Air Displacement Research Articles

Differences in Body Fat in Athletes Categorized by Resting Metabolic Rate

The purpose of the study was to examine differences in body fat percentage (BF%) across groups stratified by resting metabolic rate (RMR) when normalized to body weight. National Collegiate Athletic Association Division III athletes (n = 190; Age: 19.8 ± 1.4 year; Body Mass: 79.3 ± 20.2 kg; Height: 175.0 ± 9.3 cm, Body Mass Index: 25.6 ± 4.9 kg/m2) participated in this cross-sectional mixed cohort study. Body composition was assessed using air displacement plethysmography. RMR was assessed using indirect calorimetry. For each sex, tertiles were determined and used to create low, moderate, and high relative RMR groups as follows: low (M: <26 kcal/kg; F: <24 kcal/kg), moderate (M: 26.1–29.0 kcal/kg; F: 24.1–27.0 kcal/kg), and high (M: >29.1 kcal/kg; F: >27.1 kcal/kg). The mean ± standard deviation RMR for male and female athletes was 27.9 ± 3.2 and 25.9 ± 2.8 kcals/kg when expressed relative to body weight. When stratified by sex, males in the low RMR group had significantly higher BF% values than those in the moderate (mean difference, [95% confidence intervals]) (7.2, [2.4, 12.0] kcal/kg; p < 0.01) and high RMR groups (7.7, [2.9, 12.5] kcal/kg; p < 0.001). Female athletes in the moderate RMR group had higher body fat percentages than those in the high RMR group (mean difference, [95% confidence intervals]) (5.8, [2.4, 9.2] kcal/kg; p < 0.01). Female athletes in the moderate relative RMR group had higher BF% values than those in the higher relative RMR group (3.3, [−0.1, 6.7] kcal/kg; p = 0.049). Both male and female athletes with a low relative RMR had a higher BF%.

Preeclampsia and Future Implications on Growth and Body Composition in Preterm Infants.

Preeclampsia is associated with intrauterine growth restriction (IUGR), which can lead to impaired postnatal growth and neurodevelopment in preterm infants. Preeclampsia can also occur without IUGR and its impact on postnatal nutrition, growth, and body composition remains not fully investigated to the best of our knowledge. This study included infants born before 37 weeks of gestation who underwent air displacement plethysmography to measure body composition (fat-free mass [FFM] and fat mass [FM]) at term-equivalent age. We compared infants born to mothers with preeclampsia and IUGR (PE-IUGR group) and preeclampsia without IUGR (PE-non-IUGR group) to those born to mothers without preeclampsia (control group). In total, 291 infants were enrolled (control: n = 227; PE-non-IUGR: n = 43; PE-IUGR: n = 21). FFM was significantly lower in the PE-IUGR (mean differences -231 g (IQR: (-373, -88); p < 0.001)) and PE-non-IUGR groups (mean differences -260 g (IQR: (-372, -149); p < 0.001)) in comparison to the control group. FM was not significantly different between the three groups. This study indicates that infants of preeclamptic mothers, even without IUGR, had significantly lower FFM at term-equivalent age compared to the control group. Further research is necessary to determine if these variations can be modified.

Dietary intake, energy availability, and power in men collegiate gymnasts.

The purpose was to examine the prevalence of low energy availability (LEA), explore dietary behaviors in men collegiate gymnasts (n = 14), and investigate the relationships between energy availability (EA), body composition, and plyometric performance. Body composition was measured using air displacement plethysmography. Lower- and upper-body peak power (PWRpeak) and modified reactive strength index (RSImod) were calculated from countermovement jump (CMJ) and plyometric push-up (PP) assessments. Energy expenditure was tracked over 3 days, while daily energy and macronutrient intake were recorded. EA was calculated and used to categorize athletes into LEA and non-LEA groups. Pearson correlation coefficients were used to examine relationships between EA, body composition, and performance metrics. 85.7% of athletes (n = 12) exhibited LEA (20.98 ± 5.2 kcals/kg FFM), with non-LEA athletes (n = 2) marginally surpassing the <30 kcal/kg of fat-free mass (FFM) threshold (30.58 ± 0.2 kcals/kg FFM). The cohort (n = 14) consumed insufficient energy (30.5 ± 4.5 kcal/kg/day) and carbohydrates (3.7 ± 1.1 g/kg/day), resulting in LEA (22.36 ± 5.9 kcal/kg/FFM). EA was not correlated with body composition or performance metrics. A high prevalence of LEA may exist in men gymnasts, largely due to a low relative energy and carbohydrate intake.

