We all have optimum running speeds at which we can cover great distances with least efforts

Washington, March 20 (ANI): The efficiency of human running varies with speed, and each individual has an optimal pace at which he or she can cover the greatest distance with the least effort, according to a study.

Karen Steudel, a zoology professor at the University of Wisconsin-Madison, says that the finding debunks the long-standing view that the energy needed to run a given distance is the same whether sprinting or jogging.

Though sprinting feels more demanding in the short term, the longer time and continued exertion required to cover a set distance at a slower pace are thought to balance out the difference in metabolic cost.

However, working in collaboration with Cara Wall-Scheffler of Seattle Pacific University, Steudel has found that the energetic demands of running change at different speeds.

"What that means is that there is an optimal speed that will get you there the cheapest," Steudel says.

The researchers revealed that they determined peak efficiency by measuring runners' metabolic rates at a range of speeds enforced by a motorized treadmill.

According to them, metabolic energy costs increased at both fast and slow speeds, and revealed an intermediate pace of maximal efficiency.

They say that the most efficient running speed determined in the study varied between individuals, but averaged about 8.3 miles per hour for males and 6.5 miles per hour for females in a group of nine experienced amateur runners.

Steudel believes that much of the gender difference might be due to variations in body size and leg length, which have been shown to affect running mechanics.

She says that the larger and taller runners generally had faster optimum speeds.

Steudel has also revealed that the slowest speeds - around 4.5 miles per hour, or about a 13-minute mile - were the least metabolically efficient, which she attributes to the gait transition between walking and running.

She points out that both a very fast walk and a very slow run can feel physically awkward.

The mechanics of running, which holds great interest for athletes and trainers, may also hold clues to the evolution of the modern human body form: tall and long-limbed with broad chests and defined waists.

Steudel says that modern humans are very efficient walkers and fairly good runners, and efficient locomotion probably provided our ancestors with an advantage for hunting and gathering food.

She further states that distant ancestral forms, the australopithecines, had shorter, boxier frames with stubbier legs.

"They wouldn't have had noticeable waists - their torso looked more like the torso of an ape, except they were walking on two legs. With the genus Homo, you start getting taller individuals, larger individuals, and they started developing a more linear body form" with distinct waists that pivot easily, allowing longer and more efficient strides," she says.

Given that human walking is also known to have an optimally efficient speed, Steudel thinks that the new findings may help determine the relative importance of the different gaits in driving human evolution.

"This is a piece in the question of whether walking or running was more important in the evolution of the body form of the genus Homo," she says.

The study has been published online in the Journal of Human Evolution. (ANI)