The American Academy of Pediatrics and the American College of Sports Medicine now say that strength training is fine for kids, as long as they're supervised and don't try to lift too much weight. Read on
Teens need at least 60 minutes of moderate to vigorous physical activity on most days for good health and fitness and for healthy weight during growth.
It may not always be possible to avoid injury when playing sports, especially physical contact sports. But there are things kids can do to protect themselves. Preparing before and after a game or practice session by warming up muscles and then stretching can help.