Differentially methylated regions interrogated for metastable epialleles associate with offspring adiposity.

Aim: Assess if cord blood differentially methylated regions (DMRs) representing human metastable epialleles (MEs) associate with offspring adiposity in 588 maternal-infant dyads from the Colorado Health Start Study.Materials & methods: DNA methylation was assessed via the Illumina 450K array (~439,500 CpG sites). Offspring adiposity was obtained via air displacement plethysmography. Linear regression modeled the association of DMRs potentially representing MEs with adiposity.Results & conclusion: We identified two potential MEs, ZFP57, which associated with infant adiposity change and B4GALNT4, which associated with infancy and childhood adiposity change. Nine DMRs annotating to genes that annotated to MEs associated with change in offspring adiposity (false discovery rate<0.05). Methylation of approximately 80% of DMRs identified associated with decreased change in adiposity.

MULA, an affordable framework for multifunctional liquid automation in natural- and life sciences with a focus on hardware design, setup, modularity and validation

The implementation of automation has already had a considerable impact on chemical and pharmaceutical industrial laboratories. However, academic laboratories have often been more reluctant to adopt such technology due to the high cost of commercial liquid handling systems, although, in many instances, there would be a huge potential to automate repetitive tasks, resulting in elevated productivity. We present here a detailed description of the setup, validation, and utilization of a multifunctional liquid automation (MULA) system that can be used to automate various chemical and biological tasks. Considering that such a setup must be highly customizable, we also designed MULA with respect to modularity, providing detailed insight as far as possible. Including all 3D-printed parts and the used Hamilton gastight micro syringe, the total construction cost is approximately 700 €. This allows us to achieve a highly reliable and accurate system that exceeds the precision of a classical air displacement pipette while still retaining the ability to use closed vial (septa) setups. To encourage other groups to adopt this setup, detailed instructions and tips for every step of the process are provided, along with the complete CAD design of MULA and control code, which are freely available for download under the CC BY NC 3.0 license.

Body Composition Analysis of the Clinical Routine Using Air Displacement Plethysmography: Age-Group-Specific Feasibility Analysis among Preterm Infants.

Body composition assessments using air displacement plethysmography (ADP, PEAPOD®) have been introduced into clinical practice at a few neonatal units. To allow accurate body composition assessments in term and preterm infants, a workflow for routine testing is needed. The aim of this study was to analyze the feasibility of weekly routine ADP testing. We analyzed (1) postnatal ages at first ADP assessment, (2) the number of weekly routine in-hospital assessments, and (3) the workload of body composition measurements using ADP in clinical practice on the basis of an retrospective analysis of our own clinical operating procedures. The retrospective analysis of weekly routine ADP testing proved feasible at Nuremberg Children's Hospital. The analysis of postnatal age at the first ADP test revealed differences across groups, with extremely preterm infants starting at a mean postmenstrual age of 36.6 weeks, very preterm infants starting at 34.2 weeks, and moderate to late preterm infants starting at 35.3 weeks. The mean number of tests before discharge was significantly greater in the extremely preterm group (n = 3.0) than in the very preterm (n = 2.4) and moderate to late preterm groups (n = 1.7). The workload of the procedure is reasonable, at 8-13 min per test cycle. The study proved that weekly routine ADP assessments in preterm infants are feasible. However, the initiation of routine testing in extremely preterm infants starts at a significantly greater postnatal age than in the more mature population. ADP assessments can be safely and easily integrated into clinical practice and may be valuable tools for providing additional information on nutritional status and infant growth. A standardized routine protocol allowing identical measurement conditions across healthcare institutions and a standardized interpretation tool for age-adapted body composition data, however, would improve comparability and usability.

