Relationship between bone mineral content and bone turnover markers, sex hormones and calciotropic hormones in pre- and early pubertal children.

We investigated associations between bone mineral content (BMC) and bone-related biomarkers (BM) in pre-and early pubertal children of both sexes. In this population, we found that bone turnover markers explain a small part of BMC variance. INTRODUCTION: It is still debated whether BM including bone turnover markers (BTM), sex hormones and calciotropic (including cortisol) hormones provide information on BMC changes during growth. METHODS: Three hundred fifty-seven girls and boys aged 6 to 13 years were included in this study. BM was measured at baseline and BMC twice at 9 months and 4 years using DXA. Relationship between BMs was assessed using principal component analysis (PCA). BM was tested in its ability to explain BMC variation by using structural equation modelling (SEM) on cross-sectional data. Longitudinal data were used to further assess the association between BM and BMC variables. RESULTS: BMC and all BMs, except calciotropic hormones, increased with age. PCA in BM revealed a three-factor solution (BTM, sex hormones and calciotropic hormones). In the SEM, age accounted for 61% and BTM for 1.2% of variance in BMC (cross-sectional). Neither sex nor calciotropic hormones were BMC explanatory variables. In the longitudinal models (with single BM as explanatory variables), BMC, age and sex at baseline accounted for 79-81% and 70-75% in BMC variance at 9 months and 4 years later, respectively. P1NP was consistently associated with BMC. CONCLUSION: BMC strongly tracks in pre- and early pubertal children. In this study, only a small part of BMC variance was explained by single BTM at the beginning of pubertal growth.

Short-term cardiorespiratory adaptation to high altitude in children compared with adults.

As short-term cardiorespiratory adaptation to high altitude (HA) exposure has not yet been studied in children, we assessed acute mountain sickness (AMS), hypoxic ventilatory response (HVR) at rest and maximal exercise capacity (CPET) at low altitude (LA) and HA in pre-pubertal children and their fathers. Twenty father-child pairs (11 ± 1 years and 44 ± 4 years) were tested at LA (450 m) and HA (3450 m) at days 1, 2, and 3 after fast ascent (HA1/2/3). HVR was measured at rest and CPET was performed on a cycle ergometer. AMS severity was mild to moderate with no differences between generations. HVR was higher in children than adults at LA and increased at HA similarly in both groups. Peak oxygen uptake (VO2 peak) relative to body weight was similar in children and adults at LA and decreased significantly by 20% in both groups at HA; maximal heart rate did not change at HA in children while it decreased by 16% in adults (P < 0.001). Changes in HVR and VO2 peak from LA to HA were correlated among the biological child-father pairs. In conclusion, cardiorespiratory adaptation to altitude seems to be at least partly hereditary. Even though children and their fathers lose similar fractions of aerobic capacity going to high altitude, the mechanisms might be different.

Asthma and obesity in children: current evidence and potential systems biology approaches.

Both obesity and asthma are highly prevalent, complex diseases modified by multiple factors. Genetic, developmental, lung mechanical, immunological and behavioural factors have all been suggested as playing a causal role between the two entities; however, their complex mechanistic interactions are still poorly understood and evidence of causality in children remains scant. Equally lacking is evidence of effective treatment strategies, despite the fact that imbalances at vulnerable phases in childhood can impact long-term health. This review is targeted at both clinicians frequently faced with the dilemma of how to investigate and treat the obese asthmatic child and researchers interested in the topic. Highlighting the breadth of the spectrum of factors involved, this review collates evidence regarding the investigation and treatment of asthma in obese children, particularly in comparison with current approaches in 'difficult-to-treat' childhood asthma. Finally, the authors propose hypotheses for future research from a systems-based perspective.

Agreement between spirometers: a challenge in the follow-up of patients and populations?

