Development of novel calibration model(s) to predict whole-body density in professional football players.

INTRODUCTION: Questions continue to be raised about the validity that is in existence to estimate Db, in professional male footballer players. METHODS: Phase 1: n = 28 anthropometric variables were used on n = 206 footballers, using regression analyses to determine standard error of estimate and R2. A cut-off correlation coefficient set at r = 0.950 and 90% R2. Phase 2: all variables (z-scores, x- = 0.0, SD = ±1.0) to help reduce heteroscedasticity, ß, r, t, significance of t and P-values were calculated. Phase 3: a forced stepwise-backwards regression analysis approach with nine predictors which met the acceptance criteria (r = 0.950, R2 = 90% and ß weights) was used to develop a 'best fit' and a 'practical' calibration model. Phase 4: cross-validation of the two newly developed calibration method using LoA. RESULTS: The 'best fit' model SEM (0.115 g ml-1), the highest R2 (6.6%) (P ≤ 0.005), whereas the 'practical' calibration model SEM (0.115 g ml-1), R2 (4.7%) (P ≤ 0.005) with r values = 0.271 and 0.596 and R2 (%) coefficients = 0.3526 for the 'best fit' and 'practical' calibration models, respectively (P = 0.01). CONCLUSIONS: The two calibration models supported an ecologically and statistically valid contribution and can provide sound judgements about professional footballers' body composition.

A comparative study on the reliability and validity of body composition results by impedance method measurement device.

The purpose of this study was to analyze the reliability and validity of the body composition results for each impedance device and use them as primary data for body composition research. Total of 58 participants, including 24 men and 34 women, were recruited. The correlation was analyzed by measuring two repetitive measurements for each device. Dual energy x-ray absorptiometry (DEXA) equipment was used as reference equipment for body composition research. All data were analyzed as IBM SPSS Statistics ver. 25.0, and the validity and reliability were estimated by calculating the timely correlation coefficient. As a result of the study, repeated measurements of the measuring instrument showed high reliability by gender and age, especially in the child age group, with relatively higher reliability than those in their 50s or older. In the validity analysis between DEXA, in the case of the male group, the validity of the fat mass amount was relatively higher than the body fat amount and body fat rate. In the case of the women's group, the validity of the body fat amount and body fat rate was relatively higher than that of the fat mass amount. The company B had the highest validity for body fat rate and body fat amount in both men and women. However, the validity for men's fat mass amount was the lowest. In subsequent studies, it is believed that studies that have expanded the population further and studies targeting special groups such as athletes should be conducted.

Deep dives and high tissue density increase mean dive costs in California sea lions (Zalophus californianus).

Diving is central to the foraging strategies of many marine mammals and seabirds. Still, the effect of dive depth on foraging cost remains elusive because energy expenditure is difficult to measure at fine temporal scales in wild animals. We used depth and acceleration data from eight lactating California sea lions (Zalophus californianus) to model body density and investigate the effect of dive depth and tissue density on rates of energy expenditure. We calculated body density in 5 s intervals from the rate of gliding descent. We modeled body density across depth in each dive, revealing high tissue densities and diving lung volumes (DLVs). DLV increased with dive depth in four individuals. We used the buoyancy calculated from dive-specific body-density models and drag calculated from swim speed to estimate metabolic power and cost of transport in 5 s intervals during descents and ascents. Deeper dives required greater mean power for round-trip vertical transit, especially in individuals with higher tissue density. These trends likely follow from increased mean swim speed and buoyant hinderance that increasingly outweighs buoyant aid in deeper dives. This suggests that deep diving is either a 'high-cost, high-reward' strategy or an energetically expensive option to access prey when prey in shallow waters are limited, and that poor body condition may increase the energetic costs of deep diving. These results add to our mechanistic understanding of how foraging strategy and body condition affect energy expenditure in wild breath-hold divers.

What Is a 2021 Reference Body?

