How do fitness trackers measure your heartrate? Have you ever wondered how smartwatches and wrist-based fitness trackers can inform what your heartrate is? I’ve been putting on an Apple Watch for a couple of months now, and it’s fun to see what my heartrate is during and after workouts.
But it got me thinking about how exactly this technology works, and whether it’s accurate. According to Apple, a technology can be used by the Watch called photoplethysmography, or PPG, to measure heart rate. It’s essentially testing how much red or green light it can see when looking at the skin on your wrist.
- Let your hands relax down to a protracted position and start your shoulder raises
- Data harvesting
- Take action, every day
- Take the family dog for a walk
- Fitness gives you to essentially”be ready for anything”
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Blood is red since it demonstrates red light and absorbs green light, so when your heart beats, there’s more blood circulation in your wrist, and more green light absorption. Between center beats, there’s less absorption of green light. By flashing its LED lights a huge selection of times per second, Apple Watch can calculate the amount of times the heart beats each minute – your heartrate. You might have seen this in applications on your phone before even.
Using your phone’s camera, the same technology can be employed on-demand. In fact, this technology is old-apparently it was first found in the past due 1800s quite. At that right time, people would “hold their hand up to candle in a dark room to see the vascular structure and blood flow”. This technology is also found in hospitals-if you’ve ever seen a finger or ear clip that measures pulse and blood oxygen levels, it’s using PPG.
The Apple Watch has two heartrate monitoring modes: when you put the watch into workout setting, it will consistently track your heart rate. The rest of the right time, the heartrate sensor uses infrared light to measure your heart rate every ten minutes (unless your arm is moving, rendering it hard to obtain a reliable reading).
You can also check your heartrate anytime from the heart rate glance. Because the watch depends on testing the light absorption of your skin layer to infer your heartrate, there are several ways the watch can battle to get a precise reading-or any reading whatsoever. Tattoos, for example, can block the heartrate sensor’s light.
There’s certainly a debate about how exactly accurate this technology is even in the perfect circumstances. Users have complained about inaccurate readings during exercises that involve a lot of irregular motions, which is something Apple highlights as leading to trouble for the watch’s detectors. How the receptors are worn can also affect the result: wearing the watch too loosely can provide inaccurate readings.
Other tests show the heartrate readings to be very accurate (see graph above), but without a scholarly study with a huge sample size, a call can’t be made by us about how accurate the tech is on average. Fitbit doesn’t mention photoplethysmography, but their tech appears to be with Apple’s inline. The Fitbit bands with heart rate tracking built-in (the Charge HR, Surge, and Blaze) uses “optical heartrate sensors that still maintain extended battery life”.
Fitbit brands their heartrate tech as PurePulse-calling it “the only heartrate technology to provide automatic, continuous wrist centered monitoring for all-day health workout and insights intensity”. The Fitbit trackers have the same struggles as the Apple Watch: you will need to wear the band correctly, and tight enough for the lights to be touching your skin, and irregular exercise like boxing can throw off the measurements.