Olympic advantage: 'You have to know the flow'

In the world of swimming, milliseconds can mean the difference between gold and last place in a race in the Olympics. That is where technology comes into play.

Experimental flow measurement techniques are helping American swimmers sharpen their strokes, shaving seconds from their lap times in Beijing.

Professor Timothy Wei, head of Rensselaer Polytechnic Institute in Troy, N.Y.’s Department of Mechanical, Aerospace, and Nuclear Engineering and acting dean of the university’s School of Engineering, helped develop top-secret, state-of-the-art equipment and mathematical techniques that USA Swimming coaches have been using to help train Olympians.

A single frame from a research video illustrating the flow of water around former gold medalist and current Olympian Megan Jendrick.

“This is the real thing,” Wei said. “We have the physical system, we’re taking flow measurements of actual swimmers, and we’re getting more information than anyone has ever had before about swimming and how the swimmer interacts with the water. And so far, these techniques have contributed to some very significant improvements in the lap times of Olympic swimmers.”

In years past, swimming coaches have used computer modeling and simulation to hone the techniques of athletes. But Wei developed state-of-the-art water flow diagnostic technologies, modifying and combining force measurement tools developed for aerospace research with a video-based flow measurement technique known as Digital Particle Image Velocimetry in order to create a robust training tool that reports the performance of a swimmer in real time.

“This project moved the swimming world beyond the observational into scientific fact,” said USA Swimming Coach Sean Hutchison. “The knowledge gained gave me the foundation for which every technical stroke change in preparation for the Beijing Olympics was based.” (For videos that explain the process, visit http://www.rpi.edu/news/video/wei/videos.html.)

The secret, Wei said, is in understanding how the water moves. The new system incorporates highly sophisticated mathematics with stop-motion video technology to identify key vortices, pinpoint the movement of the water, and compute how much energy the swimmer exerts.

“You have to know the flow,” Wei said. “To see how a swimmer’s motion affects the flow, you need to know how much force the swimmer is producing, and how that force impacts the water.”

“Swimming research has strived to understand water flow around a swimmer for decades because how a swimmer’s body moves the surrounding water is everything,” said USA Swimming’s Biomechanics Manager Russell Mark. “The ability to measure flow and forces in a natural and unimpeded environment hasn’t been available until recently, and Dr. Wei’s technology and methods presented USA Swimming with a unique opportunity that United States swimmers and coaches could learn a lot from.”

Wei has been working with USA Swimming for several years, but the idea and design of the new flow measurement tool really took shape in 2007. Most of the preliminary tests occurred in October 2007, and the coaches and swimmers have spent the past several months incorporating what they have learned into their training regimes. For any swimmer, it takes time to make adjustments to their strokes and practice new techniques, Wei said.

One highlight of working on the project was when Mark arranged for Wei to attend the 2007 and 2008 U.S. Summer Nationals and be on deck with the swimmers.

“How often does a researcher get to do something like this?” said Wei, whose young son and daughter also swim competitively. “It’s been a journey into a world that someone like me would have never before gotten the privilege to see first-hand.”