Turns out the watch was underestimating my overall calorie burn during each exercise, but Slade tells me it could overestimate for someone else. You can see the rest of the calorie counts per exercise in the video on this page, but across all four workouts, the leg wearable error rate was 14% compared with 58% from the watch on my wrist. For running, the respirometry device said I burned 87 calories, the leg wearable 66 calories and the smartwatch 52 calories. The results are in - and they're surprisingĪfter gathering all the data points from each device, Slade walks me through the results. I know I'm not going to be setting any pace records with all these tools strapped to my body, but fortunately that doesn't matter - we're only tracking energy expenditure. Once we get a baseline reading from the respirometer, I start working out. After my workouts, we'll compare results from all three devices. It costs tens of thousands of dollars and weighs about 5 pounds complete with mask and backpack, so it's not really the best tool for people to use outside the lab.įinally, I strap a smartwatch to my wrist to get its calorie estimations. This monitors the carbon dioxide I breathe out and the oxygen I breathe in to give me what Slade calls the "ground truth" reading, or my actual calorie burn. I also put on a lab-grade respirometer to measure my actual energy expenditure. It feels like I have a small smartphone strapped to my midsection and I don't even notice the wires running down my legs. You strap two stretchy bands with the IMUs on your thigh and shin, then wrap a controller and battery around your waist. Putting on Slade's system is straightforward. I'll be doing four workouts for 5 minutes each: walking, running, cycling and stair stepping.
But for the purposes of testing out this new wearable, only regular gym machines like a stair climber and exercise bike are needed. To test its accuracy for myself, I've come to Stanford University's human performance lab, filled to the brim with a range of sophisticated workout equipment including an antigravity treadmill. It was tested with over a dozen participants of varying ages and weights and averaged 13% error, compared with 40% to 80% error from consumer wearables. Instead, his system breaks down motion into each step, then uses a machine-learning model to calculate energy expenditure. "How tired you are, if you had coffee, worked out, this time history makes it really volatile."ĭespite the wires, the tracker didn't get in the way during my workouts and is lightweight. "Your heart is just pumping blood through your body and has a bunch of different factors that affect it," he says. But heart rate isn't directly related to the energy you are expending, says Slade. Most consumer wearables use heart rate and wrist-based motion to calculate calorie burn during activity. Stanford graduate student Delaney Miller wearing the leg tracker.
Naturally, I wanted to put this system to the test to see if a tracker worn on my leg could really be more accurate at estimating calories burned than one on my wrist. "We want to understand the connection between physical activity and obesity so we can develop new interventions to help people live longer, healthier and more fulfilling lives," says Steve Collins, associate professor of mechanical engineering at Stanford University, who co-authored the findings with Slade. Measuring calorie burn accurately is important for a number of reasons, but mainly because it can help people manage their weight. Definitely not as convenient as strapping on a wrist-based smartwatch or tracker, but it's the first proof of concept developed by Stanford University graduate student Patrick Slade.
#Heart rate calorie calculator plus
It uses two inertial measurement units (IMUs) plus a battery unit and microcontroller worn on the hip. That's because it measures leg motion, where most of your energy is used during lower body exercises like walking, running, climbing stairs and cycling. It's not worn on the wrist - you put it on your leg. But several studies show smartwatches and fitness trackers don't do as good of a job at calculating calorie burn during activity and can be off anywhere between 40% to 80% of your actual energy expenditure.Ī new wearable developed at Stanford University claims to be far more accurate. They can monitor your heart rate during a workout and track your sleep, and some even help manage workout recovery. Smartwatches are great tools for keeping track of your activity.
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