Exoskeletons designed to reduce lower back pain can compete with valuable resources in the brain

Exoskeletons – wearable devices used by assembly line or warehouse workers to relieve stress on the lower back – can compete with valuable resources in the brain while working, negating the physical benefits of wearing them, according to a new study.

The study, recently published in the journal Applied Ergonomics, found that when people wore exoskeletons while performing tasks that required them to think about their actions, their brains worked overtime and their bodies competed with the exoskeletons rather than in harmony with them work. The study shows that exoskeletons can put such stress on the brain that potential benefits to the body are negated.

“It’s almost like dancing with a really bad partner,” said William Marras, lead author on the study, professor of integrated systems engineering, and director of the Ohio State University Institute of Spine Research.

“The exoskeleton tries to anticipate your movements, but it’s not going well, so you’re struggling with the exoskeleton, and that is what causes this change in your brain that alters muscle recruitment – and could cause higher forces on your lower back, potentially leading to Pain and possible injuries. “

For the study, the researchers asked 12 people – six men and six women – to lift a medicine ball repeatedly over two 30-minute sessions. For one of the sessions, the participants wore an exoskeleton. They didn’t do it for the others.

The exoskeleton, which is attached to the user’s chest and legs, is designed to help control posture and movement while lifting to protect the lower back and reduce the possibility of injury.

The researchers used infrared sensors to assess participants’ brain activity and measure the force on each participant’s lower back during each session. They also tracked the number of times each participant lifted the medicine ball in each session.

Then, in separate sessions, they asked the same participants to do the same task – lift a medicine ball for 30 minutes, wear an exoskeleton in one session – but added a mental task: they left participants 13 from a random number between 500. deduct and 1,000 each time they lifted the ball.

They found that the exoskeleton slightly reduced the stress on participants’ lower backs when participants simply lift and lower the ball. But when the participants had to do the math as they raised and lowered the ball, those benefits disappeared.

While assembly line exoskeleton users may not need to do calculations in their heads, any kind of mental stress, such as mental stress or instructions they need to follow, could have the same effect, Marras said.

As we looked at what was going on in the brain, there was more competition for these resources in the brain. The person did this mental arithmetic, but the brain was also trying to figure out how to help the body interact with the exoskeleton and that confused the way the brain was recruiting the muscles to do the job. “

William Marras, lead author of the study

When these muscles compete with each other, the brain worked less efficiently and the forces on the back increased, the researchers found.

“If you’re a company that spends hundreds or thousands of dollars on an exoskeleton, there’s a very good chance the exoskeleton is not doing your employees good,” Marras said.

“All exoskeletons aren’t bad, but people are messy and everyone is different: you have to use exoskeletons with some intelligence and some understanding of what the job entails.”


Journal reference:

Zhu, Y., et al. (2021) Neural and Biomechanical Tradeoffs Associated with Human-Exoskeleton Interactions. Applied ergonomics. doi.org/10.1016/j.apergo.2021.103494.