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Tori M. Stone, Jonathan E. Wingo, Brett S. Nickerson and Michael R. Esco

Control and Prevention, 2015 ; Kanis et al., 2008 ; Ralston & Uitterlinden, 2010 ). Therefore, a high BMC is associated with lower risk for developing the disease, whereas a low BMC is associated with greater risk. The conventional method to assess BMC is by using dual-energy X-ray absorptiometry (DXA

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Flinn Shiel, Carl Persson, Vini Simas, James Furness, Mike Climstein, Rod Pope and Ben Schram

Dual energy X-ray absorptiometry (DXA) uses a machine originally developed to provide information about bone mineral density, with the additional capability to assess and analyze body composition (BC) while imparting only low levels of radiation (less than a thousandth of the maximum recommended

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Ana Torres-Costoso, Dimitris Vlachopoulos, Esther Ubago-Guisado, Asunción Ferri-Morales, Iván Cavero-Redondo, Vicente Martínez-Vizcaino and Luis Gracia-Marco

skeletal growth related to PA may be important for the prevention of osteoporosis in later life. It is well known that certain sports induce osteogenic responses in the growing skeleton ( 36 ,41 ). However, monitoring osseous changes over time is not an easy task. Dual-energy X-ray absorptiometry (DXA) is

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Danielle L. Gyemi, Charles Kahelin, Nicole C. George and David M. Andrews

data have commonly been provided from a small number of cadaver segmentation studies, 5 limiting the applicability of the data across different populations. Dual-energy x-ray absorptiometry (DXA) is a valid and reliable method for analyzing body composition 6 – 9 and estimating inertial

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Nidia Rodriguez-Sanchez and Stuart D.R. Galloway

Dual energy x-ray absorptiometry (DXA) is a popular tool to determine body composition (BC) in athletes, and is used for analysis of fat-free soft tissue mass (FFST) or fat mass (FM) gain/loss in response to exercise or nutritional interventions. The aim of the current study was to assess the effect of exercise-heat stress induced hypohydration (HYP, >2% of body mass (BM) loss) vs. maintenance of euhydration (EUH) on DXA estimates of BC, sum of skinfolds (SF), and impedance (IMP) measurements in athletes. Competitive athletes (23 males and 15 females) recorded morning nude BM for 7 days before the first main trial. Measurements on the first trial day were conducted in a EUH condition, and again after exercise-heat stress induced HYP. On the second trial day, fluid and electrolyte losses were replaced during exercise using a sports drink. A reduction in total BM (1.6 ± 0.4 kg; 2.3 ± 0.4% HYP) and total FFST (1.3 ± 0.4 kg), mainly from trunk (1.1 ± 0.5 kg), was observed using DXA when participants were HYP, reflecting the sweat loss. Estimated fat percent increased (0.3 ± 0.3%), however, total FM did not change (0.1 ± 0.2 kg). SF and IMP declined with HYP (losses of 1.5 ± 2.9% and 1.6 ± 3% respectively) suggesting FM loss. When EUH was maintained there were no significant changes in BM, DXA estimates, or SF values pre to post exercise, but IMP still declined. We conclude that use of DXA for FFST assessment in athletes must ensure a EUH state, particularly when considering changes associated with nutritional or exercise interventions.

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Georgianna Tuuri and Mark Loftin

Hydrodensitometry (HD), skinfold thickness measurements (SK), and dual-energy X-ray absorptiometry (DXA) were compared for estimating percent body fat (%BF) in youth competitive swimmers. Agreement was assessed using Bland-Altman plots and linear regression of the differences between methods compared to method means. Limits of agreement between the three techniques were large. Hydrodensitometry and SK demonstrated no difference in precision. Variance was observed between DXA and the other two techniques, with DXA demonstrating a wider distribution of measurement scores than HD or SK. These methods do not appear to be interchangeable when measuring percent body fat in youth swimmers.

