Impact Of Standardised Versus Non-standardised Athlete Presentation On Technical And Biological Error In Physique Assessment Methods

Ava Kerr; Gary Slater; Nuala Byrne

doi:10.1249/01.mss.0000486655.80481.21

PURPOSE: Body mass index (BMI), since its introduction by Quetlet in 1869, has become a popular method for determining one's adiposity. It is used a surrogate marker of adiposity. Over the course of last century, similar indices have been proposed. Earlier studies had demonstrated that BMI was most fit for clinical use. However, none of those studies used percent body fat as the gold standard. My previous study evaluated BMI and Corpulence index (CI) against percent body fat as calculated by bioelectrical impedance, and showed that CI is a better predictor of adiposity than is BMI. The purpose of this study is to evaluate Body Mass Index, Corpulence Index, and waist circumference against a gold standard. Percent body mass was measured using a DXA scanner. METHODS: Data from Centers for Disease Control and Prevention (CDC's) National Health and Nutrition Examination Survey (NHANES) datasets from 2003-2004 (n=7,002) was used for this study. Percent body fat, as calculated by a DXA scanner, and the corresponding height, weight, and waist circumference were used to compare Waist circumference (WC), BMI and CI to percent body fat. Linear correlation was used to assess the relationship between these three markers and percent body fat. The analysis was repeated after the data was broken down by gender and race. Using the ASBP percent body fat guidelines, the diagnostic performance of BMI and CI was evaluated. RESULTS: In the overall analysis, CI had the better R2 value than BMI and WC. Two compartment (2C) models of physique assessment contain assumptions that can be overcome by a three compartment (3C) model, where total body water (TBW) is measured rather than assumed, or a four compartment (4C) model, where both TBW and bone mineral content (BMC) are measured. However, as TBW is the most variable component of fat free mass (FFM) the impact of athlete presentation on measurement error in 2C models has not been established. PURPOSE: To evaluate the impact of standardised versus non-standardised athlete presentation on technical and biological error on 2C and 3C models of physique assessment compared with the reference 4C model, over thirty six hours. METHODS: Thirty two athletic males underwent five test sessions using dual energy x-ray absorptiometry (DXA), bioelectrical impedance spectroscopy (BIS) and air displacement plethysmography (BOD POD) to measure body composition, with combinations of these used to establish 3C and 4C models. Tests were conducted after an overnight fast (in duplicate) and ~7 hrs later after ad libitum food/ fluid and physical activity, then repeated at 24 hrs replicating the initial test, and finally~15 min after ingestion of a standardised meal. Magnitudes of changes in the mean and typical errors of measurement were assessed by standardisation. RESULTS: Mean change scores for TBW assessment were trivial for standardised presentation tests (0.2%,-0.3%) and large for non-standardised test (~7 hrs post ad libitum) (3.4%). Standardised presentation mean change scores for fat mass (FM) were trivial for all models but substantially large for non-standardised tests (~7 hrs post ad libitum) in BIS, 3C, and 4C models (-15.1%,-6.9% and-6.7%) and post meal (9.8%, 5.7% and 5.2%). For FFM, mean change scores for standardised presentation tests were trivial for all models but non-standardised test (~7 hrs post ad libitum) produced large changes for BIS, 3C and 4C models (3.4%, 2.3% and 2.2%), small for DXA (1%) and trivial for BOD POD (0.9%). CONCLUSIONS: Models that included a measured TBW value from BIS (3C and 4C) were more sensitive to TBW changes in non-standardised conditions than 2C models in FM and FFM measurements. Biological error via acute hydration change in FFM is minimised in physique assessment models if athletes present in an overnight fasted state. (No relationships reported) PURPOSE: To determine whether the commonly used anthropometric equations or a new developed specific anthropometric equation are adequate to estimate body-fat percentage (BF%) in adolescent soccer players. METHODS: Ninety-eight players (65 males / 33 females; 13.4 ± 0.6 years) from different Spanish soccer clubs participated in the present study. Following the recommendations of the International Society of the Advancement of Kinanthropometry (ISAK), biceps, triceps, subscapular, supraspinale, iliac-crest, abdominal, front thigh and medial calf skinfolds were measured and inserted in the following prediction equations to estimate BF%: Johnston et al., Slaughter et al., Carter et al., Faulkner et al. and Deurenberg et al. Dual energy X-ray absorptiometry (DXA) was used as a reference method to evaluate BF%. Several 2-paired samples t-test were used to compare BF% from DXA and the different equations. The validity and presence of heteroscedasticity of these equations was assessed by Bland-Altman analyses. Stepwise linear-regression was used to develop the soccer-specific equation. A cross-validation for the new anthropometric equation was performed using Stein´s equation. RESULTS: The developed equation resulted as follows: %BF = 11.115 + 0.775*(triceps skinfold) + 0.193*(iliac-crest skinfold)-1.606*(sex; being sex=0 for female and sex=1 for male). The present study showed that Johnston et al. equation was the only one without differences with DXA, but with tendency towards heteroscedasticity. However, the proposed equation demonstrated high cross-validation prediction power (R2=0.85).

Impact Of Standardised Versus Non-standardised Athlete Presentation On Technical And Biological Error In Physique Assessment Methods

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