it really does not matter whether you train two a days or one a day... it matters HOW... fuck you could train five a day, but if it was shitty, no intensity, lalalalala it doesn't matter.... everyones threshold is different and overtraining to you may be different to overtraining to someone else... the key is to try different routines and find out what works for YOU... not for anyone else, but for you... when it comes to training, everyones body responds different... its just like diet... some people have to eat a certain way as opposed to others due to metabolism, body reaction, etc... The way that I train may seem like overtraining to some but for me, its not... It works for my body... That's up to you to figure out... You can try different people's approaches and see how it works and tweak it to your needs and demands... You can definitely get to a point of overtraining but to actually define what that is may be impossible because everyone's body reacts so differently... I do know this, you should be damn tired when you leave the gym... not pass the fuck out tired, but you should get your sweat on and you should feel like you really did something in there or your not working that hard and your not getting the most out of your gym time...