Overtraining is a physical, behavioral and emotional condition that occurs when the volume, intensity and frequency of an individual’s exercise exceeds his or her ability to recover. Common problem among both professional and amateur athletes, it is a major concern for active fitness enthusiasts because it’s responsible for reduced performance and increased fatigue. To avoid it, Andrea Bosio, head of the Scientific Research department of the Mapei Sport Research Center in Olgiate Olona (Va), explains us the “Rule of 3”.