How Accurate is Apple Watch Heart-Rate Monitoring?

by James A. Martin on May 1, 2015

in Apple Watch Fitness Tracking, Apple Watch vs. Fitbit

Good news: Based on two initial tests, on two different Apple Watches, Apple new smartwatch’s heart-rate monitoring is more accurate than any other wristband tracker I’ve tested so far.

Example: During a 55-minute powerwalk on the hilly streets of San Francisco, Apple Watch’s heart-rate reading was never more than about 8 beats per minute (bpm) higher or lower than the Polar H7 chest strap’s reading. Consumer Reports and The Wall Street Journal have both deemed Polar’s strap the most accurate among consumer heart-rate monitors, so I’m using it as my basis of comparison these days. (I don’t have a portable EKG device. Sorry.)

Polar heart rate monitoring iOS app

Apple Watch heart-rate monitoring

Even when Apple Watch’s heart-rate reading differed from Polar’s, it never lasted longer than, say, 10 seconds—even during peak cardio. Other activity trackers I’ve tested have differed by as much as 20 bpm during sweaty exercise and often stayed elevated until I started cooling down.

Also, Apple Watch (via its Activity app) said my average heart rate for the session was 116 bpm—exactly the same as what the Polar strap registered (and displayed in Polar’s iOS app). I noticed a big difference in the calories I burned, however, with Apple Watch giving me credit for only 395 vs. 516 from Polar.

Granted, I’ve only exercised with Apple Watch twice so far. And I’ve not had a chance to wear it while using the gym treadmill yet. I’ll update this post once I do.

UPDATE: 5/7/15:

I finally tested Apple Watch’s heart-rate monitoring while exercising on a treadmill. I compared the watch’s reading to the Polar strap’s. Apple Watch only differed from Polar by about 3 bpm at at any given time, compared to about 8 bpm difference when I was exercising outside. What’s up with that?

On a treadmill, my pace is much more consistent than it is when I’m walking up and down San Francisco hilly streets. And the greater consistency in stride means the heart-rate readings don’t have to adjust as much. That’s my theory, at least, on why Apple Watch heart-rate readings were almost always identical to the Polar strap’s readings while I was on a treadmill.

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