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揭开牙买加“闪电”博尔特奔跑如飞的秘密

更新时间:2017-7-23 9:32:35 来源:纽约时报中文网 作者:佚名

Something Strange in Usain Bolt’s Stride
揭开牙买加“闪电”博尔特奔跑如飞的秘密

DALLAS — Usain Bolt of Jamaica appeared on a video screen in a white singlet and black tights, sprinting in slow motion through the final half of a 100-meter race. Each stride covered nine feet, his upper body moving up and down almost imperceptibly, his feet striking the track and rising so rapidly that his heels did not touch the ground.

达拉斯——牙买加的尤赛恩·博尔特(Usain Bolt)身穿白色背心和黑色紧身短裤出现在一个视频画面中。视频以慢动作播放了他在一场百米赛跑中的后半程冲刺。他每一步跨越九英尺(约合2.7米),几乎察觉不到上半身的上下移动,脚掌着地后立刻弹起,脚后跟没有触地。

Bolt is the fastest sprinter in history, the world-record holder at 100 and 200 meters and the only person to win both events at three Olympics. Yet as he approaches his 31st birthday and retirement this summer, scientists are still trying to fully understand how Bolt achieved his unprecedented speed.

博尔特是史上速度最快的短跑运动员,是100米和200米短跑的世界纪录保持者,也是唯一一个在三届奥运会上同时赢得这两个项目冠军的运动员。但是,在博尔特即将迎来31岁生日,并将于今年夏天退役之时,科学家们仍在努力弄清他是如何达到这种前所未有的速度。

Last month, researchers here at Southern Methodist University, among the leading experts on the biomechanics of sprinting, said they found something unexpected during video examination of Bolt’s stride: His right leg appears to strike the track with about 13 percent more peak force than his left leg. And with each stride, his left leg remains on the ground about 14 percent longer than his right leg.

上个月,短跑生物力学领域的前沿专家、南卫理公会大学(Southern Methodist University)的研究者们表示,他们在研究博尔特跨步的视频时发现了一个出人意料的情况:他右脚触跑道时的峰值力似乎比左腿大约13%。每次跨步时,他的左脚在地面停留的时间比右脚长约14%。

This runs counter to conventional wisdom, based on limited science, that an uneven stride tends to slow a runner down.

这与传统观念相违背。基于有限的科学研究,传统观念认为,不均衡的跨步往往会降低跑步者的速度。

So the research team at SMU’s Locomotor Performance Laboratory is considering a number of questions as Bolt prepares for what he said would be his final performances at a major international competition — the 100 meters and 4x100-meter relay next month at the world track and field championships in London.

所以,在博尔特为自己最后的几场重要国际赛事做准备时——也就是下月伦敦世界田径锦标赛的100米比赛和4×100接力赛——南卫理公会大学运动表现实验室(Locomotor Performance Laboratory)的研究小组也在思考一些问题。

Among those questions: Does evenness of stride matter for speed? Did Bolt optimize this irregularity to become the fastest human? Or, with a more balanced stride during his prime, could he have run even faster than 9.58 seconds at 100 meters and 19.19 seconds at 200 meters?

这些问题包括:跨步均衡是否影响速度?博尔特是通过优化这种不均衡而成为跑步最快的人吗?又或者,如果跨步更均衡,那么他在巅峰时期是否能跑得比100米9.58秒和200米19.19秒更快?

“That’s the million-dollar question,” said Peter Weyand, director of the SMU lab.

“这是一个很有价值的问题,”南卫理公会大学相关实验室的主任彼得·韦安德(Peter Weyand)说。

The SMU study of Bolt, led by Andrew Udofa, a doctoral researcher, is not yet complete. And the effect of asymmetrical strides on speed is still not well understood. But rather than being detrimental for Bolt, the consequences of an uneven stride may actually be beneficial, Weyand said.