BACKGROUND: Long-term cohort studies and lung function laboratories are confronted with the need for replacement of spirometers. Lack of agreement between spirometers might affect the longitudinal comparison of data, notably when replacing conventional by portable spirometers. OBJECTIVES: To compare the handheld EasyOne (EO) with the conventional SensorMedics (SM) spirometer, and to analyze the interdevice reproducibility of EO spirometers. METHODS: In total, 82 volunteers completed spirometry sessions with 1 SM and 2 of 3 EO spirometers following a Latin square design. Analyses of differences in forced vital capacity (FVC), forced expiratory flow in 1 s (FEV1), FEV1/FVC and mean forced expiratory flow calculated between 25 and 75% of the FVC between spirometers used a mixed effect model with a random intercept for each subject and the effect of the device as fixed effect adjusted for sex, age, height and order of spirometer tested. Bland-Altman plots show the 95% limits of agreement. RESULTS: Comparisons between EO and SM showed relatively small mean differences of <3%, but systematically lower values for FVC and FEV1 in all EO devices. The 95% agreement exceeded the limits for FEV1 by 50 ml in 2 EO spirometers. The EO interdevice comparisons showed mean differences and limits of agreement within established thresholds, thus indicating fair accuracy when comparing devices. Repeats with the same spirometer did not result in statistically significant differences. CONCLUSIONS: This study suggests fair agreement between the handheld and the conventional spirometer. Differences slightly exceeding limits for FEV1 in 2 EO devices might be considered mostly irrelevant for clinical practice. However, the systematically lower FVC and FEV1 observed with EO may be significant for epidemiological studies, thus justifying inspection before replacing devices.

Contribution of physical education to overall physical activity.

For many children, physical activity (PA) during physical education (PE) lessons provides an important opportunity for being physically active. Although PA during PE has been shown to be low, little is known about the contribution of PA during PE to overall PA. The aim was therefore to assess children's PA during PE and to determine the contribution of PE to overall PA with special focus on overweight children. Accelerometer measurements were done in 676 children (9.3 ± 2.1 years) over 4-7 days in 59 randomly selected classes. Moderate-and-vigorous PA (MVPA; ≥ 2000 counts/min) during PE (MVPAPE), overall MVPA per day (MVPADAY), and a comparison of days with and without PE were calculated by a regression model with gender, grade, and weight status (normal vs overweight) as fixed factors and class as a random factor. Children spent 32.8 ± 15.1% of PE time in MVPA. Weight status was not associated to MVPAPE . MVPAPE accounted for 16.8 ± 8.5% of MVPADAY, and 17.5 ± 8.2% in overweight children. All children were more active on days with PE than on days without PE (differences: 16.1 ± 29.0 min of MVPADAY; P ≤ 0.001; 13.7 ± 28.0 min for overweight children). Although MVPAPE was low, PE played a considerable role in providing PA and was not compensated by reducing extracurricular MVPA.

[Physical activity and obesity in school-age]. / Bewegung und Adipositas.

Physical activity and obesity are two of the most used health expressions over the last years ranging from the lay press to the highest ranked scientific journals. Both reach their readers, as everybody is either affected him/herself or knows a person which has to be treated - or has to cover an explosive scientific topic and search for solutions to solve this worldwide problem of physical inactivity and obesity. It is obvious that we don't have the solution yet and that it will take many decades to normalize our built up construct of a motorized, extensive energy overload - if this is possible at all. Importantly, one has to acknowledge that mild overweight does not harm much, but if the muscles of the human body are not used, more disease and a reduced life expectancy occur. This is evident for the adult population, but this relation seems plausible for children as well. In this article, we will cover physical activity and overweight in the school child including diagnostic criteria, their relevance for health and describe practical approaches that may help to make of each school child an active and "normal weight" human being.

Relationship of physical activity with motor skills, aerobic fitness and body fat in preschool children: a cross-sectional and longitudinal study (Ballabeina).

BACKGROUND: Adiposity, low aerobic fitness and low levels of activity are all associated with clustered cardiovascular disease risk in children and their high prevalence represents a major public health concern. OBJECTIVE: The aim of this study is to investigate the relationship of objectively measured physical activity (PA) with motor skills (agility and balance), aerobic fitness and %body fat in young children. DESIGN: This study is a cross-sectional and longitudinal analyses using mixed linear models. Longitudinal data were adjusted for baseline outcome parameters. SUBJECTS: In all, 217 healthy preschool children (age 4-6 years, 48% boys) participated in this study. MEASUREMENTS: PA (accelerometers), agility (obstacle course), dynamic balance (balance beam), aerobic fitness (20-m shuttle run) and %body fat (bioelectric impedance) at baseline and 9 months later. RESULTS: PA was positively associated with both motor skills and aerobic fitness at baseline as well as with their longitudinal changes. Specifically, only vigorous, but not total or moderate PA, was related to changes in aerobic fitness. Higher PA was associated with less %body fat at baseline, but not with its change. Conversely, baseline motor skills, aerobic fitness or %body fat were not related to changes in PA. CONCLUSION: In young children, baseline PA was associated with improvements in motor skills and in aerobic fitness, an important determinant of cardiovascular risk.

