Hopkins study finds paddle motion is superior swimming stroke

The research involved laser scans, underwater video and special animation software. And it took thousands of hours of computer time to run simulations that crunched complex fluid mechanics equations.

All of this scientific firepower was thrown at one question: Which freestyle swimming stroke is superior: the paddle-like motion known as "deep catch," or the propeller action called sculling?

The answer: It's the deep catch, in which a swimmer's hands push water straight back toward his or her feet. In fact, that stroke crushed the sculling motion, once widely viewed as the favored means of propelling people through water.

"What we found was the deep catch beat the propeller stroke hands down," said Rajat Mittal, a mechanical engineering professor at the Johns Hopkins University's Whiting School of Engineering.

To elite swimmers and coaches, the research may largely confirm what they already knew from experience. When the Olympic Games begin in London this month, viewers can expect to see Baltimore's Michael Phelps and other competitors using what is essentially a deep-catch stroke in freestyle events.

(Mittal explained that the paddle-or-propeller question applies to the crawl, or freestyle, as well as to the backstroke. It does not apply to specific strokes such as the butterfly.)

The finding is welcome if not especially surprising, said Russell Mark, national team high-performance consultant for USA Swimming, which asked Mittal to explore the question five years ago. "I think that's what research is good for in swimming," Mark said. "It solidifies good theories and kind of ends debate on what swimmers should be aiming for."At the North Baltimore Aquatic Club, where Phelps trained, coach John Cadigan put it this way: "I'm not really sure it's earth-shattering, but it's interesting. It's nice to be able to point and say, 'See, this isn't just because this coach said this, or that coach said this, but it's been proven that this is the most effective way to swim.' "

The research amounts to a further debunking of the late James "Doc" Counsilman, a legendary swim coach who gained fame as a leading propeller-stroke advocate in the 1960s and '70s.

"When I started learning about competitive swimming and becoming a coach, it was back in the early 1980s — it was still the Doc Counsilman way," Cadigan said.

Views have changed, with the deep catch now generally accepted as the better method, Cadigan and Mark say. Few competitive swimmers today use the pronounced S-shaped motion that mimics a ship's propeller, they say, though there is always some bending of the elbow and rotation of the body.

"More recent folks, including myself, are all about just pulling water straight back," Mark said. "You want to move forward, so just push water back."

Mittal's research showed that "the deep catch beats the sculling in both the propeller-like force and paddle-like force," he said.

The Journal of Biomechanical Engineering has agreed to publish the findings, which he carried out with former doctoral student Alfred von Loebbecke.

Mittal's swimming research goes back about a decade, after he received a grant from the Navy to study the way fish swim and developed specialized computer simulation software. He figured he could probably apply the research to the way humans move through water.

He contacted USA Swimming, the national governing body of competitive swimming in the United States, and the group provided him with seed funding. In 2003, he began researching the dolphin kick. Four years later, he turned to the question of arm stroke.

Mittal's team took laser scans and underwater videos of swimmers, then matched those sequences to animation to capture the way swimmers bend their arms in water. "That animation of the arm can be inserted into simulation software," he said, allowing the two strokes to be scientifically compared.

The research did not yield quick answers. Fluid mechanics equations are extremely difficult, Mittal said. "Each simulation takes a few thousand hours of computer time," he said. "You use very large, powerful supercomputers to solve them."

He acknowledged that the issue is not black and white. Many swimmers use hybrid strokes that combine elements of deep catch and sculling. And while short-distance swimmers use more of a deep-catch approach, long-distance swimmers employ more of a propeller motion, he said.

Still, he thinks his findings could influence coaches and young swimmers who may be partial to sculling. He also thinks recreational swimmers could use the knowledge to alter their stroke to make the pastime more satisfying.

Beyond that, Mittal imagines the discovery could one day allow the military to develop new "exoskeleton" suits to help Navy SEALs swim faster.

For now, the most immediate benefit may go to people sprawled on their couch in front of the TV.

"I'm going to be watching the Olympic swimming with a very keen eye on who does what," Mittal said. "It will be fun for swimming aficionados around the world to do something similar."

Source: By Scott Calvert, The Baltimore Sun