)視器以跟蹤行蹤。結(jié)果表明，這些雙胞胎運動習慣間的相似性遠非僅憑生長在同一個環(huán)境所能解釋。研究人員得出了這樣的結(jié)論：他們是愿意去鍛煉還是想一整天都坐著不動，在很大程度上取決于遺傳。

But which genes might be involved and how any differences in the activity of those genes might play out inside the body were mysteries. So scientists at the University of Missouri recently decided to delve into those issues by creating their own avid- or anti-exercising animals.

然而，究竟有哪些基因參與其中，它們的活性差異又是如何在體內(nèi)發(fā)揮作用的，這些都仍是未解之謎。因此，最近，密蘇里大學(University of Missouri)的科學家們決定自己培養(yǎng)出喜歡和討厭運動的動物品系，進而對上述問題進行深入探討。

They accomplished this task by inter-breeding normal rats that had voluntarily run on wheels in the lab. The male rats that had run the most were bred with the female rats that also had run the most; those that had run the least were likewise mated. This scheme continued through many generations, until the scientists had two distinct groups of rats, some of which would willingly spend hours on running wheels, while the others would skitter on them only briefly, if at all.

為了達成這個目標，他們根據(jù)正常實驗室大鼠自愿在跑輪上跑動的情況，對其進行了雜交——讓最喜歡跑動的雄性大鼠與最喜歡跑動的雌性大鼠交配;同理，讓最討厭跑動的雄性大鼠與最討厭跑動的雌性大鼠交配。這一方案持續(xù)進行了許多世代，直至科學家們獲得了兩組截然不同的大鼠品系：其中一組可以一連在跑輪上跑數(shù)個小時也樂此不疲，而另一組大鼠就算上了跑輪也只是漫不經(jīng)心地從上面一竄而過——這還是在它們肯賞光動一動的情況下。

In their first experiments with these rats, the researchers found some intriguing differences in the activity of certain genes in their brains. In normal circumstances, these genes create proteins that tell young cells to grow up and join the working world. But if the genes don’t function normally, the cells don’t receive the necessary chemical messages and remain in a prolonged, feckless cellular adolescence. Such immature cells cannot join the neural network and don’t contribute to healthy brain function.

在關(guān)于這些大鼠的第一項實驗中，研究人員發(fā)現(xiàn)它們腦部某些特定基因的活性存在著一些有趣的差異。在正常情況下，這些基因會制造一些蛋白質(zhì)，指導(dǎo)幼稚細胞生長發(fā)育，好盡快加入具有工作能力的成熟細胞的行列。但如果這些基因不能正常發(fā)揮其功能，細胞接受不到必要的化學信息，就只能長期滯留在無功能的“細胞青春期”。這類未成熟細胞無法聯(lián)入神經(jīng)網(wǎng)絡(luò)，因此就不能為健康的大腦功能作出應(yīng)有的貢獻。

In general, these genes worked normally in the brains of the rats bred to run. But their expression was quite different in the non-runners’ brains, particularly in a portion of the brain called the nucleus accumbens, which is involved in reward processing. In humans and many animals, the nucleus accumbens lights up when we engage in activities that we enjoy and seek out.

一般而言，在科學家們培養(yǎng)出的“跑步愛好者”大鼠的腦部，這些基因可以正常發(fā)揮功能。但在那些“非跑步愛好者”大鼠的腦部，這些基因的表達情況截然不同，在名為“伏隔核”的腦區(qū)中尤其明顯。伏隔核與獎勵加工有關(guān)，當人類和許多動物從事自己喜歡或渴求的活動時，伏隔核就會處于激活狀態(tài)。

Presumably as a result, when the scientists closely examined the brains of the two types of rats, they found that by young adulthood the animals bred to run had more mature neurons in the nucleus accumbus than did the non-runners, even if neither group had actually done much running. In practical terms, that finding would seem to indicate that the brains of pups born to the running line are innately primed to find running rewarding; all those mature neurons in the reward center of the brain could be expected to fire robustly in response to exercise.

