I should think it would adversely affect your training/fitness - red blood cells carry oxygen all throughout your body and if you don't have enough then you probably won't be able to perform at your best. (and think about guys who get accused of cheating - they are often doing things to increase their hematocrit, since it does give you and edge even to have a little increase). It could be that not anemic is not enough for average joe couch potato to notice, but since you are an athlete you may feel the lack more acutely.