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[技巧] 自由式S型划水好,還是手入水深些,然後曲肘向後划好?

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Phelps and Thompson both employed bent-arm high-elbow recovery, but different techniques after that.  Phelps' direct pull, Thompson catch-pull.  I suggest you all imitate Phelps' soft-hand entry, full extension (thrust shoulder), "draw in" forearm, then push all the way down.


學游泳時,教練總是要我們在手入水後抓水,接著做S型的划水(S-shape sculling pull)。不可否認的這種方法讓游自由式的人在游的時候手可以感覺到「抓到」水,很有「手感」。而就因為這份手感,在我增加游泳的強度(加快速度與加長距離)後,手就吃不消了。休息一段時間之後,就又開始強度較高的游泳,結果雙手手肘都得了肌腱炎。以前打網球時覺得手肘有異樣都會減少打球,多游泳來復健。沒想到打網球沒得到網球肘,用來「復健」的輔助運動卻讓我得了網球肘。

這雙肘的肌腱炎困擾了我兩三年,一直沒法痊癒,這當然跟我常在覺得「好得差不多了」就又開始由較長程的自由式有關。但是也因為這「肌腱炎」的緣故,讓我無意中習得了另一種划水技巧。

因為肌腱炎,在抓水後若做S型的划水(S-shaped sculling pull)手肘就會痛,所以索性抓水後手直接向後撥。於是因為手肘痛,我的動作就演化成:手入水後向前延伸,曲肘,隨肩膀轉向一側,手直接向後撥。「抓水」這個手腕的動作好像沒有意義了,曲肘替代了原本要做S型的撥水所需的「抓水」,因為曲肘就會產生手直接向後撥所需「划水」的角度。這樣划水很有力,也較輕鬆。

 

也因為較輕鬆的緣故,我可以游得更快,雖然手肘仍會有些不適的感覺,但是痛點似乎有些偏移。原本手痛不敢游快的我,也因此每回去游泳池都游幾趟快的。就這樣過了兩個多月後,「肌腱炎」的存在感大幅降低,只有偶爾「不適」的感覺罷了。


所以從那之後,我兩種游法都游。剛到游泳池時體力較好,游S型的划水,畢竟這是「教科書」姿勢。體力差時,或「肌腱炎」的存在感隱隱浮現時,就曲肘、手直接向後划水。每每用S型的划水游幾趟快的,或游長一些,「肌腱炎」的存在感就隱隱浮現,所以我心裡很明白「曲肘、手直接向後划水」是較適合我泳姿。

在教我的朋友游泳提到 stroke mechanics 時,我兩種游法都介紹。但是我都建議學S型的划水,畢竟這是「教科書」姿勢。 YouTube 裡很受歡迎的萩原智子(HAGIWARA Tomoko)教自由式也是講「S字プル」(S-shaped pull);可是後來我從 Michael Phelps 的影片看到 Phelps 是採用「曲肘、手直接向後划水」的方法,所以這幾年來我建議兩個都學,然後自己選一項。不過現在有這項研究證實「曲肘、手直接向後划水」的方法是較佳的游法,所以我很心安的游著這種方法,現在已經有好一段時間沒用過S型划水游自由式了

finished at 04:58am, Oct. 6, 2012

June 25, 2012 
Paddle vs. propeller: Which competitive swimming stroke is superior?

By Phil Sneiderman, Homewood


Two swimming strokes—one that pulls through the water like a boat paddle and another that whirls to the side like a propeller—are commonly used by athletes training for the Olympic Games. (U.S. swimming trials begin today in Omaha, Neb.) But elite swimmers and their coaches have long argued over which arm motion is more likely to propel an aquatic star toward a medal.

A university research study has picked a winner. A team supervised by a Johns Hopkins fluid dynamics expert has found that the deep catch stroke, resembling a paddle, has the edge over sculling, the bent-arm, propeller-inspired motion.

“This is a result that is simple but sweet, which is something we usually struggle to arrive at in research,” said Rajat Mittal, a mechanical engineering professor in the Whiting School of Engineering. “The deep catch stroke is more efficient and effective than the sculling stroke.”

