A helping hand with walking

26 March 2019

Interview with 

Alex Sancho, MyoSwiss

GROUP-WALKING

Group walking

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The ability to move about is something most of us take for granted. But, for many people, mobility is not a simple issue, and they could really use assistance walking. Myoswiss have designed the “myosuit”, which works a little like an electric bicycle for your legs. A lightweight battery backpack is connected to a frame that wraps around each leg. When you take a step, Myosuit uses a system of metal strings at the knee which stretch and pull your leg, making the same natural movements that you leg muscles do. The idea is to give a helping hand (or leg) to anyone going through rehabilitation, or even just struggling to climb stairs. Alex Sancho showed Adam Murphy how it works... 

Alex - The Myosuit is basically an exo-muscle and what an exo-muscle does is, we provide an extra layer of assistance for patients that have some difficulty while they're walking. So be it elderly patients or patients that have a muscle dystrophy or incomplete spinal cord injury. And what we do is support them during their daily lives. So we can give support while they stand up, while they walk, while they go upstairs.

Adam - So you're here wearing what looks like a fancy robot suit. When you try to move your legs, what actually happens what goes on mechanically?

Alex - One of the beauties of our system is that compared to other similar systems which can be an exoskeleton for example is that the system is really really simple. So we have a backpack that's four and a half kilos. The backpack has two motors with two tendons attached them. The tendons are very smartly routed in such a way that when you pull on them, both your knee and your hip extend. That's a movement that you do when you stand up from a chair. On top of that we have a sensor layer that has two IMU sensors, so a gyroscope and an accelerometer per leg. And also we have one on the trunk. So what that does is we are real time creating a picture of the person wearing the suit and based on that how we can parametrise the gait cycle of the patient or the activity that you're doing and apply the force that supports them at any given point. So we are lighter and we can assist through many more activities, very dynamic because since we only have one motor that is pulling on a cable we can have very dynamic responses to the movements of the patients.

Adam - So instead of forcing the joints itself to move it pulls on tendons like exist in your body now.

Alex - Exactly, so we are always trying to mimic our own bodies. Also we have a passive layer so the tendons when pulled by the motors they extend the muscles but also we need a flexor which would assist when you are swinging your leg forward. So what we do is we assist with the motors when you put your feet on the floor. Basically give support during that time and then you move your leg backward and at some point the passive elements which are springs sort of, they get tension and the motor releases and your leg gets propulsed forward by the springs. So the beauty is that with a very simple system that actually mimics the body and the muscle structure. We are actually supporting throughout the whole gait cycle.

Adam - How does it know when to stop when you put your foot in the ground and it doesn't keep extending, how does it know you've taken a step?

Alex - So our algorithms, what they do is when you put the feet on the floor. If you look at the signals from the IMUs you get very similar signals regardless of the patient or even if it's a healthy subject. So we detect that exact moment and basically the actuation is very simple, and for the release of that what we do is ask the patients to calibrate so they walk for six steps and based on that we get more or less the way they walk. And based on that we can estimate when the suit should release the force.

Adam - Are people using this now to help them?

Alex - Yes. So what we are doing right now is a feasibility test, to test on patients and to define the usability. At the same time the patients are very happy to test it and experience the technology. So up to now we have tested on around 17 patients so incomplete spinal cord injuries, myopathies, a couple of them stroke patients. One of the virtues that the suit has is that we can assist only one leg instead of both legs. So with stroke patients that have severe damage on one side we can assist on that side and leave the other side transparent, we call it, which is when we don't assist the patient.

Adam - And how easy is it to wear and put on because I've seen you've been wearing this most of the day.

Alex - I have to say that it's comfortable like it's wearing around a 4 kilogram backpack and we are targeting lower weights for the commercial version that will show up at the end of the year. Also the knee support; we are aiming at also reducing the size. So yeah in general we want to reduce the weight significantly and also the donning time of the suit to like two minutes which would be way faster than anything on the market.

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