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Fabienne

macrumors 65816
Original poster
When I first got my Apple Watch I was entranced. It is wonderful and I will use it as part of my MO forever. Saying that, I am a fitness fanatic and have gone through Fitbits and Loops and hoped that the Apple Watch would be a reliable HRM with just it's light on my wrist.

I saw that the calories it said I expended were far less than what my chest strap said I expended. I know that I might be biased, but this was So Much. The Apple Watch was far more stingy about saying how many calories I burned at any exercise.

I decided to try out the Apple Watch for a class, and then try it out for that same class the next week. The teachers were the same (Zumba and Yoga), the final numbers were very different. I don't have the precise figures but the Apple Watch was about 1/3 less than what I got on the Polar Bluetooth Heart Rate Monitor and Digifit. I was using the Apple Watch in its exercise mode and tried to choose an activity which would closely track the activity as possible (thought there is nothing like Yoga on the Watch).

Digifit gave me far more exercise points than Apple Watch did. I think this is because the Polar Chest Strap is made to monitor your heart rate at all times when you have it on. Apple Watch only checks your heartrate at times during your time with the activity tracker on. So, if you have the activity tracker on, you might get checked on once every 15 minutes with the assumption your heart rate remains the same inbetween. It does not have activities for things like yoga. The Polar HRM does not care, it's going to give you your figures no matter what.

So though I would love to use the Apple Watch for everything, I am going to track my exercise with the Polar Chest Strap.
 
Make sure you are comparing total calories from the watch to polar/digifit calories. The AW shows you just the incremental calories from the activity, and the polar/digifit probably combines activity and BMR calories.

In workout mode, the AW captures HR continuously. Otherwise, it takes a reading about every 10 minutes.

You could use Other Workout for things like Yoga.
 
In my own experience of AW vs a chest strap (w/ Garmin 620) the AW is consistently significantly lower by 10+ beats during runs. But I don't think it's a failure of AW per say, just that Pulse Oximetry technology isn't there yet. Many other gadgets that use the technology and also have user complaints about accuracy during workouts. There is an article at Appleinsider on user complaints about the the AW's pulse deficiencies. They sound familiar to me.

Personally I've given up hope of using the AW as running watch for the near term. I've stuck with my Garmin 620 and am considering upgrading to the 630 when that watch is released soon. But the AW is a great every day watch with it's rich notifications and general health nags. It's not a sports watch, but it beats any Fitbit or similar monitor by miles unless the user just wants something basic and inexpensive.
 
I'd rather the number on calorie burn be conservative so I don't over eat than too much - I think all formulas will be anything less than perfect and like the direction of under estimating than over - when the watch came out the HR sensor was put to test side by side with the others out there and compared well even to the chest monitors.
 
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