Motor skill competence and moderate- and vigorous-intensity physical activity: a linear and non-linear cross-sectional analysis of eight pooled trials.

BACKGROUND: Few studies have examined the relationship between motor skill competence and device-measured physical activity in large samples and none have used non-linear modelling. This study assessed the linear and non-linear associations between motor skill competence and physical activity in children using pooled data from eight studies. METHODS: Cross-sectional ActiGraph accelerometer and motor skills competence data from 988 children (50.8% boys) aged 3-11 years were included. Total, object control and locomotor skill competence were assessed using the Test of Gross Motor Skill Development. Linear mixed models were fitted to examine linear associations between motor skill competence and physical activity. Then, restricted cubic splines models were used to assess potential non-linear relationships. Interactions by sex and age were assessed. RESULTS: There was evidence of positive linear associations between total skill, and object control and locomotor skills, with moderate- and vigorous-intensity physical activity; however, the associations with total skill competence and object control better fitted a non-linear model. Non-linear models indicated associations were positive but relatively weak in the low to mid ranges of TGMD/object control scores but at high ranges (~ > 70 out of 100/ and ~ 35 out of 50) the association strength increased for both moderate- and vigorous-intensity physical activity. There were sex interactions for locomotor skills only, specifically for vigorous activity with boys having a stronger positive association than girls. CONCLUSIONS: There appears to be a threshold for object control skill proficiency that children need to reach to enhance their physical activity levels which provides support for a motor skill "proficiency barrier". This provides a tangible benchmark for children to achieve in motor competence programs.

A peer coach intervention in childcare centres enhances early childhood physical activity: The Active Early Learning (AEL) cluster randomised controlled trial.

BACKGROUND: As numbers of children and time spent in childcare centres increase, so does the potential influence of these centres on early childhood physical activity (PA). However, previous reports indicate little success of interventions aimed at improving PA. The Active Early Learning (AEL) program is a multi-component pragmatic intervention designed to imbed PA into the daily curriculum. Delivered by childcare centre staff, it is directed and supported by a peer coach who works across a network of centres. The objective of the study is to investigate the effect of the AEL program on children's PA. METHODS: Fifteen childcare centres (8 intervention, 7 control centres; 314 children, 180 boys, 4.3y ± 0.4) participated in a 22-week stratified cluster randomised controlled trial. To be eligible to participate, centres needed to have ≥15 preschool children aged 3 to 5-years. The primary outcome was PA measured by accelerometer (Actigraph GT3X) during childcare centre hours over a 3-day period, calculated in min/h of Total PA and moderate-to-vigorous PA (MVPA). The effect of the intervention was evaluated using linear mixed models adjusted for age, sex, accelerometer wear time and centre clustering. RESULTS: There was an intervention effect for Total PA (+ 4.06 min/h, 95% CI [2.66 to 5.47], p < .001) and MVPA (+ 2.33 min/h, 95% CI [1.31 to 3.34] p < .001). On average, a child taking part in the intervention attending a childcare centre from 8 am to 3 pm performed 28 min more Total PA and 16 min more MVPA per day than children receiving usual practice care. CONCLUSION: In contrast with the findings of previous pragmatic trials in early childcare centres, this study shows that a peer-coach facilitated program, focussed on integrating PA into the daily childcare routine, can elicit increases in preschool children's PA of practical as well as statistical significance. TRIAL REGISTRATION: Australian New Zealand Clinical Trials registry: ACTRN12619000638134 . Registered 30/04/2019.

Does physical education influence eye-hand coordination? The Lifestyles of our Kids intervention study.