The historical 1975 Reference Man is a 'model' that had been used as a basis for the calculation of radiation doses, metabolism, pharmacokinetics, sizes for organ transplantation and ergonomic optimizations in the industry, e.g., to plan dimensions of seats and other formats. The 1975 Reference Man was not an average individual of a population; it was based on the multiple characteristics of body compositions that at that time were available, i.e., mainly from autopsy data. Faced with recent technological advances, new mathematical models and socio-demographic changes within populations characterized by an increase in elderly and overweight subjects a timely 'state-of-the-art' 2021 Reference Body are needed. To perform this, in vivo human body composition data bases in Kiel, Baton Rouge, San Francisco and Honolulu were analyzed and detailed 2021 Reference Bodies, and they were built for both sexes and two age groups (≤40 yrs and >40 yrs) at BMIs of 20, 25, 30 and 40 kg/m2. We have taken an integrative approach to address 'structure−structure' and 'structure−function' relationships at the whole-body level using in depth body composition analyses as assessed by gold standard methods, i.e., whole body Magnetic Resonance Imaging (MRI) and the 4-compartment (4C-) model (based on deuterium dilution, dual-energy X-ray absorptiometry and body densitometry). In addition, data obtained by a three-dimensional optical scanner were used to assess body shape. The future applications of the 2021 Reference Body relate to mathematical modeling to address complex metabolic processes and pharmacokinetics using a multi-level/multi-scale approach defining health within the contexts of neurohumoral and metabolic control.

Combining Anthropometry and Bioelectrical Impedance Analysis to Predict Body Fat in Female Athletes.

CONTEXT: Accurate methods for predicting the percentage of body fat (%Fat) in female athletes are needed for those who lose weight before competition. Methods mandated by sport governing bodies for minimal weight determination in such athletes lack validation. OBJECTIVE: To (1) determine whether combining anthropometry using skinfold (SF) thicknesses and bioelectrical impedance analysis (BIA) in a 3-compartment (3C) model would improve the prediction of %Fat in female athletes and (2) evaluate the Slaughter SF equation. DESIGN: Cross-sectional study. SETTING: Laboratory-based study during the preseason for collegiate sports. PARTICIPANTS: A total of 18 National Collegiate Athletic Association Division I female athletes were recruited from swim and gymnastics teams. MAIN OUTCOME MEASURE(S): We measured %Fat based on a 4-compartment (4C) criterion incorporating body density (air-displacement plethysmography), total body water (D2O dilution), and bone mineral mass (dual-energy x-ray absorptiometry) compared with predicted %Fat using SF alone (Slaughter equation), BIA (single frequency for total body water estimate), and combined SF and BIA (3C model). RESULTS: For the %Fat determined using the 4C criterion, the highest adjusted coefficient of determination and lowest prediction error (r2; ±standard error of estimate) were for the 3C model (r2 = 0.87; ±2.8%), followed by BIA (r2 = 0.80; ±3.5%) and SF (r2 = 0.76; ±3.8%; P values < .05 for all). Means differed for the %Fat determined using BIA (26.6% ± 7.5%) and the 3C (25.5% ± 7.2%) versus 4C model (23.5% ± 7.4%; analysis of variance and post hoc analyses: P values < .05). The SF estimate (24.0% ± 7.8%) did not differ from the 4C value. CONCLUSIONS: Combining SF and BIA might improve the prediction and lower the prediction error for determining the %Fat in female athletes compared with using SF or BIA separately. Regardless, the Slaughter equation for SF appeared to be accurate for determining the mean %Fat in these female athletes.

Major risk factors for obstructive sleep apnea monitored in the home. A cross-sectional study

