Dave's Not Here

Wearing two strapons . . . I mean straps!

by on May.22, 2013, under Body Stats, Dave's Rants

This morning when I biked to work, I wanted to compare the calorie count between my Garmin Forerunner 305 + hr strap, and map my fitness, using a Polar BT strap. So, I double strapped, and here are the results.

First, there’s the route. I rode 12.86 miles, in just over an hour. For this, I trust the garmin’s measurement a bit better than the iPhone’s, which has me at 13.0 miles.

So, let’s first link to the workouts.

Garmin Workout

Map My Fitness Workout (Sorry — Map My Fitness doesn’t have a cool embed like Garmin does.

Both contain heart rate details. Garmin clocks me with a 139 average, and 182 max. Map My Fitness doesn’t seem to have an overall average heart rate, but, it does max at 182, so, I think the sensors were pretty much the same.

So, then comes the calorie math. The Garmin, which I have had trouble with in the past for not relating the calories to my heart rate, has me at 1831 kcals. Map My Fitness comes in at just over a thousand (1037). So? Which is right?

This calculator computes my calories at 919 kcals, based on Garmin’s 139 HR average.

Doing the math here, I come up with (WARNING, Math ahead!) C = (0.6309 x H + 0.2017 x A + 0.09036 x W – 55.0969) x time / 4.184. In this equation, C is your calories burned, H is your average heart rate in bpm, A is your age in years, W is your weight in pounds, and T is the length of the exercise session in minutes. So, C = (0.6309 x 139 + 0.2017 x 44 + 0.09036 x 231 – 55.0969) x 62 / 4.184 = 924 kcals.

So, in a nutshell, Garmin’s math is again skewed . . . showing 2x the real calories burned . . . I’m not sure what they’re smoking, but they should share . . .


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