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Introduction to electromyography (EMG)

In this video, Kayla and Victor talk about electromyography (EMG), a method for capturing muscle tension.
Hi, I’m Kayla, and we’re just going to talk really quickly about technology called EMG. EMG stands for electromyography, which sounds really similar to other technologies you might have heard of like ECG and EEG. It measures electrical signals in your body from the surface of your body. Victor, have you ever used this before? Yeah. We have used it a lot here. For us, it’s very important to see not only the superficial movement but also what happens inside the body when we move, how do we respond to different stimuli, and how our muscles produce the movement that we are tracking. So yeah. That’s really interesting. So what kind of data is it good for?
So, what we get from this is electrical activity from your muscles. So it just tells us when the muscle is being activated by our brain basically. And then we can– then after that, we see the action happening but then this is basically before, let’s say, the action happens. So this is how the muscles are activated to produce the movement. So if you see, these are sensors. And on the back, we have these metal pieces sticking out of it. And that’s what actually contacts the surface to measure any kind of electrical signal that’s seen on that surface.
And these things actually transmit directly to this lovely antenna here so we can get live data in, and you don’t have to be wired to the sensor system here. So that’s a very good advantage of this system in particular because EMG started as not being wireless. So originally you had to have all these cables and then try to perform with those cables was cumbersome. So now with this type of technologies we can do it very noninvasively, and we also have a different– two types of sensors for different applications. So this one is bigger for larger areas, and this one comes with a smaller attachment for smaller, more detailed tracking. They also include accelerometers.
So they also track acceleration in three directions, these same sensors. So where are good locations to put EMG? Can you show– Yeah. –what’s good? So as we mentioned, they track muscular activity. So we need to put them on top of the muscle belly as it’s called. So it’s normally prominence in muscles. You have to know a little bit about anatomy and where the muscles are and what each muscle does, depending on what activity you are tracking. But when you do certain movements, you can feel some muscles expand, and we normally use those little movements to track where the muscle belly can be. And then after palpation, we can know where to put the sensor.
This– the muscles have muscle fibres, and EMG works best when you put these metallic plates aligned with those muscle fibres. So again, you have to know a little bit about anatomy when placing these [INAUDIBLE]. Yep. Yeah, so prerequisites for this technology use are an anatomy book, a simple knowledge of physiological pathways, and a few cables and plugs. It takes a lot of practise. How long did it take you before you were good at using EMGs? A couple of years. A couple of years. Yeah, so don’t expect to get this right on the first try. Yeah.
Another important thing about EMGs, because as we mentioned we are tracking electrical activity, we definitely need some good contact between the sensor and the skin, and we need to be as clean as possible on the skin. If there’s too much hair, we need to remove the hair. We need to clean properly. Yeah. So we use these double-sided stickers, super advanced technology, double-sided tape, and usually like an alcohol swab or something to clean the surface of your skin. Because as he mentioned, you need to make sure you get a good contact on skin. Also be aware if it’s really sunny out and you have sunscreen on, you’re going to need to wipe that off too. Yep.
So yeah, the procedure is quite– shouldn’t take that long, but it has to be very detailed and you have to take into account all these details to have good– good recordings. So again, as Kayla mentioned, you won’t have it right in the first trial but with practice you’ll get good. Yeah. So we mentioned a couple other technologies that start with E. Since those also pick up electrical signals in your body, where would EMG pick up those other ECG, EEG? Where on your body would you put those? Yeah.
For starters, if this is very sensitive to electric charge, so anywhere basically where there is good contact and with a clean skin you would get some electrical activity, if you put it around the chest area, you would get some heart activity. So it depends on your application. You might get only heart data that you don’t want. If what you want is pectoral activity and not heart data, you have to be careful where to put it on the chest for example. So depending on the system you have and depending on the muscles that you’re interested in, really just designing your study is important. But just expect a lot of trial and error before you get a good signal. Yep. All right.

Many people are interested in measuring muscle tension together with motion. How do you do that?

In this video, Kayla and Victor talk about electromyography (EMG), a method for capturing muscle tension. They briefly present the technology and reflect on some of the challenges in the placement of EMG sensors.

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