"Exercising too much, either by working out too long or too frequently, can backfire in a number of ways. Many fail to appreciate the importance of recovery between sessions, and research has shown that endurance training can do more harm than good in the long run. As noted in the featured article: "A common physiological response to training is the release of certain hormones into the bloodstream, such as testosterone and dopamine. Going past 45 to 55 minutes per workout can put the body into a negative hormonal state." Adrenal fatigue and reduced performance can result when you exercise excessively."