Humans are actually ‘wired for laziness’

 
No matter how hard you think you’re working, your nervous system is subconsciously trying to make things easier for you by adapting to limit the amount of calories your body burns and thus expending the least amount of energy possible, according to a new study.
In research published Thursday in the journal Current Biology, Dr. Max Donelan of the Simon Fraser University Locomotion Laboratory and his colleagues were studying the energetic costs of walking and other movements when they found that humans are constantly making slight tweaks to their gait to save minute amounts of energy – whether they know it or not.
Dr. Donelan, lead author Jessica Selinger (a student in the SFU Locomotion Lab) and colleagues set out to understand why people move the way that they do, considering there are a multitude of ways to travel from one point to another. Specifically, they wanted to find out to what degree the human body can adapt its movement in response to real-time physiological inputs.
Experiments show how the body tries to burn fewer calories
The researchers put participants into robotic exoskeletons that discouraged them from walking in their typical way by making it harder to swing their legs by putting resistance on the knee during the motion. They found that the nervous system is constantly working behind the scenes to re-optimize locomotion patterns and reduce energy expenditures.
Specifically, their experiments revealed that people adapt their step frequency to achieve a new, optimum energy consumption level in a matter of minutes, and that this takes place even though the overall energy savings is almost negligible – less than five percent, according to the authors. Even so, their findings are proof that the human body is hard-wired for laziness.
But is this a good thing or a bad thing?
“I suppose that depends on your perspective,” Selinger told redOrbit via email. “It’s a good thing if you want to conserve energy, but a bad thing if you are just trying to burn calories. A marathon runner wants to move efficiently throughout the race so they preserve energy for the final push. But, if someone is running simply to lose weight, they may curse their clever nervous system. So, I guess it depends on your goal.”
“The ability to optimize movements to reduce energy expenditure may also be an important survival strategy. While we live in a culture where calories heavy foods are widely available, that isn’t the case for all, and that certainly wasn’t the case for our prehistoric ancestors. The nervous system’s goal of reducing energy expenditure may have helped stave off starvation,” she added.
Researchers trying to learn more about this phenomenon
Moving forward, Selinger, Dr. Donelan, and their colleagues said that they plan to investigate further, with the hopes that they can answer questions about how the human body measures the energy costs associated with specific was of moving. They also hope to solve the mystery of how our systems are actually able to solve complex motion-centered optimization problems.
“We now know that humans can continuously optimize their movements patterns based on energetic cost. But we don’t know how energy use is sensed or measured by the body,” Selinger said. “We might sense it directly using known blood gas receptors that can measure oxygen consumption and carbon dioxide production, or we could sense it indirectly from some proxy signal like muscle activity. We are currently conducting some interesting experiments where we try to directly perturb blood gas sensors and see if this can disrupt the optimization process.”
She added that there are “countless ways we can get from point A to point B. So how do we so quickly discover the optimal coordination patterns? It could be that our nervous system is primed to quickly search only a reduced subspace, such as particular combinations of speeds and step frequencies or particular combinations of muscle activities, rather than attempting to continually search all possible combinations. The nervous system may also employ what we call gradient-based descent or other optimization tricks to speed the search for new energetic optima.”
“For example,” Selinger said, “if a gait parameter changes and the nervous system detects a lower cost movement, it will send a signal to continue to change that gait parameter as long as it continues to reduce cost. Alternatively, people may not initiate optimization based on energetic gradients, but may instead require explicit experience with a novel optimum in order to adapt to it. We are currently conducting experiments to try to understand which, if any, of these mechanisms underlie the optimization process.”
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