Overreaching ability could be oversimplified as mental toughness. The psychological aspect of being able to work through discomfort, even at sub par performance levels due to built up fatigue, is only a small part. The other aspect of mental toughness is subconscious. During states of fatigue the central governor will only activate muscle fibers if it “knows” that the body will not suffer permanent damage by continuing. In reality your muscles never really get tired, the body just senses markers of muscle damage and fuel depletion and ceases work to protect itself – the muscle could still fire. You can train the central governor to go into damaging levels of workload if you promise to pay it back with an unloading period. The power of the subconscious brain and biochemical feedback patterns cannot be underestimated.