Washington, Aug 27 (IANS): Know the secret behind the world's faster sprinter Usain Bolt's mind-boggling speed? The forceful punch to the ground with his foot as he starts to run and disappears in a jiffy.

According to a fascinating study, the secret to elite speeds lies in the distinct limb dynamics sprinters use to elevate ground forces upon foot-ground impact.

"Our studies show that these elite sprinters do not use their legs to just bounce off the ground as most other runners do," said Ken Clark, a human biomechanics expert from Southern Methodist University (SMU), Dallas.

"The top sprinters have developed a wind-up and delivery mechanism to augment impact forces. Other runners do not do so," he added.

Elite speed athletes have a running pattern that is distinct.

"Our data indicate the fastest sprinters each have identified the same solution for maximising speed, which strongly implies that when you put the physics and the biology together, there is only one way to sprint really fast," Clark added.

"They cock the knee high before driving the foot into the ground, while maintaining a stiff ankle. These actions elevate ground forces by stopping the lower leg abruptly upon impact," explained running mechanics expert Peter Weyand, director of the SMU's locomotor performance lab.

The tests conducted at SMU's Locomotor Performance Lab compared competitive sprinters to other fast-running athletes.

The competitive sprinting group included track athletes who specialised in the 100- and 200-meter events. They were compared to a group of athletes that included soccer players.

The findings indicate that that the fastest runners decelerate their foot and ankle in just over two-hundredths of a second after initial contact with the ground.

The studies were reported online in the Journal of Applied Physiology and The Journal of Experimental Biology.