In Australian government-funded primary schools, the responsibility for physical education (PE) falls mainly on general classroom teachers, many of whom possess limited PE training. This study sought to examine the impact of specialist-taught PE on eye-hand coordination (EHC) development. In this 4-year cluster-randomized intervention, participants were 187 boys and 172 girls initially in grade 2 in 29 primary schools, where no school employed university-trained specialist PE teachers. In 13 (intervention) schools, specialist PE teachers conducted 268 PE classes (two 45-minute sessions/wk) from grade 2 to grade 6. The intervention was based on traditional PE educational objectives, including fundamental motor skills, but did not specifically focus on EHC. The remaining 16 (control) schools continued with common-practice PE taught by general classroom teachers (30-60 min/wk). EHC was measured by a ball throw and wall-rebound catch test and recorded at ages 8, 10, and 12 (SD 0.3) at ends of grades 2, 4, and 6, respectively. There was steady yearly improvement of EHC in both groups, but no evidence of any intervention effect in boys (P=.88) or girls (P=.20). The introduction of specialist-taught PE during 4 years of primary school did not influence EHC development. Considering evidence that classroom teachers make little contribution to PE in this jurisdiction, together with the steady progression of EHC over the 4 years, other influences such as organized sport, after-school activities, natural development, and parental instruction are conceivably more influential factors in EHC development during primary school years.

Psychological distress leads to reduced physical activity and fitness in children: the Australian longitudinal LOOK study.

Stress and depression can affect an individual's level of physical activity and fitness, which may place them at risk of developing cardiovascular disease. This study investigates the longitudinal effects of stress and depression on physical activity and cardiorespiratory fitness among youth. Six hundred and seventy-six children, initially aged 8 years, from the LOOK study completed a modified version of the Children's Depression Inventory, the Children's Stress Questionnaire, and objective physical activity and cardiorespiratory fitness assessments on three occasions, every 4 years. Depressive symptoms had a direct effect (longitudinal) on the cardiorespiratory fitness of girls, with a similar trend for boys. In cross-sectional analyses, a child who identified with more symptoms of depression and stress was likely to be less fit and less physically active, which in girls extended to less moderate-to-vigorous physical activity. Our findings, that both physical activity and fitness are impacted by depression and stress may contribute to strategies directed towards achieving enhanced physical activity and reductions in obesity.

Benefits of early development of eye-hand coordination: evidence from the LOOK longitudinal study.

We investigated longitudinal and cross-sectional relationships between eye-hand coordination (EHC) and cardiorespiratory fitness (multistage run), physical activity (pedometers), percent body fat (%BF, dual energy x-ray absorptiometry), body image, and organized sport participation (questionnaires) in 406 boys and 384 girls at 8 and 10 years of age. EHC was measured by a throw and wall-rebound catch test involving 40 attempts of increasing difficulty. Median EHC improved during two years from 18 to 32 (boys) and 9 to 24 (girls), and gender differences and improvements were both significant (P < 0.001). Cross-sectional analyses showed that boys and girls with better EHC were fitter (P < 0.001), and a longitudinal relationship showed that girls who improved their EHC over the two years became fitter (P < 0.001). There was also evidence that children with better EHC possessed a more positive body image (P = 0.05 for combined sex data), but there was no evidence of any relationships between EHC and %BF or PA (both P > 0.3). Finally, even at age 8 years, boys and girls participating in organized sport possessed better EHC than non-participants. These data provide evidence for the premise that early acquisition of this single motor skill promotes the development of a child's fitness, body image, and participation in sport.

Improved running economy and increased hemoglobin mass in elite runners after extended moderate altitude exposure.

There is conflicting evidence whether hypoxia improves running economy (RE), maximal O(2) uptake (V(O)(2max)), haemoglobin mass (Hb(mass)) and performance, and what total accumulated dose is necessary for effective adaptation. The aim of this study was to determine the effect of an extended hypoxic exposure on these physiological and performance measures. Nine elite middle distance runners were randomly assigned to a live high-train low simulated altitude group (ALT) and spent 46+/-8 nights (mean+/-S.D.) at 2860+/-41m. A matched control group (CON, n=9) lived and trained near sea level ( approximately 600m). ALT decreased submaximal V(O)(2) (Lmin(-1)) (-3.2%, 90% confidence intervals, -1.0% to -5.2%, p=0.02), increased Hb(mass) (4.9%, 2.3-7.6%, p=0.01), decreased submaximal heart rate (-3.1%, -1.8% to -4.4%, p=0.00) and had a trivial increase in V(O)(2max) (1.5%, -1.6 to 4.8; p=0.41) compared with CON. There was a trivial correlation between change in Hb(mass) and change in V(O)(2max) (r=0.04, p=0.93). Hypoxic exposure of approximately 400h was sufficient to improve Hb(mass), a response not observed with shorter exposures. Although total O(2) carrying capacity was improved, the mechanism(s) to explain the lack of proportionate increase in V(O)(2max) were not identified.

