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We aim to understand the effects of hydration changes on athletes' neuromuscular performance, on body water compartments, fat-free mass hydration and hydration biomarkers and to test the effects of the intervention on the response of acute dehydration in the hydration indexes. The H2OAthletes study (clinicaltrials.gov ID: NCT05380089) is a randomised controlled trial in thirty-eight national/international athletes of both sexes with low total water intake (WI) (i.e. < 35·0 ml/kg/d). In the intervention, participants will be randomly assigned to the control (CG, n 19) or experimental group (EG, n 19). During the 4-day intervention, WI will be maintained in the CG and increased in the EG (i.e. > 45·0 ml/kg/d). Exercise-induced dehydration protocols with thermal stress will be performed before and after the intervention. Neuromuscular performance (knee extension/flexion with electromyography and handgrip), hydration indexes (serum, urine and saliva osmolality), body water compartments and water flux (dilution techniques, body composition (four-compartment model) and biochemical parameters (vasopressin and Na) will be evaluated. This trial will provide novel evidence about the effects of hydration changes on neuromuscular function and hydration status in athletes with low WI, providing useful information for athletes and sports-related professionals aiming to improve athletic performance.

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., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)

The need for a practical method for routine determination of body fat has progressed from body mass index (BMI) to bioelectrical impedance analysis (BIA) and smartphone two-dimensional imaging. We determined agreement in fat mass (FM) estimated with 50 kHz BIA and smartphone single lateral standing digital image (SLSDI) compared to dual X-ray absorptiometry (DXA) in 188 healthy adults (69 females and 119 males). BIA underestimated ( p < 0.0001) FM, whereas SLSDI FM estimates were not different from DXA values. Based on limited observations that BIA overestimated fat-free mass (FFM) in obese adults, we tested the hypothesis that expansion of the extracellular water (ECW), expressed as ECW to intracellular water (ECW/ICW), results in underestimation of BIA-dependent FM. Using a general criterion of BMI > 25 kg/m 2 , 54 male rugby players, compared to 40 male non-rugby players, had greater ( p < 0.001) BMI and FFM but less ( p < 0.001) FM and ECW/ICW. BIA underestimated ( p < 0.001) FM in the non-rugby men, but SLSDI and DXA FM estimates were not different in both groups. This finding is consistent with the expansion of ECW in individuals with excess body fat due to increased adipose tissue mass and its water content. Unlike SLSDI, 50 kHz BIA predictions of FM are affected by an increased ECW/ICW associated with greater adipose tissue. These findings demonstrate the validity, practicality, and convenience of smartphone SLSDI to estimate FM, seemingly not influenced by variable hydration states, for healthcare providers in clinical and field settings.

