You get tired by riding your bike for a long time, you get fatigued in the same way.
You get tired/fatigued by working all day, all week, whatever.
You don't get 'over-trained' by doing that; you don't get overtrained by working weeks on building sites, you get tired.
Overtraining is a completely different thing, and is over-used as a phrase when people really mean 'i'm a bit knackered'.
I work weeks, even months of nights, that leaves me tired/fatigued, but I'm not 'over-trained' at work, I'm just fecked…
Overtraining is a physical, behavioral and emotional condition that occurs when the volume and intensity of an individual's exercise exceeds their recovery capacity.
http://en.wikipedia.org/wiki/Overtraining