ABSTRACT BACKGROUND: Obstructive sleep apnea (OSA) is characterized by recurrent pharyngeal wall collapse during sleep caused by anatomical or functional changes associated with obesity or dislocation of maxillofacial structures. OBJECTIVE: To determine the major risk factors for obstructive sleep apnea monitored in the home. DESIGN AND SETTING: Cross-sectional study conducted in a private clinic in Fortaleza (CE), Brazil. METHODS: Between 2015 and 2018, 427 patients were screened for OSA with home-based monitoring, yielding 374 positives. Information was collected on age, sex, body mass index (BMI), hypertension, diabetes (DM), dyslipidemia, coronary artery disease (CAD), arrhythmia, peripheral artery occlusive disease (PAOD), heart failure (HF) and lung disease. The home sleep apnea test result was then compared with the clinical diagnosis. Lastly, parameters identified as significant in the univariate analysis were subjected to multivariate logistic regression. RESULTS: Male sex predominated, although not significantly. OSA was associated with hypertension, DM, dyslipidemia, age and BMI. The risk of OSA being associated with these parameters was 2.195 (hypertension), 11.14 (DM), 2.044 (dyslipidemia) and 5.71 (BMI). The association was also significant for BMI categories (normal, overweight or obese). No significant association was observed for CAD, arrhythmia, PAOD, HF or lung disease. After multivariate logistic analysis, only age and BMI (and its categories) remained significant. CONCLUSION: OSA was associated with hypertension, DM, dyslipidemia, age and BMI in univariate analyses, but only with age and BMI (and its categories) in multivariate logistic analysis.

Conservative Clothing Effects on Body Composition Assessment by Air Displacement Plethysmography.

Form-fitting spandex swimsuits or single-layer compression shorts are recommended during BOD POD® testing to ensure accurate results. The purpose of this study was to evaluate the effects of various outfit types on body composition measurements using the BOD POD®, and self-reported comfort level wearing each outfit. Twenty-one participants, 8 females and 13 males, (age 31.6 ± 9.8 years) wore a spandex swim cap and three different outfits during BOD POD® testing (manufacturer-recommended form-fitting spandex swimsuit, short sleeve spandex, long sleeve spandex). Measured variables include body mass, body fat percentage, body volume, and self-reported comfort level wearing each outfit. Calculated variables include BMI and body density. Mean body density when wearing the control outfit was 0.004 g/cm3 lower than both short (p < 0.001) and long sleeve (p = 0.001) alternatives. Short and long sleeve outfits resulted in body fat percentage underestimations of 2.0% and 2.1%, respectively (p < 0.001). The short sleeve outfit had the highest mean comfort rating followed by the long sleeve outfit, and the lowest was the control swimsuits. The short sleeve outfit and control outfit had the largest differences in reported comfort levels (p < 0.05). Wearing short and long sleeve spandex outfits instead of recommended form-fitting swimsuits resulted in body density increases and body fat percentage underestimations. Participants should follow manufacturer recommendations by wearing spandex swimsuits. Participants had higher self-reported comfort levels when wearing short or long sleeve outfits.

Aerial photogrammetry and tag-derived tissue density reveal patterns of lipid-store body condition of humpback whales on their feeding grounds.

Monitoring the body condition of free-ranging marine mammals at different life-history stages is essential to understand their ecology as they must accumulate sufficient energy reserves for survival and reproduction. However, assessing body condition in free-ranging marine mammals is challenging. We cross-validated two independent approaches to estimate the body condition of humpback whales (Megaptera novaeangliae) at two feeding grounds in Canada and Norway: animal-borne tags (n = 59) and aerial photogrammetry (n = 55). Whales that had a large length-standardized projected area in overhead images (i.e. whales looked fatter) had lower estimated tissue body density (TBD) (greater lipid stores) from tag data. Linking both measurements in a Bayesian hierarchical model to estimate the true underlying (hidden) tissue body density (uTBD), we found uTBD was lower (-3.5 kg m-3) in pregnant females compared to adult males and resting females, while in lactating females it was higher (+6.0 kg m-3). Whales were more negatively buoyant (+5.0 kg m-3) in Norway than Canada during the early feeding season, possibly owing to a longer migration from breeding areas. While uTBD decreased over the feeding season across life-history traits, whale tissues remained negatively buoyant (1035.3 ± 3.8 kg m-3) in the late feeding season. This study adds confidence to the effectiveness of these independent methods to estimate the body condition of free-ranging whales.

Examining Race-Related Error in Two-Compartment Models of Body Composition Assessment: A Systematic Review and Meta-Analysis.

