Child-Specific Thoracic Gas Volume Prediction Equations for Air-Displacement Plethysmography

A comparison between bioelectrical impedance analysis and air-displacement plethysmography in assessing fat-free mass in patients with motor neurone diseases: a cross-sectional study

AIM

To determine the validity of bioelectrical impedance analysis (BIA) in quantifying fat-free mass (FFM) compared to air-displacement plethysmography (ADP) in patients with a motor neurone disease (MND).

METHODS

FFM of 140 patients diagnosed with MND was determined by ADP using the BodPod (i.e. the gold standard), and by BIA using the whole-body Bodystat. FFM values were translated to predicted resting energy expenditure (REE); the actual REE was measured using indirect calorimetry, resulting in a metabolic index. Validity of the BIA compared to the ADP was assessed using Bland-Altman analysis and Pearson's r. To assess the clinical relevance of differences, we evaluated changes in metabolic index and in individualized protein demand.

RESULTS

Despite the high correlation between ADP and BIA (r = 0.93), averaged across patients, the assessed mean fat-free mass was 51.7 kg (± 0.9) using ADP and 54.2 kg (± 1.0) using BIA. Hence, BIA overestimated fat-free mass by 2.5 kg (95% CI 1.8-3.2, p < 0.001). Clinically, an increased metabolic index would be more often underdiagnosed in patients with MND using BIA (31.4% according to BIA versus 44.2% according to ADP, p = 0.048). A clinically relevant overestimation of ≥ 15 g in protein demand was observed for 4 (2.9%) patients using BIA.

CONCLUSIONS

BIA systematically overestimates FFM in patients with MND. Although the differences are limited with ADP, underscoring the utility of BIA for research, overestimation of fat-free mass may have consequences for clinical decision-making, especially when interest lies in determining the metabolic index.

Evaluation of bioelectrical impedance analysis in measuring body fat in 6-to-12-year-old boys compared with air displacement plethysmography

Air displacement plethysmography (ADP) has been considered as the 'standard' method to determine body fat in children due to superior validity and reliability compared with bioelectrical impedance analysis (BIA). However, ADP and BIA are often used interchangeably despite few studies comparing measures of percentage body fat by ADP (%FMADP) with BIA (%FMBIA) in children with and without obesity. The objective of this study was to measure concurrent validity and reliability of %FMADP and %FMBIA in 6-to-12-year-old boys with and without obesity. Seventy-one boys (twenty-five with obesity) underwent body composition assessment. Ten boys participated in intra-day reliability analysis. %FMADP was estimated by Bodpod using sex- and age-specific equations of body density. %FMBIA was estimated by a multi-frequency, hand-to-foot device using child-specific equations based on impedance. Validity was assessed by t tests, correlation coefficients and limits of agreement (LoA); and reliability by technical error of measurement (TEM) and intraclass correlation coefficients (ICC). Compared with %FMADP, %FMBIA was significantly underestimated in the cohort (-3·4 ± 5·6 %; effect size = 0·42) and in both boys with obesity (-5·2 ± 5·5 %; ES = 0·90) and without obesity (-2·4 ± 5·5 %; ES = 0·52). A strong, significant positive correlation was found between %FMADP and %FMBIA (r = 0·80). Across the cohort, LoA were 22·3 %, and no proportional bias was detected. For reliability, TEM were 0·65 % and 0·55 %, and ICC were 0·93 and 0·95 for %FMBIA and %FMADP, respectively. Whilst both %FMADP and %FMBIA are highly reliable methods, considerable differences indicated that the devices cannot be used interchangeably in boys age 6-to-12 years.

Challenges in body composition assessment using air-displacement plethysmography by BOD POD in pediatric and young adult patients

BACKGROUND & AIMS

Air-Displacement-Plethysmography (ADP) by BOD POD is widely used for body fat assessment in children. Although validated in healthy subjects, studies about use in pediatric patients are lacking. We evaluated user experience and usability of ADP measurements with the BOD POD system in healthy children and pediatric and young adult patients.

METHODS

Using the experiences of seven cohort studies, which included healthy children and patients aged 2-22 years, we retrospectively evaluated the user experience with the User Experience Questionnaire (UEQ) (n = 13) and interviews (n = 7). Technical performance was studied using the quality control data collected by the ADP-system.

RESULTS

From 2016 to 2022, 1606 measurements were scheduled. BOD POD was mostly rated 'user-friendly', with a generally neutral evaluation on all scales of the UEQ. However, questionable reliability and validity of the results were frequently (86%) reported. We found a high technical failure-rate of the device, predominantly in stability (17%) and accuracy of the measurement (12%), especially in the 'pediatric option' for children aged <6 years. Measurement failure-rate was 38%, mostly due to subject's fear or device failure, especially in young and lean children, and in children with physical and/or intellectual disabilities.

CONCLUSION

We conclude that ADP by BOD POD in children and young adults is non-invasive and user-friendly. However, in specific pediatric populations, BOD POD has several limitations and high (technical) failure-rates, especially in young children with aberrant body composition. We recommend caution when interpreting body composition results of pediatric patients as assessed with BOD POD using the current default settings.

