Two summers ago I got an Apple Watch, and I was excited to use it for one of its special capabilities –– based on how fast my heart was beating, it could calculate how many active calories I burned throughout the day doing normal things such as walking around the house and exercising. What I didn’t know was how accurate it really was, but I trusted it. It was a smart watch, after all. Cutting edge technology, right?
It turns out that fitness trackers worn on the wrist are surprisingly good at measuring your heart rate. According to a study from Stanford University, six of the seven trackers they tested were less than 5% off when compared to a medical-grade electrocardiograph, the “gold standard” for measuring heart rate. However, the trackers didn’t do so well in the energy expenditure department –– the most accurate device was off by about 30%! The researchers explained that it’s hard to train a fitness tracker’s algorithm because of how different our bodies are, as our fitness level, height, weight, and metabolism varies drastically. The same conclusion is applicable to machines in the gym; treadmills and ellipticals can be wildly off with their calorie-burn estimates, especially if you don’t enter your stats before pressing the start button.
So… what are fitness trackers good for then? Well, you can use the heart rate and energy expenditure measurements as a guide for how hard you’re pushing yourself during your workouts. If you check your wrist and see that you’re close to achieving your goal of say, 300 calories burned, you’ll know to keep going until you hit that number. Of course, some fancier fitness trackers also contain other features unrelated to exercise, like notifying you of messages and detecting falls. Just keep in mind that the calorie-burn measurements are not up to par before you purchase one, if that’s what’s got you interested.
