What makes a fast stroke fast?
In a word, efficiency. When researchers Rick Sharp and Jane Cappaert of the International Center for Aquatic Research studied the 1992 Olympics, they concluded that swimmers who made the finals actually had a power output that was 16 percent lower than those they beat. Russian champion Alexander Popov was estimated to be using 25 to 40 percent less energy than his rivals. The key to victory, Mittal explains, is not the athlete's pure power output (as is the case in sports like track and cycling) but his efficiency. "It all comes down to how well you can transfer energy from your body to a complex fluid medium," he explains. Toward that end, this year's U.S. Olympic team sent four sports science experts to Beijing, and every swim was videotaped for analysis. Phelps and co. swim faster than legends like Spitz and Schollander because they're swimming smarter.
What is Phelps's secret weapon?
The dolphin kick. This underwater kick, first used in the butterfly, is much more efficient than the conventional flutter kick. "Swimming underwater is always better than swimming on the surface because it eliminates wave drag," Mittal explains. The first inkling of the dolphin kick's remarkable efficiency came in the 1980s, when backstroker David Berkoff broke world records by swimming as much as half a lap underwater. Swimming officials had to limit its use to the first 15 meters of the lap lest swimmers try to contest the whole race underwater.
In the 1996 Olympic Games, Russian butterfly swimmer Denis Pankratov won two gold medals by resurrecting the dolphin kick, swimming 25 meters off the start and more than 15 meters off the turn underwater. The sport's governing body soon closed the loophole in this event as well. The fact that it took almost 20 years for Phelps to fully exploit the kick in freestyle events proves Mittal's point: Our understanding of human performance in this complex medium is still very much incomplete. "There's a big disconnect between cause and effect," he says. "Even when coaches have figured out things that work well, they don't know why they work well."
How did Phelps revolutionize the dolphin kick?
Ian Thorpe started using the dolphin stroke coming off turns in freestyle in the late 1990s, but Phelps has simply taken it to a different level. Phelps's coach, Bob Bowman, has said that his star pupil utilizes the dolphin kick for 13 meters on every turn, compared to Thorpe's 5.
The results can be staggering. Berkoff observed that in the 200-meter freestyle in the 2004 World Championships, Phelps opened a 2-second gap over former world-record holder Pieter van den Hoogenband—on just one turn. A similar edge at the start and each of the three turns in the 200-meter freestyle could easily account for most of the missing 8 seconds of Phelps's 10-second edge on Spitz.
Is Phelps more human, dolphin or submarine?
What makes Phelps's dolphin kick so effective is that, effectively, he swims like a dolphin. Since 2003, Mittal and his George Washington University colleague James Hahn have been analyzing the dolphin kick for USA Swimming, using computer models originally designed to refine the design of small submarines. They found several interesting things. The first is that 90 percent of the propulsion comes from below the ankles. And given that, Phelps's giant, size-14 feet become a huge advantage, functioning almost like flippers.
"Michael Phelps has incredibly flexible ankles, and he can flop his ankles like a dolphin fluke," Mittal says. "Of all the swimmers we've tested, Michael's parameters are closest to that of a dolphin." This preternatural ability to mimic the planet's most efficient swimmer is truly what makes Phelps so good. "The suits do help, and the fact that the pool is deeper and wider has some effect, but why is Phelps so fast?" Mittal asks rhetorically. "It's technique, technique, technique."
(Michael Phelps 8 Olympic Gold Medals - 2008 Beijing Olympic Swimming - Popular Mechanics)
