The bioelectrical impedance analysis (BIA) international database: aims, scope, and call for data.

BACKGROUND: Bioelectrical impedance analysis (BIA) is a technique widely used for estimating body composition and health-related parameters. The technology is relatively simple, quick, and non-invasive, and is currently used globally in diverse settings, including private clinicians' offices, sports and health clubs, and hospitals, and across a spectrum of age, body weight, and disease states. BIA parameters can be used to estimate body composition (fat, fat-free mass, total-body water and its compartments). Moreover, raw measurements including resistance, reactance, phase angle, and impedance vector length can also be used to track health-related markers, including hydration and malnutrition, and disease-prognostic, athletic and general health status. Body composition shows profound variability in association with age, sex, race and ethnicity, geographic ancestry, lifestyle, and health status. To advance understanding of this variability, we propose to develop a large and diverse multi-country dataset of BIA raw measures and derived body components. The aim of this paper is to describe the 'BIA International Database' project and encourage researchers to join the consortium. METHODS: The Exercise and Health Laboratory of the Faculty of Human Kinetics, University of Lisbon has agreed to host the database using an online portal. At present, the database contains 277,922 measures from individuals ranging from 11 months to 102 years, along with additional data on these participants. CONCLUSION: The BIA International Database represents a key resource for research on body composition.

Can Phase Angle Be Associated With Muscle Strength in Healthy Male Army Cadets?

INTRODUCTION: Phase angle (PhA) determined by bioelectrical impedance (BIA) is related to body fluid balance and cell membrane integrity. Handgrip strength (HGS) is used to assess muscle strength and as an indicator of health. We aimed to determine the relationship between PhA and HGS in healthy young males and to verify whether this relationship is dependent on body components. MATERIALS AND METHODS: Hundred and sixty-three healthy male army cadets (18.8 ± 0.6 years old) participated in the study. PhA was determined by BIA, HGS was assessed by a hydraulic dynamometer, and dual-energy X-ray absorptiometry determined: fat mass (FM), bone mineral content (BMC), and lean soft tissue (LST). Participants were divided according to the PhA tertile (first tertile: PhA < 7.14°, second tertile: 7.14° ≤ PhA < 7.83°, and third tertile: PhA ≥ 7.83°). RESULTS: Youth from the first tertile of PhA had lower BMC (2.8 kg vs. 3.0 kg and vs. 3.1 kg) and LST (51.7 vs. 53.8 kg and vs. 57.6 kg) compared to youth from the second and third tertile of PhA (P < .001), respectively. Additionally, lower HGS (83.0 kg vs. 93.1 kg) was found in the first tertile compared to the third tertile of PhA (P < .001). PhA explained 3% of the HGS variation (R2 = 0.029), while LST and BMC explained 39% (R2 = 0.385) and 22% (R2 = 0.221), respectively. Furthermore, the correlation between PhA and HGS was dependent on LST (P = .567) and BMC (P = .182). CONCLUSION: In this sample, PhA showed a small relationship with HGS, remaining dependent on BMC and LST values. These results reinforce the importance of maintaining a physically active lifestyle with great lean mass and muscle strength values.

Effects of Three Resistance Exercise Orders on Muscular Function and Body Composition in Older Women.

The purpose of the present study was to compare the effects of three resistance exercise orders on muscular strength, body composition, and functional fitness in trained older women. Forty-five women (aged ≥60 years), after performing 12 weeks of a pre-conditioning resistance-training program were randomly assigned in one of the following groups that performed the exercises in the following orders: multi-joint to single-joint order (MJ-SJ, n=15), single-joint to multi-joint order (SJ-MJ, n=15), and alternating between upper and lower body order (ALT, n=15). Specific training intervention lasted 12 weeks (3x/week) and was composed of eight exercises performed in three sets of 15/10/5 repetitions, with increasing load through the sets. Muscular strength was estimated by one-repetition maximum tests; body composition was assessed by whole-body dual-energy x-ray absorptiometry, and functional fitness was analyzed with a sequence of four motor tests. All groups improved similarly in muscular strength (Cohen's effect size: MJ-SJ=0.45; SJ-MJ=0.48; ALT=0.45), skeletal muscle mass (MJ-SJ=0.08; SJ-MJ=0.07; ALT=0.09), and functional test performance (MJ-SJ=0.38; SJ-MJ=0.20; ALT=0.31), but no change was observed for body fat (P>0.05). The results suggest that 12 weeks of resistance training induce positive changes in muscle morphofunctionality, regardless of the exercise order employed in trained older women.

