dr_lha

I agree, the number of 25% is likely a variable, it's generally quoted between 20-25%.

However, saying it can be responsible for all the variability in the measurements? Sorry, but this just doesn't work for @IBOHUNT 's last numbers:

If those numbers were correct, his body would be working at ~92% efficiency. Not possible.

bbbean 

Yes.

himespau 

Sure, it's likely true that the short time period would be inaccurate. I wonder if longer rides are more accurate than shorter rides as there will be delays in heart rate getting up to speed. I'd imagine that 10 mile ride was still probably on the order of half an hour (looks like 27-28 minutes based on his numbers), so you'd think that the heart rate lag should have smoothed out over that time. I'm just trying to get a handle on the inconsistencies in the numbers to see if there's some biological explanation instead of "oh their algorithm is crap", which it very well may be, but the scientist in me would like to explore alternative explanations and rule them out before accepting what I'd consider the null hypothesis just because their calculations are sort of a black box I can't see into, but I can make random guesses about the physiology.

IBOHUNT

Forgive me for not capitalizing whatever letter I should have. The point I am trying to make is that whatever *MY* Garmin is reporting for Calories (large C) is what MFP uses and *IS NOT, in my opinion*, what is real.

Maybe this is better, copied right out of Garmin Connect

Distance: 55.16 mi
Elevation Gain: 2,841 ft
Calories: 1,431 C
Work: 2,255 kJ

Which value would you use for the food bits you burnt up? 1431 or 2255?

himespau 

To be honest, I'd use whatever was lower because I'm trying to lose weight, so, if I could get by replacing 1400 Calories (or less), I'd be more likely to lose weight. However that 800 Calorie difference is more than I could probably do without if the work number is the accurate one, so I'd probably end up doing something in between and hoping for the best. It's like that old saying, a man with one watch knows what time it is; a man with two is never sure.

bbbean 

1431 is pretty close to 30 cal/mile and is probably pretty close to what you actually burned.

FWIW, if you do this long enough and also log your intakes and daily weight, you'll get a very good feel for what an accurate number is.

BB

dr_lha

Given that he has a power-meter measured energy number there, I'm not sure you can reconcile this as being "pretty close to what you actually burned", as burning 1431 Calories would mean his body worked at 40% efficiency during the ride.

IBOHUNT

I did, for 5 months, which is why I am throwing the BS flag at what *my* Garmin spews out for Calories. Over 5 months it's a difference of ~40,000
Others may have different results

himespau 

So you're saying you lost more than you'd expect given your garmin-hrm calculated caloric expenditure? As a clyde, I don't think that's a bad thing.

dr_lha

Yes, but that's just a more positive way of saying that Garmin's calorie calculation is mostly wrong.

IBOHUNT

In case some folks want to read an article

How Accurate is that Calorie Reading? | TrainingPeaks

Take from it what you will.

IBOHUNT

I lost what I see being reported by MFP using the values of kJ and *not* Calories.
Those values work for me.

bbbean 

I didn't see any mention of a power meter. Garmin software (as do most apps) estimate work done, and the estimated power can be dramatically at odds with what a power meter would show.

Here's the test. Use any given number for a few months, adjust your consumption accordingly, and see whether you gain or lose weight, and whether the gain or loss occurs in line with what it "should" according to your net calories over time. For me (and lots of other folks), that experience showed that 30 cal/mile (adjusted up or down for effort/wind/climbing/etc) was a workable number. Since I lost 1/2 my body weight and have maintained goal weight for a couple of years now, I know it works for me. I can't imagine it's very far off for others.

BB

Drew Eckhardt 

I'd use neither.

You only need to replace your glycogen, and can forget about the fat you burned (good riddance!)

It may provide just 20-25% of your total energy consumption when you ride below your aerobic threshold (Friel zone 1-2, anding at 55 and 74% of one hour power respectively), have enough base miles in your legs (energy source is trainable), and perhaps eat fewer carbs (that shifts the balance).

Use 500 Calories/hour (140W), eat 100 - 125 for -375 to -400.

It could be 50-70% of the total riding in zone 4 (90 - 105% of one hour power)

Use 800 Calories/hour (220W), eat 400-560 for -240 to -400.

With simple Calorie counting too much work to figure out and this a notch harder I adopted a natural eating approach which worked for me before.

Only eat when hungry. Only eat enough to be sated 30 minutes after the last bite because that's how long it takes for your appetite to catch up - go back for seconds and thirds when necessary. I was surprised to find I needed about 1/3 less than I was eating. Always eat when hungry so you don't get too ravenous to control yourself.

Marathoner/olympic medal winner/national record holder Shalane Flanagan switched to an intuitive approach and wrote a cook book

You might be surprised.

I didn't have a noticeable difference in hunger versus not riding when exclusively riding at low intensities when I was still over weight, and just sating that hunger isn't enough eating to maintain weight.

I stopped eating on my weekly 3-3.5 hour endurance ride because I don't need to, although I bring a Clif bar just in case. Without hunger following a 2 hour ride and the math supporting me I wondered about that and tried it. Working up to that to avoid bonking far from home is probably prudent.

Zone 4 and 5 days are a different story. After looking at historical data showing my weight loss stopped as I got more fit, added hard days, and swapped easy rides for tempo I decided on a long base period until I got back to a normal weight. That worked great - I lost 30% of my total weight over a year, then shrunk another ten pounds as I added back intensity with a more polarized approach. I'm the same size I was riding 18 years ago, which is lighter than when I graduated high school.

dr_lha

@IBOHUNT's numbers for work are from a Stages Power Meter, as mentioned earlier in this thread. The estimated calories are Garmin's guess.

himespau 

Huh, good to think about. I always think about doing anaerobic work or similar types of things as I try to be as efficient as possible and work out as hard as I can in the limited time available, but you're right that if I want to be burning fat, that's not the right strategy. What I teach my students and what I do myself aren't always the same thing. Need to work on that.

WalksOn2Wheels

Oh sweet lord, people.

How calorie measurement works on Garmin fitness devices | DC Rainmaker

Willbird

I hate to make "work" out of riding, I really enjoy days where o spend 90-120 minutes 140-150HR. I balance those days with ones at mostly 130 or less, trainer road last told me my LTHR is 166 if I recall right. 30 cals per mile actually pretty closely agrees with cyclemeter booting data to Strava. Cyclemeter itself may read high but Strava seems to sort it out pretty well.I'm hitting the mfp 16-20 mph window...maybe that one is around 400 per mile. The mfp number is the only one I really even look at, and at most I'll eat half that back, sometimes only 100 worth for a bag of sport beans , or 200 for a shock block bar.