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Tighten muscles

Researchers at ETH Zurich have developed a wearable exomuscle made of fabric - a kind of additional muscle layer. This is intended to give people with limited mobility more strength and endurance in the upper body.

"I'm just increasingly weak in my arms," says Michael Hagmann, who was diagnosed with Bethlem myopathy, a rare muscle disease, in 2016. To compensate for the lack of muscle strength in his arms, Hagmann makes evasive movements in everyday life, which in turn lead to awkward posture and tension. Marie Georgarakis, a former doctoral student at the Sensory-Motor Systems Lab at ETH Zurich, knows the problem. "Meanwhile, there are many good therapy devices in clinics. But they are often very expensive and large. On the other hand, there are fewer technical aids that directly support patients in their everyday lives and with which they can also train at home. We want to close this gap," says Georgarakis.

As much force as necessary

This idea gave birth to the Myoshirt, a soft, wearable exomuscle for the upper body. It consists of a kind of vest with cuffs for the upper arms and a small box containing all the technology that is not directly needed on the body. Here's how it works: An intelligent algorithm uses sensors in the fabric to detect what kind of movement the wearer wants to perform and how much force is needed to do it. A motor then shortens a cable running parallel to the muscles in the fabric - a kind of artificial tendon - and thus supports the movement. The support is always in line with the movement performed by the user and can be adjusted to individual preferences. The user is always in control and can override the device at any time.

More endurance thanks to exomuscle

The researchers have now tested this first prototype for the first time in a study with 12 test subjects - ten healthy people, one person with a muscle weakness (Michael Hagmann) and one person with a spinal cord injury. The results are promising: All participants were able to lift their arms and/or objects much longer thanks to the exomuscle. The endurance time increased by about one third in the healthy participants, by 60 percent in the participant with muscle weakness, and the subject with a spinal cord injury was able to perform the exercises for three times as long. The participants' own muscles were less strained, and the vast majority of the test participants found the device intuitive to use.

Test and improve with affected people  

However, the road to a marketable product is still a long one: "In a next step, we would like to test our prototype outside the lab in the natural environment of the future wearers and use the results to further improve the device," says Michele Xiloyannis, who also works at the Sensory-Motors Systems Lab at ETH Zurich and is conducting research on the Myoshirt. To ensure that the device can one day be worn invisibly and comfortably under clothing, it must become even smaller and lighter - today the drive and control box still weighs four kilograms. To achieve a maximally reduced product, the researchers want to continue to focus on one core function - supporting the shoulder when lifting the arms. They are also working closely with ETH spin-off MyoSwiss AG, which manufactures and sells a soft exoskeleton - a type of robotic suit that supports the legs. "I particularly like the fact that the researchers develop their ideas together with potential users and in an iterative way," says Michael Hagmann, who has already tested and thus helped develop various ETH technical aids from prototype to finished product. For him, it's clear that he wants to remain active in the future, and that's where technical support comes in handy.

Source: Wearable muscles | ETH Zurich (01.09.2022)

Tom Illauer

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