Ever wondered why it's so difficult to get the motivation to exercise, but so easy to sit on the couch and watch Netflix all day?
Though it sounds obvious – it's because the human brain is wired for laziness –researchers in Canada now think they have the proof.
They fitted volunteers with robotic exoskeletons which made it more difficult to walk, for example by putting resistance on the knee.
Within minutes, participants – without consciously thinking about it – were able to adapt their gait to compensate.
"Sensing and optimising energy use that quickly and accurately is an impressive feat on the part of the nervous system," says lead author Jessica Selinger of Simon Fraser University. "You have to be smart to be that lazy."
What surprised the researchers was that people's walks changed significantly even if the energy savings were lower than 5 percent.
"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," says co-author Maxwell Donelan.
"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."
With "literally tens of thousands" of muscles able to adapt within minutes, the researchers say the next step is to find out how the brain and body do it.
The research is published today in journal Biology.