Tuesday, May 27, 2008

Olympic Swimmers Learn From Sharks, Dolphins

When winning an Olympic gold medal in swimming is the goal, it helps to take inspiration from some of the best swimmers in the world -- sharks and dolphins -- and that is exactly what U.S. Olympic team swimmers have been doing as they train.

From suits to strokes, coaches, researchers and other advisers are making sure that their athletes benefit from fish and marine mammals' natural swimming abilities.

"Some of our athletes are now wearing what are called 'shark skin suits,'" Russell Mark, biomechanics coordinator for U.S.A. Swimming, told Discovery News.

"These aren't made of actual shark skin, of course, but they are slippery in feel, like sharks, and they make the wearer move faster than normal in the water by reducing friction and drag," he explained.

Mark also indicated that excelling at the dolphin kick can make or break a swimmer's race.
"This is when swimmers push off walls and swim underwater without moving their arms, very similar to how a dolphin swims," he said.

The move emulates how dolphins zoom through water by moving their flipper in an up and down motion. Sharks, in contrast, move side to side. Humans are mammals like dolphins and the up and down undulating motion propels people as it does dolphins. The dolphin kick is one of the most powerful moves among professional swimmers.

The move begins when an individual raises the hips, and then follows with a knee bend with flexed ankles. Put together, the sequence creates an undulating, whipping motion that runs all along the legs to the toes, minimizing water resistance and smoothly zooming the person forward.

"Our top swimmers -- Michael Phelps, Natalie Coughlin, Ryan Lochte and others -- all excel at dolphin kicking," Mark said. "Phelps is among the best in the world and probably gets as close to anyone as also having a more shark-like finesse in the water."

Sharks are some of the world's fastest swimmers. One impressive species is the shortfin mako, which has been reliably clocked at 31 miles per hour underwater. Everything about this fish is designed for swimming in short bursts of perfection. It has a streamlined body, a crescent-shaped tail supported by keels and a water-cutting, pointed snout.
Sharks, as fans of B-horror movies know, can also be quite hefty and large, yet still move quickly in the water.

"I think it has to do with surface area to volume ratio and drag," Neil Hammerschlag, University of Miami marine biologist, told Discovery News. "That is perhaps why larger, longer boats and longer airplanes move quicker."

Hammerschlag explained that big volumes have a smaller surface area to volume ratio and can move in a speedier fashion as a result, since surface drag can cause a boundary layer of water to sort of stick to the individual, potentially holding them back.

Over the years, Olympic swimmers have been beefing up by incorporating weight training into their schedules. This not only helps to combat drag, but also to simply improve power. Australian Libby Trickett, for example, has a powerful upper body, which may be behind her success in the butterfly stroke.

Rajat Mittal, associate professor in the Department of Mechanical and Aerospace Engineering at George Washington University, has worked with Mark by providing information about swimming mechanics inspired by dolphins. Mittal recently even created a computer model of a dolphin to better understand its movements.

Mittal said basic anatomical differences, such as lack of a totally flexible spine, joint structure, the nature of human musculature and the need to frequently breathe, keep humans way out of the range of shark and dolphin swimming records.

"To win, our Olympians must go all out and swim in what is essentially an inefficient manner," Mittal said. "Dolphins and sharks, by contrast never compromise their speed with efficiency. They are truly among nature's best swimmers."


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