# Most accurate calorie indicator.



## fenlandpsychocyclist (26 Feb 2012)

I understand many cycle computers have to be set with riders age, weight, height, etc, before the devices can work out calories burnt on a ride.

I have an android phone running garmin fit, a forerunner 305 watch and an edge 800 ... each can show a wildly different "calories burnt figure" when all three are used on the same ride.

Today i did 70.1 miles, with about 1100 feet of combined climbing.

Bearing in mind all the basic parameters were set identically in all devices, and all devices are gps based so they know elevations/speed/etc the results were:

Phone: 3700 calories
Watch: 3500 calories
edge 800: 2017 calories

Now most people would be happy to quote from the garmin fit app up the pub, before eating
3000 calories of pub food whilst "thinking" they are still in a calorie deficit.
Myself ... i think the 800 may be nearer the mark.

But why? What extra data is the 800 taking into account before it comes up with its calorie figure?

*EDIT* I should point out both garmin devices were receiving my heart monitor strap and cadence detector ... where the phone wasn't receiving either.


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## Mrbez (26 Feb 2012)

I would be interested in this too. 

I did 22 miles today with 1250ft of climbing. 

My Edge 705 said 1325 calories burned.


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## lulubel (26 Feb 2012)

The forerunner 305 uses speed and distance to calculate calories, even when you have the HRM connected. The edge 800 uses your heart rate.


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## vickster (26 Feb 2012)

All the sites I have seen say 30-40 cals per mile as an estimate, so for 22 miles, 600-850 ish


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## gaz (26 Feb 2012)

Between 2000 and 3000 *c*alories burnt on a 70mile ride.
Certainly something wrong there


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## broomwagon (26 Feb 2012)

Graham Obree is right, we pay too much attention to computers and gadgets and not enough on enjoying our ride...Phone, Watch, Edge? Mind boggling.


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## fenlandpsychocyclist (26 Feb 2012)

gaz said:


> Between 2000 and 3000 *c*alories burnt on a 70mile ride.
> Certainly something wrong there


Would have been more ... but i kept my speed down purely so my legs are ready for another ride tommorow. I've done this exact ride before using the edge 800 with an average speed 2.5mph faster ... and an extra 500 calories burnt. This supports what has been said about the edge 800 taking the heart rate into the calorie calculation system.


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## fenlandpsychocyclist (26 Feb 2012)

I


broomwagon said:


> Graham Obree is right, we pay too much attention to computers and gadgets and not enough on enjoying our ride...Phone, Watch, Edge? Mind boggling.



I did keep grabbing the camera on the move taking pictures ... so i did actually enjoy my ride. Most of my daylight rides are superb because i always ride solo and can change my route on a whim. Best when i'm on a mountain bike because that doubles the amount of routes that can be used.


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## gaz (26 Feb 2012)

fenlandpsychocyclist said:


> Would have been more ... but i kept my speed down purely so my legs are ready for another ride tommorow. I've done this exact ride before using the edge 800 with an average speed 2.5mph faster ... and an extra 500 calories burnt. This supports what has been said about the edge 800 taking the heart rate into the calorie calculation system.


I was hitting to the point that there is a difference between calories and Calories. The daily calorie intake for an average male is 2,500,000 calories. The daily Calorie intake for an average male is 2,500 Calories.


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## fenlandpsychocyclist (27 Feb 2012)

gaz said:


> I was hitting to the point that there is a difference between calories and Calories. The daily calorie intake for an average male is 2,500,000 calories. The daily Calorie intake for an average male is 2,500 Calories.


 
Haha!! So shouldn't we be speaking in terms of kCals ... or is it Kcals??


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## gaz (27 Feb 2012)

fenlandpsychocyclist said:


> Haha!! So shouldn't we be speaking in terms of kCals ... or is it Kcals??


kcal. yes.


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## GrasB (27 Feb 2012)

A rough estimation. 100Wh = 86 kCal. Your body is about 60% efficient at producing power iirc so that's 143kCal. So for a 12st man doing a flatish 70 miles averaging 100w (14.8mph) we get 677 kCal.


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## Hacienda71 (27 Feb 2012)

The phone apps are not accurate. My commute is all uphill and yet the calories expended going to work are the same as coming home from work using endomondo. I could freewheel for a large proportion of the homeward leg.


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## HLaB (27 Feb 2012)

I've no idea how GPS sites calculate calories etc, Garmin Connect reported 2994C, Strava reported 2238C and RwGPS reported 3274C for the same 66mile ride yesterday


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## lulubel (27 Feb 2012)

You'd think if they were all using speed/distance/terrain, they'd all give the same figure.

To the OP, they're all estimates, but the edge 800 is closer than the others. Garmins, in my experience, still tend to be rather generous with the calories most of the time, although it does vary.

I'd love to know how they calculate it because I can do exactly the same amount of time, same average and max heart rates, but a real ride on the bike will give more calories than on the turbo, while the turbo feels like I've worked harder. Very weird.


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## T.M.H.N.E.T (27 Feb 2012)

Congratulations on needlessly and somewhat anally complicating the measurement

PS: Expenditure based on HR closest to accurate ?


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## fenlandpsychocyclist (27 Feb 2012)

T.M.H.N.E.T said:


> Congratulations on needlessly and somewhat anally complicating the measurement
> 
> PS: Expenditure based on HR closest to accurate ?


 
Heart rate linked to oxygen demand, oxygen demand linked to effort put into the pedals. Sounds good to me.


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## amaferanga (27 Feb 2012)

GrasB said:


> A rough estimation. 100Wh = 86 kCal. Your body is about 60% efficient at producing power iirc so that's 143kCal. So for a 12st man doing a flatish 70 miles averaging 100w (14.8mph) we get 677 kCal.