Muscle Function, Body Composition, Insulin Sensitivity and Physical Activity in Adolescents Born Preterm: Impact of Gestation and Vitamin D Status

Whilst several studies have explored adolescent metabolic and cognitive function after preterm birth, few have explored muscle function and physical activity. We set out to examine the relationship between gestational age and muscle metabolism in a cohort of adolescents who were born preterm. Participants were recruited from the Newcastle preterm birth growth study cohort. They did not have severe neurological disease and were not on daily medication. Participants underwent an assessment of oxidative muscle function using phosphorus magnetic resonance spectroscopy that included the half-time for recovery of equilibrium of phosphocreatine, τ½PCr. In addition, we measured key variables that might affect muscle function including physical activity levels determined by 3-day accelerometry, body composition using air displacement plethysmography, insulin sensitivity using the homeostatic model assessment/Matsuda index and serum vitamin D concentrations. 60 adolescents (35F) median age 15.6 years (range 12.1−18.8) with a median gestation of 31 weeks (range 24 to 34 weeks) underwent a single assessment. Males were more active and spent less time in sedentary mode. Time spent in light activity was associated with insulin sensitivity (IS) (Matsuda Index; p < 0.05) but there were no strong correlations between activity levels and gestational age. Greater fat mass, waist circumference and body mass index were all associated with lower IS. Gestational age was negatively associated with adjusted measures of oxidative muscle function (τ½PCr). In a stepwise multivariate linear regression model, gestational age at birth was the most significant predictor of oxidative muscle function (p = 0.005). Higher serum vitamin D levels were also associated with faster phosphocreatine recovery time (p = 0.045). Oxidative function in the skeletal muscle of adolescents born preterm is associated with gestational age and vitamin D concentrations. Our study suggests that being born preterm may have a long-term impact on muscle metabolism.

Predictive model specific to young adults for estimating thoracic gas volume for air-displacement plethysmography

BACKGROUND

Thoracic gas volume either measured (mTGV) or predicted by the BodPod® (bpTGV) is used during air-displacement plethysmography to obtain a better estimate of percent body fat. Evidence suggests that bpTGV underestimates mTGV for young adults and this is especially evident for young males.

AIMS

We developed, validated, and cross-validated a TGV prediction model (pTGV) for males and females 18-30 years of age to address this underestimation.

MATERIALS & METHODS

Participants (N = 181; 18-30 years) that had their body composition assessed with the BodPod® were retrospectively randomly assigned to one of two independent subgroups, a validation (n = 145) or cross-validation (n = 36) sample. Ten iterations of the k-fold validation procedure were performed to assess the internal replicability of pTGV within the validation sample. External replicability of pTGV was evaluated by assessing the difference and standard error of the estimate (SEE) compared to mTGV in the cross-validation group.

RESULTS

The model using height, sex and body mass yielded the highest adjusted R² (0.627) and the lowest SEE (0.56 L): pTGV = 0.615338 × Sex (0 = Female, 1 = Male) + 0.056267 × Height (cm) - 0.011006 × Body Mass (kg) - 5.358839. R² remained stable across 10 iterations of the k-fold procedure (average R²  = 0.64). Differences between pTGV and mTGV were not significantly different than zero for the total cross-validation sample (-0.06 ± 0.7 L; SEE = 3.0%), for males (-0.11 ± 0.7 L; SEE = 3.7%), or for females (-0.02 ± 0.7 L; SEE = 5.3%).

CONCLUSION

We recommend that when it is impractical to obtain mTGV, the strong internal and external replicability of the new prediction model supports its use for males and females ages 18-30 years old during air-displacement plethysmography.

Anthropometric and bioimpedance equations for fat and fat-free mass in Chilean children 7-9 years of age

Assessing children's growth adequately is important due to the necessary prevention of adequate body composition, especially at pre-pubertal age. Simpler measurements such as anthropometry or bioimpedance, using equations validated in Caucasian children, have been demonstrated to overestimate or underestimate fat mass percentage (FM%) or fat-free mass (FFM) in Chilean children. In a sample of 424 children (198 boys and 226 girls) of 7-9 years old, the three component (3C) model was assessed, where total body water was determined by 2H dilution and body volume by air displacement plethysmography, in order to design and validate anthropometry and bioimpedance equations. The FM (%) equation specific for Chilean children was validated as (1·743 × BMI z-score) + (0·727 × triceps skinfold) + (0·385 × biceps skinfold) + 15·985, against the 3C model (R2 0·79). The new FFM equation (kg) generated was (log FFM = (0·018 × age) + (0·047 × sex) + (0·006 × weight) + (0·027 × resistance) + 2·071), with an R2 0·93 (female = 1 and male = 2). The Bland-Altman analysis shows a mean difference of 0·27 (sd 3·5) for the FM% in the whole group as well as 0·004 (sd 0·9) kg is the mean difference for the bioelectrical impedance analysis (BIA) FFM (kg) equation. The new equations for FM (%) and FFM (kg) in Chilean children will provide a simple and valid tool for the assessment of body composition in cohort studies or to assess the impact of nutritional programmes or public policies.

Body Composition Using Air Displacement Plethysmography in Children With Inflammatory Bowel Disease

OBJECTIVE

The aim of the study was to assess the body composition of children with inflammatory bowel disease (IBD) and to study the accuracy of clinically available tools in predicting excess body fatness. We aimed at also exploring the influence of adiposity on pharmacokinetics during early Infliximab exposure.

METHODS

Prospective cohort study in 5- to 17-year-old children with IBD initiating Infliximab therapy. Patient demographic, phenotypic, and laboratory data at the time of Infliximab initiation were recorded. Body composition was assessed using air displacement plethysmography (ADP). fat mass index (FMI = fat mass [kg]/(height [m])) was calculated to determine excess adiposity (defined as FMI ≥75th centile). Anthropometrics (weight, height, mid upper arm circumference [MUAC] and triceps skin fold thickness [TSF]) were obtained and MUAC and TSF measurements were used to calculate arm fat area (AFA) and arm muscle area z-scores. Statistical analysis was applied as appropriate.

RESULTS

Fifty-three (68% male; 55% Crohn disease [CD], 45% ulcerative colitis [UC], median [IQR] age 15 [13-16] years) children with IBD were included. Twenty-four percentage of children with IBD (21% CD, 29% UC) had excess adiposity. Four children (31%) with FMI ≥75th centile were not identified by body mass index (BMI) alone (kappa of 0.60), and 2 children (15%) were not identified by AFA z-score alone. The intra- and interobserver reliability of MUAC and TSFT measurements was excellent. There was no difference in Infliximab trough levels at the end of induction between those with FMI less than or ≥75th centile.

