Does Garmin use Firstbeat calorie calc method when biking w/ a powermeter paired?

I am sure that sports scientists have been aware of the lagging HR issue for decades. However, as it lags on increases in intensity as well as decreases in intensity, the net effect on caloric measurement is pretty small.

Thanks for your contribution, buf I am pretty sure that

1.that sport scientist have been pretty aware of the effect of different cadence on metabolic efficiency, which is substantial. Just as a reference, check page 23 on http://storage-cdn.trainingpeaks.com...h-handouts.pdf

2.. ...that sport scientists have been aware of the phenomenon :-) that pedaling backward does not generate power/work even if it means exerted effort, and therefore power based calorie calculation is inferior to HR and HRV based calorie calculation

3. .... that Garmin markets some of the features of their new watches including the calorie calculation as something developed and patented by Firstbeat, while the Firstbeat rep being responsible for sharing his knowledge here in the forums was surprised how and what Garmin implemented:

"Hi Zoltan,

I'm not quite sure I understand what you're asking/describing.

Yes, the Fenix 3HR relies on Firstbeat to provide energy expenditure.

Are you saying that a different calculation method is used when your device is paired with a power meter? I don't think that should be the case (or can't think of a reason why that would be the case), but I'm not a cyclist so I wouldn't have noticed it."

4. .... that were his colleagues, too:

Hi Zoltan,

I asked some folks in our development team, and they seemed quite surprised that this would be the case. Not to say it isn't the case, just that we weren't aware of it.

We have a great relationship with Garmin and share ideas back and forth regularly.

I'll let you know when our guys have had a bit more time to look into it."

The 5X like the 3 and 3HR before it determines calories from a power meter if one is available, and falls back on HR if that's all it has to work with.

Garmin almost certainly will not be changing this because they got it right.

Just as a simple example why the 2nd gen Firstbeat method is better. Imagine you are climbing a hill with pretty high HR. Then you are at the top, some seconds later you still have high HR, but you are coasting down with a cadence of zero, so with a power of zero. Your calorie number does not change at all for minutes and minutes, even if your heart rate is being still at an elevated level.

At the start of the climb, your HR was lower, and took 30 to 60 seconds to catch up to the power you were producing. It's just like you described, heart lags power. So in this example the power meter didn't miss anything, it just accounted for the work sooner, when it was actually happening.

Your heart rate is affected by caffeine, stress, hydration, etc. Your power output is much cleaner and more relevant.

Besides, how many heart beats are there in a calorie?

Your argument is quite OK, let me qualify it as a solid one.

1. One item to add. Yes, your HR is not a perfect reference for calorie consumption and you listed the right reasons, caffeine, stress, hydration etc. This is the reason why Firstbeat switched to another model including HRV data.

Let me quote from Firstbeat website:

"In the field of exercise physiology, oxygen consumption (VO2) is the golden standard for measuring exercise intensity. Both oxygen consumption and energy expenditure (EE) of working muscles increase during exercise. Oxygen consumption is thus intimately linked energy expenditure. Oxygen consumption and energy expenditure can be directly measured using expensive laboratory methods (e.g. direct and indirect calorimetry) but both variables can be also accurately estimated using heartbeat data, and analysis of for example heart rate level and respiration rate from this data.

To construct a more accurate estimate of VO2 when compared with previous estimates that have been based only on heart rate, additional information describing bodily functions have been added to the model by Firstbeat. Neural networks are used to construct a model that derives VO2 from HRV data, using respiration rate and on/off-response information."


2. But a sidenote your heart rate correlates more to the oxygen consumed than your power does. And since the oxygen consumedcorrelates quite highly to the calories burnt, thus I'd say your hear rate correlates more to the calories burnt than your power does. But again I don't say heart rate is the best energy expenditure factor, but I say it is better than power.

So the usefulness of factors HRV+HR >> HR >> Power.

I guess it makes no sense to fight who has better knowledge on the topic, you or me, but maybe we can assume the Firstbeat staff has better knowledge than any of us, cant we? And let me repeat what I wrote about it "I asked some folks in our development team, and they seemed quite surprised that this would be the case"

Just to set up another solid argument.

And yes Garmin presumably won't change it for F3/F3HR/F5, but maybe for the next products. Garmin never seemed to be a consistent company. They bought the konwledge of Firstbeat and re-defined some elements of it. Perhaps not conciously.

Unfortunately HermanB from Firstbeat is not appearing nowadays, the last time he logged in was 2 weeks ago, so he can't be a judge to decide in this question.

Yes, his previuos login time was on 20th February, but yesterday he re-started his visit here. Actually today in the early morning (Central Europe Time) I got a private email from him confirming that one guy from their physiology team confirmed my findings.

He did not want to promise anything regarding the future, except that they would include this item in their discussion with Garmin, because personally he does not agree with the mixed approach of Garmin. Firstbeat seems to be pretty cautious when they are speaking about the appliance of their metholod by Garmin. OK, I understand it, but even they are not fully sure whether the whole issue is not the result of a simple oversight.

And you know, they are the biggest expert in energy expenditure calculationl

Hi folks, yes, I've been busy and didn't realize this conversation was progressing or that Tisztul_A_Visztula had been pinging my PM box.

I managed to write him this morning, but can share the same notes here, if folks are really interested.

According to one of the physiologists, who had a look at his own personal data, it does seem that, when paired with a power meter, the device is outputting energy expenditure from the power meter data. It's an interesting discovery, and not something that I was aware of earlier.

Beyond that, there's not much I can say... because that's really all I know about it.

Best of luck with your investigation, guys!

Thanks for touching base with this thread HermanB. Would you mind keeping it/us up to date if you find out more in the future please?

personally he does not agree with the mixed approach of Garmin

Actually, what I said was...

"Personally, I can't think of a reason why they would want to have mixed methodologies on the same device, but that's me."

Which - while nuanced - was intended as a testament to a lack of personal knowledge and insight, not of agreement or disagreement.

Apologies for the confusion.