Anthropometric Formulas Repurposed to Predict Body Fat Content from Ultrasound Measurements of Subcutaneous Fat Thickness

Body composition assessment helps conducting a healthy life or tracking the effectiveness of a weight management therapy. Ultrasound (US)-based body composition research has gained momentum because of the emergence of portable and inexpensive instruments bundled with user-friendly software. Previously, US-based assessment of body fat percentage (% BF) was found precise, but inaccurate in certain populations. Therefore, this study sought to compute % BF from subcutaneous fat thicknesses (SFs) given by US converting an anthropometric formula that involves skinfold thicknesses (SKFs) measured at the same sites. The symmetry of the body with respect to the central sagittal plane is an underlying assumption in both anthropometry and US-based body composition assessment, so measurements were taken on the right side of the body. Relying on experimental data on skinfold compressibility, we adapted 33 SKF formulas for US use and tested their validity against air displacement plethysmography on a study group of 97 women (BMI = 25.4 ± 6.4 kg/m2, mean ± SD) and 107 men (BMI = 26.7 ± 5.7 kg/m2). For both sexes, the best proprietary formula had Lin’s concordance correlation coefficient (CCC) between 0.7 and 0.73, standard error of estimate (SEE) &lt; 3% BF and total error (TE) &gt; 6% BF—mainly because of the underestimation of % BF in overweight and obese subjects. For women (men) the best adapted formula had CCC = 0.85 (0.80), SEE = 3.2% (2.4%) BF, and TE = 4.6% (5.4%) BF. Remarkably, certain adapted formulas were more accurate for overweight and obese people than the proprietary equations. In conclusion, anthropometric equations provide useful starting points in the quest for novel formulas to estimate body fat content from ultrasound measurements.

What About Water? Implications for Body Composition Assessment in Military Personnel.

Sergi, TE, Roberts, BM, and Heileson, JL. What About Water? Implications for Body Composition Assessment in Military Personnel. J Strength Cond Res 38(9): e534-e540, 2024-Body composition standards ensure service members maintain physical fitness, wellness, and support mission readiness. Anthropometric techniques (i.e., height/mass, circumference-based "tape test") have been the primary screening and percent body fat (%BF) assessment method in military personnel for about 4 decades. Recently, the Army and Marine Corps have implemented more advanced body composition assessment methods, such as air displacement plethysmography (ADP), multifrequency bioelectrical impedance analysis (MF-BIA), and dual-energy x-ray absorptiometry (DXA), to serve as supplemental %BF assessment after failing the tape test. Although supplemental assessments are intended to improve on the accuracy and precision of the tape test, preassessment standardization, specifically regarding acute water ingestion (AWI), is lacking. Thus, the purpose of this narrative review was to (a) summarize the available literature regarding the influence of AWI on body composition estimates derived from ADP, MF-BIA, and DXA and (b) provide evidence-based recommendations for researchers and practitioners. Studies indicate that AWI increases %BF estimates with ADP (4 of 6 [4/6] observations) and MF-BIA (6/7), whereas AWI increases muscle mass (6/6) and likely decreases %BF (2/3) when obtained by DXA. In conclusion, ADP, MF-BIA, and DXA are susceptible to confounding from AWI, leading to inaccurate body composition estimates that may negatively affect the careers of military personnel. Based on the findings from this narrative review, military practitioners and researchers should (a) follow manufacturer guidelines for calorie intake [food and fluid] and exercise avoidance, (b) conduct urine-specific gravity testing [if possible], and (c) limit AWI to <250 ml before assessment.

