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Question on kJ

Old 12-12-10, 07:06 PM
  #1  
ryanhulce
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Question on kJ

Trying to figure out the estimated calories burnt on training rides.

If my PowerTap says 260kJ for a 15 minute workout how many calories would that be? I weigh 160lb.

I found the following calculator: https://www.unitconversion.org/energy...onversion.html

It shows that 260kJ would would be 62.099933123 calories.

From searching on the web it seems that it should be higher than that.

Thanks for any helpful info.

Ryan
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Old 12-12-10, 07:55 PM
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gregf83 
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Your body output 260kJ but it isn't anywhere close to 100% efficient; more like 18-24%. So you need to divide the 62 output Cals by your efficiency. A conservative rule of thumb is to just assume you burned the same number of Cals as the number of kJ output. In your case that would be 260 Cals.
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Old 12-13-10, 02:59 AM
  #3  
CdCf
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I use average power times four to get kcal, for a full hour.

200 W avg would then mean 800 kcal for an hour, or 200 kcal for 15 minutes.

This gives you a ballpark figure, and is based on an efficiency percentage in the low 20s.
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