Not just with adults trying to build muscle or lose fat. Tracking height is also important for youth who play, or anticipate playing, sports. We’ve been talking a little bit about the American Development Model and have noted that there are certain periods of development where children are especially sensitive to certain training stimuli. For example, boys respond very rapidly to speed training around age 8 and experience a second ‘window’ around ages 14-15. For girls, these windows occur around age 7, and then again around age 12. As another example, flexibility is best developed between the ages of 6-10, but is also critical during the adolescent growth spurt. Sports skills are best developed between the ages of 9-10. Missing exposure to those stimuli during these windows will likely guarantee that the child will (like most of us) not become an elite athlete.
I want to note emphatically that organized sports or strength and conditioning are NOT necessary to hit these windows: given space to play, a friend, and a projectile of some sort, a 7-8 year old will probably run as fast or throw as hard as they can enough times on a given day at the park to provide sufficient stimuli. The key is to make sure that kids have frequent enough opportunity to do so. I don’t know if there is strong data on this, but I strongly suspect that 4-6 PE classes or trips to the park each month is not enough.
But I digress. What does all this have to do with measuring height?
Because children develop at vastly different paces, two kids with a chronological age of 10 (born this month, ten years ago) might have developmental ages four years apart. One might have hit puberty, the other could be years away. The older one is likely to be taller, stronger, and have more muscle mass. On the flip side, if they’re in the midst of a growth spurt, they might not be as good at precise movement tasks such as swinging a golf club or shooting a basketball than they were previously. These two athletes will have different windows of trainability open, and should therefore not be exposed to the same amounts of the same stimuli. How do you know where your child is at?
Measure height each month. Then take those measurements, and plot their growth rate on a growth velocity curve chart. From there, it is easy to determine where your child is on the curve, and you can adjust their exposure to certain activities depending on their age.
Hopefully while making sure that they’re having fun.