Researchers at Southern Methodist University in Texas examined the gait of ordinary runners and elite sprinters, concluding that the key to speed lies in the limb dynamics of the latter. According to the researchers, sprinters have a unique way of increasing ground forces upon impact, and current models of running mechanics do not apply to them.

"Our new studies show that these elite sprinters don't use their legs to just bounce off the ground as most other runners do," says human biomechanics expert and lead study author Ken Clark, a researcher in the SMU Locomotor Performance Laboratory. "The top sprinters have developed a wind-up and delivery mechanism to augment impact forces. Other runners do not do so."

Clark's study concludes that top sprinters decelerate their foot and ankle in just over two-hundredths of a second after their foot touches the ground.

Clark told Relaxnews that the sprinters' singular gait is visible to the trained eye both on the athletic field and on the laboratory treadmill.

"We observe a more upright posture," he said. "The knee lift is higher than that of normal athletes and they strike down and back aggressively, landing stiffly on the ball of their foot.

Clark says the sprinter's gait is found in gifted athletes but he believes it will be possible to hone now that the correct technique has been identified.

"The fastest sprinters run that way naturally, but I think there's room for everybody to improve their technique and speed through training," he said.

Previous research had established sprinters' ability to create more force upon hitting the ground without expressing how they do this, and a polemic over training strategies resulted.

At the SMU Locomotor Performance Laboratory, Clark and his study co-author, running mechanics expert and director of the SMU Locomotor Performance Lab Peter Weyand, compared seven top sprinters against seven athletes from sports in which running is pivotal but not the main event such as soccer, lacrosse and football.

The sprinters included athletes who specialize in the 100 and 200 meter events, and more than half had international experience including the Olympics and Track and Field World Championships.

Both groups included four men and three women, Clark told Relaxnews.

Researchers used a custom-built high-speed force treadmill by means of which they were able to assess footfalls at speeds ranging from 3 to 11 meters per second and concluded that both participant groups had mid and forefoot strike patterns.

Researchers say that running kinesiology is heavily influenced by the "spring mass" model that was constructed in the 1980s, a general analysis of the human gait that does not explain why some people are able to run faster than others.

"The elite sprinters did not conform to the spring-model predictions," said Clark in a press release. "They deviated a lot, specifically during the first half of the ground-contact phase. Our athlete non-sprinters, on the other hand, conformed fairly closely to the spring-model predictions, even at their top speeds."

Clark says he hopes his research will lead to evidence-based training methods for honing speed now that coaches and athletes know what to focus on.

The study was published in the Journal of Experimental Biology.