Skinny Kids Should Exercise to Create Strong Bones

Filed under: Big Kids, Tweens, Teens, Development/Milestones: Babies

Dear Reggie, I have a 13-year-old daughter who is occasionally active. Several days a week she plays at recess and lunch time with her friends at school. Other days she enjoys sitting around and hanging out with her friends. Whenever she plays sports she seems a little weak. She does not have a weight problem. Rather, I suspect she is a little on the thin side. Most of the information I come across on kids' health focuses on obesity. Are there any health concerns for kids that are on the thin side?

Mrs. Plakas

Hello Mrs. Plakas,

You raise a very important issue with respect to your daughter's body type and health. In general, thinner kids who do not exercise are at a higher risk of developing bone weakness issues in their adult life. With respect to your daughter, a red flag would be raised only if she were to complain of joint pain after all activities. The fact that she is occasionally active and happily participates in sports is a good sign that she is healthy.

How exercise and weight-bearing activity builds strong bones, after the jump...

As you pointed out, most of the research out there on kids' health focuses on the need for weight loss through daily activity. The good news is the current recommendation of 60 minutes a day of intense activity for optimal health also applies to those who do not need to lose any weight. For thin kids the benefit is not of the calories burned, rather it is from the stresses placed on the body through weight-bearing activity. Slimmer kids who do not exercise, especially pre-pubescent and teen girls, are more prone to bone density issues in later life such as osteoporosis.

According to Heather McKay, a professor in the department of orthopedics at the University of B.C., childhood and early adolescence has been defined as a window of opportunity. During this period bones will have the greatest positive response to exercise and the most negative response to inactivity and unhealthy eating. By the time girls are 17 they will have reached 95 per cent of their skeletal maturity, while boys have a few more years. She goes on to say that exercise, especially in the form of weight bearing activity such as jumping, helps change the shape of the bone. For every fraction of bone that's laid down on the outside of existing bone there's a four-fold increase in strength.

Final Thoughts

The main point to keep in mind is that thinner kids still need to exercise at a high intensity on a daily basis for the purpose of developing stronger bones. Although it is never too late, the childhood years are the most important years for developing strong bones. Weight bearing activities such as jumping exercises should be on the top of your list.

Reggie Reyes is a certified kinesiologist and personal trainer. He is the president and founder of pt4kids a company that creates specialized training programs for kids all ages and fitness levels.


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Start by teaching him that it is safe to do so.