Bioelectrical impedance analysis (BIA) is the most widely used technique in body composition analysis. When we focus the use of phase sensitive BIA on its raw parameters Resistance (R), Reactance (Xc) and Phase Angle (PhA), we eliminate the bias of using predictive equations based on reference models. In particular PhA, have demonstrated their prognostic utility in multiple aspects of health and disease. In recent years, as a strong association between prognostic and diagnostic factors has been observed, scientific interest in the utility of PhA has increased. In the different fields of knowledge in biomedical research, there are different ways of assessing the impact of a scientific-technical aspect such as PhA. Single frequency with phase detection bioimpedance analysis (SF-BIA) using a 50 kHz single frequency device and tetrapolar wrist-ankle electrode placement is the most widely used bioimpedance approach for characterization of whole-body composition. However, the incorporation of vector representation of raw bioelectrical parameters and direct mathematical calculations without the need for regression equations for the analysis of body compartments has been one of the most important aspects for the development of research in this area. These results provide new evidence for the validity of phase-sensitive bioelectrical measurements as biomarkers of fluid and nutritional status. To enable the development of clinical research that provides consistent results, it is essential to establish appropriate standardization of PhA measurement techniques. Standardization of test protocols will facilitate the diagnosis and assessment of the risk associated with reduced PhA and the evaluation of changes in response to therapeutic interventions. In this paper, we describe and overview the value of PhA in biomedical research, technical and instrumental aspects of PhA research, analysis of Areas of clinical research (cancer patients, digestive and liver diseases, critical and surgical patients, Respiratory, infectious, and COVID-19, obesity and metabolic diseases, Heart and kidney failure, Malnutrition and sarcopenia), characterisation of the different research outcomes, Morphofunctional assessment in disease-related malnutrition and other metabolic disorders: validation of PhA with reference clinical practice techniques, strengths and limitations. Based on the detailed study of the measurement technique, some of the key issues to be considered in future PhA research. On the other hand, it is important to assess the clinical conditions and the phenotype of the patients, as well as to establish a disease-specific clinical profile. The appropriate selection of the most critical outcomes is another fundamental aspect of research., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Phase angle (PhA) is a recently proposed marker of nutritional status in many clinical conditions. Its use in patients with obesity presents different critical concerns due to the higher variability of the two measured parameters (resistance, R, and reactance, Xc) that contribute to the determination of PhA. Controversial is the relation between PhA and BMI that might vary with graded levels of obesity due to the variation in fat and free fat mass. Obesity is frequently associated with metabolic, hepatic, cardiovascular and kidney diseases that introduce variations in PhA values, in relation to multimorbidity and severity degree of these diseases. It is reported that the improvement of clinical condition is associated with a positive change in PhA. Also, the treatment of obesity with weight loss might confirm this effect, but with different responses in relation to the type and duration of the intervention applied. In fact, the effect appears not only related to the percentage of weight loss but also the possible loss of free fat mass and the nutritional, metabolic and structural modifications that might follow each therapeutic approach to decrease body weight. We can conclude that the PhA could be used as marker of health status in patients with obesity supporting an appropriate weight loss intervention to monitor efficacy and fat free mass preservation., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Bioelectrical impedance (BI) is a practical method to assess body composition in health and disease. This method relies on the passive conduction of an applied, safe, low-level alternating current through water and electrolytes in the body. Using a phase-sensitive device, BI yields measurements of impedance (Z) and its components, resistance (R) and reactance (Xc), that are related geometrically as phase angle (PhA). In vitro studies provide empirical evidence relating BI measurements to physiological variables. Cooking raw food samples results in greater decreases in PhA, predominantly Xc, with smaller reductions R indicating destruction of cell membrane integrity with simultaneous movement of fluid from intracellular to extracellular space. Infusion of saline into a cell-free model shows a proportional decrease in R with increases in volume. Saline infusion in a composite model of cells disproportionately decreases Xc and PhA, compared to R, demonstrating greater relative expansion of extracellular water (ECW) with a lesser relative increase in total fluid volume. Surgical patients treated with fluid infusion and diuresis demonstrate changes in Xc predominantly indicating relative changes in ECW with lesser variations in R indicating fluctuations in total fluid volume. Proteomics studies disclose strong independent associations of PhA with protein markers of fluid overload and protein proliferation. Interpretations of PhA measurements for body cell mass should be examined in the context of hydration status., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Localized bioimpedance (L-BIA) measurements are an innovative method to non-invasively identify structural derangement of soft tissues, principally muscles, and fluid accumulation in response to traumatic injury. This review provides unique L-BIA data demonstrating significant relative differences between injured and contralateral non-injured regions of interest (ROI) associated with soft tissue injury. One key finding is the specific and sensitive role of reactance (Xc), measured at 50 kHz with a phase-sensitive BI instrument, to identify objective degrees of muscle injury, localized structural damage and fluid accretion, determined using magnetic resonance imaging. The predominant effect of Xc as an indicator of severity of muscle injury is highlighted in phase angle (PhA) measurements. Novel experimental models utilizing cooking-induced cell disruption, saline injection into meat specimens, and measurements of changing amounts of cells in a constant volume provide empirical evidence of the physiological correlates of series Xc as cells in water. Findings of strong associations of capacitance, computed from parallel Xc (X CP ), with whole body counting of 40-potassium and resting metabolic rate support the hypothesis that parallel Xc is a biomarker of body cell mass. These observations provide a theoretical and practical basis for a significant role of Xc, and hence PhA, to identify objectively graded muscle injury and to reliably monitor progress of treatment and return of muscle function., (© 2023. The Author(s).)