CONCLUSIONS

Excess adiposity affects approximately 1 in 4 young patients with IBD and can be missed by routine obesity screening. Our exploratory study did not raise concerns of underexposure to infliximab in those children with excess adiposity during early drug exposure.

The effect of maternal DHA supplementation on body fat mass in children at 7 years: follow-up of the DOMInO randomized controlled trial

BACKGROUND

Animal studies have suggested that an increased supply of omega-3 long chain polyunsaturated fatty acids (LCPUFA), in particular docosahexaenoic acid (DHA), during the perinatal period can prevent later excess body fat mass. However, previous human studies have produced inconsistent findings, and few have assessed potential effects beyond 6 years of age.

OBJECTIVE

To evaluate the effect of supplementing women in the second half of pregnancy with omega-3 LCPUFA, chiefly as DHA, on the percentage body fat of children at 7 years of age, as assessed by two methods: air displacement plethysmography (BOD POD) and bioelectrical impedance spectroscopy (BIS).

DESIGN

A time-restricted follow up at 7 years of age of children born to mothers enrolled in DOMInO (DHA to Optimise Maternal Infant Outcome) randomized controlled trial, in which women took either high-DHA tuna oil (800mg/day DHA) or placebo capsules from 20 weeks' gestation to delivery, at Adelaide-based centers. Primary outcomes were the percentage body fat at 7 years of age as assessed by both BOD POD and BIS. Weight, height, waist/hip circumferences and BMI were also recorded.

RESULTS

A total of 252 DOMInO children (n=135 males, n=117 females) completed the follow up study. There were no differences between the DHA and placebo groups in percentage body fat as assessed by either BOD POD [adjusted mean difference: -0.35, 95% CI: -1.46, 2.16; P=0.71] or BIS [adjusted mean difference: 0.64, 95% CI: -0.99, 2.27; P=0.44]. BMI z-scores were also similar between groups [adjusted mean difference: 0.18, 95% CI: -0.10, 0.45; P=0.21]. There were also no differences in height, weight or waist and hip circumference between the DHA and placebo groups at 7 years of age.

CONCLUSION

DHA supplementation in the second half of pregnancy has no effect on childhood growth or fat mass at 7 years of age, supporting findings from follow ups of the DOMInO children at 3 and 5 years.

Air displacement plethysmography (pea pod) in full-term and pre-term infants: a comprehensive review of accuracy, reproducibility, and practical challenges

Air displacement plethysmography (ADP) has been widely utilised to track body composition because it is considered to be practical, reliable, and valid. Pea Pod is the infant version of ADP that accommodates infants up to the age of 6 months and has been widely utilised to assess the body composition of full-term infants, and more recently pre-term infants. The primary goal of this comprehensive review is to 1) discuss the accuracy/reproducibility of Pea Pod in both full- and pre-term infants, 2) highlight and discuss practical challenges and potential sources of measurement errors in relation to Pea Pod operating principles, and 3) make suggestions for future research direction to overcome the identified limitations.

Hand-to-foot bioelectrical impedance analysis to measure fat mass in healthy children: A comparison with air-displacement plethysmography

AIM

To identify children at risk of overweight, assessing children's body composition in a valid way is crucial. The present cross-sectional study examines the comparability of children's fat mass percentage obtained by hand-to-foot bioelectrical impedance analysis (BIA) versus BodPod air-displacement plethysmography as a reference method.

METHODS

The body composition of 206 Belgian children (7-13 years; 7.7% overweight) was measured with BodPod and hand-to-foot BIA (Tanita BC418 with built-in formula).

RESULTS

Overall, comparability was the highest in girls. Good ranking agreement (rho = 0.819) and interchangeability (intra-class correlation (ICC) = 0.757) were found in girls but not in boys (rho = 0.568; ICC = 0.512). Although bioelectrical impedance resulted in an overall overestimation of only 0.5 fat%, it underestimated and overestimated fat% in children with, respectively, higher and lower fat%. The 95% limits of agreement distance was around 17 fat%, and there was a significant difference from the line of identity (intercept ≠ 0; slope ≠ 1).

CONCLUSIONS

Despite good ranking agreement, the use of BIA as an alternative for the BodPod is not recommended because of over-/underestimation and wide limits of agreement. It is not possible to calculate a simple correction factor for the whole fat% range to make the two approaches interchangeable.

Fat Tissue Accretion in Children and Adolescents: Interplay between Food Responsiveness, Gender, and the Home Availability of Snacks

The appetitive trait “food responsiveness” is assumed to be a risk factor for adiposity gain primarily in obesogenic environments. So far, the reported results are inconsistent in school-aged children, possibly because these studies did not take into account important moderators such as gender and the food-environment. In order to better inform caregivers, clinicians and the developers of targeted obesity-prevention interventions on the conditions in which food responsiveness precedes adiposity gain, the current study investigated if this relationship is stronger in girls and in children exposed to a higher home availability of energy-dense snacks. Age- and sex-independent Fat and Lean Mass Index z-scores were computed based on air-displacement plethysmography at baseline and after 2 years in a community sample of 129 children (48.8% boys) aged 7.5–14 years at baseline. Parents reported at baseline on children's food responsiveness and the home availability of energy-dense snacks. Food responsiveness was a significant predictor of increases in Fat Mass Index z-scores over 2 years in girls but not boys. The home availability of energy-dense snacks did not significantly moderate the relation of food responsiveness with Fat Mass Index z-score changes. The results suggest that food responsiveness precedes accelerated fat tissue accretion in girls, and may inform targeted obesity-prevention interventions. Further, future research should investigate to which food-environmental parameters children high in food responsiveness mainly respond.

Body fat evolution as predictor of retinal microvasculature in children

OBJECTIVES

Microvascular changes may represent an underlying mechanism through which overweight contributes to cardiovascular disease development. Therefore, the aim of this study was to investigate whether changes in children's body fat over time are associated with the retinal microvasculature, a marker of cardiovascular aging.

