Introduction to accelerometry

OK. So now, we are in session where we’re looking at accelerometry. And, Victor, what is an accelerometer, and what do you use it for? So yeah, an accelerometer is a sensor that tracks acceleration in the three directions of movement. So this one I have here is an EMG sensor, but it contains one accelerometer as well, and it helps us tracking movement at the same time as we track EMG. But accelerometers can also be combined with other types of sensors, and we call those IMUs– Inertial Measurement Units. And that’s similar to the one you have on your phones. So IMUs can track not only acceleration, but also rotation, and magnetic fields. So it’s a combination of three types of sensors.

We have some of those as well in our lab, where we can use wireless sensors as small as these ones to track this type of activities in people. We use them for activities where we don’t want to have cameras– where we want to be as less invasive as possible on the subjects. And we have used them in a lot of music studies, as you probably know, Alexander. And they can be smaller as well, right? I mean this is fairly big, but– Yeah. Yeah. So they could be very small, they could be thinner, and they also are attached to the body with just double-sided tape or just with Velcro. So they are quite flexible for different types of applications.

And what’s the point of using an accelerometer? Why is it useful, do you think? I think the advantage is it’s much more portable than a motion-capture system, where you need cameras and suits. So these ones, you can take anywhere. Many of them just save the data inside in the memory, so you don’t even have to wire the sensors to a computer at the moment. So you can just put them on the participant and forget about them for, even, days. And then you collect the data afterwards. This sounds fantastic. So why aren’t we using accelerometers all the time? What’s the problem with this type of sensor? Yeah well, as I mentioned, they track acceleration.

So, many times, what we need is more precise position data. So extracting position from accelerometers is not so straightforward, and so it complicates things a little bit with accuracy and precision. So it’s a compromise between precision and portability. Yeah. And then, possibly, also even combining accelerometers with other– even with cameras, perhaps– Yeah. Yeah. Is that possible? Yeah, we do that a lot here as well, when we combine motion-capture systems with accelerometers and we can get both types of data. We can also validate data from the accelerometers with the gold standard, which is the optical motion-capture system. Cool.

So that’s a brief introduction to accelerometry, and we’ll write some more in the text below so that you can take a look at that as well. [EXIT MUSIC]