Calculating Calories

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Ian Watts

Ian Watts

Regular
Rob3rt said:
Taking the last 12 months worth of data accumulated using my power meter, dividing total work done (kJ) by miles I get a figure 43.8 kJ per mile.

Working on the assumption that kJ = kCal then that is 43.8 kCal per mile.

Note: This assumption of kJ = kCal will of course have limitations, however it is a FAIR assumption to make since the conversion between kJ and kCal is ~0.24 IIRC and the efficiency of the human body is somewhere around 25% (give or take a few % between individuals, this is where error is being introduced, as everyone will vary a little) in converting energy into physical action (the rest goes into heat etc) so you can see that the conversion factors pretty much cancel out leaving a 1:1 relationship between kJ and kCal burnt! Of course the calibration on my power meter will also be a source of error, however it is specified to be within +-1.5%.
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At least that gives me something scientific behind it - better to understand than "Rule of Thumb". You obviously understand this more than me. Why does this page say that 1Kcal= over 4 KJ. http://www.unit-conversion.info/energy.html - and this site - http://www.rapidtables.com/convert/energy/kj-to-kcal.htm (I realise I am arguing against myelf now that Kcal would be even less.)
I am not arguing - genuinely interested. Seriously losing faith in endomondo anyway as it seems to be uninterested in cadence / hrm sensors etc anyway. I do better with my 3 year old Garmin oregon 300, but that won't calculate calories.
 
Rob3rt

Rob3rt

Man or Moose!
Location
Manchester
Ian Watts said:
At least that gives me something scientific behind it - better to understand than "Rule of Thumb". You obviously understand this more than me. Why does this page say that 1Kcal= over 4 KJ. http://www.unit-conversion.info/energy.html - and this site - http://www.rapidtables.com/convert/energy/kj-to-kcal.htm (I realise I am arguing against myelf now that Kcal would be even less.)
I am not arguing - genuinely interested. Seriously losing faith in endomondo anyway as it seems to be uninterested in cadence / hrm sensors etc anyway. I do better with my 3 year old Garmin oregon 300, but that won't calculate calories.
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1/0.24 = ~4.
 
A

Albert

Über Member
Location
Wales
Today in chilly (10c) light wind conditions:
34.5 miles @11.3mph. 2949ft of climbing. 3hrs 2min 30secs. HR - 88mins below 70%, 93mins between 70% and 80%. 9mins between 80% and 85% (some 14%+ ramps). Ave Cadence 65. Calories 1199 - measured by Garmin 800.
I would say that this is an accurate enough measurement.
 
HB2210

HB2210

Senior Member
colly said:
Yep 40 calories per mile is what I reckon too. That equates to 1 jelly baby per mile.
Probably too many variables to be all that accurate no matter what system you use.....your weight, bikes weight, wind against you or with you, amount of uphill, rolling resistance, dunno what else but maybe even how efficient you actually push the pedals.
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Wow 1 jelly baby per mile puts your eating/workout ratio into context !!
 
Rob3rt

Rob3rt

Man or Moose!
Location
Manchester
Ian Watts said:
I can't stand Jelly babies - now if they were fruit pastilles!!
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I like them but for some reason, anything more than half a bag of Jellybabies makes me feel really sick.
 
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