南卫理公会大学的这项研究由博士研究员安德鲁·尤道法(Andrew Udofa)主导,目前尚未完成。不对称跨步对速度的影响仍未被完全了解。不过韦安德表示,对博尔特来说,不均衡跨步的结果不是有害的,而可能是有益的。

It could be that Bolt has naturally settled into his stride to accommodate the effects of scoliosis. The condition curved his spine to the right and made his right leg half an inch shorter than his left, according to his autobiography.

情况可能是,为了适应脊柱侧弯的后果,博尔特天然形成了那种跨步方式。据他的自传称,脊柱侧弯导致他的脊柱向右弯曲,他的右腿比左腿短半英寸(1.27厘米)。

Initial findings from the study were presented last month at an international conference on biomechanics in Cologne, Germany. Most elite sprinters have relatively even strides, but not all. The extent of Bolt’s variability appears to be unusual, Weyand said.

上个月,他们在德国科隆一场关于生物力学的国际会议上报告了这项研究的初步发现。大部分顶尖短跑运动员跨步相对均衡,但不是所有人都这样。韦安德表示,博尔特的变动程度似乎不同寻常。

“Our working idea is that he’s probably optimized his speed, and that asymmetry reflects that,” Weyand said. “In other words, correcting his asymmetry would not speed him up and might even slow him down. If he were to run symmetrically, it could be an unnatural gait for him.”

“我们的研究思路是,他很可能优化了自己的速度,而不对称反映了这一点,”韦安德说。“换句话说,纠正他的不对称可能不会提高他的速度,甚至可能降低他的速度。对称地奔跑对他来说会是不自然的步态。”

It was once widely assumed that the swiftest runners achieved top speed by swinging their legs more rapidly than slow runners while repositioning their limbs between takeoff and landing.

人们曾经普遍认为,跑步最快的选手实现高速度的方法是摆腿更快,在双腿腾空和落地之间的时候改变肢体的位置。

In a 2000 study, Weyand, then working with a team at Harvard, determined that elite sprinters did not swing their legs appreciably quicker through the air. Instead, they gained maximum speed by striking the ground with a greater force than others in relation to their body weight, and for a shorter period of time.

在2000年的一项研究中,当时为哈佛大学一个团队工作的韦安德发现,顶尖短跑运动员并不是在空中更快地摆腿。相反,他们获得最高速度的方式是在更短的时间里以与体重比例更大的力量触地。

For Olympic-caliber sprinters, that peak force can equal five times their body weight, providing lift and propulsion to begin the next stride. In Bolt’s case, his peak force can surpass 1,000 pounds.

对奥运会水准的短跑运动员来说,他们的峰值力可以达到体重的五倍,为开始下一次跨步提供提升力和推动力。博尔特的峰值力可以超过1000磅。

Peak impact force is delivered within 0.03 seconds of striking the track. It is one of the most critical moments of sprinting. Less force put into the ground means less pop back into the air. Laurence Ryan, a physicist in the SMU lab, calls that period “30 milliseconds to glory.”

峰值冲击力是在触地后0.03秒内发出的。它是短跑最关键的时刻之一。触地力越小意味着反弹到空中的力量就越小。南卫理公会大学实验室的物理学家劳伦斯·瑞安(Laurence Ryan)称,那段时间是“通向辉煌的30毫秒”。

In other words, Weyand said, “You win your medal or you’re out of the running based on that short duration.”

韦安德表示,换句话说,“你是赢得奖牌还是淘汰出局,取决于那一瞬间”。

Sprinters like Bolt land just behind the ball of the foot, which strikes the ground at an angle of about 6 degrees. His lower leg decelerates abruptly, absorbing 16 Gs of force. His heel drops for only 0.02 seconds — the equivalent of an inch — before rising again. The total time spent on the ground with each stride is about 0.09 seconds.

博尔特等短跑运动员的脚掌落地点在拇指掌丘后面一点,以6度左右的角度触地。他的小腿突然减速,承受了16G的力。他的脚后跟仅触地0.02秒(相当于触地一英寸,即2.54厘米)就再次抬起。每次跨步在地面上停留的时间总长约为0.09秒。

In effect, there is one biomechanical way for world-class sprinters to run extremely fast.

