[robot_jesus]

>I don't buy it, no brand can be accurate on energy expenditure because it depends on a lot more things than what the watch can monitor

To be fair, the comment you excerpted noted that the best performer was still just 71% accurate. So they’re saying they’re far from perfect.

>On watch, calorie counter is a function of time and heart rate.

Well, we just don’t know. But let’s take Apple as an example. Apple knows your workout type. And they know your weight if you’ve entered it. And lots of other sensors as well (O2, if possible, temp, accelerometers, etc).

They’ve put a crazy amount of money into their testing lab where they do have extensive metabolic rate testers, VO2 Max, etc.

Will they get as good as that equipment for a dinky watch? No. But I also am glad I don’t have to strap a face mask on during my daily bike rides.

Can they, with insane volumes of data and hard research, make pretty good directional inferences using models that match their watch sensors to gold standard tests? It seems the answer to this (both logically and in the research data) is yes.

This video is a decade old so they’ve only become more advanced and have more data since then, but there are lots of models you can build to power these estimates: https://youtu.be/BceaTNT14Ao

I’m glad you’re happy with your Casio. Keep rocking what works for you. But I’m not sure what’s so hard to believe here when other researchers have actually produced the data on their accuracy.