BACKGROUND: The Brozek and Siri formulas estimate relative adiposity (%Fat) from total body density (Db) using a 2-compartment (2C) model. Racial/ethnic differences in Db have been reported, along with subsequent errors in estimated %Fat. OBJECTIVE: The primary aim of this systematic review and meta-analysis was to examine potential race/ethnic differences in the accuracy of the Brozek and Siri 2C formulas using aggregate-level data. METHODS: Peer-reviewed studies available in English that provided 2C and 4C estimates of %Fat were located using searches of the PubMed (n = 150), Scopus (n = 170), and Web of Science (n = 138) online electronic databases. Random-effects models were used to determine potential differences between racial groups using a mean ES and 95% confidence intervals. RESULTS: The cumulative results from 78 effects indicate that the relative accuracy of the Brozek equation did not vary between racial groups (between group p = 0.053). In contrast, the Siri equation slightly underestimated %Fat for Asian adults (ESWMD = -1.40%, 95%CI -2.33% to -0.46%; p = 0.004) and Black adults (ESWMD = -1.10%, 95%CI -2.11% to -0.08%; p = 0.034), with no significant differences observed in Hispanic adults (ESWMD = 0.64%, 95%CI -1.02% to 2.31%; p = 0.448) and White adults (ESWMD = 0.08%, 95%CI -0.42% to 0.57%; p = 0.766) (between group p = 0.019). CONCLUSION: Small, but statistically significant, error was found between racial groups when estimating %Fat using the 2C Siri equation when compared to 4C models. However, the observed error due to race/ethnicity appears to be of little clinical or practical significance when using either equation.

Entropy Multiparticle Correlation Expansion for a Crystal.

As first shown by H. S. Green in 1952, the entropy of a classical fluid of identical particles can be written as a sum of many-particle contributions, each of them being a distinctive functional of all spatial distribution functions up to a given order. By revisiting the combinatorial derivation of the entropy formula, we argue that a similar correlation expansion holds for the entropy of a crystalline system. We discuss how one- and two-body entropies scale with the size of the crystal, and provide fresh numerical data to check the expectation, grounded in theoretical arguments, that both entropies are extensive quantities.

Evaluation of fat-free mass hydration in athletes and non-athletes.

PURPOSE: To evaluate the hydration of fat-free mass (FFM) in athletes and non-athletes. METHODS: We analyzed the data of 128 healthy young adults (athletes: 61 men, 36 women; non-athletes: 19 men, 12 women) using the two-component (2C), 3C and 4C models. Under-water weighing or air-displacement plethysmography and deuterium dilution methods were used for estimating body density and total body water, respectively. The bone mineral content (BMC) was determined using whole-body scans by dual-energy X-ray absorptiometry. RESULTS: There was no significant difference in FFM hydration between the athletes (men, 72.3 ± 1.3%; women, 71.8 ± 1.3%) and non-athletes (men, 72.1 ± 1.2%; women, 72.2% ± 1.0%) in the 3C model. The total mean FFM hydration (72.1% ± 1.3%) was similar to the corresponding value in the literature (~ 73%). The estimation error of the percentage fat by the 2C vs the 4C model was significantly and highly correlated with hydration (r = 0.96), BMC (r = - 0.70), and total body protein (r = - 0.86) in the 4C model FFM. CONCLUSION: Although FFM hydration was similar in athletes and non-athletes, it would be underestimated or overestimated when the 2C model is used for evaluation, and the biological FFM hydration value deviates from the 73% value inter-individually. Despite that this inter-individual variation in FFM hydration is low in terms of between-individual standard deviation (1.3%), the BMC and total body protein differ greatly in athletes, and when it affects FFM hydration, it may also affect the percentage fat measurement in the 2C model. Thus, FFM hydration would not be affected by FFM, percent body fat, or the athletic status.

On the Probability Density of the Nuclei in a Vibrationally Excited Molecule.

