Humans are Lazy: People Subconsciously Adjust Walk to Use Less Energy

First Posted: Sep 14, 2015 08:45 AM EDT

The hours you spending at the gym may be for nothing. Scientists have found that your nervous system may be subconsciously working against you by causing you to change the way you move to expend the least amount of energy as possible.

In order to better understand whether or not people move more or less efficiently when walking for long periods, the researchers asked people to walk while they wore a robotic exoskeleton. This particular contraption allowed the researchers to discourage people from walking in their usual way by making it more costly to walk normal than to walk some other way. They put resistance on the knee to make it more difficult for the volunteers to walk normally.

"We found that people readily change the way they walk-including characteristics in 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, one of the researchers, in a news 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. Here we have provided a physiological basis for this laziness by demonstrating that even with a well-rehearsed movement like walking, the nervous system subconsciously monitors energy use and continuously re-optimizes movement patterns in a constant quest to move as cheaply as possible."

The researchers found that people readapt their step frequency to converge on a new energetic optimum within minutes. In addition, people do this even when the energy savings is less than 5 percent.

The findings show that energetic costs of our activities aren't just an outcome of our movements. Instead, they play a central role in continuously shaping them.

The findings are published in the journal Current Biology.

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