Spectroscopic heart-rate sensors have become de rigueur in the latest crop of wrist wearables. The Samsung Gear Fit and all the Android Wear watches include these sensors, but don't make bold claims about their accuracy. In fact, those devices only promise what we'll call heart-rate "spot checks." They're not accurate enough to report continuously updating heart-rate numbers during the heat of exercise, and to get a single-moment-in-time heart-rate reading, you have to remain perfectly still.
But Microsoft says its Band does more than that. It promises its sensor can track heart rate during workouts (an essential component of zone training), and compares its system to chest strap monitors, the gold standard for consumer-grade heart-rate monitoring. Well, I ran a couple of real-world tests, and found the Microsoft Band falls short of its claims, at least in one familiar workout scenario.
JON PHILLIPS. The band's sensor LEDs are quite large, and that should help improve the spectroscopic heart-rate tracking. Still, it seems Microsoft still has work left to do.
My control device was LG's Heart Rate Earphones, which I've tested against a chest strap monitor from Adidas. My testing indicates the Heart Rate Earphones match the Adidas chest strap monitor heartbeat for heartbeat, and I'm confident in the Earphones' overall accuracy--especially their ability to respond to rapidly increasing or decreasing heart rates. When I speed up and slow down, the Earphones' heart rate numbers speed up and slow down accordingly.
So, for my first test, I put the Microsoft Band on my wrist, and the Heart Rate Earphones on my ears, and headed out for a one-hour hike up and down Mount Davidson. Right from the beginning of the trek, the Microsoft Band reported much lower beats-per-minute: 25 bpm less than the Earphones as I walked outside my front door. A general pattern of laughably low heart-rate numbers continued throughout the hike.
A 74 bpm deficit? Seriously?
About 10 minutes in, the Band was reporting 21 bpm less than the Earphones. A few minutes later, the Band spiked to 4 bpm more than the Earphones. A 4 bpm variance is acceptable for a consumer-grade product, but a few minutes after that, just as I was really breaking a sweat up a steep part of the mountain, the Band fell behind the Earphones by a whopping 48 bpm.
A few minutes later, I thought the Band had somehow calibrated itself, as it reported just 2 bpm more than the Earphones as I neared the top of mountain. But when I finally hit the summit--at the peak of my workout and short of breath--the Band was a ludicrous 74 bpm behind the Earphones.
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