Tracking of health-related physical fitness between childhood and adulthood.

OBJECTIVE: The aim of the present study was to analyze the tracking of indicators of health-related physical fitness between childhood and adulthood. METHODS: The study presents a longitudinal design, with the first phase of data collection occurring annually between 2002 and 2006, and the second phase carried out in 2016. A total of 142 young adults, aged between 21 and 25 years, of both sexes participated in the study. Were evaluated body mass, stature, skinfold thickness, sit and reach test; abdominal resistance/strength test, and 20-m shuttle run test. RESULTS: The intraclass correlation coefficient (ICC) indicated that all health-related physical fitness variables presented values considered moderate to high tracking (0.37-0.67; P < 0.005) between the analyzed periods. It was verified that in all variables, tracking was higher in the female group, except for the result of the running test related to the cardiorespiratory fitness component which demonstrated greater tracking in the male group (ICC = 0.37 vs ICC = 0.50). The result of the running test for males was the only variable presenting a discrepancy in the values observed between baseline and follow-up (P < 0.05; k = 0.110). CONCLUSIONS: It was concluded that the indicators of body fat, abdominal and running tests demonstrated moderate tracking, while the sit and reach test presented high tracking.

Physical training over 6 months is associated with improved changes in phase angle, body composition, and blood glucose in healthy young males.

OBJECTIVES: The aim of this study was to evaluate the association between phase angle, body composition, and blood glucose changes in healthy young males after 6 months of physical training. METHODS: Volunteers, 98 healthy males (18.8 ± 0.5 years), had 6 months of progressive physical training (5 days a week, 90 minutes a day). Resistance, reactance, and phase angle were obtained by bioelectrical impedance analysis, body composition (fat mass, bone mineral content [BMC], and lean soft tissue [LST]) by dual-energy X-ray absorptiometry, and blood glucose by reflectance photometry. Measurements were made at rest and in a fasted state, both before and after the training period. RESULTS: Phase angle, reactance, BMC, and LST significantly increased (0.6°, 3.8 Ω, 0.1 kg, and 1.9 kg, respectively; P < .01), whereas resistance and blood glucose decreased (-11.2 Ω and -4.1 mg/dL; P < .01). Changes in resistance and reactance explained those changes observed in LST (R2 = .26 and .16, respectively), but phase angle changes were not related to body composition and blood glucose alterations (P < .05). CONCLUSIONS: A 6-month period of physical training was associated with positive changes in phase angle, body composition, and blood glucose in healthy young males, reinforcing the importance of maintaining a physically active lifestyle.

Adaptive thermogenesis and changes in body composition and physical fitness in army cadets.

BACKGROUND: To analyze the association between a 34-week military training on body composition, physical fitness and compensatory changes in resting energy expenditure (REE) recognized as adaptive thermogenesis (AT). We also explored if regional body composition changes were related to AT. METHODS: Twenty-nine male army cadets, aged 17 to 22 years were tested at baseline (T0) and after 34-weeks military training (T1). Physical training was performed 5 days/week during 90 minutes/day. Measurements included body composition by dual-energy x-ray absorptiometry; physical fitness by 3000-m running, pull-up, 50-m freestyle swimming, push-up and sit-up tests; REE measured by indirect calorimetry (REEm) and predicted from fat-free mass (FFM), fat mass (FM) and ethnicity at T0 (REEp). %AT was calculated using values at T1: 100(REEm/REEp-1); and AT (kcal/day) as %AT/100 multiplied by baseline REEm. RESULTS: Physical training was associated with increases of lean soft tissue (LST) (∆1.2±1.3 kg), FM (∆1.4±1.3 kg), FFM (∆1.2±1.3 kg) and physical fitness (P<0.01), but no REE changes (∆59.6±168.9 kcal/day) and AT were observed (P>0.05). Though a large variability was found, AT was partially explained by trunk LST (r2=0.17, P=0.027). Individuals showing a higher AT response demonstrated a higher trunk LST increase (∆0.8±0.7 kg, P<0.05). CONCLUSIONS: The military training increased LST, FM, FFM and physical fitness. Though no mean changes in AT occurred, a large individual variability was observed with some participants increasing REE beyond the expected body composition changes, suggesting a spendthrift phenotype. Changes of trunk LST may play an important role in the AT response observed in these individuals.

