Calorie burn/HR monitor question

[noisemaker]

I've been using my Garmin HR monitor to calculate my calorie burn, and I'm confused by the results. Today, for example, I ran 10 miles. It calculated 806 calories burned. I thought a good rule of thumb for someone my weight (135ish) was 100 calories per mile, so the 800 seemed low, but we did run easy, no sprinting or anything. Also, I've noticed when I run faster, and therefore have a faster heartrate, it says I burn fewer calories than when I run slower--the same 5 mile route can register 400-500 calories burned, depending on how long it takes me.

So, 2 questions. 1) how accurate are these things, and 2) does it really burn more calories to run 5 miles slower than it does to run it faster?

And FYI, this is mostly just curiousity. I am trying to lose a few pounds, but I mostly run for fun/fitness not weight loss at this point, so I'm not going to slow my pace to burn 50 more calories, but I am curious.

[al320]

i always thought the 100 calories per mile estimation was for a 150 pound male, and that a woman of equal weight would burn less, so since you weigh less than that, you'd burn even less.

i would think that the speed wouldnt make a difference in total calorie count, but youd burn more per minute than when running slower. i havent tested it out though.

theyre certainly more accurate than the calorie measure on a treadmill, but im sure they're not totally accurate either. do you have your age/gender/weight input into the garmin?

[noisemaker]

Thanks. Yes, I have my info input into the Garmin.

[heybabe]

I think they're somewhat accurate, but not perfect. When I switched from my polar hrm to my garmin hrm, it gave me totals about 100-130 cal less than what the polar gave me on the same route, similar hr, same speed, etc.

A lower calorie burn on a slower run seems counterintuitive to me, but what do I know?!

[csquared]

DH and I just had this discussion the other night. Not sure of the real answer, but here was our consensus: if you run 10 miles at 9 minutes a mile, it will take you 90 minutes, but if you run the same 10 miles at 10 minutes per mile, you're running for 10 minutes more, but your heart rate probably isn't *that* much lower, so that could explain why you'd burn more calories for the slower pace.

[gnomesweetgnome]

I have heard/read that Garmin only calculates calorie burn based on the height, weight, and gender, without factoring in your HR at all. This does mean that when you complete a distance in a faster time than usual, it shows you burned fewer calories, because you were exercising for less time. Kind of defeats the purpose of the HR monitor, IMO.

[al320]

Jun 19, 2012 14:05:15 GMT -5 gnomesweetgnome said:

I have heard/read that Garmin only calculates calorie burn based on the height, weight, and gender, without factoring in your HR at all. This does mean that when you complete a distance in a faster time than usual, it shows you burned fewer calories, because you were exercising for less time. Kind of defeats the purpose of the HR monitor, IMO.

some garmins have a HRM chest strap (mine has one though i havent used it), im assuming that's what she meant?

[gnomesweetgnome]

Jun 19, 2012 14:08:15 GMT -5 al320 said:

Jun 19, 2012 14:05:15 GMT -5 gnomesweetgnome said:

I have heard/read that Garmin only calculates calorie burn based on the height, weight, and gender, without factoring in your HR at all. This does mean that when you complete a distance in a faster time than usual, it shows you burned fewer calories, because you were exercising for less time. Kind of defeats the purpose of the HR monitor, IMO.

some garmins have a HRM chest strap (mine has one though i havent used it), im assuming that's what she meant?

Oh, I know that. I have one as well. You can Google more info on how Garmin calculates calorie burn (it is different with different devices). They also have some info in their FAQs: support.garmin.com/support/searchSupport/case.faces?caseId={3a28fc00-0abf-11df-cfaf-000000000000}

[kimsy]

I asked my trainer about the accuracy of calorie burn on HRMs a while back. He said it's a decent estimate, but not accurate because your HRM doesn't know how much of your weight is lean mass vs. fat mass. Muscle burns more cals than fat, so I guess that's where the potential for error comes in.

[patches31709]

Jun 19, 2012 14:23:16 GMT -5 gnomesweetgnome said:

Jun 19, 2012 14:08:15 GMT -5 al320 said:

some garmins have a HRM chest strap (mine has one though i havent used it), im assuming that's what she meant?

Oh, I know that. I have one as well. You can Google more info on how Garmin calculates calorie burn (it is different with different devices). They also have some info in their FAQs: support.garmin.com/support/searchSupport/case.faces?caseId={3a28fc00-0abf-11df-cfaf-000000000000}

Some Garmins take heart rate into the calories burned calc and others don't. The 305 has a chest strap but doesn't use heart rate in the calc.

[noisemaker]

Thanks for all of the info ladies! I have the 110 and it looks like it does take heart rate into account. I guess I'll have to stick with the idea that it's a good guesstimate and leave it at that.