The Relationship of Muscle Dysmorphia with Exercise Addiction, Body Image and Protein Consumption in Male Power and Strength Athletes

Objectıves: Muscle dysmorphia is a psychological problem and its incidence is reported to increase with the effect of many factors. This work; to determine the presence of muscle dysmorphia in adult male power and strength athletes; The study was conducted to evaluate protein consumption, exercise addiction and body image in athletes according to the risk of muscle dysmorphia. Materıals and Methods: The research was conducted with 69 adult male power and strength athletes. General information of the participants, food consumption frequency form, muscle dysmorphia, exercise status, body perceptions were determined using scales and anthropometric measurements were taken with air displacement plethysmography. Results: The rate of athletes with bigorexia was determined as 10.1%. It was determined that as the scores of athletes on the muscle perception disorder scale increased, their exercise addiction and body image coping strategies scale scores increased. It was determined that there was a positive correlation between muscle perception disorder score and protein consumption. On the muscle perception disorder scale, 1 g change in protein consumption; It was determined that a 1-unit change in the total score on the muscle perception disorder scale contributed to positive changes in exercise addiction and body image. Conclusion: It can be concluded that the high muscle perception disorder scores in athletes are directly proportional to exercise addiction, body perception disorders and the amount of protein consumed. It should not be forgotten that power and strength athletes should be analyzed in terms of muscle dysmorphia risk and related factors (such as body image, self-esteem, exercise addiction). It was concluded that a dietician, psychologist and exercise specialist should be included as members of a multidisciplinary team in nutrition and exercise practices.

The usefulness of total body protein mass models for adolescent athletes.

The present study aimed to assess the utility of a less laborious technique for estimating total body protein (TBPro) in young athletes, using a multicomponent model as the criterion method. A total of 88 (49 boys and 39 girls) adolescent athletes (age: 15.2 ± 1.5 years; body mass index: 21.2 ± 2.7 kg/m2) participated. A 6-compartment model was used as the reference method (TBProReference) involving air displacement plethysmography for body volume, dual-energy X-ray absorptiometry (DXA) for bone mineral content, and deuterium dilution for total body water (TBW). Alternatively, DXA TBPro models were used as TBPro = lean-soft mass (LSM) - HFFFM × fat-free mass (FFM) - Ms. - G, where LSM and FFM were assessed using DXA, HFFFM is the hydration fraction of the FFM using measured TBW or assumed TBW (adult fraction of 0.732; Lohman's constants or mean observed HFFFM), Ms. is soft tissue minerals (Ms = 0.0129 × HFFFM × FFM), and G is glycogen calculated as 0.044 × (LSM - HFFFM × FFM - Ms). The maturation level was determined by self-assessment. TBPro obtained from DXA using the assumed HFFFM explained 73% to 77% of the variance compared to TBProReference. Meanwhile, using the mean values of measured HFFFM, the DXA model explained 53 and 36% for boys and girls, respectively. Larger bias (8.6% for boys and 25.8% for girls) and limits of agreement were found for the DXA model using measured HFFFM (boys for 66.9% and girls for 70%) compared to an assumed HFFFM (bias ranged from 1.5% to 22.5% and limits of agreement ranged from 31.3% to 35.3%). Less complex and demanding TBPro DXA models with the assumed HFFFM are valid alternatives for assessing this relevant FFM component in groups of adolescent athletes but are less accurate for individual results. Though future studies should be conducted to test the usefulness of these models in longitudinal and experimental designs, their potential to provide an estimation of protein mass after exercise and diet interventions in young athletes is anticipated.