Methods for data analysis of resting energy expenditure measured using indirect calorimetry.

OBJECTIVES: The aim of this study was to test the accuracy of different methods of resting energy expenditure (REE) data analysis using indirect calorimetry (IC) during traditional (30 min) and abbreviated (10 min) protocols. METHODS: Fifteen women and 15 men (21-34 y of age) completed two consecutive 30-min IC measurements. Body composition was measured using dual-energy x-ray absorptiometry. The reference method for REE analysis was 5 min in steady state (SS) during 30 min (first 5 min discarded). REE measurements were randomized to define a reference or testing method. An interval method was defined using 25, 20, and 15 min (with first 5, 10, and 15 min discarded, respectively), during 30 min, and 5 min (first 5 min discarded) during 10-min intervals. The SS method was defined using 5 min in SS (first 5 min discarded) during 30 min, 5, 4, and 3 min in SS during 10-min (first 5 min discarded) intervals. RESULTS: Interval methods during 30 min and SS and interval methods during 10 min demonstrated large bias with significantly high REEs compared to the reference method (78.8-109.0 kcal/d, all P < 0.001). Testing methods demonstrated large upper limits of agreement between 225.2 and 322.8 kcal/d. No mean differences (P > 0.05), small bias (14.3 kcal/d), and narrow limits of agreement (-125.8 to 154.4 kcal/d) were observed between 5-min SS during 30 min and the reference method. CONCLUSIONS: All interval methods and SS methods during 10 min overestimated REE. We recommend using 5-min SS during 30 min. The measurement may be repeated until all participants achieve SS.

Can anthropometric, body composition, and bone variables be considered risk factors for musculoskeletal injuries in Brazilian military students?

BACKGROUND: Musculoskeletal injuries are the main cause of premature discharge from military service and can sometimes lead to permanent disabilities. Some intrinsic risk factors are well discussed in the literature. However, the relation between body composition variables and the risk for musculoskeletal injury is not well known or recognized. METHODS: This prospective study evaluated 205 Brazilian military students. At the beginning of military service, health status and sports experience prior to military service were registered. Anthropometric variables were evaluated, and bone and body composition variables were measured using dual-energy X-ray absorptiometry. The occurrence of musculoskeletal injuries throughout the year was registered at the military physiotherapy service. At the end of 1 year of follow-up, risk factors were analysed by comparing the variables between the injured and non-injured students. RESULTS: No difference in previous health status was found between injured and non-injured groups, whereas sports experience prior to military service was identified as a protective factor (Odds Ratio (OR) 0.323; 95% CI: 0.108-0.968; p = 0.044). Anthropometric, bone, and body composition variables could not be identified as risk factors for musculoskeletal injuries in Brazilian military students. CONCLUSION: Anthropometric, bone, and body composition variables could not be considered risk factors for musculoskeletal injuries in Brazilian military students.

Accuracy of Bioelectrical Impedance Analysis in Estimated Longitudinal Fat-Free Mass Changes in Male Army Cadets.

