How fast can the fastest man in the world run? There is an overpowering compulsion to find an answer ever since Usain Bolt struck the world of 100 metres racing. After a record-breaking 9.69 seconds at the 2008 Beijing Olympics, he went on to better his record the very next year at the World Championship in Berlin with a 9.58 seconds sprint. So in a matter of just one year he sliced the record time from the pre-Beijing 9.72 seconds to 9.58 seconds. But can humans continue to shave off a few milliseconds and set newer records? And what is the defining maximum speed for humans competing in the shortest form of the sprint? Breaking the 10-second barrier was once considered a formidable task until Carl Lewis achieved it way back in the 1984 Los Angeles Olympics with a timing of 9.99 seconds in a low altitude condition. The barrier has since lost its significance as several others have accomplished it. That seven of the eight athletes ran well under 10 seconds in the just concluded final in the London Olympics reveals how insignificant that glass barrier is. A December 2008 paper in The Journal of Experimental Biology noted that unlike thoroughbreds and greyhounds, which have already reached their biological speed limit, the outer limit for male sprinters “is only a few per cent greater than that observed to date.” For women, the running speeds for 100 metres “appear to have plateaued during the 1970s.”

How fast humans can run depends on stride length and frequency of strides. At slow-paced running, the contact time of the foot with the ground is long and hence there is sufficient time for the foot to generate larger forces required to increase the stride length. But as the speed increases, the contact time with the ground shrinks and hence the force with which the limb strikes the ground reduces. It is a fact that the foot-ground contact time is less than one-tenth of one second in the case of top-rated sprinters. Beyond a 7 metres per second speed, sprinters “shift” from increasing the stride length to increasing the frequency of strides. It is not clear if the force with which the limb strikes the ground during the fleeting moment of contact has already peaked. A 2010 study found that the ground forces applied when the subjects were hopping at top speed was 30 per cent more than top-speed running, giving hope for improvement. Aside from human physiology, improved nutrition, scientifically advanced and rigorous training, sophisticated accessories, and superior track technology may continue to propel humans into running faster than ever before, even if that improvement is in the order of a couple of milliseconds.

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