Research clearly indicates that boys and girls can safely improve their muscle strength and body composition through a basic and brief program of strength exercise. In one study (Westcott, 1993), 57 preadolescents performed 5 exercises, 1 set, 8 to 12 repetitions, 3 days a week, with slow movement speed and full movement range. After 8 weeks of training, the participants increased their muscle strength by 55 percent and improved their body composition by 2 percent (4 pounds more lean weight and 2.5 pounds less fat weight). Although the long-term benefits of youth strength training have not yet been documented, it is logical to assume that leaner and stronger youth may become leaner and stronger adults. Developing a strong musculoskeletal system during the formative years may also reduce the risk of injuries and degenerative diseases during the adult years. The medically based guidelines for youth strength training programs emphasize an uncrowded facility, appropriate equipment, physician clearance, qualified instructors, brief exercise periods, gradual progression, no competition, and no maximum lifts. When appropriate training guidelines are observed, strength exercise is a recommended physical activity for teen and pre-teen boys and girls.