Effect of school-based interventions on physical activity and fitness in children and adolescents: a review of reviews and systematic update.

BACKGROUND: School-based interventions are thought to be the most universally applicable and effective way to counteract low physical activity (PA) and fitness although there is controversy about the optimal strategy to intervene. OBJECTIVES: The objective of this review was to summarise recent reviews that aimed to increase PA or fitness in youth and carry out a systematic review of new intervention studies. METHODS: Relevant systematic reviews and original controlled and randomised controlled school-based trials with a PA or fitness outcome measure, a duration of ≥12 weeks, a sufficient quality and involvement of a healthy population aged 6-18 years that were published from 2007 to 2010 were included. Results In these reviews, 47-65% of trials were found to be effective. The effect was mostly seen in school-related PA while effects outside school were often not observed or assessed. CONCLUSIONS: The school-based application of multicomponent intervention strategies was the most consistent, promising strategy, while controversy existed regarding the effectiveness of family involvement, focus on healthy populations at increased risk or duration and intensity of the intervention. All 20 trials in the review update showed a positive effect on in-school, out-of-school or overall PA, and 6 of 11 studies showed an increase in fitness. Taking into consideration both assessment quality and public health relevance, multicomponent approaches in children including family components showed the highest level of evidence for increasing overall PA. This review confirms the public health potential of high quality, school-based PA interventions for increasing PA and possibly fitness in healthy youth.

Effects and mechanisms of strength training in children.

It has been demonstrated that strength training can be organized in children in a safe and effective way. However, there is limited data regarding its impact on muscle hypertrophy. This study investigated the effects of a high-intensity strength training (HIS) on knee extensor/flexor strength, countermovement (CMJ) jumping height, postural control, soft lean mass and muscle cross-sectional area (CSA) of the dominant leg in prepubertal children. Thirty-two children participated in this study and were assigned to an intervention (INT; N=17) or a control class ( N=15). The INT participated in 10 weeks of weight-machine based HIS integrated in physical education. Pre/post tests included the measurements of peak torque of the knee extensors/flexors at 60 and 180°/s, CMJ jumping height, postural sway, soft lean mass of the leg by bioelectrical impedance analysis, and CSA (m. quadriceps) by magnetic resonance imaging. HIS resulted in significant increases in knee extensor/flexor peak torque (60°/s and 180°/s). HIS did not produce significant changes in CMJ jumping height, postural sway, soft lean mass, and CSA. Although HIS was effective at increasing peak torque of the knee extensors/flexors in children, it was unable to affect muscle size. It appears that neural factors rather than muscle hypertrophy account for the observed strength gains in children.

Long-term effects of a partially supervised conditioning programme in cystic fibrosis.

Little is known about the long-term persistence of positive effects induced by a physical conditioning programme in cystic fibrosis. Therefore, this study determined the effects of a 6-month conditioning programme on peak oxygen uptake (primary outcome) and other markers of fitness, physical activity, anthropometry, lung function and quality of life (secondary outcomes), 18 and 24 months after the programme was initiated. Patients with cystic fibrosis aged 12-40 yrs were randomly assigned to an intervention (n = 23) and a control (n = 15) group. The intervention group consented to add 3 h of sports per week for > or =6 months to their previous activities. Controls were asked to maintain their level of activity for 12 months. Patients were seen at baseline and after 3, 6, 12, 18 and 24 months. There was no significant difference between groups at baseline. The intervention induced positive effects on peak oxygen uptake (difference in changes from baseline to the 18- and 24-month assessments between groups: 3.72+/-1.23 mL.min(-1).kg(-1); p<0.01), maximal workload (0.37+/-0.11 W.kg(-1); p<0.01), vigorous physical activity (1.63+/-0.82 h.week(-1); p<0.05), forced vital capacity (6.06+/-2.87% predicted; p<0.05) and perceived health (9.89+/-4.72; p<0.05). A home-based partially supervised physical conditioning programme can improve physical fitness, lung function and perceived health long after the intervention has ended.