A two-phase flow model simulating water penetration into pharmaceutical tablets

The purpose of the study is introduce a two-phase flow model to simulate water penetration into pharmaceutical tablets. This model was built by integrating Darcy’s law with the continuity principle, on the premise that water penetration was driven by capillary actions. Notably, this model concerned both the ingress of water (wetting phase) and simultaneous displacement of air (non-wetting phase). Due to the interference of the two fluids, the relative permeability and capillary pressure vary during water penetration. Evolution of these parameters was incorporated in the model. Calibration of the model by water penetration experiments of the microcrystalline cellulose (MCC) tablet yielded an average pore radius of 42 nm. This derived result was corroborated by FIB-SEM analysis revealing the presence of extensive microporosity within MCC particles with an average radius of ∼30 nm. Further validation was achieved through close resemblance between the simulated and experimental water penetration profiles of MCC tablets possessing different porosities. Overall, this study underscored the advantage of the two-phase flow model over single-phase flow models, by capturing the dependence of permeability and capillary pressure on water saturation. Therefore it holds promise for an enhanced description of water penetration into tablets.

Reproducibility of Air Displacement Plethysmography in Term and Preterm Infants-A Study to Enhance Body Composition Analysis in Clinical Routine.

The quality-initiative analysis of weekly duplicate PEAPOD® body composition measurements was conducted from clinical practice (January to September 2021) on preterm and term infants without respiratory support. Statistical analysis, including regression analysis, Bland-Altman plots and cv-root-mean-square tests, was performed. A total of 188 duplicate (376 individual) measurements were collected from 119 infants (88 preterm, 31 term). The median absolute difference between duplicates was 31.5 g for fat-free mass (FFM). Linear correlation analysis showed R2 = 0.97 for FFM. The absolute differences in FFM and fat mass did not significantly correlate with increasing age. The %FFM differed (p = 0.02) across body weight groups of 1 kg < BW ≤ 2 kg (1.8%; IQR: 0.8, 3.6) and BW > 3 kg (0.9%; IQR: 0.3, 2.1). The median absolute differences were 1 g (IQR: 0.4, 3.1) for body weight and 5.6 mL (IQR: 2.1, 11.8) for body volume. Body volume estimation is charged with a constant absolute error, which is the main factor for differences between repeated body composition assessments. This error becomes more prominent in infants with lower body weights. Nevertheless, reproducibility of weekly PEAPOD testing is sufficient to monitor body compartment changes, offering a foundation for nutritional decisions in both preterm and term infants.

Body composition from birth to 6 months in term small-for-gestational-age Indian infants: effect of catch-up growth.

The objective of this prospective observational study was to assess the growth and body composition of term small-for-gestational-age (SGA) infants from birth to 6 months and evaluate the effect of catch-up growth (CUG) on body composition. Term SGA newborns were recruited at birth. Anthropometry and body composition were evaluated at 3 days, 6, 10 and 14 weeks, and 6 months. Fat and fat-free mass (FM and FFM) were compared between infants with and without CUG (increase in weight Z-score by > 0·67) by air displacement plethysmography. Factors that could affect body composition and CUG, including parents' BMI and stature, infants' birth weight, sex and feeding, were evaluated. A total of 143 SGA newborns (sixty-six boys) with birth weight of 2336 (sd 214) g were enrolled; 109 were followed up till 6 months. Median weight Z-score increased from -2·3 at birth to -1·3 at 6 months, with 51·9 % of infants showing CUG. Infants with CUG had higher FM (1796 (sd 491) g v. 1196 (sd 474) g, P < 0·001) but similar FFM (4969 (sd 508) g v. 4870 (sd 622) g, P = 0·380), and consequently higher FM percentage (FM%) (26·5 (sd 5·8) v. 19·7 (sd 6·9), P < 0·001), compared with those without CUG. Lower birth weight, exclusive breast-feeding and higher parental stature were positively associated with CUG. In conclusion, CUG in term SGA infants in the first 6 months of life was almost entirely attributable to greater gain in FM. Follow-up of this cohort will provide insight into the long-term effect of disproportionate gain in FM in early infancy in SGA babies.

