Total daily calories - workout + BMR, or just workout calories?

Calorie-counting from Garmin or Wahoo only works partially good if you have correct FTP set in your unit. kJ’s is the way to go because these map almost 1:1 with kcal.

And also correct (or more correct) HR zones if doing it by heart rate too. i.e. not 220 minus age.

That would be my understanding as well.
Does not seem to be how garmin is doing it, however.

If I do a 1hr ride for 800 Kjs and nothing else all day (while wearing a 935 doubling as an activity tracker) garmin will only add around 700 Calories to my daily total as “activity calories”. So they are using the same approach as with their rides where Calorie estimation comes from the FirstBeat HR algorithm for power meter equipped rides and as a result their estimated energy expenditure seems too low for me on these workout days.

This gets even worse for outdoor rides where average power is generally lower than on the trainer:
I was just looking at a ride earlier this year where I did 150 km at a relaxed pace. Garmin Edge has this at 3.041 Calories (from 3.043 kJ for…reasons? Avg. Power 125 Watts for 6:46 hours). Garmin Total Calories for the day are at 4.586 - surely this cannot be right? This is including all the walking around etc. that my 935 picked up outside this ride.

I’d strongly recommend you not use the calorie estimates from Wahoo if you have a Power Meter - they do not map to kJ and as such are going to be wildly inaccurate

Garmin total calories are counting all calories for the day including BMR.

What is exceptionally flawed with Garmin is if you use both a Edge-device and a Fenix/Forerunner to track the same activity. Then it goes bananas and counts calories from both devices as separate activities meaning you get both added to daily activities.

So how inaccurate are they then? Because calorie-counting from Garmin are pretty much 1:1 to kJ.

It depends on both the rider and the type of ride. I find that the easier the ride and the more fit the rider the worse the estimates are.

Here are two examples from this weekend for me

Ride 1 - 92 miles, 0.67 IF. Wahoo calories 2670, kJ 3617
Ride 2 - 75 miles, 0.63 IF, Wahoo calories 1731, kJ 3008

If I dig back to my last race you see that it is closer

Race - 62 miles, 0.88 IF, Wahoo calories 2082, kJ 2393

Basically the Wahoo algorithm is only taking into account my HR. So as someone with a relatively high level of fitness it really struggles with figuring out the calorie burn compared to my HR. It does better when I elevate my HR with harder rides, but is still significantly (>10%) off

Use kJ, don’t use Wahoo calories

Hrmm. Is that actually true, hot weather causes the body to burn more calories? Thats not really adding up to me. I cant imagine sweating cost calories. I think the bodies method of heat management is more like power management…it just lowers available energy expenditure, because tapping it creates heat as a byproduct.

Now, COLD managemebt is a totally different story. The body will INCREASE energy expenditure (shivering) to create heat byproduct.

I mentioned earlier that I’ve stopped using Wahoo calories from my bolt, and have switched to the kj. I wasn’t seeing the expected weight changes feeding them into my process, but I made the decision after these rides…

163km - 4149 kcal - 3393 kj
25.7km - 260 kcal - 440 kj

I’ve always seen the expected weight changes (or not) using Garmin calories (with HRM).

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True for both heat and cold.

In the heat (I have never seen an exact cut point, but I think a heat index in the mid-90s+ would probably do it), your body has to spend extra energy on thermal regulation, so the calories burned for a set level of effort are higher.

The key is “set level of effort” – say you do 250w for two hours and when it’s 65 degrees, your HR is 123. 1800kj. On a 95-degree day, that HR is going to drift up to more like 135 and you’re going to burn more than 1800 calories.

Of course, most of us would have to back off and just ride at that HR, and the power would drop. But, if you back off to 210w and the PM says 1500kj on that 95-degree day, you’ve actually burned more than that.

Geez! That was horrible. :scream:

Just to update this - I did my outdoor ride without my HRM (left it in work) on saturday, and so according to the Wahoo .fit file, I didn’t actually burn any calories. It actually gave me a zero*

*I overwrote that in connect, and then that pushed the activity through to my fitness pal.

What I was trying to say earlier – and failed in a rush – was that you have to subtract BMR/Hour from the kj total from your training session to get a more accurate view of what to add to BMR.

I’m 52, six one, 155. My measured BMR is just short of 1600 cal – so call it 1600 for the sake of easy math.