Relationship between indices of adiposity obtained by peripheral quantitative computed tomography and dual-energy X-ray absorptiometry in pre-pubertal children.

BACKGROUND/AIM: The study investigated the relationship between indices of adiposity measured by peripheral quantitative computed tomography (pQCT) and dual-energy X-ray absorptiometry (DXA) in pre-pubertal children. SUBJECTS AND METHODS: DXA-derived per cent body fat (%BF) was measured in 284 boys and 288 girls, aged 7-10 years. Cross-sections of the forearm (n=427) and lower leg (n=560) were obtained by pQCT to measure total cross-sectional area of the limb (Total CSA), Muscle CSA, Fat CSA, %Fat CSA (Fat CSA/Total CSAx100) and muscle density. RESULTS: Peripheral QCT-derived %Fat CSA in the forearm and lower leg correlated strongly with DXA-derived %BF (r=0.83-0.89, p<0.01) in both boys and girls. However, forearm and lower leg %Fat CSA were higher than whole body %BF by 5% and 10%, respectively. A better prediction of whole-body %BF was achieved by including %Fat CSA, muscle density and height into a hierarchical regression model. Using sex-specific regression equations, 87.7% of the boys and 83.7% of the girls had a predicted %BF within 3% units of the %BF obtained by DXA. CONCLUSION: In pre-pubertal children, pQCT measures of adiposity are strongly associated with whole-body per cent body fat. This reproducible method could be an alternative technique to estimate body composition in this population.

Granulocyte activation induced by intense interval running.

Activation of granulocytes has been associated with normal immune function, inflammation, and exercise-induced muscle damage. The effect of intense interval running on granulocyte activation was examined by use of flow cytometry, monoclonal antibodies, and spectrophotometric techniques. Eight trained males [maximal oxygen uptake VO2max, mean (SD) = 64.4 (3.6) ml/kg/min; age 30.1 (4.8) years] undertook an intense interval exercise (treadmill running) protocol to exhaustion. Subjects completed an average of 16.5 one-minute runs. Granulocyte expression of CR3 (CD11b), receptor for complement component C3bi (6 and 24 h post-test), and Fc gamma RIII (CD16) (24 h post-test) and the plasma concentration of elastase-inhibitor complex (1 h post-test) increased significantly (all P < .05). Subjects (8 of 8) exhibited a post-test decrease at either 1 or 6 h (P < .01) and a 24-h post-test significant increase (7 of 8; P < .05) in granulocyte 90 degrees light scattering (LS). Plasma lactoferrin (Lf) concentration, although increased by 17% at 6 h post-test, was not significantly different from resting values at any sampling point. Changes in plasma Lf and median channel 90 degrees LS were significantly correlated (r = -.43, P = .04), raising the possibility of monitoring exercise-induced granulocyte activation (degranulation) by flow cytometry. Intense interval exercise appears to induce granulocyte activation, as manifested by release of granule proteins and changes in 90 degrees LS and expression of both Fc and complement receptors.

Cytokine immunoreactivity in plasma does not change after moderate endurance exercise.

