"Intense focus on one sport and adult-driven pressures to perform are taking their psychological toll on children, causing concentration problems, fatigue, and irritability. In fact, the trend toward starting kids in organized sports at younger ages isn’t necessarily setting the stage for an active lifestyle later on in life — 70 percent of kids give up sports entirely by age 13. When asked by Michigan State University researchers why they quit sports, kids almost universally said, “It’s not fun anymore."