 
Not sure about your maths. 

100W will burn about 370 kcal/hour (accounting for human efficiency you get a roughly 1:1 equivalence of kJ to kcal -- Watts = Joules/sec so it's easy to work out kJ if you know Wattage). So if 100W will indeed lead to an average speed of 14.8 mph (which seems quite a high speed to me for not many Watts) then over 70 miles you'd burn around 1750 kcal.

Anyway, any calorie estimate based on speed or HR will be way off for most people. My Garmin Edge 500 uses HR if it's available and comes up ridiculously low. I know this because I often ride with a power meter so know typically how many Watts I put out to average a given speed for a given route. I know that if I use the kJ figure as reported when I use my power meter that I'll be as close to knowing the kcal figure as with any other practical means.

For your average cyclist assuming 400-800 kcal/hour will be as good an estimate as any Garmin or HR monitor IMO.


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## amaferanga (27 Feb 2012)

fenlandpsychocyclist said:


> Heart rate linked to oxygen demand, oxygen demand linked to effort put into the pedals. Sounds good to me.


 
HR doesn't tell you how many Watts you're producing. Two cyclists could have identical HR for a ride and even if they're the same weight, one could be putting out way more Watts that the other. It's the Watts that'll tell you how many kcal you burn, not the HR. 

So calorie guessing using HR sounds bad to me.


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## GrasB (27 Feb 2012)

amaferanga said:


> Not sure about your maths.
> 
> 100W will burn about 370 kcal/hour (accounting for human efficiency you get a roughly 1:1 equivalence of kJ to kcal -- Watts = Joules/sec so it's easy to work out kJ if you know Wattage). So if 100W will indeed lead to an average speed of 14.8 mph (which seems quite a high speed to me for not many Watts) then over 70 miles you'd burn around 1750 kcal.


I plucked that out of my brain so I may have got the wrong baseline number. 14.8mph comes from me on the hoods of my road bike averaging 103w round a concreet oval track. So that's lowish hoods on an aerodynamically clean normal tubed road bike.


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## fenlandpsychocyclist (27 Feb 2012)

I think the main thing to learn from my original post comparing three devices on the same ride, is that many calorie estimators over-read.

Meaning if you're using one of these diet-tracker apps on a smartphone, you could well put in your food consumption for the day, then add in
the (incorrect) calorie burn for the same day ... and come out with a false number.

All in all i think its best to ignore the calorie numbers shown on any bike computer + eat less + go to bed hungry every night to loose weight.


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## T.M.H.N.E.T (28 Feb 2012)

Go to bed hungry.

What?


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## amaferanga (28 Feb 2012)

Go to bed hungry maybe, but make sure you eat at the right time so your body can recover. Less important if you're just riding for fun, more important if you're training.


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## bof (28 Feb 2012)

Heart rate is a good (not perfect) indicator of Calories burned when your gender, age, weight and V02Max are also known. (type in "Prediction of energy expenditure from heart rate monitoring during submaximal exercise" into Google ).

Polar monitors have a fitness indicator (at least the model I had did) which give a decent approximation to V02Max, so I trusted their Calorie estimates. If you can find some device that allows you to increase power in a test incrementally and get a reasonably accurate measurement of power and HR at the same time, you can work out V02Max with some online calculators. 

I have just started using a Garmin Etrex 30 which measures HRM, but yet to locate a Calorie calculator that can use the GPX files it creates. Does anybody know of one?

.


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## HLaB (28 Feb 2012)

bof said:


> I have just started using a Garmin Etrex 30 which measures HRM, but yet to locate a Calorie calculator that can use the GPX files it creates. Does anybody know of one?
> 
> .


Have you tried Garmin Connect, Strava or RidewithGPS, they take gpx files and output Calorie data, I'm unsure of the accuracy though!


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## bof (28 Feb 2012)

HLaB said:


> Have you tried Garmin Connect, Strava or RidewithGPS, they take gpx files and output Calorie data, I'm unsure of the accuracy though!


Thanks - Garmin Connect does not do it for the etrex 30 GPXs - it just gives an average and, IIRC, max HR figure, which in themselves are no use. I will try the other two out when I am not at work.


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## amaferanga (28 Feb 2012)

bof said:


> Heart rate is a good (not perfect) indicator of Calories burned when your gender, age, weight and V02Max are also known. (type in "Prediction of energy expenditure from heart rate monitoring during submaximal exercise" into Google ).


 
One scientific paper from 2005 doesn't really convince me. All I know is that no calorie counter, be it on a Garmin or website, has ever given me a figure that's consistently close to the kJ figure from my power meter. I'd say HR is very hit-and-miss for calorie estimates and therefore using a rule of thumb will be better for most people.

Interestingly, my Garmin Edge 500 (and FR310xt) give a better calorie estimate for me when I'm not wearing the HR strap (from doing my regular commute with power meter, with Garmin and with Garmin+HR).


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## bof (4 Mar 2012)

HLaB said:


> Have you tried Garmin Connect, Strava or RidewithGPS, they take gpx files and output Calorie data, I'm unsure of the accuracy though!


I have now tried with RidewithGPS and I had forgotten I already use the site fore saving routes - showing what a bookmark can do to web branding. Anyway, I was able to upload the GPX directly from the eTrex 30 in "USB mode" where the Garmin looks like a disc drive,and once I had set up zones, it performed a Calorie calculation. I suspect it exaggerated the Calories a bit, but it produced an interesting set of data from the GPX.

Note that if you save the GPX with Mapsource, it loses the HRM data.


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