From the NY Times:
Can Your Brain Fight Fatigue?
These hypotheses having been around for a while now, as Timothy Noakes, of the University of Cape Town in Africa has been a leading proponent of the central fatigue model and central governor hypothesis.
Personally, I don't think the central theories can be disproved as being the driver behind performance and fatigue. The limiting factor is motivation...
Are there any studies that have been done with subjects under, which would always be subjective, MAXIMAL motivation to then ultimately determine where fatigue is ocurring first?