After 8 Golds for Phelps, 8 Big Questions on Beijing's Super Pool

By Allen St. John

Published on: August 19, 2008

Michael Phelps competes in the Men's 4x100 Medley Relay held at the National Aquatics Centre during Day 9 of the 2008 Olympic Games in Beijing, China. (Photo by Cameron Spencer/Getty Images)

Sports fans and average humans were left dumbfounded last week as Michael Phelps and his USA Swimming teammates shattered records on a daily basis. With 20 world-best marks falling in Bejing—as many as in the last two Olympics combined—what's the scientific secret weapon? And while Olympians crushed 28 records in 1972—the year Mark Spitz won his now-surpassed seven gold medals—what makes Phelps and Co. so much better than swimmers of yesteryear? PM crunches the numbers with the experts to answer these and other high-tech questions—and debunk some of the myths that have cropped up around them.


Is this world-record binge unprecedented?
No. In the 1976 games, 24 world marks were set, and in 1972, the year that Spitz won his seven golds, 28 world records were shattered.

If 1972's Mark Spitz were in competition in the 2008 Olympics, could Michael Phelps beat him?
Yes, and by a shockingly large margin. A 1972 vintage Spitz, in fact, wouldn't have even made this year's field. His then-Olympic and world-record time of 1:52.78 in the 200-meter freestyle is 4 seconds short of the Olympic A qualifying standard (1:48.72)—and close to 10 seconds slower than the new world record Phelps set last week.

And get this: Don Schollander's 1964 world and Olympic record of 4:12.2 in the 400 meters would be too slow to make the women's field in that event. That's a mind-boggling 30 seconds behind 2008 champ Tae Hwan Park of Korea, who posted a time of 3:41.86.

Are cutting-edge swimsuits behind these shocking times?
No. While suits like the Speedo LZR Racer have proved important in winning medals—the 1/100ths of a second they can shave off a time can often mean the difference between gold and silver—they seem to provide only incremental time gains. The next-gen gear works by reducing drag compared to bare skin, as well as encouraging swimmers to maintain a streamlined body position. However, Dara Torres posted a 53.78 in the Olympic trials in the 100-meter freestyle—less than a second faster than her personal best times of 54.43 and 54.45—while wearing a more conventional suit.

And for what it's worth, Phelps wore the full-length LZR suit in only three of his eight races—the 200 freestyle, the 4x100 and 4x200 freestyle relays—preferring to go bare-chested in his five butterfly and individual medley contests. "The suit is definitely a help," he told reporters in Beijing. "Without the training, nothing else happens."

Is it the super pool?
The pool in Beijing's Water Cube is one of the world's fastest. Its 3-meter depth is the deepest allowable, and it is 10 lanes wide (even though Olympic events are run with eight swimmers to a heat). These features reduce speed-robbing turbulence. But how much of a difference did those tweaks actually make this year? At last month's Olympic trials in a more conventional, 2.5-meter-deep pool in Omaha, Neb., Phelps posted a time of 1:44:10 in the 200 meters. His Olympic world-record time was 1:42.96—about a second faster.

Tech aside, what makes Phelps a superhuman phenomenon of science?
It's impossible to definitively parse Phelps's enormous 10-second edge over Spitz—not to mention his modern competition. But it seems like his sleeker suit and Beijing's faster pool probably account for a second each at most. The other 8 seconds over his forbear? Better technique.

For all it demands in the way of cardiovascular fitness and sheer strength, swimming is really the ultimate technique sport. "Why are records being broken?" asks George Washington University professor Rajat Mittal, a leading researcher in hydrodynamics. "Swimming is the most technical sport."

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."