For localized and oriented vibrationally excited molecules, the qualitative features of the one-body probability density of the nuclei (one-nucleus density) are investigated. Like the familiar and widely used one-electron density that represents the probability of finding an electron at a given location in space, the one-nucleus density represents the probability of finding a nucleus at a given position in space independent of the location of the other nuclei and independent of their type. In contrast to the electrons, however, the nuclei are comparably localized. Due to this localization of the individual nuclei, the one-nucleus density provides a quantum-mechanical representation of the "chemical picture" of the molecule as an object that can largely be understood in a three-dimensional space, even though its full nuclear probability density is defined on the high-dimensional configuration space of all the nuclei. We study how the nodal structure of the wavefunctions of vibrationally excited states translates to the one-nucleus density. It is found that nodes do not necessarily lead to visible changes in the one-nucleus density: Already for relatively small molecules, only certain vibrational excitations change the one-nucleus density qualitatively compared to the ground state. It turns out that there are simple rules for predicting the shape of the one-nucleus density from the normal mode coordinates. A Python module for the computation of the one-nucleus density is provided at https://gitlab.com/axelschild/mQNMc.

Differences in body density and percent body fat found by different methods of evaluating body composition / 体力科学

<p>The objectives of this study were 1) to quantify the differences in body densities and percent body fat using various methods for evaluating body composition (e.g., underwater weighing (UWW), air displacement plethysmography (ADP), skinfold caliper (SKF) measurement, ultrasound (US), bioelectrical impedance analysis (BIA), and dual-energy x-ray absorptiometry (DXA)), and 2) to examine the relationship between trends of the differences in body density and percent body fat obtained by these methods and characteristics of morphology and body composition. To this end, the body compositions of 73 healthy male adults were measured using UWW, ADP, SKF, US, and BIA. Twenty-seven of these 73 subjects underwent further measurement using DXA. Differences in body densities determined with ADP, SKF, and US were compared with those measured using UWW as a reference, and the differences in percent body fat estimated with UWW, ADP, SKF, US and BIA were compared with those measured by DXA as a reference. The results of this study indicate that 1) ADP is useful as a method for evaluating body density, as the results differed insignificantly from the reference method and showed no systematic errors due to differences in morphological characteristics and body composition, and 2) UWW measurements exhibited the smallest difference in percent body fat from the reference method, however, more than in any other method, there were systematic errors due to differences in morphological characteristics and body composition, specifically, trunk composition.</p>

Comparison of anthropometric-based equations for estimation of body fat percentage in a normal-weight and overweight female cohort: validation via air-displacement plethysmography.

OBJECTIVE: To evaluate the accuracy of the most commonly used anthropometric-based equations in the estimation of percentage body fat (%BF) in both normal-weight and overweight women using air-displacement plethysmography (ADP) as the criterion measure. DESIGN: A comparative study in which the equations of Durnin and Womersley (1974; DW) and Jackson, Pollock and Ward (1980) at three, four and seven sites (JPW3, JPW4 and JPW7) were validated against ADP in three groups. Group 1 included all participants, group 2 included participants with a BMI <25·0 kg/m² and group 3 included participants with a BMI ≥25·0 kg/m². SETTING: Human Performance Laboratory, Institute for Sport and Health, University College Dublin, Republic of Ireland. SUBJECTS: Forty-three female participants aged between 18 and 55 years. RESULTS: In all three groups, the %BF values estimated from the DW equation were closer to the criterion measure (i.e. ADP) than those estimated from the other equations. Of the three JPW equations, JPW3 provided the most accurate estimation of %BF when compared with ADP in all three groups. CONCLUSION: In comparison to ADP, these findings suggest that the DW equation is the most accurate anthropometric method for the estimation of %BF in both normal-weight and overweight females.

Effects of bone mineral content and density on accuracy of body fat measurement by underwater weighing / 体力科学

Underwater weighing is based on the assumption that fat-free body density is roughly constant among humans. This assumption should be examined, because fat-free body density may in fact depend on the bone mineral and water contents of the body, with fat excluded. The purpose of this study was to investigate the effects of bone mineral content (BMC) and density (BMD) on the accuracy of body fat measured underwater. The subjects were 12 young men (25.1±3.7 years, mean ± SD), some of whom were trained athletes. BMC and BMD were measured by dual-energy x-ray absorptiometry (DXA), as was body fat, as a percentage of body weight; this method is not based on the assumption that fat-free body density is the same in different individual. Body fat as a percen tage of body weight was measured underwater, also. Body fat measured by DXA was significantly correlated with that found by underwater weighing (r = 0.83, p<0.01), as expected, but the mean body fat found by DXA was 4.3% higher. The differences between results by the two methods for individuals were from -11.5% to 2.7%, and the differences were negatively correlated with BMC/fat-free weight (FFW ; r=-0.82, p < 0.01) and BMD (r=-0.85, p<0.01) . Fat-free body density ranged from 1.097 to 1.111 g/cm<SUP>3</SUP>because BMC/FFWs varied with the individual. We concluded that individual differences in BMC/FFW and BMD affected the fat-free body density. The variations in fat-free body density would give rise to systematic errors in body composition measured underwater.

