From Active's website, an unfortunately realistic calculation for cycling calorie burn........
http://www.active.com/story.cfm?story_id=12851
calories burned
Fri, 03/10/2006 - 4:50am
Fri, 03/10/2006 - 7:47am
#1
How accurate is the 'calories burned' from a HRM?
I have the Polar CS200 which provides 'calories burned.' The computer caculates this based on HR, gender, weight and max HR.
Can I take this number to the bank or is it hogwash?
Fri, 03/10/2006 - 10:03am
#2
Sort of
It is probably correct within 10-15%. Which is probably much closer than someone can estimate their daily intake.
For fun, you can always ride for an hour, do the calc from active.com, and compare that to you Polar. There are also other websites with calorie calculators that use speed, temp, bike weight, etc.
Fri, 03/10/2006 - 12:39pm
#3
Calories from Power Meter more accurate (nm)
Fri, 03/10/2006 - 2:59pm
#4
I find it much more efficient to use a scale on a regular basis and to adjust my eating habits based on the weekly trends. To be sure to absorb enough liquid, it's a good idea to check one's weight after a long ride.
If you eat healthy food and ride hard, you really can eat a lot and still lose weight. Then, you don't even bother looking at calories.
Stéphane
Fri, 03/10/2006 - 3:42pm
#5
Data
To test the accuracy of the Polar predicted calories to work obtained (and calories extrapolated), I once did a comparison. The ride was a loop from New Paltz up to Lake Minnewaska, then down Clove ride for the climb on Mohonk Rd then back to New Paltz, 26 miles, 3000 vertical feet of power.
Here are the PM Stats:
Entire ride (230w):
Duration: 1:38:50
Work: 1362 kJ
TSS: 136.7 (intensity factor 0.911)
Norm Power: 278
Distance: 26.411 mi
Speed: 16 mph
Now kjoules to kcalories needs requires conversions. Since the body is roughly 25% efficient and 4.184 kJ = 1 kcal, and the work accomplished in kJ during a ride is nearly equal to kcal burned by the body. However, individual efficiency does vary. I assume 22.5% efficiency thus kJ × 1.07 = kcal hence:
1362KJ X 1.07 = 1457 kcal.
My basal metabolic rate was recently measured to be 2150 kcal/day = 90 kcal/hr.
So for the 1:40 minute ride I burned just over 1600 kcal. The Polar predicted 1200 kcal. This is very low.
Perhaps this ride's up and down nature (3000 vertical feet of climbing) did not due the Polar's algorithm justice, since I was riding either very hard (uphill) or easy (downhill) with not much in between.
As for the formula:
16X0.0615X100+(22X3000/100)=1705
In this instance, the formula appears to be a better predictor than the Polar.
On last Sunday's ride, I expended 2500 kjoule of energy, roughly 2675 kcal, plus about 350 kcal for BMR. The route was rolling, with 3000 vertical feet of climbing but no real climbs.
The formula, without the climbing factor predicted 2400 kcal. So, if you only use the climbing factor for long climbs, this predictor is reasonably accurate.
There are far better predictors, but not simple for a long multi-terrain route and building a piecewise model can be tedious.