Introduction: Bioelectrical impedance analysis (BIA) is a practical and rapid method for making a longitudinal analysis of changes in body composition. However, most BIA validation studies have been performed in a clinical population and only at one moment, or point in time (cross-sectional study). The aim of this study is to investigate the accuracy of predictive equations based on BIA with regard to the changes in fat-free mass (FFM) in Brazilian male army cadets after 7 mo of military training. The values used were determined using dual-energy X-ray absorptiometry (DXA) as a reference method. Materials and Methods: The study included 310 male Brazilian Army cadets (aged 17-24 yr). FFM was measured using eight general predictive BIA equations, with one equation specifically applied to this population sample, and the values were compared with results obtained using DXA. The student's t-test, adjusted coefficient of determination (R2), standard error of estimation (SEE), Lin's approach, and the Bland-Altman test were used to determine the accuracy of the predictive BIA equations used to estimate FFM in this population and between the two moments (pre- and post-moment). Results: The FFM measured using the nine predictive BIA equations, and determined using DXA at the post-moment, showed a significant increase when compared with the pre-moment (p < 0.05). All nine predictive BIA equations were able to detect FFM changes in the army cadets between the two moments in a very similar way to the reference method (DXA). However, only the one BIA equation specific to this population showed no significant differences in the FFM estimation between DXA at pre- and post-moment of military routine. All predictive BIA equations showed large limits of agreement using the Bland-Altman approach. Conclusion: The eight general predictive BIA equations used in this study were not found to be valid for analyzing the FFM changes in the Brazilian male army cadets, after a period of approximately 7 mo of military training. Although the BIA equation specific to this population is dependent on the amount of FFM, it appears to be a good alternative to DXA for assessing FFM in Brazilian male army cadets.

Quantitative Ultrasonography Measurements of the Phalanges in Adolescents: A Mixed Longitudinal Study.

This study examined the effect of pubertal development on Amplitude Dependent Speed of Sound (AD-SoS), accounting for the growth in stature among adolescents. A mixed-longitudinal design with 3 assessments across a 15-mo period in 439 adolescents (girls: 215; boys: 224) aged 9-16 y was used. Bayesian multilevel models were used to describe gender-specific AD-SoS variations among participants during pubertal years. Substantial increments in AD-SoS during pubertal years were observed in both genders. AD-SoS changes were positively related to stature, and the rate of stature growth per year. Quantitative ultrasonography was sensible to describe age-related changes of bone mass during pubertal development. It seemed clinically reliable to use AD-SoS in the study of bone growth and development.

Validity of Bioelectrical Impedance Analysis to Estimation Fat-Free Mass in the Army Cadets.

BACKGROUND: Bioelectrical Impedance Analysis (BIA) is a fast, practical, non-invasive, and frequently used method for fat-free mass (FFM) estimation. The aims of this study were to validate predictive equations of BIA to FFM estimation in Army cadets and to develop and validate a specific BIA equation for this population. METHODS: A total of 396 males, Brazilian Army cadets, aged 17-24 years were included. The study used eight published predictive BIA equations, a specific equation in FFM estimation, and dual-energy X-ray absorptiometry (DXA) as a reference method. Student's t-test (for paired sample), linear regression analysis, and Bland-Altman method were used to test the validity of the BIA equations. RESULTS: Predictive BIA equations showed significant differences in FFM compared to DXA (p < 0.05) and large limits of agreement by Bland-Altman. Predictive BIA equations explained 68% to 88% of FFM variance. Specific BIA equations showed no significant differences in FFM, compared to DXA values. CONCLUSION: Published BIA predictive equations showed poor accuracy in this sample. The specific BIA equations, developed in this study, demonstrated validity for this sample, although should be used with caution in samples with a large range of FFM.

Minimum Time to Achieve the Steady State and Optimum Abbreviated Period to Estimate the Resting Energy Expenditure by Indirect Calorimetry in Healthy Young Adults.

BACKGROUND: The optimum abbreviated period for measurement by indirect calorimetry (IC) to estimate the resting energy expenditure (REE), including the acclimation period, in healthy individuals has not been established. This study aimed to determine the acclimation time required to achieve the REE steady state during a 30-minute IC measurement and to define the optimum abbreviated measurement period in the steady state to estimate the REE in healthy young adults. METHODS: Thirty-nine volunteers (27 men and 12 women; age, 18-31 years) were recruited. The REE was obtained by IC over 30 minutes. Friedman's test was used to compare the coefficient of variation (CV%) among all 5-minute intervals (REE5). To compare the REE values obtained during the first REE5 interval in the steady state with the REE average values of the subsequent measurements, Student paired t test, linear regression, and Bland-Altman test were used. RESULTS: The CV% of the first REE5 (mean ± standard deviation: 19.9% ± 13.2%) was significantly higher (P < .0001) than that of all other REE5 (second REE5: 7.4% ± 3.8%; third: 7.8% ± 5.2%; fourth: 7.1% ± 3.9%; fifth: 8.0% ± 5.7%; sixth: 8.0% ± 4.5%). No significant difference was found between the second REE5 and the REE average values of the last 20 minutes. The second REE5 explained 90% of the REE average of the last 20 minutes, with the 95% limits of agreement by the Bland-Altman test ranging from -142.92 to 150.44 kcal/d. CONCLUSION: Ten minutes can be used as an abbreviated alternative for IC measurements in healthy young adults, and values of the first 5-minute interval should be discarded.

