deacon mark

I know this has been beat to death but this bugs me. I normally use a Garmin 910fx triathlon watch for running and riding bike. I simply take off the strap and mount to bike mount. Then it uploads to Garmin Connect and goes to Strava. I have notice over the last year or even more the calorie counts have gone way down. I know it has to be wrong I have done a lot of research on the subject. Like today I road my bike 60 miles no stops in 3:20 average speed 18 mph. The garmin connect says I burn 1051 calories and then Strava uses the same amount.

I know that has to be too low. I wear a HR strap and my heart rate for the ride was 109 average. I usually cannot get my heart rate on the bike above 120 average unless I am racing. Running I can get heart rate to average from 118-132 and I am 58 years old. I know I had to burn calories more than the 1051 it said. I normally calculate about 28-32 calories per mile going 17-19 MPH on relatively flat land I live in Illinois. We have wind but nothing worse than a long hill that can be managed. In fact todays ride was one of the more hilly ones I do.

Even using heart rate to determine calorie count it comes out at about 1900 calories. How can Garmin be off that much I have put in my correct height, weigh, and age? It seems that running is more accurate which should be calorie count is easier to determine running. I still notice that even the running calorie count seems low compare to a few years ago. I know this cannot be exact but you would think it would be at least a little closer. I am sure what the calorie count really is but has to be much more than the 1051 it shows for ride about this long.

rubiksoval

Get a power meter, think in kJ, be irked no more.

Badger6

100%

TimothyH

This article is from 2013 but relevant to the issue.

https://www.trainingpeaks.com/blog/h...lorie-reading/


-Tim-

colnago62

Once you realize that heart rate based calorie expenditure is waaaay off, it is liberating. You realize the reason you are riding so much and can’t lose weight isn’t that you predisposed to being fat or that is your set point, it is just you are eating too much.

deacon mark

I am not riding to loose any weight maybe just maintain ( 6'2" 167 lbs) but I just find it laughable. If I were to eat based on what the crazy garmin said I would be gone by now. I generally eat quite a bit, drink beer, and love ice cream. I eat according to how hungry I am.

Seattle Forrest

How many heart beats are there in a calorie?

DaveLeeNC

Your heart rate is (from what I know) unusually low for the work you are doing. HR based estimates are not going to be very useful for you, I believe.

dave

Robert A

I rode 100 miles in flat conditions. My Wahoo Bolt, fed by chest HR monitor, indicated 5,500 calories. Avg HR was high 140s.

I suspect your low heart rate is contributing to the low calorie count.

Iride01 

You'll still be irked by the power meter if you continue to compare it to other methods. Back in the days of non-networked time, there was a very apt saying "give a person a watch and they'll know the time, give that person two watches and they'll never be certain of the time".

colnago62

I did 96 miles with 3,500 feet of climbing. Wahoo says 6,400 calories. The SRM says 2,900 kJ. It was a very hot day. One point it hit 111 degrees.

Hermes

This seems about right. I get about 1000 kj per 30 miles per my SRM. If I go faster over the same distance, the only thing that changes is the time but not the Kj that much.

firebird854

Hmm... that does seem a bit low... yea, if you really want to be certain, pick up a power meter.

drewguy

Does Garmin net out sedentary calories? (I.e., the figure is what you burned above sitting on your sofa).

OBoile

I don't get why Strava uses HR for calories when it has PM data readily available. One is a direct measurement of energy expended while the other is an estimate based on something that is influenced by a wide number of factors.

I had one ride where my HRM was acting up and reporting HRs in the 60-70 range. The ride was ~800 kj but Strava says I burned something like 6 calories. Then, as others have said, on hot days (and really just in general) the estimated calories are significantly overestimated.

Badger6

When power data is available, it calculates calories from the work performed based on the data of the PM.

OBoile

Not for me it doesn't. Maybe I have a setting I need to change?

https://www.strava.com/activities/2369296980

The ride I mentioned above (it was a relative effort of 6, not 6 calories burned).
1.5 hours at 188 watts. Powermeter says 1068 kj. Calories burned is 240. HR is all messed up with a "max" of 81.


