Humans 'may be able to run at 40mph'

A new study, published in the 'Journal of Applied Physiology', has offered intriguing insights into the biology and perhaps even the future of human running speed. Lead researcher Peter Weyand of Southern Methodist University said: "The prevailing view that speed is limited by the force with which the limbs can strike the running surface is an eminently reasonable one,"

"If one considers that elite sprinters can apply peak forces of 800 to 1,000 pounds with a single limb during each sprinting step, it's easy to believe that runners are probably operating at or near the force limits of the muscles, limbs.

"However, our new data clearly show that this is not the case. Despite how large the running forces can be, we found that the limbs are capable of applying much greater ground forces than those present during top-speed forward running." In contrast to a force limit, what the researchers found was that the critical biological limit is imposed by time -- specifically, the very brief periods of time available to apply force to the ground while sprinting.

In their study, the researchers took advantage of several experimental tools to arrive at the new conclusions. They used a high-speed treadmill capable of attaining speeds greater than 40 miles per hour and of acquiring precise measurements of the forces applied to the surface with each footfall. They also had subjects' perform at high speeds in different gaits.

The researchers found that the ground forces applied while hopping on one leg at top speed exceeded those applied during top-speed forward running by 30 per cent or more, and that the forces generated by the active muscles within the limb were roughly 1.5 to 2 times greater in the one-legged hopping gait by the subjects.

"Our simple projections indicate that muscle contractile speeds that would allow for maximal or near- maximal forces would permit running speeds of 35 to 40 miles per hour and conceivably faster," co-researcher Matthew Bundle of University of Wyoming said.