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converting energy output to food consumption

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Joined: 11 Jan 2004
Posts: 4368
Location: metro-motown-area

2/16/13 4:55 PM

converting energy output to food consumption

I vaguely recall that humans are roughly 25% efficient at turning kcals of food energy into work/output.

given that 1 kjoule is 0.239 kcals, is it a reasonable rule of thumb that roughly 1 kjoule of exercise output ~= 1 kcal of food energy consumed?

Last edited by walter on 2/16/13 5:18 PM; edited 1 time in total

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Joined: 19 May 2005
Posts: 8310
Location: Slowing boiling over in the steamy south, Global Warming is real

2/16/13 5:15 PM

Roughly yes, that is often accepted but I would note that Strava comes up with close but not exactly the same numbers for the two metrics. Their math is suspect wrt to power as we have discussed off the forum.

Using your power meter you should be able to compare them when the weather is good enough for you to get outdoors.

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Joined: 11 Jan 2004
Posts: 2574
Location: hillbilly heaven

2/16/13 6:35 PM

I don't know how true this is, but I've read that muscle type affects efficiency also, with sprinters being less eff. than others in the peloton. I read that the sprinters eat more during the grand tours.

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Joined: 12 Jan 2004
Posts: 2974
Location: Midland, MI

2/16/13 8:20 PM


The magic number I have seen over and over for "conditioned athletes" is 24% metabolic efficiency.

The bogus numbers repeatedly printed in Bicycling magazine suggest it's more like 15% - that makes their readers feel like they can eat a lot more on their rides. Bicycling comes up with numbers approaching 50 calories per mile.

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