Someone suggested I split off a new thread from this other thread for discussing body position tracking specifically, which seems like a good idea. Chris Armstrong from OMF brought up a device called activPAL a few months ago: Some info on activPAL: It's a device that is attached to the thigh. It detects its own physical position in space (is it vertical, horizontal, moving, etc), which translates to the position of the thigh, which translates to the position of the whole body. If the thigh is horizontal, then the person is either sitting or lying down. If the thigh is vertical, the person is standing. Some research is also done with the device in other locations, like the torso. This paper looked at position tracking with two activPALs at once - one on the thigh, one on the torso. If both are horizontal, the person is lying down. If both are vertical, the person is standing. If the torso is vertical, but the thigh is horizontal, the person is sitting. ActiGraph is another device used in research for tracking body position and activity: This seems like a very useful tracking/outcome measure for people with ME/CFS. At least for me, my main symptoms are physical fatigue, cognitive fatigue, and anxiety. They all pretty much go up and down in tandem. With this device, physical fatigue can be tracked continuously and fairly easily. Step count can be used to measure fatigue, and is fairly easy to track with cheap devices. But at least for me, I don't think I walk much more or less depending on my energy. It's mostly just things I need to do, and I do them whether I have the energy or not (unless I am extremely fatigued): work, grocery store, cooking, and a little bit of walking around the house for hobbies when I have the energy. In contrast, I think the amount of time I spend lying down, versus reclining/sitting, is a more accurate measure of how much energy I have. The more exhausted I am, the more I need to be lying down. If I'm feeling a little better, I do a little bit of sitting while playing on my phone or interacting with people. (Of course this won't really be applicable to people much more severe than me.) So I think this would be a useful measure for tracking ME/CFS fatigue or PEM in research, including treatment trials. Something like it might also be useful for personal health tracking, maybe connected to an app like Visible. Unfortunately, I haven't been able to find any such devices that can be purchased for personal use. Some smartwatches do some sort of body position tracking, but I think it's hard to get an accurate idea of what the body is doing from the position of the wrist. Though maybe I'd be surprised if I looked more into those. In the thread I linked at the top, I described how I'm trying to build my own device for tracking my body position, though I'm not sure how difficult this project will end up being. It doesn't seem very complicated in principle. Images from: 1. (Non) occupational free-living physical activity in crane operators and office workers, 2018, Kastelic et al 2. Human Activity Recognition of Individuals with Lower Limb Amputation in Free-Living Conditions: A Pilot Study, 2021, Jamieson et al 3. Using unsupervised machine learning to quantify physical activity from accelerometry in a diverse and rapidly changing population, 2023, Thornton et al
My heart rate increases with sitting or standing, so I’ve set my Fitbit to record the amount of time spent above “x” heart rate. It’s not perfect but it is useful to see the variation over days doing stuff/doinglittle.
I haven't actually tested that in myself. I don't feel my heart rate going up significantly, at least. But that could be another way to get a more "blurry" picture of how much a person's total physical activity is changing over time.
I use the Visible band so it was easy to see that when I was sitting or standing, my HR was higher than lying down. It’s not necessarily “high”.
My project to make my own sensor is taking quite a while because I'm so tired. I got to the point where the thing can constantly record its own orientation, but has no real enclosure or way to attach to the body, so I just wrapped a sports bandage around it on my torso and wore it for a couple days. I still have to look at the data it recorded. I was going to do two orientation sensors, one on my leg and one on my torso, so I could discriminate sitting, standing, and lying down, but that adds much more complexity. But anyway, even if I don't finish this, I want to share that I think that it would be very valuable for some organization to make a simple device worn on the torso to discriminate between lying down, and anything else. A device which can be worn 24/7 and can be recharged. It is fundamentally very simple. Just a microcontroller hooked up to an accelerometer, an SD card for data storage, and a rechargeable battery. Maybe bluetooth to connect to a phone to transmit data instead of having to connect the device to a computer, and also BT could sync the clock on the device, since it drifts over time without a reference. Stick it in an enclosure, and wear it around your chest like a Polar heart rate monitor. Charge it once a week or so depending on the battery size. I don't think it needs any complicated algorithms. If the device orientation is flat, the person is lying down. If it's not, they aren't. I think for ME/CFS, this simple metric of time spent lying down every day could be very useful, especially if constantly tracked over months or years. The amount of time I spend lying down feels like a pretty accurate proxy of my health. Maybe for people who have more energy, steps could be useful, but for me, I only walk when I absolutely have to: doctor's appointments, cooking, bathroom, groceries. For people even more severe who spend almost all their time in bed, steps may barely factor in. But seeing that the average amount of time doing something other than lying down, like sitting up in bed to eat or standing in the shower, is steadily creeping up or going down, may be useful, whether for a doctor monitoring a patient, a study testing a drug or looking at biomarkers of PEM, or a person with ME/CFS just seeing what's happening over time with their health. The point is it's simple enough to be cheaply produced, and a more accurate metric of "energy" in ME/CFS than step count.
Thanks for this . Yes I imagine it’s fiendishly hard to get right just from the bits you’ve written about. when I’m lying down I often have to change position constantly including lying on my front so I’m not sure where you could put one that wouldn’t cause discomfort in at least one of those positions. And of course if you lie on one side it would need to be like a spirit level I’ve also noticed that at my severe level there are times I have to be absolutely flat vs days I can be slightly reclined (which makes a difference for eg screens although of course I’m also more well in everything then including arms needing less support) . The sitting up even on good days or nearer to it is definitely an exertion so fir research this level of differentiation is useful. weirdly since the lying flat discussion I’ve also noted that when just slightly recline eg 20-30 degrees if I’m really well and comfortably supported by pillows on all body parts so nothing aches or is pulling or holding itself then it’s much more bearable and able to do - I don’t know whether when less well or if it takes less out of me because I’m so worn down by this illness currently. But I did realise that support from all sides and cosseting my head and my face having something to rest/support it is key. I often have to change position just to support that side of my head for a bit. Weird.
Maybe wouldn't be okay for everyone, but I didn't have a problem lying on my stomach either with my custom thing, which is like the size of two flat matchboxes side by side covered generously in sports bandages which flattens it out, or a Polar H10 HR monitor on my chest. Might require a soft enough bed.