METHODS

In a longitudinal design, 171 healthy Flemish children (53.8% boys) were followed-up for 7 years (2008-2015), aged 2.7-8.1 years at baseline.Z-scores of body mass index (zBMI; 4.1% overweight), waist circumference (zWC) and fat mass index (zFMI by BODPOD) were obtained using standardized protocols during each visit. Retinal arteriolar (central retinal arteriolar equivalent (CRAE)) and venular equivalents (central retinal venular equivalent (CRVE)) were measured from digital retinal photographs (2015) using IVAN software. Cross-sectional and longitudinal associations between changes in body fat and retinal microvasculature were explored using multivariable regression analysis, while controlling for age, sex, mean arterial pressure, alternate retinal caliber, physical activity, diet and birth weight.

RESULTS

In cross-sectional analysis, children with high zFMI had a higher CRVE, but only in boys (β=0.25, P=0.02). In addition, boys with high zFMI had also a lower CRAE to CRVE ratio (β=-0.26, P=0.03). No associations were seen with the CRAE, or between zBMI or zWC and the retinal microvasculature. Only changes in zFMI over time were found to be positively associated with the CRVE in boys (β=0.38, P=0.01).

CONCLUSIONS

Our analysis over a 7-year period shows that changes in body fat during childhood are already associated with the CRVE (especially in boys).

Fat and lean tissue accretion in relation to reward motivation in children

'Reward sensitivity' explains inter-individual differences in the motivation to obtain rewards when reward cues are perceived. This psychobiological trait has been linked to higher consumption of palatable food when exposed to palatable food cues. The current study aims to examine if reward sensitivity explains differences in patterns of fat and lean tissue accretion over time in children. A longitudinal observational study with measurement waves in 2011 (baseline), 2012, 2013, and 2015 was conducted. The sample was a population-based Flemish cohort of children (n = 446, 50% boys and 5.5-12 years at baseline; 38.8% of the baseline sample also participated in 2015). Baseline reward sensitivity of the children was assessed by parent ratings on the Drive subscale of the Behavioral Inhibition System/Behavioral Approach System scales. Age- and sex-independent Fat and Lean Mass Index z-scores (zFMI and zLMI respectively) were computed for each study wave based on air-displacement plethysmography. In girls, but not boys, reward sensitivity was positively associated with the baseline zFMI and zLMI (95% confidence intervals of unstandardized estimates: 0.01 to 0.11 and 0.01 to 0.10 respectively, P values 0.01 and 0.02 respectively). Further, reward sensitivity explained 14.8% and 11.6% of the change in girls' zFMI and zLMI respectively over four years: the zFMI and zLMI increased and decreased respectively in high reward sensitive girls (95% confidence intervals of unstandardized estimates: 0.01 to 0.11 and -0.12 to -0.01 respectively, P values 0.01 and 0.02 respectively). Hence, girls high in reward sensitivity had significantly higher adiposity gain over four years parallel with lower increase in lean mass than was expected on the basis of their age and height. These results may help to identify appropriate targets for interventions for obesity prevention.

Percentage of body fat in adolescents with Down syndrome: Estimation from skinfolds

BACKGROUND

Adolescents with Down syndrome (DS) have a unique morphology and body shape, and this needs to be taken into account when assessing body fat percentage (BF%).

OBJECTIVE

To develop a predictive equation from anthropometric variables (skinfolds) for estimating BF% in adolescents with DS.

METHODS

Twenty-three adolescents with DS (7 girls, 16 boys) participated in the study; seven skinfold measurements were taken (biceps, triceps, subscapular, supraspinale, abdominal, front thigh, and medial calf), circumferences and diameters were measured following ISAK recommendations. Total body volume (and then body density) was measured with air displacement plethysmography (ADP); BF% was then calculated. Correlation between anthropometry data and BF% by ADP, and stepwise regression analyses were applied to develop a specific prediction equation.

RESULTS

All the skinfolds, BMI, hip, waist and thigh circumferences correlated with BF% and were included in the regression analysis; sex and triceps were added into the model (R² = 0.89, p < 0.05). Therefore the proposed equation computed as follows: BF% = (0.97 TR) - (8.869·SEX) + 15.6 where TR is triceps skinfolds (mm) and SEX is equal to 0 for female and 1 for male.

CONCLUSIONS

The proposed prediction equation is recommended for the assessment of BF% in adolescents with DS as it is the only one specifically developed and validated in this unique population. It is a cheap, reliable and accessible method that removes the need for use of expensive equipment.

The impact of body fat on three dimensional motion of the paediatric foot during walking

Childhood obesity is commonly associated with a pes planus foot type and altered lower limb joint function during walking. However, limited information has been reported on dynamic intersegment foot motion with the level of obesity in children. The aim of this study was to explore the relationships between intersegment foot motion during gait and body fat in boys age 7-11 years. Fat mass was measured in fifty-five boys using air displacement plethysmography. Three-dimensional gait analysis was conducted on the right foot of each participant using the 3DFoot model to capture angular motion of the shank, calcaneus, midfoot and metatarsals. Two multivariate statistical techniques were employed; principle component analysis reduced the multidimensional nature of gait analysis, and multiple linear regression analysis accounted for potential confounding factors. Higher fat mass predicted greater plantarflexion of the calcaneus during the first half and end of stance phase and at the end of swing phase. Greater abduction of the calcaneus throughout stance and swing was predicted by greater fat mass. At the midfoot, higher fat mass predicted greater dorsiflexion and eversion throughout the gait cycle. The findings present novel information on the relationships between intersegment angular motion of the foot and body fat in young boys. The data indicates a more pronated foot type in boys with greater body fat. These findings have clinical implications for pes planus and a predisposition for pain and discomfort during weight bearing activities potentially reducing motivation in obese children to be physically active.

