Ava Kerr

Validation of Bioelectrical Impedance Spectroscopy to Measure Total Body Water in Resistance-Trained Males

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.

Impact of food and fluid intake on technical and biological measurement error in body composition assessment methods in athletes

Two, three and four compartment (2C, 3C and 4C) models of body composition are popular methods to measure fat mass (FM) and fat-free mass (FFM) in athletes. However, the impact of food and fluid intake on measurement error has not been established. The purpose of this study was to evaluate standardised (overnight fasted, rested and hydrated) v. non-standardised (afternoon and non-fasted) presentation on technical and biological error on surface anthropometry (SA), 2C, 3C and 4C models. In thirty-two athletic males, measures of SA, dual-energy X-ray absorptiometry (DXA), bioelectrical impedance spectroscopy (BIS) and air displacement plethysmography (BOD POD) were taken to establish 2C, 3C and 4C models. Tests were conducted after an overnight fast (duplicate), about 7 h later after ad libitum food and fluid intake, and repeated 24 h later before and after ingestion of a specified meal. Magnitudes of changes in the mean and typical errors of measurement were determined. Mean change scores for non-standardised presentation and post meal tests for FM were substantially large in BIS, SA, 3C and 4C models. For FFM, mean change scores for non-standardised conditions produced large changes for BIS, 3C and 4C models, small for DXA, trivial for BOD POD and SA. Models that included a total body water (TBW) value from BIS (3C and 4C) were more sensitive to TBW changes in non-standardised conditions than 2C models. Biological error is minimised in all models with standardised presentation but DXA and BOD POD are acceptable if acute food and fluid intake remains below 500 g.

Athlete Considerations for Physique Measurement

Physique traits are one of an array of variables known to influence performance of athletes across a wide range of sports. The routine monitoring of physique traits has become common practice amongst athletic populations, affording an opportunity to objectively assess the impact of training and diet and subsequently adjust these variables to optimise adaptations. An array of techniques is available to assess the physique traits of athletes. When selecting the most appropriate technique, a range of factors should be considered, including technical (safety, validity, precision and accuracy of measurement) and practical issues (availability, financial implications, portability, invasiveness, time effectiveness and technical expertise necessary), including the ability of the technique to accommodate the unique physique traits of athletes. Guidelines to assist with facilitating standardisation of athlete presentation prior to assessments are provided, with application to the majority of physique assessment techniques commonly applied amongst athletic populations such as dual-energy X-ray absorptiometry, air displacement plethysmography (i.e. Bod Pod) and bioelectrical impedance analysis. The exception may be surface anthropometry given results are minimally impacted by athlete presentation.

Optimising Physique for Sports Performance

Physical morphology or physique, including body mass or composition, size and shape, is important to optimise athletic performance in many sports. Routine monitoring of body composition amongst athletic populations remains a common practice and provides insight into growth, diet and training adaptations not otherwise available. Examples provided include weightlifting and bodybuilding, sprinting, combat and aesthetic sports. Characteristics such as body mass, lean mass and fat mass are plastic and are able to be manipulated.

Imaging Method: Dual-Energy X-Ray Absorptiometry

Dual energy X-ray absorptiometry is used for the assessment of physique traits of athletes. Given the use of X-rays and thus exposure to radiation, specific training by a suitably accredited national organisation is required before dual energy X-ray absorptiometry can be operated, and consideration of the cumulative X-ray dose for athletes needs to be considered. Standardisation of subject presentation (euhydrated and glycogen replete, overnight fasted and in minimal clothing) and positioning on the scanning bed (centrally aligned in a standard position using custom-made positioning aids) and manipulation of the automatic segmentation of regional areas of the scan results are necessary. The International Society for Clinical Densitometry has established good clinical practice guidelines relating to the acquisition and analysis of dual energy X-ray absorptiometry data.

Non-imaging Method: Bioelectrical Impedance Analysis

Bioelectrical impedance analysis allows measurement of total body water, which is used to estimate fat-free body mass and, by difference with body mass, body fat. An athlete appointment of 15 min is needed for body mass and standing stature measurement, electrode placement, and then 1 min of data collection. The method is popular due to the procedure being simple and non-invasive, good portability of the equipment and its relatively low cost compared to other methods of body composition analysis. However, precision and validity can be low without a standardised protocol of assessment that includes guidance for subject presentation. Sensitivity to monitor change of physique is low given variation in athlete presentation for testing can affect the results (e.g. levels of hydration). Training is available from equipment suppliers; however, there are no accreditation systems. The techniques to collect the data are easy; however, interpretation of the data is impeded given the black box approach to the data. Studies that compare results from bioelectrical impedance analysis to other body composition techniques are outlined, and example reports to athletes are provided.

Non-imaging Method: Air Displacement Plethysmography (Bod Pod)

Air displacement plethysmography is used to measure body volume. The Bod Pod (COSMED USA Inc., Concord, CA) is an easy-to-use, convenient, non-invasive device that can accommodate a large spectrum of athletic physiques, assessing fat and fat-free mass reliably and accurately. Estimates of body density are in close agreement to those using the hydrostatic weighing technique, with Bod Pod now considered the gold standard for assessment of body density in multi-compartment models. It often underestimates fat mass compared to other physique assessment techniques; however, this may be due to poor standardisation practices. When undertaken in a well-controlled standardised manner, Bod Pod has proven to be an accurate and reliable technique for tracking physique changes over time. It is valuable in large athletes who may be more comfortable undertaking physique assessment via Bod Pod compared to other techniques where reliability in this population might be an issue.

Resources: YouTube Videos and the JELCKC Website and Archive

Additional resources to support the content in Best Practice Protocols for Physique Assessment in Sport are available at the J.E. Lindsay Carter Kinanthropometry Clinic and Archive (JELCKCA) website jelckca-bodycomp.com, which links you to the YouTube channel http://tinyurl.com/YouTubeChannel-ProfPatria. YouTube videos include introduction of experts and their background in physique assessment, demonstration of physique assessment procedures and commentary from experts on issues related to physique assessment. The physical kinanthropometry archive is located at the Auckland University of Technology Millennium precinct in Auckland, New Zealand.