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An example of variation and pattern in saltation and stasis growth dynamics

The serial data from two siblings, aged 6.6 and 7.5 years of age at the initiation of the study, measured each evening for total standing height during 365 days, are analysed by two methods to investigate the nature of the underlying growth pattern. The saltation and stasis model, designed to identify the presence of statistically significant pulses in sequential data, is compared for goodness-of-fit to first to sixth degree polynomial functions, used to investigate the presence of a slowly varying smooth continuous function in the data, and high order polynomials of the same degree of flexibility as the individual's saltation and stasis results. The saltation and stasis model is found to better-fit the experimental data than the slowly varying smooth continuous functions (p < 0.01 to 0.001). The timing characteristics of the saltation and stasis patterns are investigated and the temporal patterns are suggestive of a non-random, aperiodical deterministic system.

Wrinkles induced by the use of smoothing procedures applied to serial growth data

This paper elucidates the effects of moving average filters when applied to serial growth measurements. This is a question of interest because smoothing procedures are inherently part of a number of analytical methods presently employed in auxological analyses. Particular attention is paid to sequential growth data analysed to identify what has been described as pulsatile, saltation and stasis patterns or mini-growth spurts. When applied to pulsatile, or saltatory, time series data the process of smoothing itself creates artifactual temporal patterns in the time series data similar to previously described mini growth spurts while removing the actual pulsatile characteristics of the data. These observations illustrate that smoothing approaches add noise to time series data while removing meaningful patterns in the original data sequence. Analyses employing such approaches produce results that include waveforms or other fluctuations compatible with an underlying pulsatile driving mechanism, but do not necessarily reflect the temporal characteristics of the original biological process.

Short-term growth: evidence for chaotic series of mini growth spurts in rat growth

Five thousand and eighteen quadruplet daily measurements of lower-leg length of 62 female and 81 male rats, were performed in order to characterize short-term growth. Within a short time, growth proceeds irregularly and consists of multiple incremental bursts (mini growth spurts) with no evidence for strict periodic behavior. Mini growth spurts are S-shaped incremental patterns that can be characterized by double-exponential functions (Gompertz's functions). Gompertz's functions are S-shaped, and can be defined by three parameters that identify amplitude, inflection point (age at peak growth velocity), and slope. The latter not only refers to the rapidity of each incremental burst, but also alludes to the duration that one incremental burst needs for completion. In regard to these characteristics, mini growth spurts differ significantly between the sexes in rats. Mean amplitude of mini growth spurts was 2153 microm (SD 1034 microm) in female rats and 2958 microm (SD 1614 microm) in male rats. Peak growth velocity of mini growth spurts appeared lower in male rats than in female rats. Female rats showed mean gamma of -1.23 (SD 0.72), whereas male rats showed mean y of -0.96 (SD 0.72). Partial growth hormone deficiency led to a modification in rats that was reversed when exogenous growth hormone was administered. Mean intervals between subsequent mini growth spurts ranged between 4.2 and 4.6 days, but the large variation of these intervals (SD between 1.6 and 2.3 days) and the fact that neither spurt-spurt interval nor spurt amplitude appeared predictable, strongly suggest chaotic behavior of mini growth spurts.

Heart 'growth stagnation' during the year following menarche

During puberty, most body structures show an acceleration followed by deceleration in growth, while some grow at a constant rate. This study analyses heart growth dynamics during puberty. The focus was directed towards detection of 'unexpected' events in pubertal physiological growth, such as an episode of a heart growth stagnation or even a temporary reduction in size. A longitudinal study was performed in 173 healthy children (81 girls and 92 boys), aged 11.5 years at the beginning and 14.5 years at the end of the study. Changes in echocardiographic (parasternal M-mode) cardiac dimensions and in anthropometric and ergometric size of related body structures and functions were recorded annually. Direction (positive, zero or negative) and sizes of yearly increments were determined from the measurements, and three annual growth rates were compared for each variable by paired sample t-test. All observed variables increased following the usual growth velocity curve in boys. In girls, body height and weight, lean body mass, aortal root and left atrium, as well as diastolic blood pressure changed in the expected way during puberty, but cardiac left ventricle and endurance time did not. At the age of 13, thickness of the left ventricular walls and length of endurance time did not increase; later the growth of these variables resumed. Menarche onset (12.6 years) immediately precedes these events. Possible mechanisms are: temporary reduction of myocardial cells growth and division, and physiological heart "remodelling' due to changed growth pattern favouring longitudinal instead of transverse myofibrils growth, increased myocardial diastolic compliance and oscillatory blood volume increase.

Evaluation of methodology for nutritional assessment in children: anthropometry, body composition, and energy expenditure

Nutritional status in children is an indicator of health and well-being at both the individual and the population level. Screening for malnutrition should be an integral part of pediatric care universally. Nutritional intervention requires repeated measurement of nutritional status to assess severity and to track progress over time. Methodological issues in the assessment of nutritional status are reviewed with emphasis on anthropometric measurement, body composition, and energy expenditure of children at risk for malnutrition. Use of reference data, measurement error, maturational effects, and hereditary factors are among the issues reviewed and serve as guidelines in the interpretation of measurement of nutritional status.

Model of normal prepubertal growth

Growth over the short term is a highly complex non-linear process. Contrasting models of short term growth have been proposed which include periodic growth cycles versus abrupt growth spurts with intervening growth arrest ('saltation and stasis'). The variability of short term growth has been characterised from a study of 46 healthy prepubertal children measured three times a week over one academic year using a combination of descriptive statistical approaches and regression modelling. Growth in childhood over one year is represented by a biphasic process comprising three to six unpredictable growth spurts, each of mean length 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 at least 20% of the period of observation. This is superimposed on strong seasonal trends in growth with a declining growth rate over the autumn months reaching a nadir in midwinter, followed by a growth spurt in the spring. Human growth over short periods is therefore a discontinuous, irregular, and unpredictable process.