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Sidnei Jorge Fonseca-Junior, Aldair J. Oliveira, Luiz Lannes Loureiro and Anna Paola Trindade Pierucci

Purpose:

Body composition of adolescent athletes is often evaluated scientifically and in sports by using reference equations developed from nonathlete adolescent populations. The aim of this study was to analyze the validity of predictive equations based on skinfold measurements, as compared with dual-energy X-ray absorptiometry (DXA), to estimate body fat in adolescent modern pentathlon athletes.

Methods:

51 athletes, 27 male (mean age = 15.1 years; standard deviation, SD = 1.5 years) and 24 female (mean age = 14.2 years; SD = 2.5 years), were assessed using DXA, anthropometric parameters, sports practice anamnesis, and pubertal stages. Agreement between methods was tested with boxplots of mean comparisons using Student’s t test (p < .05), and Bland-Altman plots.

Results:

The body density equations of Durnin & Rahaman (1967) and Durnin & Womersley (1974) showed better agreement with DXA than the other predictive equations, for both females (difference between means=-2.03; 2SD = 8.44) and males (difference between means = 0.98; 2SD = 7.30). There were no mean differences between these equations and the reference method (DXA; p > .05), but they did display high variability (2SD).

Conclusion:

The high variability among results indicated imprecision. Predictive skinfold equations developed for nonathlete adolescents do not offer good validity for modern adolescent pentathlon athletes, and should be avoided.

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Alisa Nana, Gary J. Slater, Arthur D. Stewart and Louise M. Burke

Dual energy X-ray absorptiometry (DXA) is rapidly becoming more accessible and popular as a technique to monitor body composition, especially in athletic populations. Although studies in sedentary populations have investigated the validity of DXA assessment of body composition, few studies have examined the issues of reliability in athletic populations and most studies which involve DXA measurements of body composition provide little information on their scanning protocols. This review presents a summary of the sources of error and variability in the measurement of body composition by DXA, and develops a theoretical model of best practice to standardize the conduct and analysis of a DXA scan. Components of this protocol include standardization of subject presentation (subjects rested, overnight-fasted and in minimal clothing) and positioning on the scanning bed (centrally aligned in a standard position using custom-made positioning aids) as well as manipulation of the automatic segmentation of regional areas of the scan results. Body composition assessment implemented with such protocol ensures a high level of precision, while still being practical in an athletic setting. This ensures that any small changes in body composition are confidently detected and correctly interpreted. The reporting requirements for studies involving DXA scans of body composition include details of the DXA machine and software, subject presentation and positioning protocols, and analysis protocols.

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Alisa Nana, Gary J. Slater, Will G. Hopkins and Louise M. Burke

Dual-energy X-ray absorptiometry (DXA) is becoming a popular tool to measure body composition, owing to its ease of operation and comprehensive analysis. However, some people, especially athletes, are taller and/or broader than the active scanning area of the DXA bed and must be scanned in sections. The aim of this study was to investigate the reliability of DXA measures of whole-body composition summed from 2 or 3 partial scans. Physically active young adults (15 women, 15 men) underwent 1 whole-body and 4 partial DXA scans in a single testing session under standardized conditions. The partial scanning areas were head, whole body from the bottom of the chin down, and right and left sides of the body. Body-composition estimates from whole body were compared with estimates from summed partial scans to simulate different techniques to accommodate tall and/or broad subjects relative to the whole-body scan. Magnitudes of differences in the estimates were assessed by standardization. In simulating tall subjects, summation of partial scans that included the head scan overestimated whole-body composition by ~3 kg of lean mass and ~1 kg of fat mass, with substantial technical error of measurement. In simulating broad subjects, summation of right and left body scans produced no substantial differences in body composition than those of the whole-body scan. Summing partial DXA scans provides accurate body-composition estimates for broad subjects, but other strategies are needed to accommodate tall subjects.

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Grant M. Tinsley and Brett S. Nickerson

of common methods, including dual-energy X-ray absorptiometry (DXA). However, the requirement of an overnight fasting period imposes limitations for when and how many assessments can be conducted. Nonetheless, the importance of an overnight fast prior to DXA assessment has been confirmed by reports