The Growth Spurt

At the peak of the height spurt, males grow an average rate of 10 cm per year (10.3 ± 1.5 cm/year). Females grow about 9 cm per year (9.0 ± 1.0 cm/year). The mean age for this growth spurt is fourteen years old (range 12 to 17 years) for males, and twelve years (range 10.5 – 13 years) for females. This growth spurt occurs at a very specific time in a child’s development.

The next chapter will give parents guidelines for determining when this growth spurt will occur for each of their individual children. The timing among children is markedly variable. The earlier the growth spurt, the greater its velocity; the later, the taller the individual ultimately becomes.

In the subsequent chapters I will be describing in great detail the different SMR (sex maturity ratings) so that a parent can identify which stage of growth their child is in. The parent will then be able to answer for themselves such questions as:

An adolescent growth spurt in full progress is an impressive phenomenon, with daily growth increments nearly visible and with the child having a voracious appetite to match. Though the daily growth increment is then large (up to 0.4 mm/day for some months), it is scarcely enough to account for adolescent clumsiness as asserted in some textbooks. And it is actually small compared to daily variation in size (approximately 1cm). Adolescents are not necessarily clumsy and certainly not clumsy specifically because of their growth spurt.²

The pattern of acceleration of linear growth throughout the body is also fairly predictable. The first body part to elongate (and also the first to cease growing) is the foot. Because of the high price of shoes, parents can provide accurate historical information about this growth parameter ("Ah yes, last year he outgrew his sneakers three times before even wearing them out!"). Approximately six months after onset of accelerated foot growth, there is elongation of the calf, followed by the thigh. Similarly, in the upper limb, distal (farther from the torso) bones elongate before those more proximal (closer to the torso). The result in transient disproportion in hand and foot size contributes to the clumsiness that often characterizes teenagers. Approximately four months after the peak of leg length growth, the hips and chest broaden, the latter more so in males than females.⁴

Puberty may begin from age 8.0 to 14.9 years for females, and from age 9.7 to 14.1 years for males. Puberty is completed by age 12.4 to 16.8 years for females, and by age 13.7 to 17.9 years for males.⁵ As you can see by this wide range, it becomes clear why some girls at roughly age 12½ appear to be "full grown" women, whereas other girls are much smaller in stature and body dimensions until much later.