MODEL OF NORMAL PREPUBERTAL GROWTH

Growth over the short term is a highly complex non-linear process. Con trasting models of short term growth have been proposed which include periodic growth cycles versus abrupt growth spurts with intervening gr owth arrest ('saltation and stasis)). The variability of short term gr owth has been characterised from a study of 46 healthy prepubertal chi ldren measured three times a week over one academic year using a combi nation of descriptive statistical approaches and regression modelling. Growth in childhood over one year is represented by a biphasic proces s comprising three to six unpredictable growth spurts, each of mean le ngth 56 days (range 13-155 days), separated by periods of stasis (less than or equal to 0.05 cm height increment over more than seven days), each lasting a mean of 18 days (range 8-52 days) and accounting for a t least 20% of the period of observation. This is superimposed on stro ng seasonal trends in growth with a declining growth rate over the aut umn months reaching a nadir in midwinter, followed by a growth spurt i n the spring. Human growth over short periods is therefore a discontin uous, irregular, and unpredictable process.