Is the human body instinctively lazy? A new study explores.

The human body, as it turns out, is wired to find the least energy costly movements in certain situations. That's what Jessica Selinger and her colleagues found out after conducting a study on the adaptability of human movement. If humans are forced to modify hard wired motions such as walking to save energy, no matter how little, the body is quick to adapt the enforced changes.

In the process of developing an energy harvesting knee brace, Selinger, student from Simon Fraser University and the University's Locomotion Laboratory head, Max Donelan, conducted the study to determine what makes humans move the way they do and up to what extent can they adapt their movements upon application of external, physiological stimuli. "For 50 years at least, we've known that people prefer ways of moving that minimize their energetic cost," Donelan says. "But what's unknown is how we do this."

In their study, Selinger and Donelan used a previously developed leg-mounted brace on volunteers to measure energy and applied resistance to the knee. Volunteers were then made to walk on the treadmill three times. First at their own pace, then guided by a metronome, then back again to their own pace. During each walk, the researchers modified the resistance on the brace, decreasing if new methods of walking were used and increasing if they reverted to the old ones. "We think of our experiment like dropping someone into a new world with all new rules," Selinger explained, "Any walking strategies that may have developed over evolutionary or developmental time scales are now obsolete in this new world,"

While no changes were noted during the first walk, the volunteers were seen to quickly settle in to the newly found, energy saving cadence after the metronome guided walk. This showed that after a few minutes of exploring and learning, the brain was quick to override old walking techniques in favor of the newly discovered, more energy efficient one. "We found that people readily change the way they walk - including characteristics of their gait that have been established with millions of steps over the course of their lifetime - to save quite small amounts of energy," said Donelan.

However, the experiment also proved that the body is wired to conserve energy no matter how little the savings may be. "While we suspected that the nervous system could optimise energy use, it was surprising to us how small of a cost it cared about," Donelan added. "Had they simply suffered this small penalty, their energetic debt after one hour of walking would be roughly equivalent to the energy contained in a single peanut. The savings were literally peanuts!"

With the findings of this research, Selinger and Donelan aim to continue to further understand what makes the human body so efficient in determining which walking style saves it more energy.

Photo: Shorefast Foundation|Flickr

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