Could you tell me how much exercise is considered overtraining?

You stop improving!: You fail to improve. You start experiencing fatigue. And your bones, joints, tendons, & muscles do not have time to repair. So minor injuries accumulate in men, cortisol rises and testosterone falls. In women, periods cease. In both sexes, osteoporosis is a consequence. Counter productive obviously, and can be a manifestaion of compulsive behavior!