評論
打印
Exercise and addiction
鍛煉與上癮
Fun run
有趣的跑步
People, it seems, have evolved to be addicted to exercise
人們似乎越來越沉迷于鍛煉
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.
每年春天都有大批的健身愛好者和跑步愛好者們走出家門，奔跑在陽光之下，由此可見，跑步可以帶來樂趣。更確切的說，跑步能激發大腦分泌一種叫做內源性大麻素的化學物質，它能產生強烈的愉悅感。就像它們的名字那樣，這些內源性大麻素和大麻的活性成分擁有同樣功效。
legions of：大批的 Legions of birds 一大群鳥 endocannabinoids：內源性大麻素
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.
從進化角度來看，這種內源性大麻素的增多，以及由它引起的“跑步者的亢奮情緒”是有道理可循的。對于古人來說，能在游戲之后還有足夠的體力奔跑，逃離掠奪者和敵人是生存下去的根本。然而，其他哺乳動物是否也是因內源性大麻素而進行鍛煉就不得而知了。現在，亞利桑那州的戴維•瑞奇連做了一項研究，揭示出奔跑者的亢奮情緒還存在于其他一些物種身上，并非全部都有。
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.
瑞奇連博士進行假設，由內源性大麻素引起的鍛煉亢奮情緒可能同樣會發生在那些足部進化較快的哺乳動物身上，如羚羊、馬和狼。但是，他還認為這些情緒不會出現在像雪貂這樣快速靈活卻不善長跑步的動物身上。為了驗證這些觀點，他和一組同事設計了一個試驗，觀察不同的物種在跑步機上走或跑過一段路程后，各自內源性大麻素的變化情況。
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.
試驗用到的動物是十個人、八條狗和八只雪貂。瑞奇連博士讓他們各自在跑步機上或走或跑上30分鐘。由于不同物種走或跑的速度不同，跑步機設定的速率也要因人而異，因此他們的心跳速度會上升到一個相同的高度。人每秒的奔跑速率設為2.5米，狗為每秒1.83米，雪貂為每秒0.84米。人每秒的步行速度為1.25米，狗為1.1米。事實證明雪貂無法堅持在跑步機上保持行走，所以這部分研究他們只能靜靜的呆在籠子里。每個參與者都要分別走上和跑上一段，但是這兩段路程需分開進行以免過度疲勞。每段路程的開始和結束都要進行抽血，以此判斷他們體內內源性大麻素的含量。
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.
研究者們在《試驗生物學雜志》上發表報告稱，30分鐘的步行（或籠中靜坐）后，參與者的內源性大麻素含量都沒有升高。但是，跑步后，人體內的內源性大麻素平均含量從每毫升2.4皮摩爾上升到6.1皮摩爾。狗體內的內源性大麻素也從2.4皮摩爾上升到8.0皮摩爾。不同的是，盡管雪貂的內源性大麻素也有所上升，但只從3.0上升到3.9，從統計學上看，這并不是很高的數值。這些發現表明，狗會產生“跑步者的亢奮情緒”，而雪貂卻不會。
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.
瑞奇連博士認為，雪貂在進行過心腦血管運動后，體內沒有補償性的機制是有原因的，因為這些運動會消耗太多能量，有可能使他們受傷，而且它們常常小心翼翼的潛入洞穴，在熟睡中就將兔子們殺死，這些運動對他們來說毫無意義。但是，內源性大麻素是否曾經存在于遠古物種的體內，只是由于不再需要而在某些哺乳動物科身上消失了，還是它僅僅在某些活躍的物種加速進化過程中產生，這些都不得而知。假設人類生活在叢林中的猿類祖先沒有奔跑的需要，則后者很有可能是事實。但是為了證實這一點，瑞奇連博士需要再把一些和雪貂不同的動物放上跑步機。
