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Comment by Swizec | Hacker News Reader

> Maybe it's looking at my heart rate and extrapolating?

Yes. At least that's what I hope/assume mine is doing.

> Anyway, I'd be very much interested in some kind of fitness tracker that can provide better estimates on caloric burn.

The 2nd most accurate formula involves weight and heart rate. http://fitness.stackexchange.com/questions/12435/is-it-possi...

Your Charge HR knows both of those, so I would hope it uses them. That's the whole reason I bought one in the first place.

It looks like measuring VO2max is even more accurate. But that's very annoying and invasive to measure as it involves breathing through a tube.

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I do not believe Fitbit uses heart rate to track calories. If it uses heart rate to track calories, it would be able to work well with cycling exercises, but it does not. From fitbit website: "Fitbit trackers are optimized for walking, running, and general lifestyle activities but are not recommended for tracking cycling"[0]. Sounds like it uses the step counter and not heart rate to estimate calorie burn along with your weight and age etc.

The Charge HR heart rate functionality could be useful to keep my heart rate in a specific range during cardio. However, it doesn't seem like it's good for that either[1].

[0]https://help.fitbit.com/articles/en_US/Help_article/Does-the...

[1]http://arstechnica.com/tech-policy/2016/01/lawsuit-claims-fi...

When I use it for boxing, the calorie burn graph seems to very closely follow the heart rate graph. But only if the tracker was in exercise mode (longpress the button).

As for the article about inaccuracies. Their manual clearly states that during exercises that involve a lot of forearm flexing and vigorous arm movements the tracker will be inaccurate.

And I am sceptical that people wouldn't be able to tell from how they're feeling that they are at a dangerously high heart rate. But I guess it's possible.

The highest number my fitbit ever reported was about 170 (sprinting) so it's definitely cspable of measuring high heart rates.

I wonder why it's not recommended for cycling then. Cycling is my main exercise. Very little arm movement on a bike.

My old Fuelband used to register quite a bit of activity while cycling, surprisingly. It would register about half as many Nikefuel per hour as running, but still way way way way above, say, walking, let alone being seated.

I haven't cycled much since I got my fitbit charge hr.

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