So when muscle starts pumping out IL-6 into the system chronically it goes to the brain and makes people fatigue sooner.  This happens when glycogen levels get depleted and we know that exercise performance is harmed when this occurs.  And suddenly we have a potential link from the earlier observation of muscle glycogen being involved in overtraining.

However, by the strictest definition, overtraining has not truly occurred unless the athlete’s actual performance level has fallen.  He may be tired, he may feel run down but if performance hasn’t actually dropped, he hasn’t become overtrained.  At least not yet.

It became clear early on that true overtraining, whereby it took months to recover to previous performance levels, was fairly rare.