Background/objectives: Bioelectrical impedance (BIA) whole-body and regional raw parameters have been used to develop prediction models to estimate whole-body lean soft tissue (LSTM), with less attention being given to the development of models for regional LSTM. Therefore, we aimed to develop and validate BIA-derived equations predicting regional LSTM against dual x-ray absorptiometry (DXA) in healthy adults., Subjects/methods: 149 adults were included in this cross-sectional investigation. Whole-body and regional LSTM were assessed by DXA, and raw bioelectrical parameters of distinct body regions were measured using a 50 kHz phase sensitive BIA analyzer. BIA-derived equations were developed using a stepwise multiple linear regression approach in 2/3 of the sample and cross-validated in the remaining sample., Results: Slopes and intercepts of predicted LSTM and DXA measured LSTM did not differ from 1 and 0, respectively, for each region (p ≥ 0.05), with the exception for the trunk (p < 0.05). The BIA-derived equations exhibited a strong relationship (p < 0.001) between the predicted and measured LSTM for each of the following body regions: right and left arms (R = 0.94; R = 0.96), right and left legs (R = 0.88; R = 0.88), upper body (R = 0.96), lower body (R = 0.89), right and left sides of the body (R = 0.94; R = 0.94), and trunk (R = 0.90). Agreement analyses revealed no associations between the differences and the means of the predicted and DXA-derived LSTM., Conclusion: The developed BIA-derived equations provide a valid estimate of regional LSTM in middle-aged healthy adults, representing a cost-effective and time-efficient alternative to DXA for the assessment and identification of LSTM imbalances in both clinical and sport-specific contexts., (© 2022. The Author(s), under exclusive licence to Springer Nature Limited.)

Background & Aims: Severe acute COVID-19 has taken on pandemic proportions with growing interest in identification of prognostic factors for mortality. Standardized bioelectrical impedance (BI) phase angle (SPhA), which is PhA adjusted by age and sex, has been related to mortality in patients with several diseases but never investigated in COVID-19. Inflammation, a consequence of COVID-19 infection, affects fluid status (hydration) and can be identified with PhA. The aim of this study was to determine the predictive role of PhA on 90 days survival of adults with COVID-19., Methods: We studied 127 consecutive patients diagnosed with COVID-19. BI measurements determined with a 50 kHz phase-sensitive BI device, body composition parameters and laboratory markers were evaluated as predictors of mortality., Results: Non-surviving COVID-19 patients had significantly lower PhA and SPhA values (p < 0.001) and increased hydration (p < 0.001) compared to surviving patients. Patients in the lowest SPhA quartile had increased (p < 0.001) mortality and hospital stay, hyperhydration (p < 0.001), increased inflammation biomarkers [CRP (p < 0.001)], decreased nutritional parameters: body mass cell index [BCMI (p < 0.001) albumin (p < 0.001)], and reduced other biomarkers [D-dimer (p = 0.002)]. Multivariate analysis (Cox regression) revealed that PhA and hydration status, adjusted for age, sex, BMI, diabetes, hypertension, dyslipidaemia or heart disease, were associated (p < 0.001) with increased mortality. The hazard ratio was 2.48 (95% CI, 1.60-3.84, p < 0.001) for PhA and 1.12 (95% CI, 1.04-1.20, p = 0.003) for hydration percentage. PhA <3.95° was the cut-off for predicting mortality in acute COVID-19 with 93.8% sensitivity and 66.7% specificity. PhA offers greater sensitivity as a predictive prognostic test at admission, compared to the established analytical parameters of poor prognosis (CRP, lymphocytes, prealbumin)., Conclusions: Low PhA (<3.95°), independent of age, sex, BMI, and comorbidities, is a significant predictor of mortality risk in COVID-19. These findings suggest that the evaluation of body composition with single-frequency phase-sensitive BI measurements should be included in the routine clinical assessment of COVID-19 patients at hospital admission to identify patients at increased mortality risk., Competing Interests: Conflict of interest The authors declare that they have no conflict of interest., (Copyright © 2021 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.)