Physical activity, bodyweight, health and fear of negative evaluation in primary school children.

Fear of negative evaluation (FNE) is regarded as being the core feature of social anxiety. The present study examined how FNE is associated with physical activity (PA), body mass index (BMI) and perceived physical health (PPH) in children. Data were collected in a sample of 502 primary school children in first and fifth grades taking part in a randomized-controlled trial ("Kinder-Sportstudie KISS") aimed at increasing PA and health. PA was assessed by accelerometry over 7 days, PPH by the Child Health Questionnaire and FNE by the Social Anxiety Scale for Children--Revised. BMI z-scores were calculated based on Swiss norms. Cross-sectional analyses indicated that children high in FNE exercised less, reported lower levels of PPH and had higher BMI z-scores (P<0.01). Using mixed linear models, the school-based PA intervention did not manage to reduce FNE scores. Overweight children demonstrated a greater increase in FNE (P<0.05) indicating that enhanced weight may be a risk factor for FNE. In conclusion, the associations among high FNE, low PA and increased BMI should be considered when promoting an active lifestyle in children.

Children at high altitude have less nocturnal periodic breathing than adults.

Although children commonly travel to high altitudes, their respiratory adaptation to hypoxia remains elusive. Therefore, in the present study respiratory inductive plethysmography, pulse oximetry (S(p,O(2))) and end-tidal CO(2) tension (P(ET,CO(2))) were recorded in 20 pre-pubertal children (aged 9-12 yrs) and their fathers during 1 night in Zurich (490 m) and 2 nights at the Swiss Jungfrau-Joch research station (3,450 m) following ascent by train within <3 h. In children, mean+/-sd nocturnal S(p,O(2)) fell from 98+/-1% at 490 m to 85+/-4 and 86+/-4% at 3,450 m (nights 1 and 2, respectively); P(ET,CO(2)) decreased significantly from 37+/-6 to 32+/-3 and 33+/-4 mmHg (3,450 versus 490 m). In adults, changes in nocturnal S(p,O(2)) and P(ET,CO(2)) at 3,450 m were similar to those in children. Children spent less time in periodic breathing at 3,450 m during night 1 and 2 (8+/-11 and 9+/-13%, respectively) than adults (34+/-24 and 22+/-17%, respectively), and their apnoea threshold for CO(2) was lower compared with adults (27+/-2 and 30+/-2 mmHg, respectively, both nights). S(p,O(2)), P(ET,CO(2)) and time in periodic breathing at altitude were not correlated between children and their fathers. In conclusion, children revealed a similarly reduced nocturnal O(2) saturation and associated hyperventilation at high altitude as adults but their breathing pattern was more stable, possibly related to a lower apnoea threshold for CO(2).

Higher pulmonary artery pressure in children than in adults upon fast ascent to high altitude.

The response of pulmonary artery pressure to high altitude has not been studied in children. It is also not known whether the individual response is hereditary. Therefore, the response of pulmonary artery pressure to high altitude was measured in pre-pubertal children in comparison to that in their biological fathers. Echocardiography was performed at 450 m and over 3 days at 3,450 m. Systolic pulmonary artery pressure was estimated from the pressure gradient of tricuspid regurgitation. The increase in pulmonary artery pressure in children was greater than that in adults at day 1 of high altitude (15.5+/-9.1 versus 7.9+/-6.4 mmHg), but returned to adult levels on day 2. The increase in pulmonary artery pressure from low to high altitude of each child correlated with that in the father. Pre-pubertal children transiently develop greater pulmonary hypertension than their fathers when exposed to high altitude. The individual response of pulmonary pressure to high altitude seems to be at least partly hereditary.

Weight-bearing bones are more sensitive to physical exercise in boys than in girls during pre- and early puberty: a cross-sectional study.

