I can imagine that this post will make me unpopular with some but I feel that this subject needs some attention. There is no fixed age that in the teens or even people in their early 20’s can be sure they have stopped growing. The growing vertebral body is not as strong as the fully developed. Growing spines have more cartilage growth centers on the top and the bottom and are prone to fracture. If care is not taken to limit the compressive loading on the spine ( think squats and deadlifts) a condition known as Scheuermann’s disease may develop. Scheuermann’s disease involves fractures of the top and bottom of the vertebral bodies. Scheuermann’s disease can be painful and the spinal deformities are often permanent.

The prevailing method of measuring spinal maturity has been to take x rays of the long bones  an look for the growth plates. As you can see in the x-ray of the knee below the growth plates are line of cartilage where the growing body adds new bone tissue.

Red arrows point to growth plates

The prevailing method of measuring spinal maturity has been to take x rays of the long bones an look for the growth plates. As you can see in the x-ray of the knee below the growth plates are line of cartilage where the growing body adds new bone tissue.

The idea being that once the growth plates have closed the person has likely stopped growing and has reached skeletal maturity. Unfortunately, there is no sure way to X-ray the spine to see if the growth plates are closed. The vertebral bodies do not have growth plates like the long bones ( arms and legs.) Rather the spine has growth centers that are located on the top and the bottom of each vertebra. The spinal growth centers cannot be seen on x ray, are made of cartilage and do not stand up to compressive force like bone.  Once the growth plates of the long bones have closed the spine can continue to grow for up to two years.

 

When the vertebra are loaded beyond the ability of cartilage to hold, a failure of the growth center cartilage can occur.  When this happens the jelly like substance of the intervertebral disc can be forced onto the soft bone marrow cavity inside the vertebral body. This can be painful and since the growth center is destroyed it will never heal.

So how do we use this information?

Here is the good news: CrossFit has already done a tremendous amount of legwork on the safety of exercise in children and teenagers. They have produced an excellent document on the subject. You can download the entire document here: http://www.crossfit.com/cf-seminars/SMERefs/Kids/CFK_TrainerCourse.pdf

I would like to highlight some of the more important items that CrossFit has made in their training manual:

  1. If you are aware of an underlying disease (scoliosis, Juvenile rheumatoid arthritis for example) then get your chiropractor or pediatrician’s clearance first.
  2. This is serious stuff.  If your teen is not mature to take it seriously then wait.
  3. Proper form for each exercise is a shield against injury. Don’t perform heavy lift unless the form can be maintained 2 sets 8 reps flawlessly with lighter weight.
  4. Competition and one rep max lifts should be avoided until skeletal maturity has occurred.*
  5. Resistance should be increased gradually.  The muscles may grow faster than the bone.
  6. Hydration, nutrition, rest and exercise are equal in importance.
  7. During the sports season decrease the intensity to avoid over training.

*Skeletal maturity has occurred is generally 1-2 years after growth plates have closed.