Background: COVID-19 has taken on pandemic proportions with growing interest in prognostic factors. Overhydration is a risk factor for mortality in several medical conditions with its role in COVID-19, assessed with bioelectrical impedance (BI), gaining research interest. COVID-19 affects hydration status. The aim was to determine the hydration predictive role on 90 d survival COVID-19 and to compare BI assessments with traditional measures of hydration. Methods: We studied 127 consecutive COVID-19 patients. Hydration status was estimated using a 50 kHz phase-sensitive BI and estimated, compared with clinical scores and laboratory markers to predict mortality. Results: Non-surviving COVID-19 patients had significantly higher hydration 85.2% (76.9−89.3) vs. 73.7% (73.2−82.1) and extracellular water/total body water (ECW/TBW) 0.67 (0.59−0.75) vs. 0.54 (0.48−0.61) (p = 0.001, respectively), compared to surviving. Patients in the highest hydration tertile had increased mortality (p = 0.012), Intensive Care Unit (ICU) admission (p = 0.027), COVID-19 SEIMC score (p = 0.003), and inflammation biomarkers [CRP/prealbumin (p = 0.011)]. Multivariate analysis revealed that hydration status was associated with increased mortality. HR was 2.967 (95%CI, 1.459−6.032, p < 0.001) for hydration and 2.528 (95%CI, 1.664−3.843, p < 0.001) for ECW/TBW, which were significantly greater than traditional measures: CRP/prealbumin 3.057(95%CI, 0.906−10.308, p = 0.072) or BUN/creatinine 1.861 (95%CI, 1.375−2.520, p < 0.001). Hydration > 76.15% or ECW/TBW > 0.58 were the cut-off values predicting COVID-19 mortality with 81.3% and 93.8% sensitivity and 64 and 67.6% specificity, respectively. Hydration status offers a sensitive and specific prognostic test at admission, compared to established poor prognosis parameters. Conclusions and Relevance: Overhydration, indicated as high hydration (>76.15%) and ECW/TBW (>0.58), were significant predictors of COVID-19 mortality. These findings suggest that hydration evaluation with 50 kHz phase-sensitive BI measurements should be routinely included in the clinical assessment of COVID-19 patients at hospital admission, to identify increased mortality risk patients and assist medical care.

Background: Bioelectrical impedance analysis (BIA) is a widely used method for estimating body composition. Avoiding foods/beverages containing caffeine is a frequently enforced pre-test protocol to ensure reliability of BIA measurements. However, few studies have evaluated whether this is necessary, with conflicting results. We aimed to determine whether the coffee consumption differing in caffeine content influences BIA parameters in healthy adults., Methods: Twenty-five healthy adults were enrolled in a randomized, double-blind cross-over trial. Three amounts of caffeine were given with 200 mL of coffee: 0 mg (11 g of decaffeinated), 200 mg (5.5 g of caffeinated plus 5.5 g of decaffeinated), and 400 mg of caffeine (11 g of caffeinated). BIA measurements were conducted at 6 different times, and coefficient variations (CV) explored., Results: No differences were observed for group × time interaction on impedance, resistance, or reactance (p > 0.05). Values of BIA parameters increased after 30-min of coffee consumption, independently of the caffeine dosage (all p < 0.001). Body fat percentage followed the same pattern and increased after 45-min (p < 0.05). Median CV for consecutive impedance, resistance, and reactance measurements were >95%CI of expected device measurement error over 70-min, without difference between groups. Urine output volume was not different between groups (decaffeinated: 440.45 ± 197.57 mL; 200 mg: 471.80 ± 171.88 mL; 400 mg: 489.30 ± 204.10 mL, p > 0.05)., Conclusion: Coffee consumption influenced BIA-derived results after 70-min but was not related to caffeine content, likely due to water intake., (© 2021. The Author(s), under exclusive licence to Springer Nature Limited.)