We investigated whether increased concentrations of circulating cytokines may be responsible for exercise-induced priming of blood neutrophils (J. A. Smith et al. Int. J. Sports Med. 11: 179-187, 1990). The plasma concentrations of tumor necrosis factor-alpha, interleukin- (IL) 1 beta, IL-6, granulocyte-macrophage colony-stimulating factor, and neopterin in trained and untrained human subjects were measured by immunoassay before and after 1 h of cycling at 60% of maximal oxygen uptake. C-reactive protein and creatine kinase (CK) were also measured before and 24 h after exercise as markers of the "acute-phase response" and muscle damage (C. Taylor et al. J. Appl. Physiol. 62: 464-469, 1987), respectively. The small changes in the plasma concentrations of cytokines or neopterin observed after exercise in both trained and untrained subjects were not significantly different to those found in a control group of nonexercised subjects. However, untrained subjects did exhibit an acute-phase response (P = 0.04) 24 h after exercise without additional release of CK into plasma. Baseline training differences were confined to a twofold elevation in CK activity (P = 0.04). The results show that circulating cytokines are unlikely to be responsible for the priming of neutrophil microbicidal activity observed after moderate endurance exercise (J. A. Smith et al. Int. J. Sports Med. 11: 179-187, 1990).

Footstrike is the major cause of hemolysis during running.

There is a wide body of literature reporting red cell hemolysis as occurring after various forms of exercise. Whereas the trauma associated with footstrike is thought to be the major cause of hemolysis after running, its significance compared with hemolysis that results from other circulatory stresses on the red blood cell has not been thoroughly addressed. To investigate the significance of footstrike, we measured the degree of hemolysis after 1 h of running. To control for the potential effects of oxidative and circulatory stresses on the red blood cell, the same subjects cycled for 1 h at equivalent oxygen uptake. Our subjects were 10 male triathletes, who each completed two separate 1-h sessions of running and cycling at 75% peak oxygen uptake, which were performed in random order 1 wk apart. Plasma free hemoglobin and serum haptoglobin concentrations were measured as indicators of hemolysis. We also measured methemoglobin as a percentage of total hemoglobin immediately postexercise as an indicator of red cell oxidative stress. Plasma free hemoglobin increased after both running (P < 0.01) and cycling (P < 0.01), but the increase was fourfold greater after running (P < 0.01). This was reflected by a significant fall in haptoglobin 1 h after the running trials, whereas no significant changes occurred after cycling at any sample point. Methemoglobin increased twofold after both running and cycling (P < 0.01), with no significant differences between modes of exercise. The present data indicate that, whereas general circulatory trauma to the red blood cells associated with 1 h of exercise at 75% maximal oxygen uptake may result in some exercise-induced hemolysis, footstrike is the major contributor to hemolysis during running.

Improved running economy in elite runners after 20 days of simulated moderate-altitude exposure.

To investigate the effect of altitude exposure on running economy (RE), 22 elite distance runners [maximal O(2) consumption (Vo(2)) 72.8 +/- 4.4 ml x kg(-1) x min(-1); training volume 128 +/- 27 km/wk], who were homogenous for maximal Vo(2) and training, were assigned to one of three groups: live high (simulated altitude of 2,000-3,100 m)-train low (LHTL; natural altitude of 600 m), live moderate-train moderate (LMTM; natural altitude of 1,500-2,000 m), or live low-train low (LLTL; natural altitude of 600 m) for a period of 20 days. RE was assessed during three submaximal treadmill runs at 14, 16, and 18 km/h before and at the completion of each intervention. Vo(2), minute ventilation (Ve), respiratory exchange ratio, heart rate, and blood lactate concentration were determined during the final 60 s of each run, whereas hemoglobin mass (Hb(mass)) was measured on a separate occasion. All testing was performed under normoxic conditions at approximately 600 m. Vo(2) (l/min) averaged across the three submaximal running speeds was 3.3% lower (P = 0.005) after LHTL compared with either LMTM or LLTL. Ve, respiratory exchange ratio, heart rate, and Hb(mass) were not significantly different after the three interventions. There was no evidence of an increase in lactate concentration after the LHTL intervention, suggesting that the lower aerobic cost of running was not attributable to an increased anaerobic energy contribution. Furthermore, the improved RE could not be explained by a decrease in Ve or by preferential use of carbohydrate as a metabolic substrate, nor was it related to any change in Hb(mass). We conclude that 20 days of LHTL at simulated altitude improved the RE of elite distance runners.