Adipokines measured during pregnancy and at birth are associated with infant negative affect

BackgroundIncreased adiposity during pregnancy may be related to offspring risk for mental health disorders, although the biological mechanisms are poorly understood. One promising hypothesis is that factors secreted from adipocytes such as leptin and adiponectin may explain this association. The current study examined whether pregnancy or umbilical cord blood concentrations of leptin and/or adiponectin a) predict elevated infant negative affect at 6 months (an early life marker of risk for psychopathology); and b) help explain the association between pregnancy adiposity and increased infant negative affect. MethodsData came from a prospective cohort (N = 305) of pregnant individuals and their offspring. Second trimester adiposity was assessed using air displacement plethysmography. Concentrations of leptin and adiponectin were measured in second trimester plasma and umbilical cord plasma. Infant negative affect was assessed by standardized observation at 6 months. Second trimester inflammation was assessed using a comprehensive panel of cytokines. ResultsLower second trimester adiponectin was associated with elevated infant negative affect, and mediated the effect of pregnancy adiposity on infant negative affect. This association was independent of the effect of second trimester inflammation. Umbilical cord leptin also predicted higher infant negative affect and mediated the association between pregnancy adiposity and infant negative affect. ConclusionsThis is the first study to link pregnancy adiponectin or cord blood leptin to infant markers of risk for psychopathology, and the first to demonstrate that these adipokines mediate the association between pregnancy adiposity and offspring behavioral outcomes, suggesting novel markers of risk and potential mechanisms of effect.

Association between preterm infant body composition in the first 3months of life and preschool age: a cohort study.

Compared with full-term infants, preterm infants have fat-free mass deficit in the first months of life, which increases the risk of metabolic diseases in the future. In this cohort of children born under 32-week gestational age or less than 1500g, we aimed to evaluate the associations of body composition at term equivalent age and in the first 3months of life with fat-free mass and fat mass percentage at 4 to 7years of life. Body composition assessments by air displacement plethysmography and anthropometry were performed at term, at 3months of corrected age, and at 4 to 7years of age. Multiple linear regression analysis was used to observe the associations between body composition at these ages. At term, fat mass percentage showed a negative association and fat-free mass a positive association with fat-free mass at 4 to 7years. The fat-free mass at 3months and the gain in fat-free mass between term and 3months showed positive associations with fat-free mass at 4 to 7years. Conclusion: Body composition at preschool age is associated with fat-free mass in the first 3months of life, a sensitive period for the risk of metabolic diseases. What is Known: • Preterm infants have a deficit in fat-free mass and high adiposity at term equivalent age compared to full-term infants. • Fat-free mass reflects metabolic capacity throughout life and therefore is considered a protective factor against the risk of metabolic syndrome. What is New: •Fat-free mass gain in the first 3months of corrected age is associated with fat-free mass at preschool and school ages. •The first 3months of life is a sensitive period to the risk of metabolic diseases.

Advancing body composition assessment in patients with cancer: First comparisons of traditional versus multicompartment models

