Smartwatches aren't fully baked when it comes to calorie burn

Speaker 1: If you wear a smart watch to track your workouts, you're probably used to glancing down at your wrist and taking a look at that calorie bird number. But what if that number wasn't accurate? Researchers at Stanford university have come up with a new wearable design that they say more accurately reflects overall energy expenditure and calorie burn. So that just means it's one thing we have to do. I am gonna go check it out and do a couple of workouts to see how accurate this really is. [00:00:30] There are plenty of reasons why people want to track calorie burn, but one is helping to manage your weight. This is Patrick slate, a graduate student at Stanford. He's showing me his new wearable with two sensors worn on the upper and lower part of the leg where most of your energy is used during exercises like walking, running, stair climbing, and cycling. Okay. So tell me why [00:01:00] traditional smart watch and wearables that we wear on our wrist aren't necessarily as accurate as something that's measuring from our Speaker 2: Lower body. Yeah. People are often really confused when I tell them that smart watches have 40 to 80% air, which can be a lot. And so the challenge is if you use heart rate, it's actually not directly related to the energy that you're spending. So if your muscles are burning that energy, um, your heart rate is just pumping blood through your body. And it's, uh, has a bunch of different factors which affect it. Like how tired you are if you had coffee. Um, [00:01:30] if you worked out previously, so this kind of time history makes it really volatile. So we're using just the actual leg motion. And from that kind of extracting what the muscles are doing Speaker 1: Most wearables will on, on the wrist, calculate calorie burn by starting with four pieces of information, your height, weight, age, and gender. This determines your basal metabolic rate, all the number of calories you need to maintain vital functions at rest, during activity or a workout. [00:02:00] It also uses sensors like heart rate GPS, the accelerometer, or the gyroscope, depending on the exercise you're doing to help determine calorie credit, add these two numbers together, and your watch gives you total calories burned in a day. It's an estimate. As many other factors go into how many calories you actually burn to test Patrick's claim. I climbed into the most scientifically system to measure energy expenditure in the lab. Speaker 2: So this is the respiratory system, [00:02:30] which is mobile. So you'll wear this like a backpack and this mask, um, you'll have it on your face. And so it'll capture every breath that you take and we'll be able to compute sort of your crown truth, energy expenditure that way. And then we have our lab smartwatch here. And so this we'll have you put on and punch in some information like your height and your weight. Uh, and then that will give you estimates through its app. And then we have our system and it consists of a couple components. So here's our micro controller battery and the two IMU. So you'll wear it like a waist pack. [00:03:00] And then we'll put these on your legs. How does that feel? Yes. Good. If Speaker 3: Only I had this throughout the whole pandemic, I already felt much Speaker 1: Cooler Patrick's system also needs vitals, like weight and age to make its calorie calculations. And before I start working out, we take a baseline reading [00:03:30] from the respirometer then I'm good Speaker 4: To go. Speaker 3: Okay. I'm gonna do a nice Leslie five minute walk on the treadmill. So let's start Patrick. I'm ready when you are. All Speaker 2: Right, let's do it. Speaker 3: All right. It doesn't feel that hard to wear or anything. I think the real chest will be when I'm running. Speaker 2: You can go ahead and climb up. [00:04:00] All right. Speaker 4: All Speaker 2: Right. Okay, awesome. Yeah. Take a minute. You can take the mask off if you want and get a drink, get a breather. Yeah, get a water. Speaker 3: Okay. We're outside. I'm gonna do a five minute run, more likely a five minute slow jog because I'm not gonna be setting any records with [00:04:30] my pace. Fortunately, pace doesn't matter. It's all just about measuring my energy expenditure. Speaker 2: All right. Right. Go ahead and stop. Speaker 3: Maybe you could like hear how deep and heavy my breathing was. I mean, you probably can very dark. All right. So I'm gonna target about 80. [00:05:00] How PM. Let's see. There we go. Speaker 2: All right. And you can go ahead and start. Speaker 1: So I'm so excited to see these results. Can we have a look at the data and tell us what, um, the respiratory device was giving us and then also, um, your device and then compare that to the smartwatch? [00:05:30] What the differences there? Speaker 2: Yeah, definitely. So for running specifically, so the respiratory, the ground truth had an estimated 87 calorie spray. Um, my device was a little bit lower, 66 and then the smart watch was 52. Speaker 1: Wow. So it was significantly lower on the smart watch. Yeah. I was not expecting that. I was honestly expecting to see the watch to overestimate my calorie burned instead. Um, so that was a running. What about [00:06:00] the other Speaker 2: Activities? Yeah, let's look at stair climbing. So stair climbing, it said that you burned, uh, 135 calories with the retry. Um, my system said 110 calories, and then it looked like the smart watch said 67 calorie. Whoa. Speaker 1: And as a percentage of, of error, what's, what's that that's Speaker 2: 62%. Speaker 1: 62%. Yeah. Wow. That's incredible. Yeah. I was not expecting such a huge difference. [00:06:30] On average across all the exercises, the leg wearable had a 14% error rate while the smart watch was a staggering 58%. And just because the watch was underestimating for me, it could overestimate for someone else. This means you can't scale the watch's calorie burn estimate up or down by a fixed amount to make it work for everyone while Patrick's system is way more accurate. It's only a proof of concept, but he's already thinking about ways to [00:07:00] improve its accuracy for both upper and lower body Speaker 2: Movement. And we're starting to think now, in terms of research, how do we build a system which can cover a whole body energy expenditure or maybe piece together things. So if you're playing a sport where you're using your arms and your legs, can you sort of separate those two elements, figure out how much is being contributed from both parts. And then tell the person in total how much they're burning. Speaker 1: He's also working on a smaller version that could be integrated into something like smart clothes. So your workout, leggings or top become your fitness tracker, [00:07:30] just speed up its development. He's also released a full guide on how to build your own version in the future. We could be looking at different kinds of wearables all over the body. So it's not time to throw away your fitness tracker just yet. They're the best tools we've got right now. And they do a lot more than just calculate calorie, burn, like track your heart rate, help you train for a marathon. And perhaps most importantly, motivate you to move more. So there you have it. The [00:08:00] future of wearables might not necessarily be on your wrist, but maybe they will be in your clothes. Thank you so much for watching. There is a list of very helpful links for you in the description below, to lots more details about everything we talked about today. Now I am gonna go and get myself that very well earned slice of pizza, but I'm going to jog because it turns out I actually ended up burning more calories than my watch tells me. See ya. Speaker 4: [00:08:30] How's Speaker 2: That? Speaker 3: Okay. Let's stop the workout. Oh Yes. You didn't properly. Take a minute. Yeah, I'll take a minute.