Not long ago, physicians and physiologists believed that weight training was not important for prepubescent athletes.  In fact, some experts believed strength was dangerous for youngsters.  Now, more and more sports medicine professionals are supporting supervised weight training for the pre-adolescent.
 
There used to be scant little research in the area of prepubescent strength training until about 20 years ago, which then revealed that a well designed, well supervised program can prove beneficial to young athletes.  Earlier opposition to strength training was based on some widely held, but incorrectly assumed beliefs that prepubescent athletes were incapable of making significant gains because they lacked the necessary levels of circulating male hormones, namely androgen.  And that strength training does not improve motor performance, and may, in fact, be dangerous to growth plates.
 
Based on a number of scientific studies, it was consistently found that the strength trained prepubescent "test" boys tested significantly stronger than did the control groups when evaluated on Cybex isokinetic training equipment.  What the researchers found most compelling in the study was that reported injuries usually take place when youngsters are unsupervised and are using free weights.
 
If, however, Nautilus, Universal, or other weight machine-types are used for training and properly adapted to youngsters, if the environment is safe and is properly supervised by a trained professional, then strength training can be performed safely.
 
In designing a strength training program for preadolescents, a great resource should include the guidelines developed by the American Orthopaedic Society for Sports Medicine:

1. A physical exam should be performed prior to participating.
2. The child must have the emotional maturity to accept coaching and instruction.
3. There must be adequate supervision by coaches who are knowledgeable about strength training and the special problems of prepubescents.
4. Strength training should be part of an overall comprehensive program designed to increase motor skills and level of fitness.
5. Strength-training equipment should be of appropriate design to accommodate the preadolescent.
6. Strength training should be preceded by a warm-up period and followed by a cool down.
7. Emphasis should be on dynamic concentric contractions.
8. All exercises should be carried through a full range of motion.
9. Competition is prohibited.
10. No maximum lifts should ever be attempted.
11. Training should be done two or three times a week for 20 to 30 minute periods.
12. One to three sets per exercise should be done; six to fifteen repetitions equal one set.
13. Resistance is increased in one to three pound increments after the child does 15 repetitions in good form.