Don't dawdle, people say. Well, they're wrong. A new study has found that humans are essentially wired for laziness, with the way we walk showing that we subconsciously fine-tune our movements in order to minimise energy expenditure.
Researchers from Simon Fraser University in Canada strapped volunteers into a robotic exoskeleton that made it harder for them to walk with their natural stride, obliging them to modify their gait in order to save on energy use.
And modify they did. The researchers found it took very little obstructive encouragement from the exoskeleton before participants subconsciously took the hint and adapted to a new walk.
"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 Max Donelan, co-author, in a press release.
"This is completely consistent with the sense that most of us have that we prefer to do things in the least effortful way, like when we choose the shortest walking path, or choose to sit rather than stand," he added. "Here we have provided a physiological basis for this laziness by demonstrating that even within a well-rehearsed movement like walking, the nervous system subconsciously monitors energy use and continuously re-optimises movement patterns in a constant quest to move as cheaply as possible."
What surprised the researchers was just how quickly the nervous system adapted to new coordination patterns in order to find the right balance between energy cost and the body's accustomed way of walking – and also for extremely minimal gains.
"While we suspected that the nervous system could optimise energy use, it was surprising to us how small of a cost it cared about. We found that people would adapt their gait even in response to remarkably small energetic savings, at times for less than five per cent of their total cost," Donelan said. "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!"
The researchers will now continue their studies in order to understand how the body calculates that some methods of walking will expend less energy than others – and also to look into how the body arrives at this conclusion so efficiently.
"Walking requires the coordination of literally tens of thousands of muscle motor units," said Donelan. "How do we so quickly discover the optimal combinations?"
The findings are published in Current Biology.