Prediction of pulmonary residual volume from anthropometric measurements and its applicability to calculate body density in underwater weighing method / 体力科学

The purpose of the present study was to derive regression equation based on anthropometric measurements to estimate pulmonary residual volume (RV) and to ascertain its applicability in calculation of body density (BD) . Subjects were 30 males and 25 females living in Santa Barbara, California, USA, ranging in age 17 to 52 years.<BR>Nine anthropometric measurements, actual RV, vital capacity (VC), and BD using the conventional underwater weighing method were made on each subject. In males four measurements (age, height, biiliac diameter, and chest diameter) were selected by Wherry-Doolittle test selection method. Likewise, four measurements (height, age, shoulder circumference, and chest diameter) were selected in females. The prediction formulas obtained by using these measurements were as follows:<BR>(1) RV=38.89 (X1) +30.43 (X2) -12.43 (X3) +10.70 (X4) -4573.4 (formales)<BR>(R=0.832, SEE =251.9 m<I>l</I>)<BR>where RV: predicted RV (m<I>l</I>), X1: age (years), X2: height (cm), X3: biiliac diameter (mm), X4: chest diameter (mm), R: multiple correlation coefficient, SEE: standard error of estimation.<BR>(2) RV=26.21 (X1) +8.71 (X2) -4.71 (X3) +12.94 (X4) -1284.2 (for females)<BR>(R=0.768, SEE =225.9 m<I>l</I>)<BR>where X1: height (cm), X2: age (years), X3: shoulder circumference (mm), X4: chest diameter (mm) .<BR>When these formulas were used to calculate RV, mean absolute differences between BDs obtained by using measured and the predicted RVs were 0.00331 g/cm<SUP>3</SUP> for males and 0.00353 g/cm<SUP>3</SUP> for females. On the other hand, the absolute differences using the formula of Goldman and Becklake, the fractions of VC, and the constant values were 0.0047 g/cm<SUP>3</SUP>, 0.00763 g/cm<SUP>3</SUP>, and 0.00787 g/cm<SUP>3</SUP> for males, 0.00642 g/cm<SUP>3</SUP>, 0.00646 g/cm<SUP>3</SUP>, and 0.00620 g/cm<SUP>3</SUP> for females respectively.<BR>It was concluded that using the formulas obtained in the present study to predict RV would be a useful method in the situation where mass management were nessesary and more precise measurements were required than the other simplified estimations. Because in predicting RV our formulas could largely diminish the extent of the potential error as compared with the other predictions. In addition they would not require special knowledge, technique, and devises.

ANTHROPOMETRY AND FAT STORE DURING PREGNANCY / 营养学报

Weight gain, skinfold thickness, circumference and body density were measured in 30 primiparous women aged from. 23-31 years (averaged 26.3 years old).The average body weight gained 13kg from 6 to 37 weeks of pregnancy.The suprailiac skinfold thickness in 24-37 weeks and the subscapular skinfold thickness in 37 weeks increased significantly from the 6th week of pregnancy, but the triceps and biceps skinfold thickness did not change significantly. The density of the body in 24th and 37th week of pregnancy decreased significantly.The change and the body fat (%) calculated by means of 4 skinfolds increased in 3.7% (5.7kg of fat). The mean values of the hip circumference in 24th and 37th week were significantly different from that in 6th week of pregnancy. The upper thigh in the 24th and 37th week also increased slightly but not significantly different as compared with the 6th week. The mean values of arm, mid-thigh and calf circumference did not change during pregnancy.