Background & Aims: Obesity is characterized by fat mass excess (FM), extra cellular water increase (ECW) and, with ageing, decrease in fat free mass (FFM). The validity of body impedance analysis (BIA) in patients with mild to severe obesity is still debated. The purpose of this study is to describe the Resistance (Rz) and Reactance (Xc) values obtained by Body Impedance Analysis (BIA) in a wide cohort of Italian patients with mild to severe obesity. The secondary endpoint is to describe the resulting body composition values (as percentage and indexes) in this population., Methods: The study enrolled adult in-patients with mild to severe obesity (classified with class I, II and III obesity) undergoing clinical care rehabilitation program for obesity complications and weight loss. BIA values were grouped by sex, BMI and age classes., Results: A total of 8303 patients with obesity, aged 18 to 90 y, were studied. The Resistance (Rz) and Reactance (Xc) were reported by sex, age and BMI classes. In women and men both, the phase angle (PhA) decreases with increasing BMI (kg/m 2 ) and the resulting BIA vector was significantly shifted. The FM index (FMI) was higher (p < 0.0001) in women while FFM index (FFMI) was higher in men (p < 0.0001) and significantly associated with BMI. FFMI decreased with age in both sex (p < 0.0001). Skeletal mass (SM) presents a progressive reduction in relation to age and gender both., Conclusions: The present BIA-based body composition analysis in a wide cohort of mild to severe obese patients revealed a significantly decreased Rz and Xc values with a consequent significant decrease of PhA in a BMI-dependent manner. The body compartments estimation with available equations was BMI, sex and age dependent. These observational results could be the basis for the development of new equations adapted for patients suffering from obesity., Competing Interests: Conflicts of interest The authors declare no conflict of interest., (Copyright © 2021 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.)

The body composition phenotype of an athlete displays the complex interaction among genotype, physiological and metabolic demands of a sport, diet, and physical training. Observational studies dominate the literature and describe the sport-specific physique characteristics (size, shape, and composition) of adult athletes by gender and levels of competition. Limited data reveal how body composition measurements can benefit an athlete. Thus, the objective is to identify purposeful measurements of body composition, notably fat and lean muscle masses, and determine their impact on the health and performance of athletes. Areas of interest include relationships among total and regional body composition measurements, muscle function, sport-specific performance, risk of injury, return to sport after injury, and identification of activity-induced fluid shifts. Discussion includes the application of specific uses of dual X-ray absorptiometry and bioelectrical impedance including an emphasis on the need to minimize measurement errors and standardize protocols, and highlights opportunities for future research. This focus on functional body composition can benefit the health and optimize the performance of an athlete., Competing Interests: The authors report no conflicts of interest. They also guarantee, beyond the absence of any conflict of interest, that the manuscript was created consistent with the ethical standards of the International Journal of Sports Medicine 148., (Thieme. All rights reserved.)

Background: It is important for highly active individuals to accurately assess their hydration level. Bioelectrical impedance (BIA) can potentially meet these needs but its validity in active individuals is not well established., Methods: We compared whole-body bioimpedance measurements obtained from multi-frequency bioelectrical impedance spectroscopy (BIS, Xitron 4200) at a 50 kHz frequency with those determined by a phase-sensitive single-frequency device (SF-BIA, BIA-101, RJL/Akern Systems) in two populations: active adults and elite athletes., Results: One hundred twenty-six participants, including active males involved in recreational sports (N = 25, 20-39 yr) and elite athletes (females: N = 26, 18-35 yr; males: N = 75, 18-38 yr) participated in this study. Reactance (Xc), Resistance (R), Impedance (Z), and phase angle (PhA) were obtained by BIS and SF-BIA. Small but significant differences (R: -9.91 ± 15.09 Ω; Xc: -0.97 ± 2.56 Ω; Z: -9.96 ± 15.18 Ω; PhA: 0.12 ± 0.2°) were observed between the bioimpedance equipment in all measured variables (p < 0.05) though differences were within the devices' technical error of measurements. Device-specific values were highly (p < 0.0001) correlated [R 2 ranged from 0.881 (Xc) to 0.833 (R)], but slopes and intercepts were different (p < 0.0001) from 1 and 0, respectively. Relatively large limits of agreement were observed for R (-40 to 21 Ω), Xc (-6 to 4 Ω), PhA (-0.4 to 0.5°), and impedance (-40 to 20 Ω)., Conclusion: Bioimpedance measurements from the current single- and multi-frequency devices should not be used interchangeably. The of lack of agreement between devices was observed in determining individual values of R, Xc, Z and PhA of highly active populations possibly due to methodological and biological factors.

