A quick post about the table of numbers I presented yesterday. It was intended to paint a picture of the breakdown curve and the last column reflects an example of the area under that curve. I thought it was interesting how the total in column 3 just kept increasing rapidly after 90 minutes, something you don't always appreciate immediately when you actually look at a graph of those numbers.
And as I stated in the original post, it's just from memory and the numbers are only for comparison to themselves and should not be considered very accurate in a quantitative sense. But I think I remember the shape and nature of how this breakdown occurs, and all my experiences the last 13 years have only reinforced that Burke was right on.
I would also make the following points:
1) Increasing the intensity of the energy consumption would almost certainly activate the breakdown curve both earlier and more steeply.
2) If you were to drop out of a 3-hour marathon at the 1-hour mark, your total breakdown would be close to 1/9th the breakdown that you would undergo if you finished the race. There is also a 4:1 ratio between a two hour run and a one hour run at the same pace. Insights like these are the intention behind why I posted that information. I would like to reiterate again that I have tried to err toward less breakdown later - reality is probably actually much higher breakdown later in the activity.
3) Supplementing carbs and/or protein cannot keep up with the energy requirements. If it could, we could just start a marathon with 26 gel packs and finish with full glycogen. Pretty sure someone has tried this and it doesn't work.