UNLABELLED: We carried out a cross-section study of the sex-specific relationship between bone mineral content and physical activity at sites with different loading in pre- and early pubertal girls and boys. There was significant sensitivity of bone mineral content of the hip to physical exercise in boys, but not in girls. BACKGROUND: Since little is known whether there are sex differences in sensitivity of bone to loading, we investigated sex differences in the cross-sectional association between measures of physical activity (PA) and bone mass and size in pre- and early pubertal children of both sexes. METHODS: We measured bone mineral content/density (BMC/BMD) and fat-free mass (FFM) in 269 6- to 13-year-old children from randomly selected schools by dual-energy X-ray absorptiometry. Physical activity (PA) was measured by accelerometers and lower extremity strength by a jump-and-reach test. RESULTS: Boys (n = 128) had higher hip and total body BMC and BMD, higher FFM, higher muscle strength and were more physically active than girls (n = 141). Total hip BMC was positively associated with time spent in total and vigorous PA in boys (r = 0.20-0.33, p < 0.01), but not in girls (r = 0.02-0.04, p = ns), even after adjusting for FFM and strength. While boys and girls in the lowest tertile of vigorous PA (22 min/day) did not differ in hip BMC (15.62 vs 15.52 g), boys in the highest tertile (72 min/day) had significantly higher values than the corresponding girls (16.84 vs 15.71 g, p < 0.05). CONCLUSIONS: Sex differences in BMC during pre- and early puberty may be related to a different sensitivity of bone to physical loading, irrespective of muscle mass.

[How to treat childhood obesity? Importance of primary prevention]. / Comment traiter l'obésité de l'enfant? Importance de la prévention primaire.

The prevalence of childhood obesity increases dramatically. First signs of cardiovascular diseases and type 2 diabetes appear early in life. The treatment of childhood obesity aims at weight maintenance during growth, normalization of body mass index at long-term and prevention of complications. The family based behavioural therapy is a promising approach. It provides simultaneous treatment for the overweight parent and child in order to modify the family environment, to provide role models and support for child behaviour changes. However, this requires group leaders and multiple counselors to meet with families. The treatment should be initiated as soon as possible, as its efficacy is reduced after the onset of puberty. Early preventive interventions that aim to modify both individual's behaviours and the environment are needed.

Kinetics of oxygen uptake at the onset of exercise in boys and men.

The objective of this study was to compare the O2 uptake (VO2) kinetics at the onset of heavy exercise in boys and men. Nine boys, aged 9-12 yr, and 8 men, aged 19-27 yr, performed a continuous incremental cycling task to determine peak VO2 (VO2 peak). On 2 other days, subjects performed each day four cycling tasks at 80 rpm, each consisting of 2 min of unloaded cycling followed twice by cycling at 50% VO2 peak for 3.5 min, once by cycling at 100% VO2 peak for 2 min, and once by cycling at 130% VO2 peak for 75 s. O2 deficit was not significantly different between boys and men (respectively, 50% VO2 peak task: 6.6 +/- 11.1 vs. 5.5 +/- 7.3 ml . min-1 . kg-1; 100% VO2 peak task: 28.5 +/- 8.1 vs. 31.8 +/- 6.3 ml . min-1 . kg-1; and 130% VO2 peak task: 30.1 +/- 5.7 vs. 35.8 +/- 5.3 ml . min-1 . kg-1). To assess the kinetics, phase I was excluded from analysis. Phase II VO2 kinetics could be described in all cases by a monoexponential function. ANOVA revealed no differences in time constants between boys and men (respectively, 50% VO2 peak task: 22. 8 +/- 5.1 vs. 26.4 +/- 4.1 s; 100% VO2 peak task: 28.0 +/- 6.0 vs. 28.1 +/- 4.4 s; and 130% VO2 peak task: 19.8 +/- 4.1 vs. 20.7 +/- 5. 7 s). In conclusion, O2 deficit and fast-component VO2 on-transients are similar in boys and men, even at high exercise intensities, which is in contrast to the findings of other studies employing simpler methods of analysis. The previous interpretation that children rely less on nonoxidative energy pathways at the onset of heavy exercise is not supported by our findings.

Enhanced fibrin formation in high-altitude pulmonary edema.

