Calories burned (Garmin)

[deskrider]

Why does the Garmin computer say 1800+ calories burned when I am NOT wearing the heart rate monitor and about 300 calories burned when I AM wearing the monitor (same distance and route) ??

[limewave]

What Garmin is it? And what setting do you have it at (running, biking, other)? That can make a difference. Maybe not as great as a difference of 1500, but it can be significant if you have it set to running and then had it set to cycling.

[deskrider]

Ooops there is a TYPO in my subject line. It is the new Garmin Edge 500, set on biking.

[limewave]

Huh. I don't know. Mine has been consistent. I have a Garmin 305. I had to split my long run up yesterday, first half without hrm second half with. The calories burned per mile were nearly identical.

[OakLeaf]

The newer Garmins use a heart rate-based calorie algorithm. For whatever reason, the firmware updates to the older computers don't include that feature.

I brought my 705 (distance and time algorithm) and my 310XT (heart rate algorithm) both on a run once - mainly to get the more accurate elevation profile from the 705's barometric altimeter. There wasn't that much of a difference in the calorie projection, as I remember. I don't honestly think either one is all that accurate. It might be different for cycling, though, since your effort level is so variable depending on wind and grade. I don't think I've ever brought both computers on a ride. You've got me curious now. :p

[sgf726]

I don't see that big a difference but I do see a significant distance with and without the HR Monitor. I have the 310XT in running mode with the HR monitor is about 60% of without the heart-rate monitor. I am not sure why and I think specifically on some longer runs the w/HR calories burned seems very low.

[OakLeaf]

AFAIK, the HR algorithm takes your weight into account as well, where the time/distance algorithm doesn't. So it will always be less for a smaller person. Most of these devices grossly overstate the calorie burn IMO. My basal metabolism isn't so slow that I could possibly be burning that many calories and not eating any more than I do!

[BikeDutchess]

No offense to the developers, but I think there's lots of issues with the algorithms on these types of devices. I have both the Edge 305 and the Edge 500. After I just got the 500, I used both in the same session with a single heart rate strap (paired with both devices) and same programmed settings, and the 500 showed 80% more calories burned than the 305. I tested it both with rides and with walks, with the same result. I thought the 305 showed more realistic calorie numbers, so I fiddled with the settings on the 500 until they were reasonably close. Even so, I take the calorie counts with several grains of salt.

[OakLeaf]

You got me curious. I brought both devices on my 53-mile club ride this morning. I'm about 90% recovered from the hand and wrist sprain, but just getting back on the road bike, so I sat in for almost the entire ride except for a couple of short pulls.

Edge 705 (time and distance based): 2680 Kcal
Forerunner 310XT (HR based) 888 Kcal

I think the Forerunner's calculation is probably pretty close to reality - roughly 300 Kcal/hr, with a riding time of 2:53. The Edge with the non-HR algorithm is obviously way overinflated. Both of them are set with the same user profile (weight, age, sex, HR zones).

[OakLeaf]

It occurred to me over dinner that the accuracy probably depends quite a bit on how accurately you've entered your HR zones.

My old Garmin 301 would calculate HR zones for running. Obviously, since HR doesn't correlate well with cycling speed, it couldn't calculate zones for cycling. For some reason, later models don't have this feature. I assume it must not have been very accurate, although it always seemed to correlate very closely with my subjective perceptions in my individual case. So I've carried over those zones as I've upgraded my equipment, even though my MHR has probably dropped a beat or two over the years.

What method did you use to calculate the zones you're using?



ETA ... and since HR does correlate well with running speed, that would mean that the HR-based calorie calculation for running would probably not be far off the time-and-distance calculation, which is what I recall from the one time I carried both devices on a run.