实际上,世界级短跑运动员有一个生物力学模式,可以让他们跑得极快。

“They’re machine-like,” Weyand said. “It’s incredible the extent to which they do the same thing.”

“他们就像机器,”韦安德说,“他们动作的类似程度十分惊人。”

The SMU researchers did not know that one of Bolt’s legs was longer than the other when they began their study six months ago. They were testing a new motion-based technique, called the two-mass model, which allows them to determine ground forces by using high-speed video of races instead of specially equipped treadmills in the lab.

六个月前,南卫理公会大学的研究员们开始进行研究时,并不知道博尔特的一条腿比另一条腿长。当时他们正在试验一种基于运动的新技术,名为双块模型(two-mass model)——他们可以使用高速比赛视频确定触地力,而不用通过特殊装备的实验室跑步机。

Udofa, the lead researcher, examined 20 steps apiece taken by Bolt and three other elite 100-meter sprinters, using video from a race in Monaco in 2011.

首席研究员尤道法使用2011年摩纳哥一场比赛的视频分别研究了博尔特和另外三名顶级百米短跑选手的20个跨步。

On average, Bolt struck the ground with 1,080 pounds of peak force on his right leg and 955 pounds on his left leg. Because his right leg is shorter, it has a slightly longer drop to the track, contributing to a higher velocity for that step.

平均而言,博尔特右腿的峰值击地力为1080磅,左腿为955磅。由于他的右腿较短,所以触地时间略长,从而提高了这一步的速度。

“The logical thing to think is, well, you want both legs to deliver as much force as possible and if one is not delivering as much force, if it delivered more force, he’d go faster,” Weyand said. “But that superficial logic doesn’t really flesh out.”

“符合逻辑的思路是,呃,你想让两条腿都尽可能发出最大的力量,如果其中一条腿发出的力量不如另一条,那么假设它发出更大的力量,他会跑得更快,”韦安德说。“但这种粗浅的逻辑并不真的能实现。”

A natural adaptation for Bolt has been to keep his left leg on the ground for slightly more time with each step — 0.97 seconds, compared with 0.85 seconds for the right leg. This gives him slightly more time to generate force with the left leg, Weyand said, providing greater lift off the ground.

对博尔特来说,一个自然的调整方式就是让左脚在地上停留的时间更长一点——大约是0.97秒——而右脚的停留时间是0.85秒。韦安德说,这样他就有略长的时间用左腿发力,从而产生更大的离地力。

Ralph Mann, a pioneering biomechanics researcher in the United States, said he could detect a kind of gallop in Bolt’s uneven stride. But a variability of 13 or 14 percent was surprising, Mann said, given that his consulting work with USA Track and Field generally found an asymmetry between zero and 7 percent among elite sprinters.

美国顶尖生物力学研究员拉尔夫·曼(Ralph Mann)表示,他能在博尔特不均衡的跨步中探测到颠簸的感觉。不过拉尔夫·曼表示,13%或14%的变化幅度令人意外,因为他在为美国田径协会(USA Track and Field)提供咨询的过程中通常发现,顶级短跑运动员的不对称幅度在0至7%之间。

“That’s a huge number; when you see that you’re going to find a physical abnormality,” said Mann, who won a silver medal in the 400-meter hurdles at the 1972 Munich Olympics. But by strengthening the so-called weaker leg, he added, “I can think of no reason why that’s not going to improve performance.”

“那是一个很大的数字。你看到它,就会发现一种反常的物理现象,”拉尔夫·曼说。他曾在1972年的慕尼黑奥运会上夺得400米跨栏比赛银牌。不过他还说,通过加强所谓的弱腿,“应该能够提高成绩,我想不出任何反对的理由”。

There is one person who apparently does not find the SMU research particularly interesting. That is Bolt himself, according to his agent, Ricky Simms, who said in an email, “He isn’t the kind of person who studies this type of thing.”

有一个人显然对南卫理公会大学的研究不感兴趣。那就是博尔特本人。他的经纪人里奇·西姆斯(Ricky Simms)在接受电子邮件采访时说:“他不是那种会研究这类事情的人。”

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