Sprinters are different from other people

Is athletic prowess attained or innate? Those who have suffered the tongue-lashing of a tyrannical games master at school might be forgiven for doubting the idea that anyone and everyone is capable of great sporting achievement, if only they would put enough effort into it. Practice may make perfect, but not all are built in ways that make it worth bothering in the first place.

The latest evidence of this truth has been gathered by Sabrina Lee of Simon Fraser University in Vancouver and Stephen Piazza at Pennsylvania State University. They have looked at the anatomy of sprinters and found that their feet are built differently from those of couch potatoes.

Dr Lee and Dr Piazza already knew that sprinters tend to have a higher proportion of fast-twitching muscle fibres in their legs than more sedentary folk can muster. (These fibres, as their name suggests, provide instant anaerobic pulling power, rather than the sustained, oxygen-consuming effort that is needed by longer-distance runners.) They suspected, though, that they would find differences in the bone structure as well. And they did.

They looked at seven university sprinters who specialise in the 100-metre dash and five 200-metre specialists, and compared them with 12 non-athletic university students of the same height. In particular, they looked at the sizes of bones of the toes and heel. They also used ultrasonic scanning to measure the sliding motion of the Achilles tendons of their volunteers as their feet moved up and down. This allowed them to study the length of the lever created by the tendon as it pulls on the back of the heel to make the foot flex and push off the ground.

Dr Lee and Dr Piazza found, as they report in the Journal of Experimental Biology, that the toes of their sprinters averaged 8.2cm in length, while those of non-sprinters averaged 7.3cm. The length of the lever of bone that the Achilles tendon pulls on also differed, being a quarter shorter in sprinters.

These findings suggest sprinters get better contact with the ground by having longer toes. That makes sense, as it creates a firmer platform to push against. In a sprint race, acceleration off the block is everything. Cheetahs, the champion sprinters of the animal kingdom, have non-retractable claws that give a similar advantage.

The reason for the difference in the Achilles tendons, though, is less immediately obvious. At first sight, sprinters might be expected to have more Achilles leverage than average, not less. First sight, however, is wrong. When muscles have to contract a long way, they usually do so quickly and with little force. When contracting short distances, though, they move more slowly and generate more force. Having a short Achilles lever allows the muscles that pull on the tendon to generate as much as 40% more force than the same muscles in a non-sprinter would be able to manage.

It is possible—just—that these anatomical differences are the result of long and rigorous training. But it is unlikely. Far more probable is that the old adage of coaches, that great sprinters are born not made, is true. Everyone else, games masters included, should just get used to the idea.
短跑选手和常人不同

运动员高超的技能是靠后天训练获得的，还是天生的？那些曾在学校里面受到专横的体育老师训斥的学生可能会怀疑这样的观点，即只要足够努力，任何一个人都能在体育上取得了不起的成就。他们的怀疑或许是有道理的。熟或许能生巧，但是，不是所有人天生就适合争夺冠军。

来自温哥华（Vancouver）西蒙弗雷泽大学（Simon Fraser University）的Sabrina Lee和宾夕法尼亚州立大学（Pennsylvania State University）的Stephen Piazza收集了有关这种说法的最新证据。在研究了短跑运动员的解剖结构信息后，他们发现这些运动员的足部和那些经常不运动的人的足部不一样。

Lee和Piazza博士早就已经知道，和长期伏案工作的人相比，短跑运动员的腿中快速收缩肌纤维含量更高一些（正如其名字所揭示的一样，这种纤维提供瞬 间的拉伸力，属于无氧运动，而对于长跑运动员来所，他们需要的是提供持续有氧拉伸力的肌纤维）。不过，Lee和Piazza推测，在这两类人中的骨骼结构 中，他们也能找到差异。结构他们真地发现了差异。

他们对12名大学生短跑运动员和12名非运动员进行了对比研究。在这12名短跑运动员中，有7名运动员的专项是100米，另外5名运动员的专项是200 米。非运动员和这些运动员的身高都是一样的。Lee和Piazza博士特别研究了这些人的脚趾骨骼和足跟的大小。在该研究的自愿者的脚上下移动的时候，他 们还利用超声波扫描技术测量了跟腱的滑动。这样他们就能研究跟腱所产生的“杠杆”的长度。跟腱拉伸足跟背部，从而使得足部弯曲，从而蹬离地面。

Lee和Piazza博士发现，这些短跑运动员脚趾的平均长度为8.2厘米，而那些非短跑选手脚趾的平均长度为7.3厘米。他们的研究结果发表在《实验生 物学杂志》（Journal of Experimental Biology）上。他们还发现，跟腱拉伸时所产生的“杠杆长度”也有差别，短跑运动员的“杠杆长度” 要短四分之一。

这些研究表明，因为短跑运动员的脚趾长一些，所以它们和地面的接触面积就更大一些。这对运动员是有利的，因为大的接触面积更加有利于足部蹬地。在短跑比赛 中，起跑加速决定着胜负。猎豹是动物中的短跑之王，它的脚爪是不能伸缩的，这给猎豹提供了类似的优势（译注：即和地面的接触面积更大）。

不过，对于跟腱为什么会有这些差别，目前还不清楚。乍看起来，短跑运动员似乎应该比普通人拥有更长的跟腱“杠杠”，而不是更短。然而这种第一感觉是错误 的。当肌肉必须收缩很长距离的时候，它移动更快，产生的力量也更小。不过，当肌肉做短距离收缩的时候，它们移动更慢，产生的力量更大。和非短跑选手相比， 短跑运动员较短的跟腱“杠杆”能使拉伸跟腱的肌肉产生的力量高出40%。

这些解剖上的差异也许---仅仅是也许---是长期艰苦训练的结构。但是，这种可能性不大。更加可能的是，教练们的“格言”——伟大的短跑选手是天生的，而不是训练出来的----是真的。其他任何人，包括体育老师在