Background and aimsMeasurement of body composition using computed tomography (CT) scans may be a viable clinical tool for low muscle mass assessment in oncology. However, longitudinal assessments are often infeasible with CT. Clinically accessible body composition technologies can be used to track changes in fat-free mass (FFM) or muscle, though their accuracy may be impacted by cancer-related physiological changes. The purpose of this study was to examine the agreement among accessible body composition method with criterion methods for measures of whole-body FFM measurements and, when possible, muscle mass for the classification of low muscle in patients with cancer. MethodsPatients with colorectal cancer were recruited to complete measures of whole-body DXA, air displacement plethysmography (ADP), and bioelectrical impedance analysis (BIA). These measures were used alone, or in combination to construct the criterion multicompartment (4C) mode for estimating FFM. Patients also underwent abdominal CT scans as part of routine clinical assessment. Agreement of each method with 4C model was analyzed using mean constant error (CE = criterion – alternative), linear regression including root mean square error (RMSE), Bland-Altman limits of agreement (LoA) and mean percentage difference (MPD). Additionally, appendicular lean soft tissue index (ALSTI) measured by DXA and predicted by CT were compared for the absolute agreement, while the ALSTI values and skeletal muscle index by CT were assessed for agreement on the classification of low muscle mass. ResultsForty-five patients received all measures for the 4C model and 25 had measures within proximity of clinical CT measures. Compared to 4C, DXA outperformed ADP and BIA by showing the strongest overall agreement (CE = 1.96 kg, RMSE = 2.45 kg, MPD = 98.15 ± 2.38%), supporting its use for body composition assessment in patients with cancer. However, CT cutoffs for skeletal muscle index or CT-estimated ALSTI were lower than DXA ALSTI (average 1.0 ± 1.2 kg/m2) with 24.0% to 32.0% of patients having a different low muscle classification by CT when compared to DXA. ConclusionsDespite discrepancies between clinical body composition assessment and the criterion multicompartment model, DXA demonstrates the strongest agreement with 4C. Disagreement between DXA and CT for low muscle mass classification prompts further evaluation of the measures and cutoffs used with each technique. Multicompartment models may enhance our understanding of body composition variations at the individual patient level and improve the applicability of clinically accessible technologies for classification and monitoring change over time.

Growth and body composition of infants born moderate-to-late preterm fed a protein- and mineral-enriched postdischarge formula compared with a standard term formula until 6 months corrected age, a randomized controlled trial

BackgroundInfants born moderate-to-late preterm (i.e., 32 wk–35 wk 6 d gestation) are, analogous to those born very preterm, at risk of later obesity, hypertension, and diabetes. Appropriate early life nutrition is key for ensuring optimal growth and body composition, thereby mitigating potential cardiometabolic risks. ObjectivesWe aimed to compare growth and body composition between infants born moderate-to-late preterm fed isocaloric but protein- and mineral-enriched postdischarge formula (PDF) or standard term formula (STF) until 6 mo corrected age (CA; i.e., after term equivalent age [TEA]). MethodsAfter enrollment (≤7 d postpartum), infants received PDF if (fortified) mother’s own milk (MOM) was insufficient. At TEA, those receiving >25% of intake as formula were randomized to either continue the same PDF (n = 47) or switch to STF (n = 50); those receiving ≥75% of intake as MOM (n = 60) served as references. At TEA and 6 mo CA, we assessed anthropometry and body composition using both dual-energy x-ray absorptiometry (DXA) and air displacement plethysmography (ADP). ResultsFeeding groups had similar gestational age (median [25th percentile;75th percentile]: 34.3 [33.5; 35.1] wk), birthweight (mean ± standard deviation [SD]: 2175 ± 412 g), anthropometry, and body composition at TEA. At 6 mo CA, infants fed PDF had slightly, but significantly, greater length (67.6 ± 2.5 and 66.9 ± 2.6 cm, P < 0.05) and larger head circumference (43.9 ± 1.3 and 43.4 ± 1.5 cm, P < 0.05) compared to infants fed STF. Also, infants fed PDF had higher lean mass (LM) and bone mineral content estimated by DXA (4772 ± 675 and 4502 ± 741 g; 140 ± 20 and 131 ± 23 g, respectively; P < 0.05). ADP estimates, however, were not statistically different between feeding groups. ConclusionsInfants born moderate-to-late preterm demonstrated modest increases in length, head circumference, LM, and bone mineral content when fed PDF compared to STF for 6 mo after TEA.This trial was registered at the International Clinical Trial Registry Platform as NTR5117 and NTR NL4979.

