What Are the Limits to Stamina?

If you could continually eat and refuel, could you continually run? So I think that if we're talking about a marathon, or something like that, I think the figure is something like 3,000 calories to run a marathon. There was an amazing gentleman called Gary McKee, who ran 365 marathons last year. The things that become limits to that do really become mental limits, and also those limits of, well as you get more fatigued and your muscles are maybe not generating as much force,. And what is fatigue of physiologically? That's a really hard question. For some people it will be the mental trigger of, I just can't keep doing this. For others it