It's a common misconception that in order to get fit, you must live at the gym. Overdoing it can actually be harmful to your health. Excessive exercising is defined as working out for more than three hours a day and/or being so obsessed with exercise that it interferes with other parts of a person's life.{relatedarticles} Overdoing it can also be frustrating if you set and don't reach unrealistic goals. Also, you will be more likely to quit your program sooner. It puts you at risk for injuries such as stress fractures, tendonitis and joint injuries. If you're a woman of childbearing age, then it can interrupt your menstrual cycle.