Competitive Swimming and Handball Participation Have a Positive Influence on Bone Parameters as Assessed by Phalangeal Quantitative Ultrasound in Female Adolescents.

PURPOSE: To examine the influence of participation in competitive sports on bone parameters, as assessed by quantitative ultrasound (QUS) of the phalanges in female adolescents. METHODS: Female adolescents (n = 329, 13.0-16.7 years old) were classified into handball (n = 55), swimming (n = 49) and control (n = 225) groups. QUS was used to evaluate the amplitude-dependent speed of sound (AD-SoS) and bone transmission time (BTT), and their z-scores (zAD-SoS and zBTT) were calculated. Anthropometric measurements and Tanner's stages were also obtained. RESULTS: Swimmers had higher AD-SoS (2089 ± 43.8 m/s) and zAD-SoS (0.47 ± 0.8) than controls (2060 ± 54.0 m/s; 0.09 ± 1.0; both p ≤ .05) and both groups of athletes had higher BTT (handball: 1.44 ± 0.2 µs; swimming: 1.45 ± 0.2) and zBTT (handball: 0.71 ± 0.8; swimming: 0.72 ± 1.1) than the control group (1.37 ± 0.2 µs; 0.32 ± 0.9; all p ≤ .05). Swimmers had a higher total training time (TTT: 52.5 ± 27.6 months) and frequency of training per week (FT: 5.38 ± 0.1) compared with the handball group (35.9 ± 18.1; 3.32 ± 0.8; p ≤ .05). zAD-SoS, BTT and zBTT were positively correlated with FT, while BTT and zBTT showed a positive correlation with TTT. CONCLUSIONS: Sports practice influences bone parameters and higher bone parameter values are related to the amount of time and frequency of weekly training. The differences in phalangeal QUS parameters are independent of the impact of weight-bearing exercise.

Assessment of total body water and its compartments in elite judo athletes: comparison of bioelectrical impedance spectroscopy with dilution techniques.

Bioelectrical impedance spectroscopy (BIS) is an inexpensive and non-invasive technique to measure total body water (TBW), extracellular water (ECW), and intracellular water (ICW). The purpose of this study was to validate TBW, ECW and ICW assessed by BIS, using dilution techniques as the reference method (REF) in elite judo athletes. Thirty-two Portuguese elite male judo athletes were evaluated during a period of weight stability. TBW, ECW and ICW were assessed by BIS (Xitron 4000). Deuterium and bromide dilution techniques were used as the criterion method for measuring TBW and ECW, while ICW was calculated as the difference between the two. BIS explained 96%, 77% and 94% of the total variability from REFs for TBW, ECW and ICW, respectively. BIS also demonstrated high precision (ρ ≥ 0.88) and accuracy (Cb = 0.98), with a minimum concordance coefficient correlation of 0.87 for ECW. The mean bias demonstrated that BIS slightly overestimated the REF in 1.1 kg (2.3%), 0.3 kg (1.6%) and 0.8 kg (2.7%) for TBW, ECW and ICW, respectively. The 95% limits of agreement ranged from -1.2 to 3.3 kg in TBW, from -1.8 to 2.4 kg in ECW and from -1.0 to 2.6 kg in ICW. A non-significant trend was found between the difference and the mean of reference and alternative methods. These findings highlight the efficacy of BIS as a valid non-biased tool for the assessment of TBW and its compartments in elite male judo athletes, during a period of weight stability.

Performance of phalangeal quantitative ultrasound parameters in the evaluation of reduced bone mineral density assessed by DX in patients with 21 hydroxylase deficiency.