To obtain this result, Mittal’s team started with high-precision laser scans and underwater videos of elite swimmers. The researchers then used animation software to bend and otherwise change the shape of the static arm in such a way as to match the video sequence. This software allowed the researcher to insert a “joint” into the arm so that the limb could be moved in a realistic manner. The team then ran computer simulations to study the flow of fluid around the arm and the forces that acted upon the limb. Each simulation involved about 4 million degrees of freedom and required thousands of hours of computer processing time.

The findings concerning the deep catch and sculling strokes were featured in the doctoral thesis of Alfred von Loebbecke, who studied under Mittal, and in a report by Loebbecke and Mittal that has been accepted for publication in the Journal of Biomechanical Engineering.  Mittal, a recreational swimmer, joined the Johns Hopkins faculty in 2009. His research into motion through water began almost a decade ago, when, while based at George Washington University, he was awarded a U.S. Navy grant to figure out how fish use their fins to swim so well. To tackle this task, Mittal’s team developed software and computer models to study the movement of marine animals.

Mittal later contacted USA Swimming to see if he might use these high-tech tools to crack the secrets of elite swimmers. Russell Mark, the biomechanics coordinator of USA Swimming, was intrigued, and he provided Mittal’s team with underwater videos of top swimmers and startup funding. With this support, Mittal and Loebbecke collaborated on studies of the “dolphin kick” used in butterfly events and, increasingly, during starts and turns in freestyle and backstroke races.

After completing that study for USA Swimming, Mittal’s team turned its attention to the debate among top coaches about the merits of deep catch and sculling strokes. In the 1960s, the sculling stroke gained popularity thanks to James “Doc” Counsilman, then the head men’s swimming coach at Indiana University. Counsilman, highly regarded for his science-based approach to swimming stroke mechanics, also was head coach of the U.S. men’s swim team that won a combined 21 gold medals in the 1964 and 1976 Olympic Games. Counsilman encouraged his swimmers to use the propeller-like sculling stroke, in which the elbow is raised to a higher position and the arm moves inward and outward in an S-shaped, propeller-like pattern during the propulsion phase of the stroke, when the swimmer’s hand is pushing on the water.  While supervising the current study, Mittal considered Counsilman’s reasoning. “A propeller, when it rotates, is producing a lift force, and it is that lift force that pushes a boat forward,” he said. “Counsilman believed that to travel efficiently in a fluid, a swimmer should be using lift forces.”

This contradicted the advice given by many swimming instructors. “In the past, the analogy for a swimming stroke was that it was like a paddle in a boat: Put the paddle in the water, push it back as hard as possible,” Mittal said. “This is called drag-based propulsion. You’re actually dragging the water back, and the water drags you forward.”

Counsilman insisted that the lift force—generated by that propeller-like movement—was a more effective way of producing thrust than drag force. But Mittal and Loebbecke’s research suggests that the fluid dynamics of this stroke are more complicated than the renowned coach had imagined.

“Sculling, in my view, is a swimming stroke that is based on an incomplete understanding of fluid mechanics,” Mittal said. “We found that Doc Counsilman was not correct overall about the sculling, but in some ways he was more correct than he would have ever thought. We did find that lift is indeed a major component in thrust production for both strokes, and that certainly indicates that the arm does not behave simply like a paddle. However, the simulations also indicate that exaggerated sculling motions, which are designed to enhance and exploit lift, actually reduce both the lift and drag contributions to thrust. So, lift is in fact important, but not in the way envisioned by these early coaches who were trying to bring fluid mechanics into swimming.”

Mittal has shared his findings with USA Swimming. He also pointed out that many top swimmers use variations of the classic deep catch and sculling strokes. Outside of competitive swimming, Mittal’s findings could be useful in designing exoskeleton suits that the U.S. Navy is seeking to help elite military forces swim more quickly and efficiently.At the same time, Mittal said, the research could have more down-to-earth applications by steering recreational swimmers toward the most-effective strokes.

“People sometimes stop swimming because they feel they are not doing it well enough,” he said. “If this research can help recreational swimmers swim more effectively and feel better about their swimming at an early stage, I think that could have an impact on health and fitness.”


http://gazette.jhu.edu/2012/06/25/paddle-vs-propeller-which-competitive-swimming-stroke-is-superior/
   
  

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