Yes, there is such a thing, it's a real issue, and I HATE that it exists...
Over-training; it's a result of the “no pain no gain” concept which has been marketed so heavily over the last decade. The fitness experts plastered all over your TV have perpetuated the fallacy that no matter who you are, or what your current fitness level is, high-intensity training is the only method to achieve physical fitness.
What they neglect to tell you is that if you train hard, and you train hard often, there are some serious side effects which don't include toned muscles and chiseled abs.
IF fitness is the goal, over-training is as far away from fitness as one can get.
Most over-trainers will attempt to work out as hard as they can 4 or more days a week with the notion that it will increase results. Ironically, because they tend to repeatedly work similar muscle groups with similar exercises, not giving their bodies and muscles a chance to recover, they set themselves up for diminished results which include but are not limited to, adrenal fatigue,decreased overall strength, an increased likelihood of injury,
and in some extreme cases depression, irritability and poor sleep patterns.