Edit to add: I did some digging, and it looks like Strava uses imported calorie counts from other devices if they do them. I have a Wahoo computer that records, then uploads my rides... it uses HR. So that is why I see HR based calories in Strava I think.

Badger6

Interesting, and I stand corrected. I found an official Strava reply in their support pages, after reading your reply, where they express that they import the calorie calculation from a .fit or .tcx file if that is how your linked device saves the activity. Now that you've mentioned this, I realized that the calories in Strava have been exactly matching Garmin for some time now. Thanks for the digging, I assumed that the Strava counts were still being calculated by Strava.

But, that said, I've not been alarmed by them as they seem to continue to match the rule of thumb for work to calorie correlation of nearly 1:1, meaning the power data to derive total work (kJ) correlates almost 1:1 for calories has continued with no issues, I guess because Garmin hasn't messed this up.

With respect to relative effort, that is based on HR data. The abnormally low (I assume) HR on the linked ride is what that number is so low when it would appear it should be higher...but remember, the relative effort is relative to you. So if your HR zones are set incorrectly, it will give reading that don't seem to match the RPE.

Machka 

I go with 100 calories for every 5 km.

OBoile

It was just an abnormal reading form an HRM that was dying. Yes, that's what caused the relative effort to be so low (since the HR reported was essentially my resting HR). It's also what caused the calorie burn to be so low (via my Wahoo).

Racing Dan

Did you try the same route with and without the HR monitor to see how/if HR affects the energy calculation?

OBoile

I have ridden that route multiple times... but there's no need to re-test. My total power output in terms of kilojoules is recorded and listed (1068). That's the actual amount of work I've done. Based on the ratio of kJ to Calories (roughly 4:1) and the body's efficiency (about 20-25%) you get a result of roughly 1:1 between kJ and Calories burned. So, anything less than say 950 or greater than 1200 or so is suspect. My calories burned was listed at 240. And again, my HR was way off. I'm not getting dropped with a max hr of 81, that's lower than my casual waking HR.

Edit to add: Just for kicks, here are some of my other rides:

Bad Calorie Count due to HR (posted above)
https://www.strava.com/activities/2369296980

HR monitor working properly the following week (calorie count likely overestimated as again, using HR isn't great).
https://www.strava.com/activities/2387652030

No HR monitor the following week, calorie count much closer to kJ (Strava calculating this):
https://www.strava.com/activities/2406138528

You'll notice the total kJ on each of the rides was fairly consistent. The calories burned was not.

Anyway, the point was, using HR is silly when you have the actual amount of energy expended as an available input. I've made a request to Wahoo to change this (and I got a response) so maybe things will get better.

wipekitty

The low heart rate is doing it.

IME, I can do a longer course (both mileage and obviously time) with a slower group and average HR ~120 BPM and end up with fewer calories burned than a shorter course with average HR in the 150s. I strongly suspect that, unless you've entered some other kind of data, Garmin is using the standard 220 minus age calculation to set heart rate zones. This is likely not accurate for you.

Unrelated, I had a brief glitch about a year ago when Strava was taking my weight in kilograms and then calculating calories based on that number in pounds. That was pretty funny.

DrIsotope

You can also use Fitfiletools.com to strip the bad HR data from the files, to get a (more) accurate calorie count. Relative Effort on Strava is 100% HR-based.

Badger6

It is likely not accurate for most people...but, what is accurate is kJ. I get it, a PM is another investment, more money to be spent, etc. But, if the OP, or anyone for that matter, really cares what the calories burned is for a ride, the only way to get it accurately reported is to know how much work was performed, and the only way to know that with any kind of precision is a PM. Anything else is no more than an educated opinion...without PM data and using only HR, for instance, my calorie expenditure seems 30-40% higher (based normal burn on my commute). It has utility, but without PM derived calorie burn, I wouldn't base dietary choices on HR derived data.