或許正是因為這個原因，在科學家們仔細檢查了這兩組大鼠的腦部后，他們發(fā)現(xiàn)：同樣是處于年輕成年期，“跑步愛好者”大鼠伏隔核中的成熟神經(jīng)元要多于 “非跑步愛好者”大鼠，即使在兩組大鼠實際上都未進行過大量跑動時依然如此。從實際角度而言，這一研究結(jié)果表明，“跑步愛好者”大鼠品系的幼崽在頭腦里天生就覺得奔跑是一大快事;可以想見，在運動的刺激下，它們腦部獎勵中心的所有成熟神經(jīng)元都將強烈地興奮起來。

Conversely, the rats from the reluctant-running line, with their skimpier complement of mature neurons, would presumably have a weaker innate motivation to move.

相反，在“非跑步愛好者”大鼠品系中，成熟神經(jīng)元“供應(yīng)不足”，因此它們參加運動的先天性動機可能就比較弱。

Those results would be disheartening, except that in the final portion of the experiment the scientists had reluctant runners exercise by setting them on running wheels, while also providing some born-to-run animals with wheels. After six days, the unwilling runners had accumulated far less mileage, about 3.5 kilometers (two miles) per rat, compared to almost 34 kilometers each by the enthusiasts.

乍一看來，這些研究結(jié)果頗令人沮喪，但實驗的最后部分重又燃起了人們的希望。在這一階段的實驗中，科學家們把“跑步愛好者”大鼠與“非跑步愛好者” 大鼠一起放在跑輪上，這樣，當前者歡快地奔跑時，后者也被迫要跟著走幾步。六天后，它們的累積奔跑里程約為平均每只大鼠3.5千米(兩英里)，遠遠少于 “跑步愛好者”大鼠(平均每只大鼠近34千米)。

But the halfhearted runners’ brains were changing. Compared to others in their family line that had remained sedentary, they now showed more mature neurons in their nucleus accumbens. That part of their brain remained less well developed than among the naturally avid rat runners, but they were responding to exercise in ways that would seem likely to make it more rewarding.

然而，在這些三心二意的跑步者的腦部，改變正在悄然發(fā)生。研究顯示，現(xiàn)在它們伏隔核中的成熟神經(jīng)元數(shù)量已經(jīng)超過了同一品系中依然保持久坐不動生活習慣的同伴們。雖然就該腦區(qū)的發(fā)育程度而言，它們?nèi)匀徊荒芘c那些天生的跑步愛好者們相提并論，但它們腦部對運動的應(yīng)答方式很可能已經(jīng)開始促進它們更加樂于運動。

What, if anything, these findings mean for people is “impossible to know at this point,” said Frank Booth, a professor of biomedical sciences at the University of Missouri who oversaw the study. Rat brains are not human brains, and rat motivations are at best opaque.

這些研究結(jié)果對人類意味著什么——是說，如果它們的確具有一定意義的話——“尚未可知，”該研究的負責人，密蘇里大學的生物醫(yī)學教授弗蘭克·布思(Frank Booth)說。大鼠的腦并不能等同于人類的腦，況且，現(xiàn)在人們對于大鼠的動機充其量也只是一知半解的狀態(tài)。

Even so, Dr. Booth said, his group’s data would seem to suggest “that humans may have genes for motivation to exercise and other genes for motivation to sit on the couch,” and over generations, one set of these genes could begin to predominate within a family. But predispositions are never dictatorial.

即便如此，布思博士指出，他團隊的研究數(shù)據(jù)表明：“在人類體內(nèi)，很可能也存在激勵運動的基因，以及讓人賴在沙發(fā)上充當‘沙發(fā)土豆’的其他基因。”經(jīng)歷數(shù)代之后，其中一組基因或許會開始在某一家族內(nèi)占據(jù)主導(dǎo)地位。但是，先天性傾向從來都不會是唯一的決定因素。

“People can decide to exercise,” whatever their inheritance, Dr. Booth said, and, as his study’s final experiment suggests, they could rewire their brains so that moving becomes a pleasure.

無論遺傳背景如何，“人們都一樣可以選擇去做運動，”布思博士說，正如他研究中最后的實驗所顯示的，人們可以重整腦部的神經(jīng)連接，讓運動成為一種樂趣。