We’re Lazy by Nature

A new study says we naturally take it easy.

by Theresa Fisher 

Successful startups — full-blown industries, even — have capitalized on our predilection for moving our legs as little as possible, otherwise known as laziness. Why walk across the street to pick up pad thai when you can Seamless? Why hobble downstairs to hail a cab when you can Uber?
While we should certainly hang our heads in shame (there’s a fleet of available taxis directly outside), our reticence to move those stumps of flesh and atrophied muscle we call legs may have some biological basis. A new study, published in the journal Cell, suggests that we continuously adjust our gaits as we walk to exert a minimum amount of energy, even when the payoff is nearly null.
Movement science novices, take note: A central, decades-old principle in the field says that “people prefer to move in energetically optimal ways” and, according to some modern theories, “will adjust their movements to continuously optimize energetic cost.” But, while previous studies have shown that people do in fact fine tune how they move so their bodies work more economically, the goal underlying the fine tuning isn’t so clear. It’s possible that our nervous systems prioritize a different goal, such as stability or accuracy, and that decreased energy output is merely a byproduct.
So, in the current study, researchers focused on what they saw as a likelier reflection of energy conservation: step frequency, a “fundamental characteristic of gait.” We all have natural gaits — you’ve got your shufflers and strutters; leaden-foot stompers and brisk-paced striders — and, absent some compelling reason, our bodies cling to those gaits.
People who volunteered for the study donned robotic exoskeletons. After getting strapped in, they hopped on treadmills and stepped as they normally would. Then, researchers increased resistance on the exoskeletons, so participants felt as though they were lugging around heavier bodies. Participants were randomly assigned to receive one of two levels of resistance.
Researchers kept pressure low enough to allow relatively normal walking, because, as they explained in the study, saddling participants with bone-crushing weight would have made it hard to tell if they changed their gaits to save energy or to minimize the pressure load.
At one point in the study, participants spent 15 minutes walking around. Researchers told them to explore their “novel energetic landscape” at higher and lower step frequencies, as well as match their steps to a variety of steady metronome beats. Then, after forced exploration ended, participants walked however they pleased, at which point, the study says, they quickly adapted to energy-conserving step frequencies. And these preferred frequencies differed from their stepping styles both pre-exoskeleton and after researchers increased resistance (to see how they stepped to accommodate heavier weight).
Basically, researchers made them step in every which way, and measured changes in frequency.
“Subjects achieved most of the cost savings immediately after the exploration period,” wrote researchers, “yet they continued to fine-tune their step frequency for vanishingly small energetic savings.”
So there you have it: We may be wired to be lazy, even when we’re hardly saving energy. But don’t blame your nervous system when your Seamless bill rivals your rent. All you need to do is start moving your legs, and your body will make your walk as effortless as possible.