My 14-year-old son is gearing up for freshman high school football in the fall. Team weightlifting starts next week. Is it healthy? Can this stunt long-term growth? The American Academy of Pediatrics has issued June 6, 2001 guidelines for strength training by children in adolescence. Weightlifting can increase strength in adolescents and preadolescents, and can increase muscle size in adolescents. It does not increase running speed, jumping ability, or overall sports performance. It has not been proven to decrease sports injuries. Gains in strength or muscle size are lost after 6 weeks if training is stopped. Injuries to growth plates can occur, but can be prevented by avoiding 'maximal lifts' - trying to lift as much as possible one time. The greatest benefits and smallest risks occur when 8 to 15 repetitions can be performed with a given weight before adding weight in small increments.