Edge 520 Calories Too High?

Check that you set your weight correctly. Re-check HR zones.
Calorie burn is calculated using weight and HR zones.

Edge 520 overestimates calorie burn when used without HR (up to 1.5x of actual), but may underestimate when used with HRM and your fitness level is really high (e.g. you can output steady 200W @ 120 bpm).

For me, Edge 520 reports 20-22 calories per mile (and this is hilly course, approximately 500 meters of ascent on a 35 km ride).

Hi Max, thanks for the response. One other thing I should mention... my heart rate was a bit higher than usual today (possibly due to being somewhat fatigued from work the evening before), which may have contributed to the higher calorie reading.

My weight and height are entered correctly. I checked my heart rate zones... I had them set the same as they were on the Edge 500:

Resting: 58 / Max: 177
Zone 1: 50-60% (89-106)
Zone 2: 60-70% (106-124)
Zone 3: 70-80% (124-142)
Zone 4: 80-90% (142-159)
Zone 5: 90-100% (159-177)

I changed the zone setting to the default ("custom" button switched off), and it generated different numbers:

Zone 1: 66-73% (117-129)
Zone 2: 73-80% (129-141)
Zone 3: 80-86% (141-153)
Zone 4: 86-93% (153-165)
Zone 5: 93-100% (165-177)

Those percentages look odd, as I thought the zones were always in 10% increments with the aerobic zone 3 being 70-80%. But I'm going to give these default settings a try on the next ride and see what happens.

An update... with those modified HR zone settings, and also some tweaks to my resting and max. HR after looking through my data over the past few months (changed to 64 / 179), and I'm still getting about the same calories calculated (about 45 calories per mile, at a moderate zone 3 pace).

When I got home from that ride, I looked over the settings on the unit, and although the height, weight, HR zones, etc. were all correct, it had my height listed as 2'4" (despite being set to 5'9" in the Garmin Connect app). Excited that perhaps this could be the explanation, I tried changing the height on the app a few times, and although it indicated it was syncing to the 520, the height remained at 2'4". So, I changed it on the unit itself, and went out for another brief ride. Disappointingly, however, calories remained at about 45 per mile.

That sounds strange
Can you share a link to any workout showing this behaviour?

Here's a short test ride from yesterday...

https://connect.garmin.com/modern/activity/1083762045

Tried some more things this afternoon. I did a factory reset on the 520, and set it all back up from scratch... still 45 calories/mile.

I did notice one peculiarity during this... in the series of user settings (height, weight, age, etc.) there's a "Cycling Ability" setting, with the following as the choices: Untrained, Fair, Good, Excellent, and Superior. I had chosen Good originally, and intended to try different options this time to see if it made a difference (I have no idea if this is used in calorie calculations... I'm grasping at straws). However, in the process of doing so, I came across an anomaly, as I noticed when I did the Initial Setup again this Cycling Ability setting was on Excellent, instead of Good as I had set it (all the other personal settings were still as I had set them). However, if I then changed it to Good (or Fair) and immediately went through the Initial Setup again, the setting was retained.

Through some trial and error, I determined that it was being changed to Excellent whenever I sync'd from the Garmin Connect (for instance, if I changed the heart rate zones), which is strange because I can't find anywhere in the app where Cycling Ability can be specified.

I don't know if this is the source of my problem, because, again, it does seem like the Cycling Ability setting sticks as long as I don't sync with the iPhone app (plus I don't even know if it affects calories anyway). But still, it's an indication that there are definitely some firmware bugs that need to be sorted out.

Also, here's the ride I did today:

https://connect.garmin.com/modern/activity/1084978318

On this ride, I averaged about 41 calories per mile according to the Edge 520 (took an even more leisurely pace for the second half of the ride, since the sprint I did at about 15 minutes into the ride to test max HR kinda wiped me out)


For comparison, here is basically that same route a few weeks ago with the Edge 500:

https://connect.garmin.com/modern/activity/1079871503


Unfortunately, it's not an apples-to-apples comparison... average HR was a bit higher on the Edge 520 ride, with the Edge 500 ride have a slightly faster average speed. But still, looking through my history of rides over the past few years, I see that the Edge 500 would generally show 26-35 calories per mile (for instance, a half century I did last year at an average speed of about 16mph / 149bpm came out to about 31.5 calories per mile, which seems fairly reasonable.

Now, one interesting thing... i looked all the way back to when I first got my Edge 500, and for the first few months of rides, it was actually calculating about 45 calories per mile also for my usual 15mph pace. It wasn't until I fiddled around with the Activity Level that I was able to get it down to the neighborhood of around 30 calories per mile.

That said, I found a Garmin support document last night for the Forerunner 310XT that stated "Improvements in FirstBeat technology now no longer require the activity class." I wonder if the same changes to FirstBeat apply to the Edge 520, and that it does not utilize the Activity Class setting (even though it's still in the Garmin Connect app)?

Then again, in searching for more information about all this, I've only come across people who are complaining about the Edge 520 calculating calories TOO LOW, not too high like me. And you said that yours is showing a mere 20-22 calories per mile. So I really don't know what to make of it.

Hmm, strange. Yes, your Edge 520 overestimates calorie burn.
Normally it happens when HR zones are set too low (so Edge thinks 130bpm is near a threshold) or weight set too high.

Activity Class does not seem to affect calorie burn estimation (at least I could not find any correlation).

I was not able to make Edge 520 calculate calorie burn properly. So I just ended up riding with Power Meter, and never had a problem since that.

I'd also recommend trying Strava to get approximate estimation for calorie burn, it seems to do mush better job.

Tomorrow I will try setting an artificially low weight to see if that reduces the calorie calculation. Another couple of observations... I did a brief ride (just one mile) WITHOUT the HRM strap, and found that the calories were about the same. So, next, wondering if perhaps heart rate was somehow being ignored in favor of the basic (and usually severely exaggerated) speed/distance calorie algorithm, I put the HRM strap on and went for a drive in the car (thinking that if speed/distance was being used instead of HR, this would result in a very high calorie count), but calories were minimal (since there was no effort), indicating that the HR was indeed being used.

Doesn't really help solve the problem, but still interesting.

Agree, it seems like your Edge does not take HR into account when calculating calorie burn. I wonder if you use bundled HRM or some other device?

Ok, so even though it was midnight, I hopped on the bike for a quick ride through the dark streets out of curiosity... with my weight changed from 184lbs to 90lbs, a one mile ride resulted in about 30 calories. So, even though I shouldn't have to do that, it's at least good news that there is a way to tweak the HR/calories algorithm. Will try to do a longer ride tomorrow to see if it holds up at longer distances.