Athletics, Technology in

The differences in skill among athletes who compete at the highest levels of their sports are actually very small. Mere hundredths of a second are likely to separate those standing on the winner's platform from the also-rans after the Olympic 100-meter dash or 100-meter freestyle swimming competition. On any given day, the margin of victory of the world's top-ranked professional tennis player over, say, the 10th-ranked player can be just a few key points at critical moments in a handful of key games. The difference between being ranked number one and number ten is likely to be not just raw ability but the consistency with which a player exercises that ability from game to game, even point to point, during a match.

In this highly competitive environment, athletes look for any edge that will help them win. To achieve that end, they have enlisted the aid of science and technology. World-class bicyclists, for example, are as likely to be as knowledgeable about the latest advances in metallurgy as they are about their sport so that they can design aerodynamic, lightweight bicycles that will help them shave seconds off their times. They also carefully select their helmets and clothing to minimize wind resistance, again in an effort to eliminate any factor that would slow them down.

Athletes who rely on repetitive motions—the stride of a runner, the serve of a tennis player, the stroke through the water of a swimmer—use any technology that will help make those motions more consistent and eliminate wasted energy. The increasingly high-tech tools used include computer simulations, advanced video cameras, wind tunnels, and sophisticated mathematical and physics models that enable athletes to break down their physical motions into their component parts in order to look for flaws or ways to improve. In a sense, a person does not have to choose between being an athlete and a scientist, for increasingly the two fields are merging in exciting ways.

Aerodynamics in Sports Technology

Although virtually any sport could be used to illustrate this new role of high technology—fencing, swimming, golf, cycling—tennis provides a good example. In the twenty-first century, world-class tennis players (and their coaches and trainers) must have a basic understanding of the laws of aerodynamics in order to truly understand the sport and gain an edge over competitors whose abilities match their own.

The National Aeronautics and Space Administration (NASA) has developed a research program called "Aerodynamics and Sports Technology." The goal of the project is to examine tennis—which involves making a ball fly within the boundaries of an enclosed space—from an aerodynamic point of view, much as aircraft designers do. Researchers seek to answer basic questions. How does a tennis ball fly in the first place? How do its flight and direction change? What is its speed, and how and where does its speed change? How much does a tennis ball spin , and how does the spin of different types of shots differ from player to player? What happens to the ball when it hits the court? How does the ball interact with the air during its flight? The results of scientific research examining these questions provide a good example of how mathematics, physics, computer technology, and biomechanics can contribute to athletic performance.

Ball Speed, Ball Spin, and Biomechanics. One of the questions that interests sports scientists is ball speed. The usefulness of a radar gun is limited because it cannot measure changes in the ball's speed at different points in its flight. To measure ball speed, scientists had to develop photographic techniques that could freeze the movement of a ball traveling up to 120 miles an hour. Regular video does not work very well, for it records images at a speed of 30 frames per second at a relatively slow shutter speed. For this reason, television replays of tennis shots tend to be blurry, for the ball is simply moving too fast and the typical video camera is too slow.

To solve this problem, sports scientists make use of cameras that have a high-speed shutter. While the camera still records action at 30 frames per second, a high-speed shutter allows the camera to take a picture with a duration of perhaps of a second—or even a mere of a second. This shutter speed enables sports scientists to get clear pictures of the ball as it moves through the air and thus allows them to measure accurately its speed, and the change in its speed, during flight.

A second problem is measuring the ball's spin, and in particular the various types of spin, such as topspin and underspin . The difficulty with normal cameras, even those with very high shutter speeds, is that the ball can spin several times in of a second over a distance of several feet. To solve this problem, scientists enlisted a new technology called "high-speed digital recording."

Instead of recording at 30 frames per second, these new cameras can record from 250 to 2,000 frames per second. Combined with high-speed shutters, they theoretically could take 2,000 pictures per second, each with a duration of of a second, of a tennis ball during its flight. However, practically, investigators have found that 250 frames per second provide as much data as they need. With this type of equipment, scientists for the first time are able to actually see the spin of a ball as it moves through the air. They now know that during a serve a tennis ball can spin at a rate of up to 1,000 revolutions per minute.

