According to the National Sports Medicine Institute, the three stages of overtraining are:  1. Functional overreaching:The athlete executes periods of increased trainingand notices performance declines unless proper rest periods are integrated into his or her training program. 2. Non-functional overreaching: After continued functional overreaching, the athlete starts to notice a myriad of physiological and psychological symptoms, including hormonal imbalances, constant fatigue, or personality changes. 3. Overtraining syndrome:Non-functional overreaching has progressed into overtraining syndrome, which includes a slew of physical and mental symptoms and can take months to recover from.