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Ava Kerr, Gary Slater, Nuala Byrne and Janet Chaseling

The three-compartment (3-C) model of physique assessment (fat mass, fat-free mass, water) incorporates total body water (TBW) whereas the two-compartment model (2-C) assumes a TBW of 73.72%. Deuterium dilution (D2O) is the reference method for measuring TBW but is expensive and time consuming. Multifrequency bioelectrical impedance spectroscopy (BIS SFB7) estimates TBW instantaneously and claims high precision. Our aim was to compare SFB7 with D2O for estimating TBW in resistance trained males (BMI >25kg/m2). We included TBWBIS estimates in a 3-C model and contrasted this and the 2-C model against the reference 3-C model using TBWD2O. TBW of 29 males (32.4 ± 8.5 years; 183.4 ± 7.2 cm; 92.5 ± 9.9 kg; 27.5 ± 2.6 kg/m2) was measured using SFB7 and D2O. Body density was measured by BODPOD, with body composition calculated using the Siri equation. TBWBIS values were consistent with TBWD2O (SEE = 2.65L; TE = 2.6L) as were %BF values from the 3-C model (BODPOD + TBWBIS) with the 3-C reference model (SEE = 2.20%; TE = 2.20%). For subjects with TBW more than 1% from the assumed 73.72% (n = 16), %BF from the 2-C model differed significantly from the reference 3-C model (Slope 0.6888; Intercept 5.093). The BIS SFB7 measured TBW accurately compared with D2O. The 2C model with an assumed TBW of 73.72% introduces error in the estimation of body composition. We recommend TBW should be measured, either via the traditional D2O method or when resources are limited, with BIS, so that body composition estimates are enhanced. The BIS can be accurately used in 3C equations to better predict TBW and BF% in resistance trained males compared with a 2C model.

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Mollie G. DeLozier, Bernard Gutin, Jack Wang, Charles E. Basch, Isobel Contento, Steven Shea, Matilde Irigoyen Patricia Zybert, Jill Rips and Richard Pierson

Anthropometric and bioimpedance regression equations were developed for young children using total body water (TBW) as the criterion. Ninety-six boys and girls, 4-8 years of age, served as subjects. Measures included height, weight, five skinfold thicknesses, three circumferences, total body bioimpedance, and separate bioimpedance measures of the arm, trunk, and leg. Height and weight alone accounted for .70 of the variance in TBW. Adding other measures did not significantly increase the R 2. Standard errors of estimate for TBW were similar to those reported for older individuals (1.39-1.44 1) but may be too large relative to the small size of the subjects for the equations to be acceptable.

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Vincent J. Dalbo, Michael D. Roberts, Scott E. Hassell, Jordan R. Moon and Chad M. Kerksick

Background:

This investigation examined the safety and efficacy of a silica-based mineral antioxidant complex (MAC) that has been suggested to influence body water and buffer lactate.

Methods:

In a double-blind, randomized crossover design, male participants completed testing for 3 conditions: water only (baseline), rice flour (placebo), and MAC supplementation. Participants visited the laboratory on 5 occasions: familiarization, baseline, Testing Day 1, washout, and Testing Day 2. Baseline and Testing Days 1 and 2 consisted of fasting blood, pre- to postexercise body-water assessment and determination of VO2peak on a cycle ergometer. The supplementation protocols were separated by 1 wk and balanced to minimize an order effect.

Results:

No differences between conditions were found for heart rate, blood pressure, or serum-safety markers (p > .05). Before exercise there were no differences between conditions for total body water (TBW), intracellular water (ICW), or extracellular water (ECW). No significant interactive effects for supplementation and exercise were found for TBW, ICW, or ECW (p > .05). A time effect for TBW (p < .01) and ICW (p < .001) was present. Within-group changes in TBW occurred in the MAC condition, and within-group changes for ICW occurred in the MAC and placebo conditions. Ratings of perceived exertion and blood lactate increased (p < .05) with exercise. No significant effects were found for performance variables.

Conclusions:

MAC supplementation had no impact on aerobic exercise performance and lactate response. Increases in TBW and ICW occurred after MAC consumption, but these changes appeared to have minimal physiological impact.