Armed with high-speed digital recording cameras, however, sports scientists can also focus the camera not on the ball but on the player, thus freezing the movements of the player as he or she strokes the ball. Say, for example, that a player is having trouble with her serve. Nothing seems to be wrong with the player's toss, swing, or footwork, but for some reason she's "lost" her serve. High-speed digital recording might provide answers.

Video taken of the player's serve can be used to create sophisticated computer diagrams that show the precise path and speed of the player's racket, allowing the player and her coach to break the serve down into each tiny movement. Furthermore, multiple diagrams can be superimposed one over the other, exposing subtle changes in movement, racket speed, the angle of the racket head, where the racket strikes the ball, the position of the player's body and feet, and so forth.

With this information, players and coaches can modify a player's serve (or other stroke), look for tiny changes in the player's serve over time, examine differences between first serves and second serves (which are typically slower than first serves), and find a service technique that best fits that player's size, strength, and the strategy he or she wants to adopt depending on the unique skills of an opponent. Similar tools could be used by a fencer, baseball batter, swimmer, golfer, sprinter, or any other type of athlete.

Wind Tunnels and Computational Fluid Dynamics. Airplane designers and auto manufacturers have long studied what happens when a plane or car moves through the air, which creates resistance and drag. They learned early on that their results remained the same, regardless of whether a plane or car was moving in space or if the air was blown over a stationary plane or car in a wind tunnel. Sports scientists enlist the aid of wind tunnels to model the aerodynamics of baseballs, golf balls, and tennis balls. In particular, they want to identify what they call "transition," or the change from "laminar" (smooth air flow) to "turbulence" (rough air flow).

Wind tunnels, however, can be large and cumbersome, often as large as, or larger than, a typical room. But the action of a wind tunnel can be modeled mathematically, meaning that a "virtual" wind tunnel can be created on a computer. This type of work, based on the physics of fluids, is called computational fluid dynamics (CFD). CFD investigators begin by programming into the computer all of their available data. In the case of tennis simulations, they need to know the tennis ball's size and the configuration of its seam (typically an hourglass shape). They also program in the ball's speed and rate of spin—which they can now measure accurately using the video cameras discussed earlier. Because of the immense amount of data, a CFD simulation can sometimes take weeks to run on the computer, though tennis simulations take about half a day. With this information, the computer is able to model how the flight path of a ball changes during its flight.

These and other high-tech tools will not turn a weekend tennis player, golfer, or swimmer into an Olympic-class athlete, nor will they replace drive, dedication, and the will to win. But as the world's best athletes search for an edge, they provide invaluable information that was unavailable less than a generation ago. They also provide yet another example of the practical applications of science and mathematics.

see also Computer Animation; Computer Simulations; Sports Data.

Michael J. O'Neal

Bibliography

Davis, Susan. The Sporting Life (Accidental Scientist). New York: Holt, 1997.

Goodstein, Madeline. Sports Science Projects: The Physics of Balls in Motion. Berkeley Heights, NJ: Enslow Publishers, 1999.

Maglischo, Ernest W. Swimming Even Faster: A Comprehensive Guide to the Science of Swimming. Mountain View, CA: Mayfield, 1994.

WHAT WAS IT LIKE IN THE OLD DAYS?

At the turn of the twentieth century, men dressed in long white pants whereas women wore long, bulky tennis dresses to play tennis. Today, male players wear shorts and shirts, and the women favor short, sleeveless dresses or tops with short skirts. Moreover, early tennis players used rackets made of wood, whereas graphite is now commonly used.

UNLOCKING THE SECRETS TO A GREAT SERVE

One discovery made using high-speed digital video analysis was that Pete Sampras, winner of seven Wimbledon titles and known for his devastating serve, maintains a consistent racket speed throughout the course of his serve. This consistency enables him to maintain a highly fluid motion that is consistent from serve to serve.