The influence of dairy consumption and physical activity on ultrasound bone measurements in Flemish children

The study's aim was to analyse whether children's bone status, assessed by calcaneal ultrasound measurements, is influenced by dairy consumption and objectively measured physical activity (PA). Moreover, the interaction between dairy consumption and PA on bone mass was studied. Participants of this cross-sectional study were 306 Flemish children (6-12 years). Body composition was measured with air displacement plethysmography (BodPod), dairy consumption with a Food Frequency Questionnaire, PA with an accelerometer (only in 234 of the 306 children) and bone mass with quantitative ultrasound, quantifying speed of sound (SOS), broadband ultrasound attenuation (BUA) and Stiffness Index (SI). Regression analyses were used to study the associations between dairy consumption, PA, SOS, BUA and SI. Total dairy consumption and non-cheese dairy consumption were positively associated with SOS and SI, but no significant association could be demonstrated with BUA. In contrast, milk consumption, disregarding other dairy products, had no significant effect on calcaneal bone measurements. PA [vigorous PA, moderate to vigorous physical activity (MVPA) and counts per minute] was positively associated and sedentary time was negatively associated with BUA and SI, but no significant influence on SOS could be detected. Dairy consumption and PA (sedentary time and MVPA) did not show any interaction influencing bone measurements. In conclusion, even at young age, PA and dairy consumption positively influence bone mass. Promoting PA and dairy consumption in young children may, therefore, maximize peak bone mass, an important protective factor against osteoporosis later in life.

The ability of the PACER to elicit peak exercise response in youth [corrected]

PURPOSE

A graded exercise test (GXT) is the standard laboratory method of determining peak aerobic fitness (V˙O2peak). The FITNESSGRAM's Progressive Aerobic Cardiovascular Endurance Run (PACER) test is commonly used to estimate the peak oxygen consumption in the youth in the field.The objective of this study is to compare the peak physiological variables and RPEpeak during a treadmill GXT and the PACER test in 10- to 15-yr-old youths.

METHODS

Participants (20 boys and 25 girls, 12.7 ± 1.7 yr) completed the PACER and treadmill GXT in a randomized order, separated by at least 24 h. HRpeak was measured via telemetry, V˙O2peak and RERpeak were measured using a portable metabolic system, and participants reported RPEpeak at the end of each test.

RESULTS

No significant differences were found between the GXT and PACER HRpeak (197 vs 197 beats·min), RERpeak (1.13 vs 1.12), V˙O2peak (45.0 vs 45.9 mL·kg·min), and RPEpeak (8.4 vs 8.3). The SE of the measurement between the GXT V˙O2peak and PACER V˙O2peak was 1.4 mL·kg·min.

CONCLUSIONS

It appears that the PACER elicits similar peak exercise responses compared with a treadmill GXT. The PACER can also be administered for fitness and functional capacity assessments in healthy and clinical populations.

Caucasian children's fat mass: routine anthropometry v. air-displacement plethysmography

The present paper will use fat mass percentage (FM%) obtained via BOD POD® air-displacement plethysmography (FMADP%) to examine the relative validity of (1) anthropometric measurements/indices and (2) of FM% assessed with equations (FMeq%) based on skinfold thickness and bioelectrical impedance (BIA). In 480 Belgian children (aged 5–11 years) weight, height, skinfold thickness (triceps and subscapular), body circumferences (mid-upper arm, waist and hip), foot-to-foot BIA (Tanita®) and FMADP% were measured. Anthropometric measurements and calculated indices were compared with FMADP%. Next, published equations were used to calculate FMeq% using impedance (equations of Tanita®, Tyrrell, Shaefer and Deurenberg) or skinfold thickness (equations of Slaughter, Goran, Dezenberg and Deurenberg). Both indices and equations performed better in girls than in boys. For both sexes, the sum of skinfold thicknesses resulted in the highest correlation with FMADP%, followed by triceps skinfold, arm fat area and subscapular skinfold. In general, comparing FMeq% with FMADP% indicated mostly an age and sex effect, and an increasing underestimation but less dispersion with increasing FM%. The Tanita® impedance equation and the Deurenberg skinfold equation performed the best, although none of the used equations were interchangeable with FMADP%. In conclusion, the sum of triceps and subscapular skinfold thickness is recommended as marker of FM% in the absence of specialised technologies. Nevertheless, the higher workload, cost and survey management of an immobile device like the BOD POD® remains justified.

Air-displacement plethysmography pediatric option in 2-6 years old using the four-compartment model as a criterion method

The objective of this study was to determine the accuracy, precision, bias, and reliability of percent fat (%fat) determined by air-displacement plethysmography (ADP) with the pediatric option against the four-compartment model in 31 children (4.1 ± 1.2 years, 103.3 ± 10.2 cm, 17.5 ± 3.4 kg). %Fat was determined by (BOD POD Body Composition System; COSMED USA, Concord, CA) with the pediatric option. Total body water (TBW) was determined by isotope dilution ((2)H(2)O; 0.2 g/kg) while bone mineral was determined by dual-energy X-ray absorptiometry (DXA) (Lunar iDXA v13.31; GE, Fairfield, CT and analyzed using enCore 2010 software). The four-compartment model by Lohman was used as the criterion measure of %fat. The regression for %fat by ADP vs. %fat by the four-compartment model did not deviate from the line of identity where: y = 0.849(x) + 4.291. ADP explained 75.2% of the variance in %fat by the four-compartment model while the standard error of the estimate (SEE) was 2.09 %fat. The Bland-Altman analysis showed %fat by ADP did not exhibit any bias across the range of fatness (r = 0.04; P = 0.81). The reliability of ADP was assessed by the coefficient of variation (CV), within-subject SD, and Cronbach's α. The CV was 3.5%, within-subject SD was 0.9%, and Cronbach's α was 0.95. In conclusion, ADP with the pediatric option is accurate, precise, reliable, and without bias in estimating %fat in children 2-6 years old.