Purpose: The exercise-induced increase in skin and body temperature, cutaneous blood flow and electrolyte accumulation on the skin affects the validity of bioimpedance analysis (BIA) to assess post-exercise changes in hydration. This study aimed to assess the influence of a 10-min cold (22°C) shower on the time course of impedance measurements after controlled exercise., Methods: Ten male athletes (26.2±4.1 yr and BMI 23.9±1.7 kg/m 2 ) were tested on two different days. During both trials, athletes ran for 30 min on a treadmill in a room at 22°C. In a randomized cross-over trial, the participants underwent a 10-min cold shower in the trial occasion and did not shower in the control trial. BIA variables were measured before running (i.e. baseline (T0)), immediately after exercising (T1), then at 20 (T2), 40 (T3) and 60 min (T4) after the exercise. The shower was performed after T1 in the shower trial., Results: Body weight decreased similarly after running (-0.4±0.1%, p<0.001 and -0.4±0.1%, p<0.001). Resistance and vector length returned to baseline at T2 in the shower trial, whereas baseline values were achieved at T3 in the control trial (p>0.05). In the control trial, reactance remained at a lower level for the entire testing period (38.1±6.9 vs. 37.3±6.7, p<0.001). Forehead skin temperature returned to baseline values at T2 with shower, while it was still high at T4 without shower (p<0.001)., Conclusions: The present data show that a 10-min cold shower enables the stabilization of BIA measurements within 20 min after exercise, which might facilitate the assessment of hydration change after exercise.

Purpose of Review: Malnutrition affects prognosis in many groups of patients. Although screening tools are available to identify adults at risk for poor nutritional status, a need exists to improve the assessment of malnutrition by identifying the loss of functional tissues that can lead to frailty, compromised physical function, and increased risk of morbidity and mortality, particularly among hospitalized and ill patients and older adults. Bioimpedance analysis (BIA) offers a practical approach to identify malnutrition and prognosis by assessing whole-body cell membrane quality and depicting fluid distribution for an individual., Recent Findings: Two novel applications of BIA afford opportunities to safely, rapidly, and noninvasively assess nutritional status and prognosis. One method utilizes single-frequency phase-sensitive measurements to determine phase angle, evaluate nutritional status, and relate it to prognosis, mortality, and functional outcomes. Another approach uses the ratio of multifrequency impedance values to indicate altered fluid distribution and predict prognosis., Summary: Use of basic BIA measurements, independent of use of regression prediction models and assumptions of constant chemical composition of the fat-free body, enables new options for practical assessment and clinical evaluation of impaired nutritional status and prognosis among hospitalized patients and elders that potentially can contribute to improved patient care and clinical outcomes. However, these novel applications have some technical and physiological limitations that should be considered.

Purpose: Bioelectrical impedance analysis (BIA) equations can predict total body water (TBW) and extracellular water (ECW) in non-athletic healthy populations. This study aimed: a) to develop BIA-based models for TBW and ECW prediction based on dilution methods in a sample of national level athletes; and b) to validate the new models with a cross-validation approach in a separate cohort using dilution methods as criterion., Methods: Two hundred and eight highly trained athletes (21.3 ± 5.0 years) were evaluated during their respective competitive seasons. Athletes were randomly split into development (n = 139) and validation groups (n = 69). The criterion method for TBW was deuterium dilution and for ECW was bromide dilution, where ICW was the respective difference between both. Resistance (R) and reactance (Xc) were obtained with a phase-sensitive 50 kHz BIA device and used for the estimation of TBW and ECW., Results: Athletic BIA-based models were developed for TBW and ECW [TBW = 0.286 + 0.195*S(2)/R + 0.385*Wt + 5.086*Sex; ECW = 1.579 + 0.055*S(2)/R + 0.127*Wt + 0.006*S(2)/Xc + 0.932*Sex, where sex is 0 if female or 1 if male, Wt is weight (kg), S is stature (cm), and R and Xc are in ohm (Ω)]. Cross validation revealed R(2) of 0.91 for TBW and R(2) 0.70 for ECW and no mean bias., Conclusions: The new equations can be considered valid, with no observed bias, thus affording practical means to quantify TBW and ECW in national level athletes., (Copyright © 2015. Published by Elsevier Ltd.)

