Sensor Technology Helps Athletes Pursue Peak Olympic Performance

When Olympians take the stand this summer, dignitaries will hand them a medal and a freshly cut bouquet. The significance of the award will last, but the hoarse joy - like the rose, will fade away.

For the athletes, coaches, scientists, and engineers who work here at the US Olympic Training Center, the memory that does not fade is not the achievement of greatness, but its never-ending pursuit.

Engineers at the center's Sport Science and Technology Lab design and build a range of electronic sensors that coaches and athletes use to streamline training and improve performance.

The sensors, which follow the athlete onto the water or out to the firing range, help coaches evaluate the form and the strength of archers, cyclists, rowers, sharpshooters, and swimmers.

"These tools give us a sophisticated way of assessing where coaches and athletes should focus their training to improve performances," says Jay Kearney, a physiologist for the US Olympic Committee.

Tom Westenburg, design engineer at the Sport Science and Technology Lab, and Marty Hull, a dentist from San Carlos, Calif., built a tow system to measure water resistance as a swimmer glides or strokes the length of the training center pool. Their design and one swimmer's hard work yielded striking results.

Amy Van Dyken trained using the tow system for six weeks. Last summer at the Pan Pacific Games, she set the US women's record for the 50-meter freestyle. This spring in Indianapolis, she qualified to swim five events at the Olympic Games.

The tow system combines a harness that pulls a swimmer through the water with an underwater camera that tracks her motion as she speeds up and down the pool.

As a swimmer is towed, she can rotate her arms and legs faster than normal. When an athlete swims faster than usual, synchronization between upper and lower body falls apart. The harness can teach an athlete to swim faster before she is able.

"Amy used the harness to streamline her stroke," Tom says. "She would place her head or arch her back to determine which position created the least amount of drag. Sometimes water started flying, and she'd veer all over the lane. Other times, the waves died down and she moved through the water like a torpedo."

By reviewing the videotape and sensing resistance for each set, Amy and her coach decided which position propelled her most efficiently through the water.

A sharper aiming technique

Tammie Forster, two-time World Cup and Pan American Games rifle champion, spent much of 1995 wondering why she couldn't shoot straight.

Time Conrad, design engineer and assistant to the shooting coach, explains: "Tammie was holding her aim well within the bull's-eye. She sensed some movement of the barrel, but didn't realize that it was insignificant."

Using a force platform and a video camera, Conrad persuaded Forster that she could hold an infrared laser sight on the bull's eye for six seconds. The force platform sensed how far her aim strayed from the center ring.

"The force platform and video display gave me the confidence that my hold was good," Forster says. "Knowing that allowed me to focus on trigger control."

To improve her control, Time created an electronic sensor that slips over the trigger and is wired to a computer.

When Tammie fired the rifle, the sensor transmitted a signal that the computer reported as applied force over time. Reading a chart that appeared beneath a video transmission of Forster firing the rifle, they determined how gently she pulled the trigger.

"Using the video overlay [and] trigger-pressure system convinced Tammie that while her hold was solid, she was not pulling the trigger smoothly," Time explains. "If you don't pull the trigger smoothly, you can disturb the aim of the gun. We gave her something specific to work on."

"And my performance has improved ever since," says Forster. For the air rifle event, she fires a pellet from 10 meters piercing a half millimeter bull's-eye 35 out of 40 times. "I was shooting 392 out of 400. Now I'm shooting 395." That is one point short of the Olympic record.

At this level of competition, few athletes can improve performance through brute strength alone. Forster and other athletes who train here achieve much more by refining technique.

Measuring oar power

Michael Porterfield recalls the day his eight-man scull lost a bronze medal the 1989 World Championships by 4/100ths of a second. "Technology could have made the difference," says Porterfield, a rower for the US men's resident team this year.

The 60-foot scull glides over the water at five meters per second or 11 mile per hour. LIke a V8-engine that fires all cylinders at once, the crew applies power in spurts.

To understand how well each crew member rows, Tom placed sensors on oars that are wired to a computer placed on the back of the scull. The sensors gather data that measure oar force, oar angle - or degrees of sweep, boat speed, and acceleration. They transmit data to the computer, which relays it to a laptop that rides alongside the coach in the pursuit boat.

The coach can view a power curve (force versus angle) for each rower and suggest changes to technique as the training session occurs.

"Even if you watch a videotape of the workout, it's difficult to know how you're applying force to the oar," says Chris Swan, another crew member.

Coach Michael Sprackin uses the information to refine the technique of individual rowers, balance the power for each position within the boat, and test new equipment.

"I can remember an East German boat rigged up with similar technology in 1990," Porterfield admits. "Technology is an important ingredient. We've caught up with the rest of the world."