Overtraining is a general (i.e., whole-body) condition wherein the body is unable to keep up with the demands placed on it. Basically, it’s when the exercise overwhelms recovery.  The most important aspect of avoiding overtraining is to adequately rest, of course. This can possibly be accelerated and enhanced by unconventional strategies, including sauna and breathing techniques to promote the parasympathetic nervous system.  Nevertheless, ensuring both adequate calories and the right type and amounts of proteins (i.e., animal proteins) and fats can help narrow the recovery window.