Charge 6 calories burned inaccuracies

[ZhivagoTX]

First workout today:

Indoor cycling using Elite Direto XR smart trainer/ergometer with Cyclemeter. 15 minutes. Average cadence 75. Average power 98 watts. Average heart rate 115. CALORIES BURNED 161

Charge 6...set to "spinning" 15minutes. Average heart rate 112. CALORIES BURNED 112

Second workout....walking outside

Apple watch. "outdoor walk" 20 minutes. .96 miles. Average heart rate 98. CALORIES BURNED 122

Charge 6 20mins. .88 miles shown. Average heart rate 97. CALORIES BURNED 166

Sorry that I didn't add in my Polar Pacer Pro too, but I forgot. But for myself, I'm taking the Charge 6 back.

[JohnnyRow]

Did you use the Exercise App or log the workout manually afterward?

[ZhivagoTX]

Both devices were started and stopped at the same time.

[Triletics]

@ZhivagoTX every device uses different methods and algorithms. Which one is correct? None. All are just estimates. However, calories from your smart trainer seem to be inflated. 15min at 98W is roughly 88kcal (active kcal). Even if we assume that 161kcal is active + bmr then your BMR for a day would be 7000kcal. Not realistic. Fitbit is closer to the truth here. If your smart trainer software calculates calories some other way than only from power you generate then change it for something that follows standards (I assume it has actual power meter not estimates power from speed and cadence like ie. Zwift's zPower algorithm). This round wins Charge 6, it's closer to the truth 🤷

[ZhivagoTX]

Lets set the cycling aside for now while I get more data. 

But how about the walk? I know the course I the route I took is 1 mile long. Apple watch series 8 got it at .96 and fitbit was at .88. Heart rate was in line with each other, but calories burned were very different. Why?

[JohnnyRow]

So, for the,walk. You seem to have started out with the basic assumption that Fitbit is wrong because it does not get same result. Could be, but could it also be that Apple watch is wrong?

Distance: As so many seem to do, you might have not taken into account that there are several ways of measuring distance on Fitbit.  That's why I never (usually) respond to questions about distance being wrong without more info being provided.  Sometimes distance can be measured just by step count times stride length, sometimes by GPS, sometimes with different GPS options, sometimes combinations, sometimes you might use GPS but start out before getting GPS connection.  I'm not up on the Charge 6 and not going to research it for this discussion.  The point I want to make is that there are several possible variables, and I'm not sure the one test you describe is enough to prove the superiority of one over the other without much more information.  It well could be that Fitbit is the least accurate of the 3, and I'm not arguing otherwise; just that the info you provided was not sufficient to convince me.  if it was enough to convince you, that's fine for you and if you think you will be happier with another product, then by all means, do so.

[Triletics]

@ZhivagoTX I have very little trust in optical HR (especially that Charge 6 can't get my running HR right). But this aside (you said they matched anyway) the algorithms are also different. Like I said, neither is correct. They may be closer or further to the true but this is all being estimated and based on model each company uses. Distance is irrelevant for calories. Both watches certainly use HR and your body data (weight) but there may be slight differences. If I get to compare my runs (took me a while to find just one run with HR that Charge 6 didn't screw up too badly), I can see differences between all the devices I own. It's up to me which one I decide to follow. Example from 58min Hill Repeat workout. Garmin: 656kcal, Fitbit: 695kcal, Stryd: 211W = 740kcal. My experience tells me that Stryd is closer to reality (for workouts like hill reps, when HR goes up and down all the time HR isn't best source to estimate calories, power on the other hand isn't bullet proof but is deeply embedded in physics and we can't cheat laws of physics). When I do steady state activity, all numbers more or less align but there are differences because, as I pointed out, different algorithms. You need to figure out what works for you and how to interpret the data.

[Turoxus]

I am new in this world of "smart" bands. I did the setup on the charge 6 with my personal data (age, heigth, sex and weight; the weight is updated every 2 or three days) I log the food with high accuracy: I see an over estimate of daily burned calories on 10% sure (after 1 month of use). So, I know that there is a bias and I adjust by myself my food intake. Probably the calculation of calories consumtion on rest is based on more young or active people.

[JohnnyRow]

@Turoxus  " Probably the calculation of calories consumtion on rest is based on more young or active people."  Nope.

You can look up BMR (basal metabolic rate) daily calorie burn that Fitbit uses against several standard online BMR calculators and see very little differences. inputting age, sex, hgt, weight.  Fitbit uses one of the standard formulas (I forget which one), but they all take age into account.  As for activity, that is accounted for by heart rate as measured continuously throughout the day.  Not saying calorie measurement is perfect, but don't think there is any age bias built in.