Air-displacement plethysmography for the measurement of body composition in children aged 6-48 months

INTRODUCTION

Air-displacement plethysmography (ADP) is an age-appropriate method for measuring relative fat mass (%FM) in children; however, the accuracy of this method has not been evaluated in children aged 5 y or younger.

RESULTS

Mean %FM values measured by ADP (17.9 ± 8.0%) and by total body water (TBW) (23.7 ± 6.3%) were significantly different (P < 0.001). Regression analysis of %FM by ADP vs. TBW provided a line of best fit with a slope of 0.089, r(2) = 0.013, and standard error of the estimate (SEE) = 6.3% FM (P = 0.40).

DISCUSSION

The error was related to child weight and %FM, but not to behaviors (movement or vocalizations) occurring during the test sequence. A large portion of the error was attributable to imprecision in measuring small volumes. As currently designed, ADP is not an accurate method for measuring %FM in young children. Further investigation of the sources of variability will provide insight into ways of improving the accuracy of this technology for this population.

METHODS

This study examined the accuracy of an ADP system modified for young children (BOD POD; Life Measurement, Concord, CA) by comparing %FM results from ADP with those obtained from TBW by deuterium (D(2)O) dilution (reference method) in 72 children aged 6-48 mo.

Paradoxical Increase in Arterial Compliance in Obese Pubertal Children

We determined whether arterial compliance measured by pulse wave analysis is impaired in obese pubertal children compared to normal weight controls, and assessed whether arterial compliance is associated with ambulatory activity. Body fat percentage was significantly different between the normal (n = 33) and obese (n = 34) participants ( P < .001). Large ( P = .012) and small ( P < .001) arterial compliance were lower in the normal-weight group. After adjusting for height, systolic and diastolic blood pressure, race, sex, and Tanner stage, large arterial compliance was no longer different between groups ( P = .066), whereas small arterial compliance remained higher in the obese group ( P < .001). Obese pubertal children have paradoxically increased small arterial compliance compared to that of normal weight children, even after adjusting for height, blood pressure, race, sex, and Tanner stage. Thus, obesity in adolescence is not associated with impairments in small arterial compliance.

Whole body composition analysis by the BodPod air-displacement plethysmography method in children with phenylketonuria shows a higher body fat percentage

BACKGROUND

Phenylketonuria (PKU) causes irreversible central nervous system damage unless a phenylalanine (PHE) restricted diet with amino acid supplementation is maintained. To prevent growth retardation, a protein/amino acid intake beyond the recommended dietary protein allowance is mandatory. However, data regarding disease and/or diet related changes in body composition are inconclusive and retarded growth and/or adiposity is still reported. The BodPod whole body air-displacement plethysmography method is a fast, safe and accurate technique to measure body composition.

AIM

To gain more insight into the body composition of children with PKU.

METHODS

Patients diagnosed with PKU born between 1991 and 2001 were included. Patients were identified by neonatal screening and treated in our centre. Body composition was measured using the BodPod system (Life Measurement Incorporation©). Blood PHE values determined every 1-3 months in the year preceding BodPod analysis were collected. Patients were matched for gender and age with data of healthy control subjects. Independent samples t tests, Mann-Whitney and linear regression were used for statistical analysis.

RESULTS

The mean body fat percentage in patients with PKU (n = 20) was significantly higher compared to healthy controls (n = 20) (25.2% vs 18.4%; p = 0.002), especially in girls above 11 years of age (30.1% vs 21.5%; p = 0.027). Body fat percentage increased with rising body weight in patients with PKU only (R = 0.693, p = 0.001), but did not correlate with mean blood PHE level (R = 0.079, p = 0.740).

CONCLUSION

Our data show a higher body fat percentage in patients with PKU, especially in girls above 11 years of age.

The recognition and treatment of growth disorders - a 50-year retrospective

The past 50 years have seen great progress in the understanding and treatment of classic growth disorders. Advances such as the recognition of hormone receptor defects, the development of recombinant growth hormone, and the expanding awareness of epigenetic phenomena affecting growth are among these great achievements. Yet growth failure remains a pervasive problem among children with complex health conditions, such as survivors of childhood cancers, premature infants, organ transplant recipients, and children with cystic fibrosis. The significant increases in life expectancy among these groups underscores the potential consequences of poor growth, whether due to the underlying conditions or medical treatments, as they may have long-lasting effects into adulthood. The ongoing contributions of human biologists to the study of human growth remain essential in the recognition and treatment of growth disorders, by defining normal patterns of growth and body composition, the interplay of growth and maturation, the role of environmental, behavioral and genetic factors, and the long-term consequences of growth patterns. Examples will be given based on two common genetic disorders, cystic fibrosis and sickle-cell anemia, to highlight the relationships between growth failure, survival, and malnutrition. Also, a study of bone mineral accretion in children with cystic fibrosis will illustrate the importance of understanding patterns of growth in healthy children, and their application in the diagnosis and management of children with chronic disease. These examples accentuate the need for continued participation of human biologists in the study of growth and development and the care of children.

Interaction of clothing and body mass index affects validity of air-displacement plethysmography in adults

OBJECTIVE

We determined the effect of clothing type on the validity of air-displacement plethysmography (ADP) to estimate percentage of body fat (%BF) and ascertain if these effects differ by body mass index (BMI).

METHODS

The %BF by dual x-ray absorptiometry (DXA) and %BF, density, and body volume by ADP were assessed in 132 healthy adults classified by normal (N; 18.5-24.9 kg/m2), overweight (OW; 25-29.9 kg/m2), and obese (OB; 30-39.9 kg/m2) BMIs.

