CAMBRIDGE, Mass. — Not getting enough sleep makes people more clumsy, according to a new study. Researchers found that making up for lost shut-eye — even with a brief nap — can help reduce fatigue-induced clumsiness.
There is plenty of evidence to show that sleep, and how much we get, can affect how well people perform when doing everyday tasks, such as reading a book or getting off at the right train station. However, the less explored question is whether sleep influences the way we walk or carry out other activities that scientists assume are less mentally taxing.
A team from the Massachusetts Institute of Technology (MIT) and the University of São Paulo in Brazil found that a lack of sleep can affect our gait (or walking style). During an experiment with student volunteers, the team found that overall, the less sleep the students got, the less control they had when walking during a treadmill test.
For the students who pulled an all-nighter before the test, they struggled to put one foot in front of the other. The participants who didn’t stay up all night, but who generally had less-than-ideal sleep during the week and treated themselves to a relaxing weekend, performed better than those who didn’t.
“Scientifically, it wasn’t clear that almost automatic activities like walking would be influenced by lack of sleep. We also find that compensating for sleep could be an important strategy. For instance, for those who are chronically sleep-deprived, like shift workers, clinicians, and some military personnel, if they build in regular sleep compensation, they might have better control over their gait,” says Professor Hermano Krebs, the principal research scientist in MIT’s Department of Mechanical Engineering, in a university release.
There’s more to walking than meets the eye
Walking was once seen as an entirely automatic process, involving very little conscious, cognitive control. However, previous studies that have observed animals on treadmills have suggested that walking relies on reflexive spinal activity, rather than the cognitive control of the brain.
“This is the case with quadrupeds, but the idea was more controversial in humans,” Prof. Krebs explains.
Since those experiments, scientists including Prof. Krebs have proved that the act of walking involves more than previously thought. Over the last decade, Prof. Krebs has extensively studied gait control and the mechanics of walking in order to develop strategies and assistive robotics for patients who have suffered strokes or other motion-limiting conditions.
Throughout his career, Prof. Krebs has shown that walking actually involves subtle, conscious influence in order to walk in different environments and avoid potential obstacles, in addition to more automatic processes. In 2013, he embarked on a collaboration with Professor Forner-Cordero and the team explored whether more subtle stimuli, such as hearing sounds, might influence walking.
In these initial experiments, the team asked volunteers to walk on a treadmill while the scientists played and slowly shifted the frequency of a metronome. Without realizing it, the volunteers matched their steps to the beat.
“That suggested the concept of gait being only an automatic process is not a complete story. There’s a lot of influence coming from the brain,” Prof. Krebs reports.
Forner-Cordero and Krebs continued to investigate the mechanics of walking and general motor control by enlisting student volunteers in their experiments. Prof. Forner-Cordero noticed that towards the end of the school term, when the students faced multiple exams and project deadlines, they were more sleep-deprived and happened to do worse in the team’s experiments.
All-nighters are bad for coordination
Instead of calling it quits, the scientists embraced the situation — which informed their future research. In their new study, the team enlisted students from the University of São Paulo to take part in an experiment, which focused on the effects of sleep deprivation on gait control.
The students used an activity tracker for two weeks, giving the scientists an idea of when and how long the students were either sleeping or active each day. In order to record their natural sleep patterns, the students received no instruction on how much sleep they should get.
On average, each student slept for approximately six hours a day and some managed to catch up on their sleep over the weekends. Before the experiment’s 14th day, some of the students found themselves in the Sleep Acute Deprivation Group and scientists asked them to stay awake all night in the team’s sleep lab.
On the morning of the study’s final day, all the students met in the lab to perform a walking test. Researchers recorded each student walking on a treadmill set at the same speed, with the faint sound of a metronome in the background.
The students had to keep step with the beat and, without telling the students, the researchers raised and lowered the metronome’s beat. Cameras captured the moment the students’ heels would strike the treadmill, in comparison to the beat of the metronome.
“They had to synchronize their heel strike to the beat, and we found the errors were larger in people with acute sleep deprivation. They were off the rhythm, they missed beeps, and were performing in general, worse,” Prof. Forner-Cordero says.
Working all night? Grab a nap whenever you can
Although this in itself may not be entirely surprising, the researchers did find an unexpected difference when comparing the students to those who pulled an all-nighter. The students who performed better were those who had compensated and got slightly more sleep on the weekends, even when they performed the test at the tail end of the week.
“Even at the peak of when most people would be tired, this compensating group did better, which we didn’t expect,” Prof. Forner-Cordero adds.
“The results show that gait is not an automatic process, and that it can be affected by sleep deprivation. They also suggest strategies for mitigating effects of sleep deprivation. Ideally, everyone should sleep eight hours a night. But if we can’t, then we should compensate as much and as regularly as possible,” Prof. Krebs concludes.
The findings were published in the journal Scientific Reports.
South West News Service writer Georgia Lambert contributed to this report.