Children do not grow continuously but in spurts.

The description of the human growth pattern in limited largely to the traditional vocabulary of "linear growth rates," i.e., height or length increments divided by certain time intervals such as months or years. These studies have been performed using conventional techniques of body length or stature measurement with a technical error of approximately 1.5 mm. During the last 10 years, measurements of lower leg length (knemometry) have been performed with a significantly lower technical error (0.09-0.16 mm). Repeated determinations of lower leg length at short intervals are now feasible, and evidence indicates that "short term growth" is a phenomenon that includes both length increment and decrement. At measurement intervals of exactly 1 week, growth appears periodic showing marked spurts that alternate with intervals of decreased growth velocity with a peak-to-peak distance of 30-55 days (mini growth spurts). These spurts have significant clinical importance and can be used as predictive criteria for successful growth promotion in growth hormone therapy of short stature. Lower leg length measurements at 24-hour intervals provide evidence for the existence of circaseptan periodicity. © 1993 Wiley-Liss, Inc.