RESULTS

Compared with DXA, ADP underestimated (P < 0.0001) %BF from scrubs (SC) and t-shirt/shorts (TS) in N (11.4%; 8.6%) and OW (6.8%; 4.9%) BMI groups, respectively. ADP compared with DXA overestimated (P < 0.0006) %BF in the OW group (1.2%), but underestimated (P < 0.0001) it in the N group (2.4%). ADP also overestimated (P < 0.006) %BF in the OB group wearing spandex (SP; 4.8%), but not in those wearing SC (0.7%; P = 0.10) and TS (0.5%; P = 0.22) versus DXA.

CONCLUSION

All three clothing types showed significant error in estimating %BF with ADP compared with DXA in N and OW BMI. Use of spandex provided the least error and is the preferred attire to obtain valid body composition results when testing N and OW subjects. However, SP provided the greatest error in the OB group. Error in ADP %BF in OB was minimal in SC and TS and similar to the within-subject variability in %BF estimates with ADP. Thus, TS and SC are acceptable alternatives to SP in adults with excess body weight.

Fetal programming of body dimensions and percentage body fat measured in prepubertal children with a 4-component model of body composition, dual-energy X-ray absorptiometry, deuterium dilution, densitometry, and skinfold thicknesses

BACKGROUND

Intrauterine programming of body composition [percentage body fat (%BF)] has been sparsely examined with multiple independent reference techniques in children. The effects on and consequences of body build (dimensions, mass, and length of body segments) are unclear.

OBJECTIVE

The study examined whether percentage fat and relation of percentage fat to body mass index (BMI; in kg/m2) in prepubertal children are programmed during intrauterine development and are dependent on body build. It also aimed to examine the extent to which height can be predicted by parental height and birth weight.

DESIGN

Eighty-five white children (44 boys, 41 girls; aged 6.5-9.1 y) had body composition measured with a 4-component model (n = 58), dual-energy X-ray absorptiometry (n = 84), deuterium dilution (n = 81), densitometry (n = 62), and skinfold thicknesses (n = 85).

RESULTS

An increase in birth weight of 1 SD was associated with a decrease of 1.95% fat as measured by the 4-component model (P = 0.012) and 0.82-2.75% by the other techniques. These associations were independent of age, sex, socioeconomic status, physical activity, BMI, and body build. Body build did not decrease the strength of the associations. Birth weight was a significantly better predictor of height than was self-reported midparental height, accounting for 19.4% of the variability at 5 y of age and 10.3% at 7.8 y of age (17.8% and 8.8% of which were independent of parental height at these ages, respectively).

CONCLUSIONS

Consistent trends across body-composition measurement techniques add strength to the suggestion that percentage fat in prepubertal children is programmed in utero (independently of body build and BMI). It also suggests birth weight is a better predictor of prepubertal height than is self-reported midparental height.

Methodological agreement between two-compartment body-composition methods in children

Increases in childhood obesity have emphasized the importance of accurate and accessible body composition assessment, especially in monitoring prevention and treatment efforts. Previous pediatric studies, comparing measures from air-displacement plethysmography (ADP) to dual-energy X-ray absorptiometry (DXA) and anthropometry (ANTH, skinfold measures), were performed in small numbers of children or in children across large age and body-size ranges. The objectives of this study were: 1) to compare body fat percentage (%BF), fat mass (FM), and fat-free mass (FFM) from ADP with DXA and ANTH, to determine the agreement between techniques; 2) to identify factors that influence agreement or lack of agreement; and 3) to determine if the agreement is constant over a range of body fatness. Healthy children (n = 125), 7-10 years old, participating in a longitudinal pediatric bone health study, were evaluated. Body composition was assessed by ADP, DXA, and ANTH to determine %BF, FM, and FFM. ADP underestimated %BF compared to DXA and ANTH by 5.0% and 1.4%, respectively. Agreement between techniques was influenced by body fatness, height, age, and gender (all P < 0.05). Relatively good agreement was observed between ADP and both DXA and ANTH for FM and FFM. In conclusion, the underestimation of %BF by ADP compared to DXA may be of a magnitude that is clinically significant, especially when using %BF in children to confirm a diagnosis of obesity. Further development of body-composition techniques for young children need to account for variability in age, gender, and level of fatness.

Statistical validation of air-displacement plethysmography for body composition assessment in children

BACKGROUND

Body composition assessment of children has been hindered by the absence of a safe, quick, and easily tolerated gold standard technique. Existing validation studies of air-displacement plethysmography (ADP) have been based on small, narrowly defined samples, using simple linear regression or Bland-Altman analyses.

AIM

Correlations within a multitrait-multimethod matrix (MTMM) and factor analytic methodologies were used to evaluate ADP as a valid and reliable body composition technique for children.

SUBJECTS AND METHODS

Fat mass (FM), fat-free mass (FFM) and per cent body fat (%BF) were measured in 139 children, 7-10 years old, by ADP, dual energy X-ray absorptiometry (DXA) and anthropometry (ANTH). MTMM and factor analysis were used to compare assessment techniques.

RESULTS

Reliability estimates were lower for ADP than for either ANTH or DXA. Convergent and discriminant correlations between ADP and ANTH or DXA were high for identical as well as non-identical measures. Two body composition factors (Fatness, Leanness) and two technique-related factors (Bod Pod, Anthropometry) were identified.

CONCLUSION

ADP offers a valid and reliable means of assessing body composition in children but does not perform as well as ANTH or DXA. MTMM and factor analytic methodologies offer an effective alternative to assessing body composition.

Validity of new child-specific thoracic gas volume prediction equations for air-displacement plethysmography

BACKGROUND

To determine the validity of the recently developed child-specific thoracic gas volume (TGV) prediction equations for use in air-displacement plethysmography (ADP) in diverse pediatric populations.

METHODS

Three distinct populations were studied: European American and African American children living in Birmingham, Alabama and European children living in Lisbon, Portugal. Each child completed a standard ADP testing protocol, including a measured TGV according to the manufactures software criteria. Measured TGV was compared to the predicted TGV from current adult-based ADP proprietary equations and to the recently developed child-specific TGV equations of Fields et al. Similarly, percent body fat, derived using the TGV prediction equations, was compared to percent body fat derived using measured TGV.