Sex, sport, and body-size dependency of hematology in highly trained athletes.

Blood hemoglobin concentration, hematocrit, red cell count, white cell count (WBC), and plasma ferritin concentration were measured on 1604 occasions from 706 nationally ranked athletes in 12 sports. The blood samples were taken from a forearm vein amidst periods of moderate to intense training but at least 6 h after a training session. A multiple regression model, accounting for correlations between variables and incorporating the categorical variables of sex and sport revealed the following. Each blood variable was found to be dependent on body mass index, (mass/height2, BMI), with the exception of WBC in the males. As BMI increased so did the magnitude of these blood variables (P less than 0.01). Each blood variable was also dependent on the sport (P less than 0.01), significant differences being observed between several sports in each case. Furthermore, as has been previously reported, the magnitude of the blood variables was dependent on the sex of the athlete, each being significantly greater in males (P less than 0.01), with the exception of the WBC, which was greater in females (P less than 0.01). These data indicate that the rationality of interpreting the hematology in highly trained athletes may be increased by taking BMI and sport into account, as well as gender.

The effect of intense interval exercise on iron status parameters in trained men.

Iron and iron-binding proteins play a critical role in the physiology of many human systems, including the immune system. Intense interval exercise in trained men (mean [SD] age = 31.5 [4.5] yr; VO2max = 64.3 [3.8] ml.kg-1.min-1) is associated with significant modulation of iron status parameters. The concentration of red blood cells, hemoglobin, and transferrin all increased significantly immediately post-test (P < 0.01), increases which can largely be attributed to hemoconcentration. Serum iron was elevated by approximately 25% both immediately and 1 h post-test (P < 0.08). Maximum post-test serum iron values (either immediately or 1 h post-test) were significantly elevated with respect to rest (P < 0.01). Transferrin concentration was also significantly elevated at 24 h post-test (P < 0.05). Transferrin saturation was not significantly altered by this protocol (P > 0.10). Despite a trend toward elevation at 24 h post-test, ferritin concentration was not significantly different from the resting value at any sampling point. Intense interval exercise appears to be associated with significant modulation of iron status, the biological importance of which remains to be determined.

Iron status and diet in athletes.

Plasma ferritin (F) concentrations were measured (range 12-245 ng.ml-1) as an indicator of iron status in 24 male and 45 female healthy, nonanemic athletes. Usual food intake was assessed using a self-completed but supervised food frequency questionnaire. Linear regression was applied to determine the relationship between log F (as data was skewed) and average daily intake of iron (Fe), meat (M), protein (Pr), carbohydrate (CHO), fat (Fa), fiber (Fi), and kilojoules (Kj). There were negative correlations between F and each of Kj (P < 0.01) and CHO (P < 0.001), and a positive correlation between F and Pr/Kj (P < 0.01). No significant relationship existed between F and any of Fe, M, Fa, or Fi. These data suggest that iron or meat intake may not be important determinants of iron status in these athletes. Instead, the percentage of protein in the diet may be more influential on F, as may the (negative) effect of Kj and CHO intake, or at least their reflection of energy expenditure.

The response of leukocyte subsets and plasma hormones to interval exercise.

