I've been doing some reading for an article that I am writing on the nature of fatigue and the Brain's role in exhaustion.
Once the article has been published I'll post some of it here, but for now I just wanted to point to the work of Samuele Marcora
There is a good interview with him here - Perception is everything
and his key studies are
· The limit to - Marcora SM, Staiano W. Eur J Appl Physiol. 2010 Jul;109(4):763-70. Epub 2010 Mar 11.
· Mental fatigueMarcora SM, Staiano W, Manning V. J Appl Physiol. 2009 Mar;106(3):857-64. Epub 2009 Jan 8.
· The face of fatigue de Morree HM, Marcora SM. Biol Psychol. 2010 Dec;85(3):377-82. Epub 2010 Sep 9.
In his model, fatigue is a psychological issue, not a physical one. When the perception of effort excedes the reward from that effort we give up. The key is in modifying our perceptions.