RESULTS

Predicted TGV from adult-based equations was significantly different from measured TGV in girls from each of the three ethnic groups (P < 0.05), however child-specific TGV estimates did not significantly differ from measured TGV in any of the ethnic or gender groups. Percent body fat estimates using adult-derived and child-specific TGV estimates did not differ significantly from percent body fat measures using measured TGV in any of the groups.

CONCLUSION

The child-specific TGV equations developed by Fields et al. provided a modest improvement over the adult-based TGV equations in an ethnically diverse group of children.

Air-displacement plethysmography: here to stay

PURPOSE OF REVIEW

Air-displacement plethysmography holds promise as an alternative to more traditional body composition techniques, although our understanding of air-displacement plethysmography is less than complete. Specifically, factors that influence its validity and application in certain populations, for example children, the obese, and athletes, must be better understood. This review will summarize recent findings on the validity and precision of air-displacement plethysmography and will focus primarily on papers published since 2004, with particular attention on its use in infants.

RECENT FINDINGS

The most significant recent findings in the air-displacement plethysmography literature are mechanistic in nature specifically dealing with measurement issues such as heat, moisture, clothing, and recently, inter-device variability.

SUMMARY

It is important to recognize that air-displacement plethysmography can be a practical instrument in the evaluation of body composition in a wide range of populations. Therefore, based on the body of literature that has emerged, air-displacement plethysmography appears to be a suitable and reliable instrument in the assessment of body composition. Of particular interest is its use in pediatric and obese individuals, areas requiring further study. Research is also needed to help us better understand sources of measurement error.

Comparison of air displacement plethysmography to hydrostatic weighing for estimating total body density in children

BACKGROUND

The purpose of this study was to examine the accuracy of total body density and percent body fat (% fat) using air displacement plethysmography (ADP) and hydrostatic weighing (HW) in children.

METHODS

Sixty-six male and female subjects (40 males: 12.4 +/- 1.3 yrs, 47.4 +/- 14.8 kg, 155.4 +/- 11.9 cm, 19.3 +/- 4.1 kg/m2; 26 females: 12.0 +/- 1.9 yrs, 41.4 +/- 7.7 kg, 152.1 +/- 8.9 cm, 17.7 +/- 1.7 kg/m2) were tested using ADP and HW with ADP always preceding HW. Accuracy, precision, and bias were examined in ADP with HW serving as the criterion method. Lohman's equations that are child specific for age and gender were used to convert body density to % fat. Regression analysis determined the accuracy of ADP and potential bias between ADP and HW using Bland-Altman analysis.

RESULTS

For the entire group (Y = 0.835x + 0.171, R2 = 0.84, SEE = 0.007 g/cm3) and for the males (Y = 0.837x + 0.174, R2 = 0.90, SEE = 0.006 g/cm3) the regression between total body density by HW and by ADP significantly deviated from the line of identity. However in females, the regression between total body density by HW and ADP did not significantly deviate from the line of identity (Y = 0.750x + 0.258, R2 = 0.55, SEE = 0.008 g/cm3). The regression between % fat by HW and ADP for the group (Y = 0.84x + 3.81, R2 = 0.83, SEE = 3.35 % fat) and for the males (Y = 0.84x + 3.25, R2 = 0.90, SEE = 3.00 % fat) significantly deviated from the line of identity. However, in females the regression between % fat by HW and ADP did not significantly deviate from the line of identity (Y = 0.81x + 5.17, R2 = 0.56, SEE = 3.80 % fat). Bland-Altman analysis revealed no bias between HW total body density and ADP total body density for the entire group (R = 0.-22; P = 0.08) or for females (R = 0.02; P = 0.92), however bias existed in males (R = -0.37; P < or = 0.05). Bland-Altman analysis revealed no bias between HW and ADP % fat for the entire group (R = 0.21; P = 0.10) or in females (R = 0.10; P = 0.57), however bias was indicated for males by a significant correlation (R = 0.36; P < or = 0.05), with ADP underestimating % fat at lower fat values and overestimating at the higher % fat values.

CONCLUSION

A significant difference in total body density and % fat was observed between ADP and HW in children 10-15 years old with a potential gender difference being detected. Upon further investigation it was revealed that the study was inadequately powered, thus we recommend that larger studies that are appropriately powered be conducted to better understand this potential gender difference.

Need for optimal body composition data analysis using air-displacement plethysmography in children and adolescents

Air-displacement plethysmography (ADP) is now widely used for body composition measurement in pediatric populations. However, the manufacturer's software developed for adults leaves a potential bias for application in children and adolescents, and recent publications do not consistently use child-specific corrections. Therefore we analyzed child-specific ADP corrections with respect to quantity and etiology of bias compared with adult formulas. An optimal correction protocol is provided giving step-by-step instructions for calculations. In this study, 258 children and adolescents (143 girls and 115 boys ranging from 5 to 18 y) with a high prevalence of overweight or obesity (28.0% in girls and 22.6% in boys) were examined by ADP applying the manufacturer's software as well as published equations for child-specific corrections for surface area artifact (SAA), thoracic gas volume (TGV), and density of fat-free mass (FFM). Compared with child-specific equations for SAA, TGV, and density of FFM, the mean overestimation of the percentage of fat mass using the manufacturer's software was 10% in children and adolescents. Half of the bias derived from the use of Siri's equation not corrected for age-dependent differences in FFM density. An additional 3 and 2% of bias resulted from the application of adult equations for prediction of SAA and TGV, respectively. Different child-specific equations used to predict TGV did not differ in the percentage of fat mass. We conclude that there is a need for child-specific equations in ADP raw data analysis considering SAA, TGV, and density of FFM.