Yeah, certainly can be.
It's usually used by athletes shortly after training to reduce training fatigue and speed recovery.
(This might be interesting: glutamine's used up quickly during and after exercise - one of the effects of this is lowered immune function. I've noticed the same thing, re: viral symptoms after exercising for a short while.)
Likewise Branch-Chain Amino acids. (which also, interestingly, have a direct effect on central nervous system fatigue by reducing uptake, I think, of Tryptophan.)
I think BCAA's and glutamine together might have a better shot at improving exercise recovery and general fatigue.
The other things athletes use are acid buffers - to neutralize lactic acid build-up from exercise which can cause: pain, stiffness, fatigue, etc. (Potassium Bicarbonate, Sodium/Potassium Phosphate, etc.)
Good article here about the Krebs cycle linked to training recovery here
http://www.nutritionreview.org/library/krebs.html
My big interest at the moment is seeing how much sports nutrition/research can be applied to CFS... So many sports supplements are tailored to do exactly what we use CFS supplements for: increasing ATP production/regeneration, buffering lactic acid, feeding the cells, recovery from muscle fatigue, overtraining, etc...
[i]Could[/i] be enough in itself, in some cases, to lift the body out of an energy crisis and gradually start restoring normal function.
Conflicting results in trials with Glutamine and general CFS - might have to take it in larger doses than standard to see direct results?