there are sometimes rumours that they had happen, but nothing with proof but i think the probability is very very low if they exist.
Edit:
And only when training has a (big) random factor in it, else you would hve consistent up every week when training it, because skill raise had to be higher then one. Sometimes i believe it is not totally free from random, but this argument against it comes to my mind after posting my answer.
Last edited by CrazyEye at 2/13/2010 12:30:02 PM