Background: Interventions to attenuate the adverse effects of age-related loss of skeletal muscle and function include increased physical activity and nutritional supplementation., Objective: This study tested the hypothesis that nutritional supplementation with whey protein (22 g), essential amino acids (10.9 g, including 4 g leucine), and vitamin D [2.5 μg (100 IU)] concurrent with regular, controlled physical activity would increase fat-free mass, strength, physical function, and quality of life, and reduce the risk of malnutrition in sarcopenic elderly persons., Design: A total of 130 sarcopenic elderly people (53 men and 77 women; mean age: 80.3 y) participated in a 12-wk randomized, double-blind, placebo-controlled supplementation trial. All participants concurrently took part in a controlled physical activity program. We examined body composition with dual-energy X-ray absorptiometry, muscle strength with a handgrip dynamometer, and blood biochemical indexes of nutritional and health status, and evaluated global nutritional status, physical function, and quality of life before and after the 12 wk of intervention., Results: Compared with physical activity and placebo, supplementation plus physical activity increased fat-free mass (1.7-kg gain, P < 0.001), relative skeletal muscle mass (P = 0.009), android distribution of fat (P = 0.021), handgrip strength (P = 0.001), standardized summary scores for physical components (P = 0.030), activities of daily living (P = 0.001), mini nutritional assessment (P = 0.003), and insulin-like growth factor I (P = 0.002), and lowered C-reactive protein (P = 0.038)., Conclusion: Supplementation with whey protein, essential amino acids, and vitamin D, in conjunction with age-appropriate exercise, not only boosts fat-free mass and strength but also enhances other aspects that contribute to well-being in sarcopenic elderly. This trial was registered at clinicaltrials.gov as NCT02402608., (© 2016 American Society for Nutrition.)

Background & Aims: Determine the accuracy of body density (Db) estimated with upper-body skinfold thickness (SFT) measurements compared to air-displacement plethysmography (ADP) and ascertain whether body mass index (BMI) impacts the accuracy of SFT to assess Db., Methods: We estimated Db with SFT and ADP in 131 healthy men and women with normal (N; 18.5-24.9kg/m(2)), overweight (OW; 25-29.9kg/m(2)), and obese (OB; 30-39.9kg/m(2)) BMI., Results: Compared with ADP, SFT overestimated (p<0.05) Db in OW and OB females and in OB males (-0.0047, -0.0164 and -0.0119g/cc, respectively), and underestimated (p<0.05) Db in N females and males (0.0050 and 0.0068g/cc, respectively) but did not differently estimate Db in OW males. The gender by BMI group interaction was not significant. SFT underestimated (p<0.05; 0.0058g/cc) Db in the N and overestimated (p<0.05; 0.0113g/cc) Db in the OB BMI groups. The error in predicting Db did not change significantly over the range of Db within the N (r=0.239, p=0.06) and OB (r=0.160, p=0.934) BMI groups. Limits of agreement were -0.0165 to 0.0284g/cc and -0.0365 to 0.0085g/cc for the N and OB BMI groups, respectively. The error of estimating Db with SFT was correlated with mean Db in the aggregate sample (r=0.495, p<0.0001) and the OW group (r=0.394, p<0.009). The regression-based limits of agreement were +/-0.0226g/cc in the total group and +/-0.0168g/cc in the OW group., Conclusions: Although SFT offer practical advantages, the validity of SFT to estimate Db among individuals with N and OB BMI is adversely affected., (Copyright 2009. Published by Elsevier Ltd.)

