What happens to your bones when you overtrain?

Pain, stress injury: Overtraining is manifested in your bones by causing pain and a spectrum of injury. Your long bones have an outer layer call the periosteum that can become inflamed (periositis, [-itis, inflamed]) and painful with activity and to the touch. Bones can further develop a stress reaction often not seen with regular x-rays and better seen by mri. A stress fracture is the final event with overtraining.

Stress response: Overtraining can lead to a stress response in the bone. This can vary from pain and inflammation to a stress fracture. If the increased training is at a manageable pace, then the body will adapt and the bone can strengthen as a response to the increased load.