The purpose of this study was to verify the performance of quantitative ultrasound (QUS) parameters of proximal phalanges in the evaluation of reduced bone mineral density (BMD) in patients with congenital adrenal hyperplasia due to 21-hydroxylase deficiency (21 OHD). Seventy patients with 21 OHD (41 females and 29 males), aged between 6-27 y were assessed. The QUS measurements, amplitude-dependent speed of sound (AD-SoS), bone transmission time (BTT), and ultrasound bone profile index (UBPI) were obtained using the BMD Sonic device (IGEA, Carpi, Italy) on the last four proximal phalanges in the non-dominant hand. BMD was determined by dual energy X-ray (DXA) across the total body and lumbar spine (LS). Total body and LS BMD were positively correlated to UBPI, BTT and AD-SoS (correlation coefficients ranged from 0.59-0.72, p < 0.001). In contrast, when comparing patients with normal and low (Z-score < -2) BMD, no differences were found in the QUS parameters. Furthermore, UBPI, BTT and AD-SoS measurements were not effective for diagnosing patients with reduced BMD by receiver operator characteristic curve parameters. Although the AD-SoS, BTT and UBPI showed significant correlations with the data obtained by DXA, they were not effective for diagnosing reduced bone mass in patients with 21 OHD.

Measurement properties of radial and tibial speed of sound for screening bone fragility in 10- to 12-year-old boys and girls.

The objective of this study was to analyze measurement properties of the radial and tibial speed of sound (SoS) evaluated by quantitative ultrasound (QUS) for screening bone fragility. Bone fragility was defined as low whole body less head bone mineral density (WBLH BMD) measured by DXA (first tertile, 95% CI -1.1 to -0.9) and as past fractures evaluated by questionnaire. The sample included 319 nonobese boys and girls, ages 10-12 yr. All bone variables were standardized. The results revealed concordance coefficient correlations between WBLH BMD and radial and tibial SoS of 0.129 and 0.038, respectively. The regression lines between DXA and QUS variables were different from the identity lines. Cross-classification analysis by Kappa statistic showed that only 34% and 36% of the 113 participants categorized in the first tertile of WBLH BMD were also categorized in the first tertile of tibial and radial SoS, correspondingly. Logistic regression with gender and maturity adjustments demonstrates that radial SoS was the single significant variable in predicting OR for identifying participants with past fractures. In conclusion, the radial QUS revealed itself to be a valuable tool for screening bone fragility in youth of 10-12 yr, despite the absence of agreement with DXA WBLH BMD.

Total body water and its compartments are not affected by ingesting a moderate dose of caffeine in healthy young adult males.

Acute and chronic caffeine intakes have no impact on hydration status (R.J. Maughan and J. Griffin, J. Hum. Nutr. Diet. 16(6): 411-420, 2003), although no research has been conducted to analyze the effects using dilution techniques on total-body water (TBW) and its compartments. Therefore, the aim of this study was to investigate the effects of a moderate dose of caffeine on TBW, extracellular water (ECW), and intracellular water (ICW) during a 4-day period in active males. Thirty men, nonsmokers and low caffeine users (<100 mg·day(-1)), aged 20-39 years, participated in this double-blind, randomized, crossover trial (ClinicalTrials.gov: No. NCT01477294). The study included 2 conditions (5 mg·kg(-1)·day(-1) of caffeine and placebo (malt-dextrin)) of 4 days each, with a 3-day washout period. TBW and ECW were assessed by deuterium oxide and sodium bromide dilution, respectively, whereas ICW was calculated as TBW minus ECW. Body composition was assessed by dual-energy X-ray absorptiometry. Physical activity (PA) was assessed by accelerometry and water intake was assessed by dietary records. Repeated-measures analysis of variance (ANOVA) was used to test main effects. No changes in TBW, ECW, or ICW and no interaction between the randomly assigned order of treatment and time were observed (p > 0.05). TBW, ECW, and ICW were unrelated to fat-free mass, water ingestion, and PA (p > 0.05). These findings indicate that a moderate caffeine dose, equivalent to approximately 5 espresso cups of coffee or 7 servings of tea, does not alter TBW and fluid distribution in healthy men, regardless of body composition, PA, or daily water ingestion.