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John B. Leiper and Ron J. Maughan

Total body water (TBW) and water turnover rates (WTR) of 8 competitive swimmers (SW) and 6 age-matched non-training individuals (CON) were determined using deuterium oxide dilution and elimination. During the 7-day study, individuals in the SW group trained 9 times, swimming on average 42.4 km, while the CON group did no regular exercise. Water temperature in the swimming pool was between 26 and 29 °C during training sessions. Body mass at the beginning and end of the study period remained essentially the same in the SW (67.8 ± 6.3 kg) and CON (61.1 ± 8.5 kg) groups. Mean ± SD TBW of the SW (38.7 ± 5.6 L) was similar to that of the CON (37.5 ± 8:0 L). Mean WTR was faster in the SW (54 ± 18 ml · kg · day−1) than the CON (28 ± 21 ml · kg · day−1). Mean daily urine output was similar in the SW (14 ± 5 ml · kg · day−1) and CON (14 ± 3 ml · kg · day−1). Calculated non-renal daily water loss was faster in the SW (41 ± 21 ml · kg · day−1) than the CON (13 ± 20 ml · kg · day−1). This study demonstrates that WTR are faster in young swimmers who exercise strenuously in cool water than in non-training individuals and that the difference was due to the approximately 3-times greater non-renal water losses that the exercising group incurred. This suggests that exercise-induced increases in sweat rates are a major factor in water loss in swimmers training in cool water.

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Scott B. Going, Daniel P. Williams, Timothy G. Lohman and Michael J. Hewitt

This paper reviews age related changes in body fat, fat-free body mass, and the subcomponents of FFM including protein, mineral, and body water. It gives an overview of common methods and their limitations in the elderly and reviews the effects of physical activity on body composition in middle-aged and older individuals. Surprisingly little information is available on this important topic in men and women >80 years of age. Although research to date has described a number of qualitative trends with aging and shown the correlations between changes in fat and FFM with disease risk, quantification of rate of change has proven difficult. This is partly because changes in the aging body affect the indicators of body composition, leading to estimation errors, and because few long-term longitudinal studies have been completed. The increasing awareness of the important relationships among health, nutrition, and body composition, and the profound change in population demographics projected for the next 25 to 50 years, has focused attention on this problem and will undoubtedly stimulate additional research in this area.

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Yoram Epstein and Lawrence E. Armstrong

Body water and electrolyte balance are essential to optimal physiological function and health. During exercise, work, or high temperatures, a significant level of dehydration can develop, and the ratio of extracellular to intracellular fluid can change, despite an ample supply of water. Physical and cognitive performance are impaired at 1-2% dehydration, and the body can collapse when water loss approaches 7%. Because fluid needs and intakes vary, formulating one general guideline for fluid replacement is difficult. Knowing the amount of water lost in sweat may enable predicting fluid needs via mathematical models for industrial, athletic, and military scenarios. Sodium imbalance might result from excessive Na+ loss or from gross o verity dration. In most work or exercise lasting < 3-4 hr, the major concern is that fluid be available to prevent heat-related illnesses, which can be prevented if fluid and electrolyte losses are balanced with intake, using the recommendations presented.

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Reid Reale, Gary Slater, Gregory R. Cox, Ian C. Dunican and Louise M. Burke

-in. Common and effective methods include active and passive sweating; diuretics; fluid and sodium restriction (reducing body water) and reduction of gut contents via laxative use, fasting, reducing food volume; and reduced carbohydrate and/or fiber intake ( Franchini et al., 2012 ; Reale et al., 2016

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Francesco Campa, Catarina N. Matias, Elisabetta Marini, Steven B. Heymsfield, Stefania Toselli, Luís B. Sardinha and Analiza M. Silva

standardized for the subject’s stature to classify differences in total body water (TBW; negatively related to vector length) and cell mass (positively related to PA). Even if the accuracy of classic BIVA in assessing the percentage of fat mass (%FM) and hydration status (ie, detection of hyper- or hypo

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Francesco Campa and Stefania Toselli

median line of the body and the upper limbs, distant 30° from the trunk. After cleansing the skin with alcohol, the operator placed 2 electrodes (Biatrodes Akern, Florence, Italy) on the back of the participant’s right hand and 2 electrodes on the neck of the right foot. 2 , 7 Total body water (TBW

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Alex S. Ribeiro, Matheus A. Nascimento, Brad J. Schoenfeld, João Pedro Nunes, Andreo F. Aguiar, Edilaine F. Cavalcante, Analiza M. Silva, Luís B. Sardinha, Steven J. Fleck and Edilson S. Cyrino

the square of height (m). Bioelectrical Impedance and Body Composition Measurements Spectral bioelectrical impedance equipment (Xitron Hydra, model 4200; Xitron Technologies, San Diego, CA) was used to estimate total body water (TBW), intracellular water (ICW), extracellular water, resistance ( R