Originally Posted by
SapInMyBlood
Do the online calculators take this into account? Because if you hold 400W x 1 hour, a decent portion of those watts (for me anyways) will result from anaerobic glycolysis. Conversely, if you did 100W x 4 hours, it can be 100% aerobic glycolysis / lipolysis, which based on the ATP conversion rates, will actually require much less calories.
400 Watts might be anaerobic for you but if you could actually hold 400W for one hour the work would be mostly aerobic. Also, if your FTP were 400W then a very large portion of those Calories used would be from glycogen. It doesn't take too long - maybe five minutes - before the portion is mostly aerobic. I also think, though I can't find it now, that a lot of the waste products of anaerobic work get recycled.