Estimation of percent body fat based on anthropometric measurements in children and adolescents with congenital adrenal hyperplasia due to 21-hydroxylase deficiency.

BACKGROUND & AIM: Congenital adrenal hyperplasia due to 21-hydroxylase deficiency is associated with a high risk for obesity. Anthropometric measures are simple and inexpensive methods to assess body fat. However, the accuracy of alternative methods in these patients is unknown. This study aim to develop and evaluate the accuracy of predictive anthropometric equations in the estimation of percent body fat in individuals with congenital adrenal hyperplasia due to 21-hydroxylase deficiency. METHODS: A total of 31 female and 22 male patients, aged 7-20 years, were evaluated. Dual-energy X-ray absorptiometry was used as the reference method for body fat, and anthropometric measurements were performed. RESULTS: Three new predictive equations showed similar results: Equation (1) (R² = 0.85; SEE = 2.89%), Equation (2) (R² = 0.86; SEE = 2.82%), and Equation (3) (R² = 0.86; SEE = 2.81%). Internal cross-validation procedures showed a high R² (range, 0.84-0.85) and low SEE (<3%). The limits of agreement ranged from -5.6% to 5.6% and no trend was observed. CONCLUSION: In children and adolescents with congenital adrenal hyperplasia due to 21-hydroxylase deficiency, three new predictive equations were validated for the estimation of percent body fat, with dual-energy X-ray absorptiometry as the reference method.

Body composition in taller individuals using DXA: A validation study for athletic and non-athletic populations.

Dual energy X-ray absorptiometry (DXA) cannot be used to evaluate participants taller than the scan area. We aimed to analyse the accuracy of bone mineral content, fat mass, and lean mass assessed with DXA whole-body scan and from the sum of two scans (head and trunk plus limbs). Participants were 31 athletes (13 males and 18 females) and 65 non-athletes (34 males and 31 females), that fit within the DXA scan area. Three scans were performed using a Hologic Explorer-W fan-beam densitometer: a whole-body scan used as the reference; a head scan; and a trunk and limbs scan. The sum of the head scan and the trunk and limbs scan was used as the alternative procedure. Multiple regression and agreement analysis were performed. Non-significant differences between methods were observed for fat mass (0.06 kg) and lean mass (-0.07 kg) while bone mineral content from the alternative procedure differed from the reference scan (0.009 kg). The alternative procedure explained > 99% of the variance in the reference scan and low limits of agreement were observed. Precision analysis indicated low pure errors and the higher coefficients of variation were found for fat mass (whole-body: 3.70%; subtotal: 4.05%). The method proposed is a valid and simple solution to be used in individuals taller than the DXA scan area, including athletes engaged in sports recognised for including very tall competitors.

Is bioelectrical impedance spectroscopy accurate in estimating total body water and its compartments in elite athletes?

BACKGROUND: Bioelectrical impedance spectroscopy (BIS) provides an affordable assessment of the body's various water compartments: total body water (TBW), extracellular water (ECW) and intracellular water (ICW). However, little is known of its validity in athletes. AIM: To validate TBW, ECW and ICW by BIS in elite male and female Portuguese athletes using dilution techniques (i.e. deuterium and bromide dilution) as criterion methods. SUBJECTS AND METHODS: Sixty-two athletes (18.5 ± 4.1 years) had TBW, ECW and ICW assessed by BIS during their respective pre-season. RESULTS: BIS significantly under-estimated TBW by 1.0 ± 1.7 kg and ICW by 0.9 ± 1.9 kg in relation to the criterion methods, with no differences observed for ECW. The values for the concordance correlation coefficient were 0.98 for TBW and ECW and 0.95 for ICW. Bland-Altman analyses revealed no bias for the various water compartments, with the 95% confidence intervals ranging from - 4.8 to 2.6 kg for TBW, - 1.5 to 1.6 kg for ECW and - 4.5 to 2.7 kg for ICW. CONCLUSIONS: Overall, these findings demonstrate the validity of BIS as a valid tool in the assessment of TBW and its compartments in both male and female athletes.