More and more school-age athletes in the US are ending up in the emergency room with concussions(脳しんとう、衝撃). Between 1997 and 2007, emergency room visits for concussions sustained in organized youth sports more than tripled for 14- to 19-year-olds and doubled among those ages 8 to 13. Because their brains are still developing, young athletes may be more vulnerable to lasting damage, such as learning difficulties, memory problems, and chronic headaches, from these injuries. Doctors therefore caution parents and coaches against encouraging young athletes to "tough out" such injuries, recommending instead that they be examined by a medical professional.