In the early 1960s, Dick Fosbury tried his hand at almost every sport, but never excelled at anything, until, at the age of 16, he turned to the high jump. But when he couldn't compete against the strong athletes at his college using the standard high jump techniques of the time, Fosbury tried to jump a different way: backwards. Instead of jumping with his face towards the bar, bringing each leg over in the traditional straddle method, he jumped with his back towards the bar. Fosbury improved his record by over half a foot, and left his coaches amazed by this strange new style of high jumping. During the next few years, Fosbury perfected his high jump style, won the U.S. National trials, and assured his place in the 1968 Olympics in Mexico. In the Olympic Games, Fosbury amazed the world with his new technique, winning a gold metal with an Olympic record leap of 2.24 meters. By the next Olympic Games, almost all of the competing of high jumpers had adopted what came to be known as the Fosbury Flop. What's the secret behind the technique? It lies in a physics concept called the center of mass. For every object, we can locate the average position of all of its mass by taking into account how the mass is spread around the object. For instance, the center of mass of a flat, rectangular object of uniform density will be in the intersection of both diagonals, in equal distance from each corner. We can find the center of mass for other objects by similar calculations, or by finding the object's balancing point, which lies right underneath its center of mass. Try balancing a broom by holding it and slowly bringing your hands together until they meet. This balancing point lies right underneath the broom's center of mass. We humans also have a center of mass. When most people stand up, their center of mass is around the belly, but what happens to your center of mass when you lift your hands in the air? Your center of mass moves upwards. It moves all the time as you move through the day, based on how your body is positioned. It can even move outside of your body. When you bend forward, your center of mass is located below your bent belly in a place where there is no mass at all. Weird to think about, but that's the average position of all your mass. Many objects' center of mass are outside their bodies. Think of doughnuts or boomerangs. Now look at the Fosbury Flop, and follow the position of the center of mass of the jumper. The jumper runs very fast, so he can divert his horizontal velocity to vertical velocity, and jumps. Wait for it...there. Look at the jumper's center of mass as his body bends backward. It's below the bar. That is the secret behind the jump. With the old, pre-Fosbury techniques, the jumper had to apply enough force to lift his center of mass above the bar by a few inches in order to clear it. The Fosbury Flopper doesn't have to do that. The genius of the Fosbury Flop is that the jumper can apply the same amount of force, but raise his body much higher than before. That means he can raise the bar so high that even when his center of mass can't go any higher, his arching body can. Fosbury's technique brought the high jump to new heights by splitting the jumper's body away from his center of mass, giving it that much more room to clear higher and higher bars. So the Fosbury Flop may be sports history's only great leap forward, that is also a great leap backward.
1960 年代初 Dick Fosbury 幾乎遍嘗各種體育項目, 卻始終沒在哪一項出類拔萃。 直到 16 歲那年,他相中了跳高運動。 起初他仍然無法擊敗 學院中的無數優異選手 --使用當時的標準式跳法, Fosbury 轉而嘗試與眾不同的方法:背躍。 不像一般選手般面向桿子翻轉 兩腳依次翻過 的剪刀式(straddle)跳法, Fosbury 轉而以背向越過橫桿。 如此使他的成績躍進了 15.24 公分, 也使教練目瞪口呆, 折服在這詭異的新跳法面前。 往後數年, Fosbury 完成了他的背躍絕技, 通過了美國的國手選拔, 並在 1968 年墨西哥城奧運會 掙得了他的歷史定位。 在奧運會上,Fosbury 驚艷了全世界 並以他的獨門絕活一舉奪下金牌, 還順便推進了奧會記錄,由 2.22 到 2.24 公尺。 於是下一屆奧運會中 幾乎所有選手都轉而使用了 新的背躍式跳法,或者 其傳世名號:Fosbury 的魚躍。 (flop 有重摔、失敗之意,為一個制勝絕技取這個不相稱名字的是一名記者,認為以彎曲的背部墜落軟墊,像上岸的魚亂跳 ) 這個招式背後的祕密為何? 答案藏在一個物理概念裡: 稱為質量中心(質心)。 對任何物體 我們都可以藉由 考慮物體質量 在三維空間中的分佈情形 來確定其質量的平均位置。 例如,一個扁平、長方形、 密度均一的物體,其質心 會落在兩對角線的交點, 與四個角落等距。 對於別的物體 我們可以透過類似的方法 去尋找其質量中心。 或是直接找物體的平衡點, 平衡點會落在質心的正下方。 試試看,雙手虎口托著掃把的柄, 並輕輕用力讓兩手往內滑動,直到手掌合十。 這時掃把應該還是平衡的, (試著想想看原理為何) 掃把的質心就在兩手正中上方某處。 講到人類,人體自然也有一個質心。 大多數人站直時, 質心位在肚臍附近。 當你舉起雙手,你的 質心會發生什麼事? 質心會向上移動。 在你一天的活動中,你的質心據你的姿勢 四處動來動去。 甚至有些姿勢,會讓 你的質心位在身體的外部。 例如腰向前仰 質心會在你的腹部前(下)方, 即使那一點空無一物。 想起來似乎怪怪的,但它確實是這時 你身體所有部分的平均位置。 還有許多物品的質心 處在物品外面, 例子有甜甜圈,和回飛鏢。 現在我們能回來看 Fosbury 的後躍了, 注意動作中運動員的質心位置。 選手首先高速助跑,於是 可藉由最後的一蹬,將一部分的水平速度 轉移成垂直起跳的速度。 留神......就是這裡。 注意到選手身體往後弓起時 質心所在位置嗎? 事實上它還在橫桿之下! 這就是背躍絕技的奧秘。 在 Fosbury 登場以前,跳高的技術 全仰賴選手拼命使勁 為了將他們的質心抬到桿子以上數吋 才能避免越過時把桿子撞掉。 但背躍式跳法迴避了這個瓶頸。 Fosbury 方法的天才之處在於, 選手花同樣力氣,其質心和原本一樣高, 身體卻能處在更高位。 這代表桿子能繼續往上擺, 即使質心的高度再也提升不了 彎曲的身體卻可以由上方溜過去。 Fosbury 的新招式讓跳高的 世界紀錄連創新高, 原理是盡量彎曲身體, 使選手的質心離身體越遠越好, 因此有更多空間能運用於 閃過不斷加高的橫桿。 因此可以說,Fosbury 絕技是運動史上 的一次向前大飛躍, 藉由......向後飛躍。