Aerobic exercise has an established role in modulation of peripheral leukocyte concentrations. However, the effects of intense interval exercise, as employed by athletes in a range of sports, has been given little attention. Eight trained male athletes of mean age (SD) = 31.5 (4.5) yr; VO2max = 64.3 (3.8) ml.kg-1.min-1 undertook an intense interval exercise protocol (treadmill running) to exhaustion. Subjects completed an average of 15.6 1-min efforts. The protocol produced a biphasic leukocytosis: an initial (immediately posttest) leukocytosis resulting from mobilization of lymphocytes (CD3+, CD4+, CD8+, CD16+/56+, CD3+HLA/DR+) (all P < 0.01), with the later (6 h) leukocytosis resulting from mobilization of granulocytes and monocytes (both P < 0.01). This protocol modified significantly the peripheral blood concentration of the hormones cortisol (both total and free), norepinephrine, DHPG, and dopamine (all P < 0.01). Modulation of peripheral leukocyte subsets induced by interval exercise correlated with both the number of exercise efforts performed and the concomitant changes in peripheral hormone concentrations. Sustained alterations in plasma catecholamine levels in the posttest period may have important metabolic and immunological implications for athletes undertaking regular interval training.

Anaerobic exercise causes transient changes in leukocyte subsets and IL-2R expression.

There is evidence that the stress of intense athletic competition and training depresses cellular immunity and predisposes athletes to increased infection. This paper reports changes in circulating leukocyte subsets of trained (group I: VO2max = 67.2 +/- 5.4 ml.kg-1min-1; age = 22.0 +/- 6.2 yr) and untrained (group II: VO2max = 55.0 +/- 4.9 ml.kg-1min-1; age = 21.4 +/- 2.0 yr) males following 1 min of bicycle ergometry at maximum effort. Significant post-exercise increases in concentrations of total leukocytes, monocytes, lymphocytes, CD3+, CD4+, CD8+ lymphocytes were observed in both groups (all P < 0.01). The CD4/CD8 ratio decreased significantly (P < 0.01) but the granulocyte concentration was not altered (P > 0.05). Despite groups I and II not differing in either peak power or total work performed during the exercise test (P > 0.05), group II had a significantly greater concentration and percentage of CD8+ lymphocytes immediately after exercise (P < 0.01). All of the early changes were transient, with normalization occurring within 1 h. Only trained subjects showed a significant decrease in the percentage of CD25+ lymphocytes following PHA stimulation of whole blood obtained 6 h post-exercise. Alterations in leukocyte subpopulations found in response to predominantly anaerobic exercise appear to be associated with a significant, but possibly transient, alteration in the mitogenic responsiveness of lymphocytes that is restricted to aerobically trained subjects.

Effects of an intensive 12-wk training program by elite swimmers on neutrophil oxidative activity.

The effects of an intensive 12-wk training program by 12 national-level swimmers on neutrophil oxidative activity were studied. Eleven sedentary (untrained) subjects (6 males and 5 females) served as environmental controls. Blood samples (10 ml) were taken at rest from an antecubital vein and neutrophils isolated by standard separation techniques. The oxidative burst activity of isolated neutrophils was assessed with an in vitro flow cytometric assay that used the fluorescent probe dihydrorhodamine 123. Two-way ANOVA (repeated measures) showed that oxidative activity was lower (P < 0.05) in the elite swimmers compared with the sedentary control group across the 12-wk period. Analysis of cells from swimmers in training was made: repeated measures ANOVA provided evidence of a significant decline (P < 0.05) in the number of cells responding positively ito in vitro challenge. Despite this decline, there was no significant difference in self-reported upper respiratory tract infection rate between the swimmers and sedentary individuals. These data show that: (i) elite swimmers undertaking intensive training have a significantly lower neutrophil oxidative activity at rest than do age- and sex-matched sedentary individuals; (ii) aspects of oxidative activity in swimmers are further suppressed during periods of strenuous training, and (iii) the extent of the suppression does not appear to be of clinical significance.

Neutrophil oxidative activity is differentially affected by exercise intensity and type.

