The analysis of short-term growth.

The analysis of short-term growth needs repetitive measurements of body stature or of segments of the body. When body stature is measured at monthly intervals, an irregular incremental pattern becomes obvious with a number of large-scale components such as series of prepubertal and pubertal growth spurts, seasonal influences on height gain, and influences of the psychosocial and economic background. When measurement intervals decrease, incremental patterns appear even more irregular, and a number of short-scale components become apparent that are distinct from measurement error. The review summarizes the analysis of short-term growth, and presents the current findings supporting different views on how growth progresses at short term. In particular, observations are presented that suggest growth being a pulsatile, a periodic, a saltatory, and a chaotic event. Some recent animal studies and studies in human newborns are added in detail as they illustrate short-term growth on the basis of accurate 24-hour measurements of the lower leg. The latter investigations support the idea of short-term growth being characterized by chaotic series of'mini growth spurts' that occur at intervals of approximately 4-5 days, not only in human neonates, but also in rats. The amplitude of mini growth spurts ranges between 2 and some 10 mm, and growth velocity of each spurt also varies considerably so that one spurt needs between less than 1 and up to several days for completion.