Originally Posted by
MonsieurChrono
Does time play any role in this?
Can somebody burn the same amount of calories per hour in a short (< 2 hours) as in a long (> 4 hours) high-level performance ride? Or, in other words, can somebody maintain the same high-level performance (say, push 400 W, burn roughly 1 500 calories, per hour) in a short or long ride, if nutrition was not the issue?
Unless somebody looks like Vingegaard or other pros, who are at around 5% body-fat, is it necessary to match the calorie deficit entirely with sugar to achieve high-level performance?
Theoretically - yes. If you stay under threshold levels of power, or in Zone 3+/-, and you could mentally stand the suffering & have decent fitness - you could sustain the higher level of effort for 2-3-4-5+ hours. Eventually you will run out of the capacity to fuel the effort. The body typically can burn more than it can process. All of it is trainable to a point, like Vingo and being able to consume and process 100+ grams per hour. Where most of us would end up with some intestinal distress trying to do that without training the body to accept that level of sugar.
And no, the effort is not fueled entirely with sugar. Below threshold levels are a mix of carbs and fat. Zone 2 and below can be entirely fueled by fat energy. And one can train the body to become more efficient at burning fat, allowing you to ride even harder for longer periods. Even Vingo at 5% body fat has 100's of thousands of stored calories from fat. And he trains in ways that help him access that energy.
Adam Yates during the last stage of the Vuelta was probably in Zone 3 for 90%+ of the 4-5 hour duration. Possibly with some time at threshold, and some bursts above threshold. He was burning both fat and sugar in Z3 and is well trained to do that. And he slightly bonked out at the end. He was unable to keep up with nutrition and hydration.
At some point the wheels fall off.