The differential effects of exercise intensity and type on neutrophil activation were assessed in eight well-trained male runners. Each subject undertook, on different days, three separate 40 min interval (8 x 5 min) treadmill bouts: an intense uphill run (90% VO2 max), a moderate-intensity near-level run and an eccentrically-biased downhill run (both at 52% VO2 max). Blood granulocyte count increased (p< 0.05) after all three treadmill bouts (range 25-108%). Chemiluminescence activity of isolated neutrophils decreased (p< 0.05) immediately after (-58%) and 1-h after (-72%) uphill running, but became significantly elevated (p< 0.05) at 6-h after the near-level (+71%) and downhill (+84%) runs. The ability of neutrophils to release the superoxide anion radical was reduced (p< 0.05) immediately after near-level (-29%) and uphill (-21%) running in cells stimulated with opsonized zymosan. Epinephrine concentration increased by 430% (p=0.01) after uphill but not with near-level or downhill running. The plasma concentration of elastase increased (p< 0.05) immediately after uphill and near-level running, and one hour after uphill running. These results suggest that a population of neutrophils mobilised into the circulation became directly activated in response to exercise, and that neutrophil oxidative activity is affected differentially by both the intensity and type of exercise undertaken.

Temporal divergence of percent body fat and body mass index in pre-teenage children: the LOOK longitudinal study.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT: The index of body mass related to stature, (body mass index, BMI, kgm(-2) ), is widely used as a proxy for percent body fat (%BF) in cross-sectional and longitudinal investigations. BMI does not distinguish between lean and fat mass and in children, the cross-sectional relationship between %BF and BMI changes with age and sex. WHAT THIS STUDY ADDS: While BMI increases linearly with age from age 8 to 12 years in both boys and girls, %BF plateaus off between 10 and 12 years. Repeated measures in children show a systematic decrease in %BF for any given BMI from age 8 to 10 to 12 years. Because changes in BMI misrepresent changes in %BF, its use as a proxy of %BF should be avoided in longitudinal studies in this age group. BACKGROUND: Body mass index (BMI, kgm(-2) ) is commonly used as an indicator of pediatric adiposity, but with its inability to distinguish changes in lean and fat mass, its use in longitudinal studies of children requires careful consideration. OBJECTIVE: To investigate the suitability of BMI as a surrogate of percent body fat (%BF) in pediatric longitudinal investigations. METHODS: In this longitudinal study, healthy Australian children (256 girls and 278 boys) were measured at ages 8.0 (standard deviation 0.3), 10.0 and 12.0 years for height, weight and percent body fat (%BF) by dual-energy X-ray absorptiometry. RESULTS: The patterns of change in the means of %BF and BMI were different (P < 0.001). While mean BMI increased linearly from 8 to 12 years of age, %BF did not change between 10 and 12 years. Relationships between %BF and BMI in boys and girls were curvilinear and varied with age (P < 0.001) and gender (P < 0.001); any given BMI corresponding with a lower %BF as a child became older. CONCLUSION: Considering the divergence of temporal patterns of %BF and BMI between 10 and 12 years of age, employment of BMI as a proxy for %BF in absolute or age and sex standardized forms in pediatric longitudinal investigations is problematical.

NTproBNP concentrations in healthy children.

INTRODUCTION: There have been limited studies generating BNP and NT-proBNP reference intervals for paediatric populations. We prospectively assessed NT-proBNP levels in a cohort of 854 healthy school children from the Lifestyle of Our Kids (LOOK) prospective longitudinal study. MATERIALS AND METHODS: NT-proBNP analysis was performed on 172 girls and 212 boys with average age 8.1 years, 183 girls and 181 boys, average age 10.1 years and 183 girls and 180 boys with average age 11.9 years. Data were stratified according to age and gender with the median, range of results and 2.5th and 97.5th percentiles calculated RESULTS: There were no significant differences between males and females at any of the 3 study ages. Significant differences were seen between the 8 and 12 year-olds, 10 and 12 year-olds and the 8 and 12 year-old boys. DISCUSSION: Our study demonstrated that NT-proBNP concentrations in healthy children progressively decline between ages 8 and 12 years. Our selection of unambiguously healthy children produced similar median but lower 97.5th percentile NT-proBNP concentrations to previously published studies.