Yesterday I did a 2 hr session on the trainer (no 96-degree heat after a full day of work for me, thanks), doing 1700 kj worth of work.

If I concluded that I needed to eat 3300 calories (Imagine I had been in bed all day, so just BMR), I’d be about 100 calories on the high side. Why? Because that measure of work the rider does in the lab – you did 1700kj, so when we factor in gross metabolic efficiency, you burned ~1700 calories – includes the rider’s BMR/Hour. So, you have to subtract BMR/Hr from the KJ total to get a more accurate figure, otherwise you overestimate energy demand (FItzgerald gets into this in Racing Weight).

With my BMR/Hr of ~67 calories, I should knock off about 140-150 (because BMR is higher when awake than asleep) calories from that 1700. Call it 1550.

It’s a small thing, but if you’re always 100 calories or so over because you’re not accounting for BMR/Hr during the training session, well, that’s why you’re not losing any weight even though by your math you’re maintaining a deficit, or why you’re slowly gaining weight even though you’re training regularly.

I still don’t understand this reasoning. Assuming you’re using a power meter, that power meter is measuring work delivered to the pedals. That power meter doesn’t know your BMR and nor does it need to.

BMR is the same whether you do any cycling that day or not, so why would you then decide that there was 2 hours in the day when BMR doesn’t count?

In summary:

  1. BMR is BMR. you burn this every day regardless of additional exercise
  2. The power meter measures additional exercise, ie work to the pedals, and nothing else
  3. These are 2 seperate numbers, in isolation of each other, so both need to be considered when calculating total energy expenditure for the day.

Happy to be proven wrong on this but your explanation still doesn’t seem right.

I think the crux of this argument is that you think power meters include BMR in their energy expenditure calculation and I don’t.

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No, I don’t think power meters include BMR in their energy calculations. And I’ve been using them since 1998.

The rub is when you start converting kj to calories – that math depends on lab measurements, and the energy expenditure of the rider in the lab also includes BMR/Hr.

Of course, if you haven’t actually had your GME on the bike measured, then you can’t be certain of how your kj translates to calories, either.

How is the KJ measured in the lab? I’m assuming it isn’t something the the OP is using on their rides outside.

If the maths depends on lab measurements and the energy expenditure of the rider then how can you give such certain advice when there are clearly many variables.

Either way, it seems we both agree that if you’re using a power meter to measure your work in KJs then that expenditure can be added to your BMR for total calories expended.

The KJ of work measurement, of course, comes from the powermeter. Where else would it come from?

Conversion to calories would come from measuring the energy expenditure in the lab and then looking at the KJ of work done, and then doing the conversion math. That’s going to depend on the accuracy of the PM, and the GME of the rider (likewise, have a runner run on a treadmill and measure the calories in lab conditions – the conversion of calories expended to work performed is going to require a conversion, and the calories expended are necessarily going to have to include the BMR/hr. Again, see Fitzgerald on this in Racing Weight).

The calorie measurement would, of course, include BMR//hr.

All conversions of KJ to calories involve guesswork, and none should be taken as “certain advice,” unless you’ve had your BMR and your GME lab-measured, and you’ve static tested your PM to make sure that the 300w it reads is actually 300 watts.

Deducting BMR/hr from the kj to calories conversion is just another part of the guesswork.

Why would the calorie measurement include BMR? I could understand if you said that lab testing was necessary to see how efficiently you converted energy to watts, in order to get the correct calories burnt. But you seem to be saying that lab measured BMR would have an effect on the KJs burnt whilst cycling, which I don’t think it would since BMR and calories burnt during activity are seperate of one another.

It seems misleading to suggest in your first post today that a calorie difference as small as 100 cals could be the cause of the not losing the expected weight, but then follow up by saying that there’s an element of guesswork. Is it not possible that the “guesswork” could easily account for the 100cal discrepancy you mentioned? (even though I still cant agree that this discrepancy exists)

I don’t understand why you both are overcomplicating stuff.

Take your week’s expenditure, workouts measured in kJ, divide it by 7 and add that to your everyday BMR and subtract 2, 3, 4 or 500 kcals and you’re set.

If you do a 4000kJ ride one day and have another 4000kJ planned the next the you probably need to re-fuel properly in-between. In all other cases your body refuels properly if you eat “normal” everyday.

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That’s exactly what I’ve said, no overcomplication here. Simply add exercise calories to BMR for your total daily burnt calories

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