Overtraining causes psychological, physiological, and hormonal changes. These changes come with mental, physical, and behavioral symptoms, including:
Decreased performance
Poor sleep
Loss of appetite
Increased heart rate and blood pressure, both during activity and at rest
Irritability and restlessness
Arriving late to practice and/or not seeming as engaged as usual
Injuries, such as stress fractures or elbow injuries (especially for pitchers)
Ultimately, overtraining can lead to burnout. Burnout is the body’s response to chronic stress. Athletes who feel burned out often quit, despite the fact that they once loved the sport.