Blood coagulation, fibrinolysis, and arterial blood gases were examined in 66 nonacclimatized mountaineers at 4,557 m. Subjects were classified according to a clinical score as healthy (n = 25), having mild acute mountain sickness (AMS) (n = 24), showing severe AMS (n = 13), and suffering from high-altitude pulmonary edema (HAPE) (n = 4). Coagulation times, euglobulin lysis time, and fibrin(ogen) fragment E were normal in all groups without significant changes. Fibrinopeptide A (FPA), a molecular marker of in vivo fibrin formation, was elevated in HAPE to 4.2 +/- 2.7 ng/ml (P less than 0.0001) compared with the other groups showing mean values between 1.6 +/- 0.4 and 1.8 +/- 0.7 ng/ml. FPA was normal in one patient with HAPE, however. Severe AMS was accompanied by a significant decrease in arterial PO2 due to an increase in alveolar-arterial O2 difference, whereas arterial PCO2 did not change significantly. We conclude that activation of blood coagulation is not involved in the pathogenesis of AMS and the impairment of gas exchange in this disease. Fibrin generation occurring in HAPE is probably an epiphenomenon of edema formation.

Anaerobic performance in 5- to 7-yr-old children of low birthweight.

PURPOSE: This study was intended to determine whether anaerobic muscle performance is deficient in 5- to 7-yr-old children of extremely low birthweight (ELBW, 500-999 g) and very low birthweight (VLBW, 1000-1499 g). METHODS: Fourteen ELBW and 20 VLBW children were compared with 24 normal birthweight (NBW, >2500 g) term controls. Peak (PP) and mean (MP) muscle power were determined by the Wingate anaerobic test. Bioimpedance analysis and anthropometry were done to assess fat-free mass (FFM) and lean cross-sectional area of the thigh and calf. RESULTS: The ELBW group had significantly lower MP and PP, compared with the VLBW and, in particular, with the NBW group. This lower performance was apparent also when values were corrected for total body mass (MP) and FFM (MP and PP), but not when corrected for cross-sectional area of thigh and calf. CONCLUSION: The lower anaerobic muscle performance in ELBW children may be partly due to their smaller muscle mass, but may also reflect a low percentage of fast-twitch muscle fibers, low muscle phosphagen content, or deficiency in motor control.

Preventing dehydration in children with cystic fibrosis who exercise in the heat.

PURPOSE: In healthy children who exercise in the heat, the addition of flavor, carbohydrate, and 18 mmol x L(-1) NaCl to water induced a major increase in voluntary drink intake compared with the intake of unflavored water. This increase was sufficient to prevent voluntary dehydration. We hypothesized that, to achieve a similar effect in children with cystic fibrosis (CF), whose NaCl losses in sweat are markedly excessive, the drink should include an NaCl concentration higher than 18 mmol x L(-1). METHODS: Eleven subjects with CF (6 girls, 5 boys, ages 10.9-19.5 yr) attended three 3-h sessions of intermittent exercise of moderate intensity (four 20-min bouts), at 35 degrees C, 50% relative humidity. Either water (W), flavored water (FW), or a 30 mmol x L(-1) NaCl plus 6% carbohydrate solution (Na30) was offered ad libitum, in a counterbalanced sequence. Six subjects performed an additional session in which they drank a 50 mmol x L(-1) NaCl-6% CHO solution (Na50). RESULTS: There was no significant drink effect on body fluid balance, core temperature, heart rate, or serum electrolytes with W, FW, or Na30. Serum osmolality decreased throughout the sessions from 290.6 +/- 1.1 (mean +/- SEM) to 281.3 +/- 1.2 mmol x kg(-1) (P < 0.0005), serum sodium from 143.1 +/- 0.5 to 141.1 +/- 0.7 mmol x L(-1) (P = 0.01) and serum chloride from 109.1 +/- 0.5 to 107.5 +/- 0.5 mmol X L(-1) (P < 0.001). In contrast, the 50 mmol x L(-1) NaCl drink induced a near significant (P = 0.08) higher fluid intake, and it significantly ameliorated the rate of progressive dehydration. CONCLUSIONS: The marked loss of NaCl in the sweat of CF patients may induce an hypo-osmolar state in the serum, even when the drink contains 30 mmol x L(-1) NaCl. This may diminish the thirst drive triggered by hypothalamic osmoreceptors and may lead to voluntary dehydration. A flavored drink with an even higher salt content (50 mmol X L(-1)), however, enhances drinking and attenuates the voluntary dehydration.