Motor skill development (or lack of) combined with immature connective tissue are the primary structural reasons teenagers do not engage in high load resistance training. Hypertrophy-based stimulus is also a key factor in training younger athletes (so as to increase muscle cross-section and therefore potential strength/power) – which is another reason that high load training is considered less than productive.

In terms of stunted growth, this has proven to be a myth more than anything else (although many people THINK the reality applies).

GRF in running and jumping are proportionately higher than with resistance training, and yet no one prevents younger athletes from doing these activities. In fact, the American Academy of Pediatrics actually supports resistance training for PRE-adolescent athletes (provided appropriate guidelines are followed). Muscle pull (which is occurs when contracting muscles ‘tug’ on their boney insertions) actually serves to increase osteoblastic acitvity and adds bone strength.

The key to resistance training for younger athletes is low/moderate load, moderate/high intensity, with a STRICT approach to form and execution of EACH rep.

I wrote an article on this exact subject recently. I will post it later on today or tomorrow.

Thanks!

– Brian

From PhysicsForum.com…

“”From personal trainers I’ve talked to previously, they’ve said that lifting weights will not stunt your growth unless you lift too much, and with improper form.””

From the website SteadyHealth.com, the answers and responses have been mostly mixed with some people saying stay away from it and other people saying weightlifting won’t affect it.

I think the concluding message can be found off of the Bodybuilding Section in About.com (source HERE)

Question: Bodybuilding FAQ – Does Bodybuilding Training and Lifting Weights Stunt Growth?

My son just started bodybuilding training and though I am very happy about that, I have heard that lifting too heavy a weight will cause growth to be stunted in kids. Is there an ideal weight range that my son can use so that he can reach his bodybuilding goals but also attain his ultimate height?

Answer: The whole notion of growth being stunted by bodybuilding training is a myth that I have been fighting for years. In conversations with my grandfather who used to be an Orthopedic Surgeon graduated from Northwestern University with top honors, I learned that as long as the resistance is not so high that it would cause the bones to become more dense and thus close the epiphysis (the growth area of a long bone) then there should not be any detrimental effects.

As a matter of fact, the American Academy of Pediatrics recently changed their policy (PEDIATRICS Vol. 107 No. 6 June 2001, pp. 1470-1472) regarding this topic by stating that “strength training programs do not seem to adversely affect linear growth and do not seem to have any long-term detrimental effect on cardiovascular health” as evidenced in recent studies.

I should also point out that the compression forces on your son’s legs and spine are far greater in running and jumping than they will ever be in a bodybuilding exercise like squatting. Compression forces in running and jumping can exceed 5 times his bodyweight. If he’s not squatting over 700 pounds, he’s generating greater compression in normal daily activities.Ideal Training Weight

I wouldn’t recommend that he lift any weight that he can’t do in a controlled fashion and with perfect form for at least 10 repetitions until he’s 18 or so. A weight that he can perform with perfect form for 10-15 repetitions will give him excellent bodybuilding results. Once 18, he can introduce weeks of heavier lifting, never going below 5 repetitions, as in my opinion, that is not needed for bodybuilding.

To be honest, when it comes to kids and bodybuilding training my concern isn’t so much the risk of stunting growth (which won’t happen with proper training); I am more concerned about the risk of injuring tendons, ligaments, or joints that are unused to the demands of heavy lifting. This is the reason why I can never emphasize enough the importance of proper weight selection and perfect exercise execution.

Conclusion

If you look at it, lifting weights didn’t do a thing to stunt the growth of Shaquille O’Neal, David Robinson, Karl Malone, Michael Vick, etc. All started lifting in their early teens, and all have gone on to be over 6′ tall and star in professional sports. Dave Draper and Arnold Schwarzenegger started lifting younger than that; again, both are 6’1″ or taller. Many high school teams start their freshmen on lifting programs, meaning your son started at a perfectly appropriate age.

Provided that exercise form, proper weight selection and safety are always emphasized, your son won’t find his growth stunted by lifting; rather, he’ll find that he grows into his body much better and much more quickly than most of the peers around him.

From TeenBodyBuilding.com…

Will weight training stunt an adolescent’s growth? How old is old enough to begin weight training? What type of program should adolescents follow? These are all questions commonly asked when dealing with weight training and adolescents.

By: Derek Charlebois    May 19, 2003

* This article is only meant to inform, not diagnose. The information presented does not replace talking with your doctor. If you are pregnant, talk to your doctor about exercising and follow his recommendations.

Will weight training stunt an adolescent’s growth? How old is old enough to begin weight training? What type of program should adolescents follow? These are all questions commonly asked when dealing with weight training and adolescents. More often than not, the answer received is an opinion. This article will answer these questions and more by examining what science says.

Note: The term strength training is synonymous with weight training and resistance training.

“Does Weight Training Stunt Growth?”

The biggest concern amongst parents as well as children is whether strength training will stunt the child’s growth. This is a common public belief. Is this belief true or just a myth? Science proves it is a myth. So where did this myth originate?

This myth that strength training damages the growth plates of children, which would cause decreased stature growth, is believed to have stemmed from an old report which examined children in remote areas of Japan (Kato & Ishiko, 1964). This report stated that these children, who performed heavy labor, were short in stature. It should also be noted that these children “performed heavy labor in mountainous villages for several hours a day” in addition working and living on a poor diet (Faigenbaum, 2001). From this, it was speculated that strength training could damage the composition of the epiphyseal junctures, or “growth plates”, from which bone continues to emanate until complete skeletal growth is achieved. This belief was not based on scientific findings, but an anecdote.

On the contrary to this belief, strength training strength training improves the bone mass density of children and adolescents (Morris et al., 1997). Osteoporosis, a progressive disease which causes bones to lose their mineral mass and become brittle and spongy, is an ever growing disease that affects more than 20 million Americans. Due to an insufficient intake of calcium, the body begins to use bone calcium for its needs. This is a problem in itself, but is further aggravated by the sub-optimal levels of bone mass on adults due to inactivity. Bone mass also decreases as one ages (Katch & McArdle, 1993). Without going into too much detail, exercise, more specifically weight bearing exercise, leads to the buildup of calcium in bones, assuming calcium intake is adequate. By exercising at an early age, children can give their bones a head start in the fight against osteoporosis.

Science does not support the myth that strength training has a negative effect on the growth of children, but rather it has positive effects on the their bone health and growth. These facts have lead to The American College of Sports Medicine (site), American Orthopaedic Society for Sports Medicine (site), and the National Strength and Conditioning Associate supporting child and adolescent participation in strength training programs.

My Conclusion: Since the anecdotal stories linking stunted growth and short stature to heavy exercise is very weak, I can only agree at this point with what all the other sources are saying. Even the official sicentific communities are trying to disprove this myth of “weighting lifting causes growth stunting” Heavy weightlifting can possibly cause stunted growth because it can cause tearing and fractures in the growth plates if it is too high and done improperly. I would rather bet that moderate weightlifting done in the profer form and postures will actually increase height from the excess release of growth hormones and the fact that bone remodeling theory states that the peristeum would adapt itself and get thicker and wider thus increase bone length.