Science and technology.
科技。
Exercise and addiction.
鍛煉也會上癮。
Fun run.
奔跑的奧秘。
People, it seems, have evolved to be addicted to exercise.
人類似乎在進化過程中對鍛煉上癮了。
AS THE legions of gym bunnies and jogging enthusiasts who race out into the spring sunshine every year clearly demonstrate, running can be fun. More specifically, running triggers the release of brain chemicals called endocannabinoids that create a potent feeling of pleasure. As their name suggests, these endocannabinoids work in the same way as the active ingredient of marijuana.
那一大批在春日和煦的陽光中奔跑著的健身愛好者無不向我們展示著奔跑的樂趣。更確切地講,在奔跑時人體內有一種化學物質被釋放,從而使人產生一種強烈的愉悅感。正如其名字的含義一般,這些endocannabinoids有著跟大麻中的有效成分一樣的效果。
From an evolutionary standpoint this surge of endocannabinoids, and the "runner's high" it creates, make sense. For ancient humans, remaining fit enough to run after game and away from predators and enemies was vital for survival. Yet whether other mammals are also driven to exercise by endocannabinoids has remained a mystery. 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.
從進化論的觀點來看,人體內endocannabinoids水平的上升及由此而生的"賽跑者的亢奮"對人類的發展是有意義的。那些遠古時代的人類,為了能夠順利追捕到獵物并從其他獵食者的追擊中逃脫,必須將身體狀態始終維持在一個良好的水平。既然人類如此,那么其他哺乳動物是否也會在endocannabinoids的內在驅動下而進行鍛煉呢?這仍是個未解之謎。現在一項由Arizona大學的David Raichlen博士領銜的研究已經在其他哺乳動物體內---并非全部都有——發現了endocannabinoids的存在。
You expect me to what?
你猜我在干什么?
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. 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. 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.
Raichlen先提出了一個假設:像羚羊,馬和狼這樣一些因擁有"飛毛腿"而在進化過程中受益的哺乳動物中也存在著"鍛煉產生的興奮"現象;而那些以靈動著稱,卻非憑奔跑文明的動物,如雪貂,則不會出現此現象。為了檢驗這些猜想,Raichlen和由其同事所組成的團隊設計了一個實驗——對在跑步機上行走,奔跑過后的動物體內的endocannabinoids水平進行監控。
The experimental animals in question were ten people, eight dogs and eight ferrets. Dr Raichlen had them run or walk on the treadmill for 30 minutes. 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. Running speeds were thus set at 2.5 metres a second for people, 1.83 for dogs and 0.84 for ferrets. Walking speeds were set at 1.25 metres a second for people and 1.1 for dogs. The ferrets proved too easily distracted to walk consistently on the treadmills and were thus left to sit quietly in their cages for this part of the study. Each participating animal ran for one session and walked for one other, and did so on separate days, to avoid exhaustion. Before and after each session, blood was drawn from each and the endocannabinoid levels in it were measured.
被考慮用來進行實驗的動物有以下三種:十個人,八條狗和八只雪貂。Raichlen博士先讓他們在跑步機上行走或奔跑30分鐘。由于不同的動物速度不一,所以跑步機的傳送帶速度設置是以使不同動物的心率達到同一水平為依據。這樣設置的結果便為:奔跑速度為人類2.5米/秒,狗1.83米/秒,雪貂0.84米/秒;行走速度為人類1.25米/秒,狗1.1米/秒。雪貂由于太易分心,沒辦法讓它持續在跑步機上行走,所以在進行該部分實驗時它們被留在了籠中靜靜地坐著。每只動物會跑一段走一段,為了避免動物們出現筋疲力盡的情況,實驗是分成幾天進行的。在實驗前和試驗后,動物們都會被抽血以檢驗其中的endocannabinoid水平。
The researchers report in the Journal of Experimental Biology that, after 30 minutes of walking (or sitting in a cage), participants' endocannabinoid levels did not rise. After running, however, the average human's endocannabinoid levels rose from 2.4 picomoles per millilitre (pmol/ml) to 6.1. Dogs showed a similar trend, with levels rising from 2.4 pmol/ml to 8.0. Ferrets were different. Although they did show an increase, from 3.0 to 3.9 pmol/ml, this was not a statistically significant rise. These findings suggest that dogs experience a "runner's high" but ferrets do not.
研究人員在《生物學實驗》雜志中提到,在經過30分鐘的行走(雪貂是呆在籠中)之后,參加實驗的動物的endocannabinoid水平并沒上升。然而在奔跑過后情況則有所不同:那10個人的平均endocannabinoid水平從2.4 pmol/ml上升到了6.1 pmol/ml。狗的變化趨勢與人類似——由2.4 pmol/ml升至8.0 pmol/ml。唯獨雪貂例外。他們的endocannabinoid水平雖亦有所上升——3.0 至 3.9 pmol/ml,但仍處于統計學上可不被納入考慮的范圍內。這些發現表明狗中同樣存在著"賽跑者的亢奮"現象,而雪貂則沒有。
Dr Raichlen argues that it makes sense for ferrets not to have systems that reward cardiovascular activity, since such exercise consumes a lot of energy, may cause injury, and is not crucial to the stealthy hunting technique of sneaking down burrows and killing rabbits in their sleep. What is not clear is whether the endocannabinoid reward is an ancient mechanism that has been lost on branches of the mammalian tree that do not need it, or is something that evolves quickly in species which become active. Given that humanity's arboreal simian ancestors would presumably have had little need to run, it is probably the latter. But to be sure Dr Raichlen will need to put animals far less co-operative than ferrets on the treadmill.
看來雪貂體內并不存在對心血管活動進行陽性強化刺激的系統,Raichlen博士認為這對雪貂的發展同樣是有意義的,要知道太劇烈的運動會消耗掉過多的能量, 甚至引發受傷,且這并非是雪貂捕獵技術中的關鍵——它們一般只需偷偷溜進兔子窩并在兔子們熟睡時將其殺死即可。仍有待考證的是,究竟這種endocannabinoid刺激機制是從遠古時代起即為哺乳類動物所擁有(但在一些不需此機制的哺乳類分支中漸漸退化),還是從某些活躍的個別物種中進化出來的?鑒于人類的祖先—類人猿是樹棲動物,據推測它們很少有奔跑的需要,因此正確結論很可能是后者。但若要確認此假設,Raichlen博士需將更多如雪貂般不太合作的動物哄上跑步機。