Brain slows down exoskeleton

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Exoskeletons have gone from fantastic laboratory constructions that let the paralyzed walk again, to everyday devices that are increasingly used in industry – often to reduce the strain on the lower back. The adaptation of one’s own movements to the machine support works largely unconsciously. But it still occupies valuable resources in the brain.

However, when people wore exoskeletons while performing tasks that require them to think about their actions, those resources may become overloaded, causing people to work against the exoskeletons rather than being assisted by them. That’s the result a study, which was recently published in Applied Ergonomics.

For the study, William Marras of Ohio State University and colleagues had twelve people – six men and six women – lift a medicine ball repeatedly in two 30-minute sessions. At one of the sessions, participants wore an exoskeleton that is attached to the user’s chest and legs. They did not wear it at the other session. The researchers measured the force that acted on the lower back of the participants during each session and how often the participants picked up the ball. They then asked the same participants in separate sessions to do the same task, but had participants subtract 13 from a random number between 500 and 1,000 each time they lifted the ball.

The result: the exoskeleton reduced the stress on participants’ lower backs when participants simply had to lift and lower the ball. But when the participants had to do the math in their heads as they raised and lowered the ball, those benefits vanished. “It’s almost like dancing with a really bad partner,” said William Marras, lead author of the study. “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 injury. “

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This coincides with a result that researchers at MIT had achieved. They had military members with and without an exoskeleton in 2020 run on a training course, and given them various cognitive tasks. Among other things, the researchers found that the reaction time and memory performance of those with active exoskeletons deteriorated significantly. However, there was also a relatively wide distribution among the test subjects. “The bottom line is that the use of exoskeletons involves many compromises,” writes Marras. “It’s not that easy to lay them on the workers’ backs and then just start them.” One must consider the cognitive requirements associated with a specific task (such as precise placement, choosing the right parts, dealing with constraints such as limited space) in order to understand the potential benefits of the exoskeleton. “So it’s about more than just the physical side. The mind and the body are connected!”


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