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Olympic science: Re-engineering swimming styles

New research will not directly influence swimmers at the London Olympics, but may eventually help make improvements -- and new world records -- possible.jontidmarsh / flickr

Swimmers are always striving for the best form, but the complicated physics of flowing water has usually meant research lags far behind the latest techniques. 

Now, new technology is starting to catch up with the needs of swimmers and their coaches, and may help to improve training regimens for the next generation of Olympians.

Every component of a race -- the start, the turns, the stroke -- can be analyzed separately. For swimmers of equal size and proportion, maximizing the production of thrust from the stroke determines much of the difference in speed.

"What the coach really wants to know is how much thrust the swimmer is actually producing," said Timothy Wei, an engineering professor at the University of Nebraska-Lincoln.

Wei has been working on a system to take high-speed film of swimming athletes and track a point on their bodies. By measuring the swimmer's speed between each frame, Wei said he can estimate the swimmer's acceleration and how much thrust is produced throughout every motion.

The idea is to keep the system simple so coaches can obtain fast and accurate data. Currently the best way to measure a swimmer's thrust from millisecond to millisecond is to tether them to a force gauge and have them swim in place. The data from this is incomplete, because the swimmer really isn't swimming through the water. Wei's system lets athletes swim through the lane like they would during a competition. He hopes to try out his new technique on U.S. Olympians after they return from London.

Wei had previously worked with the U.S. Olympic team in 2008 to study the popular dolphin kick. He used computers and high-speed cameras to track the motions of tiny bubbles surrounding the swimmer in the water, a technique called digital particle image velocimetry. The paths of these bubbles told him a great deal about how much thrust a free swimmer was generating and where it was coming from, but it is a slow and computationally intensive process. While Wei's simplified motion-tracking system won't tell him from which part of the body the swimmer's forward force is coming from, it can determine the net force generated by the swimmer millisecond to millisecond.

'Doc was the original. He used videos and used different methodologies to improve his swimmers' performances.'

- Mike Bottom, head coach at the University of Michigan swim team

The slow, deliberative pace of scientific verification is what hampers the results from being more fully integrated into coaching. In the fast-paced world of top-level swimming, new coaching techniques are rarely backed by conclusive scientific research.

"You don't wait for the scientific research to come out, if you did you'd be 20 years behind," said Mike Bottom, head coach at the University of Michigan swim team. He added that the proof of new techniques is in fast times and first place finishes.

Efforts to fuse science and competitive swimming were first started by the legendary U.S. coach James "Doc" Counsilman in the 1960s. Coaches today remember him for being the first to incorporate new technology and research to train his athletes. 

"Doc was the original," Bottom said. "He used videos and used different methodologies to improve his swimmers' performances."

Counsilman, head coach at Indiana University, led the U.S. team to 21 combined gold medals in the 1964 and 1976 games. During his time, he was a proponent of an innovative arm stroke, called "sculling," that was thought to propel swimmers through the water using forward lift forces. He thought lift would give the swimmers an extra boost using the same hydrodynamics principle that a propeller uses to drive a boat.

"A propeller blade is not moving in the direction of motion of the boat, the propeller blade is actually rotating perpendicular to the direction of motion," Said Rajat Mittal, an engineering professor at Johns Hopkins University. "So a propeller blade is actually using lift for propulsion, not drag. A paddle is using drag for propulsion."

Though it has since fallen out of common usage among professional swimmers, the debate about sculling's merits lingered. Only this year have researchers had access to the computing power necessary to be able to put his theory fully to the test.

Sculling is a variation on the front crawl. In the basic front crawl the swimmer faces toward the bottom of the pool and alternates the arms, swinging them in front of the head and pulling through the water. In Counsilman's variation, the swimmer emphasizes the side-to-side motions of the submerged hand, but it doesn't seem to produce as much forward thrust from lift as had been previously thought.

Mittal simulated a sculling stroke, and compared it to another common stroke he called the "deep catch." Strokes that use deep catch methods are widely taught today where the swimmer keeps the lead arm straight to reach deep under water.

"We found that deep catch was producing measurably more thrust," Mittal said. "The deep catch was approximately, at least 18-20 percent, better than a comparable sculling stroke done at the same speed with approximately the same stroke frequency."

It turns out that the deep catch generates a significant amount of lift on its own when the swimmer plunges each hand down deep into the water. The swimmer's moving hand works like a propeller and directs the flow of water back along the length of the swimmer's body.

This is not to say that a swimmer using the sculling stroke will always lose against one using the deep catch. Swimmers each have their own styles that work best for them. In addition, Mittal's research only models the motion of a hand after it enters the water, and doesn't incorporate the rest of the body. Other factors, like the rotation of the swimmer's shoulders, haven't been incorporated.

"What Rajat can do, he has the ability to get very detailed and accurate information over a very specific part of the body, namely the arm," Wei said. "He can actually go in and do the very detailed analysis, looking at different hand positions and arm positions."

The new research will not directly influence swimmers at the London Olympics, but may eventually help make improvements -- and world records -- possible.

"[Research is] all a part of the process, it's part of improving and getting good knowledge," said Russell Mark, USA Swimming's high performance consultant. "To attribute [success] just to one piece of research, or one anything would be a misunderstanding of how things get better in swimming."

Reprinted with permission from Inside Science, an editorially independent news outlet of the American Institute of Physics, a nonprofit organization supporting the dissemination of science news and information to society.