Objective: This study tested the hypothesis that bioelectrical impedance vectors, group and individual, are valid indicators of total body water (TBW) and hydration status in women experiencing fluid gain and loss during and after pregnancy., Methods: We measured TBW, assessed with D(2)O dilution, and resistance (R) and reactance (Xc), determined with 800 microA at 50 kHz and standardized for height (H) and plotted on a bivariate (R-Xc) graph, in 15 women, 21-37 y of age, longitudinally before and during pregnancy and postpartum (PP)., Results: Body weight (61.9 +/- 2.3 to 75.5 +/- 2.3 kg) and TBW (31.4 +/- 1.1 to 38.2 +/- 1.1 L) increased (P < 0.05) from before pregnancy to the third trimester of pregnancy and decreased PP (67.0 +/- 2.3 kg and 32.7 +/- 1.1 L, P < 0.05). R/H and Xc/H decreased during pregnancy (P < 0.05, 361 +/- 10 to 318 +/- 10 and 44 +/- 1 to 36 +/- 1 omega/m, respectively) and increased PP (P < 0.05, 355 +/- 10 and 41 +/- 1 Omega/m). Vector length decreased (P < 0.05, 363 +/- 10 to 320 +/- 10 Omega) during pregnancy and increased PP (P < 0.05, 357 +/- 10 Omega). Changes in vector length and TBW during pregnancy and PP were correlated (r = -0.599, P < 0.001). Women with vectors exceeding a 75% tolerance interval had greater TBW gain (10-12 versus 5-6 L) during pregnancy compared with other women with vectors within this tolerance level., Conclusion: These findings indicate that impedance vectors provide quantitative evidence of hydration status during pregnancy and that the impedance vector method is useful in monitoring hydration status in pregnancy.

Objective: This study tested the hypothesis that supplementation of chromium picolinate (CrPic), 200 microg Cr/d, compared with an equivalent amount of picolinic acid (1720 microg) in CrPic and placebo, decreases body weight, alters body composition, and reduces iron status of women fed diets of constant energy and nutrients., Methods: We fed 83 women nutritionally balanced diets, used anthropometry and dual x-ray absorptiometry to assess body composition, and measured serum and urinary Cr and biochemical indicators of iron status before and serially every 4 wk for 12 wk in a double-blind, randomized trial., Results: CrPic supplementation increased (P < 0.0001) serum Cr concentration and urinary Cr excretion compared with picolinic acid and placebo. CrPic did not affect body weight or fat, although all groups lost (P < 0.05) weight and fat; it did not affect fat-free, mineral-free mass or measurements of iron status., Conclusion: Under conditions of controlled energy intake, CrPic supplementation of women did not independently influence body weight or composition or iron status. Thus, claims that supplementation of 200 microg of Cr as CrPic promotes weight loss and body composition changes are not supported.

The in vivo effects of gavage administration of the synthetic, functional biomimetic cation [Cr(3)O(O(2)CCH(2)CH(3))(6)(H(2)O)(3)](+) to healthy and type 2 diabetic model rats are described. After 24 weeks of treatment (0-1,000 microg Cr/kg body mass) of healthy Sprague Dawley rats, the cation results in a lowering (P < 0.05) of fasting blood plasma low-density lipoprotein (LDL) cholesterol, total cholesterol, triglycerides, and insulin levels and of 2-h plasma insulin and glucose concentrations after a glucose challenge. Zucker obese rats (a model of the early stages of type 2 diabetes) and Zucker diabetic fatty rats (a model for type 2 diabetes) after supplementation (1,000 microg Cr/kg) have lower fasting plasma total, high-density lipoprotein, and LDL cholesterol, triglycerides, glycated hemoglobin, and insulin levels and lower 2-h plasma insulin levels in glucose tolerance tests. The lowering of plasma insulin concentrations with little effect on glucose concentrations suggests that the supplement increases insulin sensitivity. The cation after 12 and 22 or 24 weeks of administration lowers (P < 0.05) fasting plasma glycated hemoglobin levels in the Zucker diabetic and Zucker obese rats, respectively, and thus can improve the glucose status of the diabetic models. The effects cannot be attributed to the propionate ligand.