Determination of resistance at zero and infinite frequencies in bioimpedance spectroscopy for assessment of body composition in babies

Objective. Bioimpedance spectroscopy (BIS) is a popular technique for the assessment of body composition in children and adults but has not found extensive use in babies and infants. This due primarily to technical difficulties of measurement in these groups. Although improvements in data modelling have, in part, mitigated this issue, the problem continues to yield unacceptably high rates of poor quality data. This study investigated an alternative data modelling procedure obviating issues associated with BIS measurements in babies and infants. Approach. BIS data are conventionally analysed according to the Cole model describing the impedance response of body tissues to an applied AC current. This approach is susceptible to errors due to capacitive leakage errors of measurement at high frequency. The alternative is to model BIS data based on the resistance–frequency spectrum rather than the reactance-resistance Cole model thereby avoiding capacitive error impacts upon reactance measurements. Main results. The resistance–frequency approach allowed analysis of 100% of data files obtained from BIS measurements in 72 babies compared to 87% successful analyses with the Cole model. Resistance–frequency modelling error (percentage standard error of the estimate) was half that of the Cole method. Estimated resistances at zero and infinite frequency were used to predict body composition. Resistance-based prediction of fat-free mass (FFM) exhibited a 30% improvement in the two-standard deviation limits of agreement with reference FFM measured by air displacement plethysmography when compared to Cole model-based predictions. Significance. This study has demonstrated improvement in the analysis of BIS data based on the resistance frequency response rather than conventional Cole modelling. This approach is recommended for use where BIS data are compromised by high frequency capacitive leakage errors such as those obtained in babies and infants.

Impact of spatial layout on vertical wind conditions and comfort levels in high-rise residential buildings in Shenzhen

Urban residential areas' rational spatial height distribution plays a crucial role in achieving a more balanced wind speed distribution, smoother air exchange, and improved space comfort. This study used Shenzhen as a representative city to analyse the effect of high-rise residential building layouts on vertical ventilation. Nine typical height-layout schemes were determined within an area of 220 × 200 m. Wind tunnel tests were conducted to validate the accuracy of the enhanced computational fluid dynamics simulations. Various parameters were comprehensively evaluated, including wind speed, wind pressure, mean age of air (MAA), and the universal thermal climate index (UTCI). The results show that different height layout schemes affect the distribution rates of wind speed, wind pressure, MAA, UTCI, and the rate of change with height. Compliance with the building row spacing specification enabled the nine schemes to obtain >83% of the windward wind speed and >48% of the leeward reasonable wind speed; the reasonable wind pressure distribution was >32% higher on the leeward side than that on the windward side. MAA statistics show that the air displacement efficiency per unit volume is generally between 120 and 300 s. >90% of the windward space in the UTCI was comfortable, and >60% of the leeward space felt slightly hot. This study shows the impact of high-rise residential layouts on comfort in hot summer and warm winter areas. It clarifies a reasonable height layout that helps realise the green liveability of residential areas.

Study on the aerodynamic characteristics and ventilation effects of ultra-high-speed elevator car-counterweight system under the influence of multiple parameters

When the ultra-high-speed elevator car-counterweight system runs opposite each other, significant piston effects are caused, seriously affecting the elevator operation's stability. In order to explore the aerodynamic characteristics of the whole operation process of a car-counterweight system under multi-parameters, this study first establishes a three-dimensional transient model of the car-counterweight system and a multi-region dynamic layering numerical simulation method based on this model is proposed. Then, the actual elevator experiment validates the correctness of the model and the method. Finally, the influence rules of key parameters on the car's aerodynamic characteristics and ventilation effect are analyzed, and the car's aerodynamic characteristics at intersection time are analyzed emphatically. The results show that with the increase in the blocking ratio, the pressure drag and viscous drag have similar change trends at each stage, but the influence of pressure drag is more significant. The air displacement ratio increases by 34.1%, 75.8%, and 117.3%, respectively. With the increase in the hoistway height, the air displacement ratio decreases by 0.9%, 2.4%, and 2.9%, respectively. The spacing significantly affects the car's aerodynamic characteristics at the intersection time. The drag peak increases by 6.8%, 13.6%, and 20.5% and the lift peak by 21.2%, 47.8%, and 82.5%, respectively.