Joanne Wallace

Body composition of English Premier League soccer players: Influence of playing position, international status, and ethnicity

Abstract Body composition is a key consideration in the physical make-up of professional soccer players. The aims of the present study were to determine whether the body composition of professional soccer players varied according to playing position, international status or ethnicity, and to establish which variables best distinguished the soccer players from a reference group. Body composition was assessed using dual-energy X-ray absorptiometry in 64 male professional soccer players. Measured variables included bone mineral density and the relative amounts of lean and fat mass. Data were analysed using analysis of variance and stepwise discriminant function. The soccer players recorded better values than a reference group (n = 24) for all body composition compartments. Percent lean mass and bone mineral density were the variables best able to identify the soccer players (95.5% correctly classified). Differences in body composition were evident between goalkeepers and outfield players, but not between outfield playing positions. No differences were found on the basis of international status. The non-Caucasian players demonstrated significantly lower percent body fat (9.2 ± 2.0%) than the Caucasian players (10.7 ± 1.8%). It was concluded that body composition is important for elite soccer players, but that homogeneity between players at top professional clubs results in little variation between individuals.

A Macro-quality Evaluation of DXA Variables Using Whole Dissection, Ashing, and Computer Tomography in Pigs

IntroductIon Although body composition (BC) data acquisition and ad hoc analysis are both popular and important, selecting an appropriate method or technique for accurate and/or precise assessment of individuals and/or groups remains a challenging task within various sectors of public health. Since 1950s and 1960s, with the pioneer work of Keys and Brozek (1), Forbes et al. (2), Siri (3), Brozek et al. (4), Behnke (5), and Durnin and Rahaman (6), BC almost became a scientific discipline profiling itself with the development of many methods, techniques, and equipments. Popular approaches have been criticized over the years because they are subject to measurement errors and/or violation of basic assumptions underlying their use such as hydrodensitometry (7–11) or anthropometry, e.g., skinfolds (12–16) and the universally accepted new method of choice, the dual-energy X-ray absorptiometry (DXA) (7,17–21). Curiously, after reviewing the literature of DXA application, one cannot avoid obtaining a very controversial impression of this new method. On the other hand, we find an important number of validation and application studies (too many to refer to all) that support the DXA technique as convenient, as the criterion for % fat for lean body mass (LBM), and as a criterion for bone mineral content (BMC) (8,10,11,22,23). A number of authors as mentioned in Provyn et al. (21) suggest DXA as the gold standard for validation of other techniques essential for the measurement of BC (24–26). In addition to the violation of basic assumptions as referred to earlier, one needs to repeat and underline that DXA, hydrodensitometry, anthropometry, air, gas, and water displacement methods, bioelectrical impedance are all indirect in vivo techniques for measuring BC. Validation or even cross-validation in between indirect methods cannot guarantee both accuracy and reality precision. Perfect correlations and low coefficients of variation allow for good predictions and assumptions only (18,21). Possibly the greatest problems with accuracy/ precision in DXA are found with fat and lean tissue estimates (27), with its projected areal bone density (17,20,28) and with the basic confusion between overall BC terminology, e.g., fat, adipose tissue (AT), fat-free mass (FFM), LBM, lean and AT free mass (ATFM), bone mineral density (BMD), surface and volume density, BMC, ash weight, actual mineral content, and BMC, with or without soft tissue (ST) covering (12,21,29). These issues give rise to concern, but the accuracy of absorptiometry can be affected by the choice of calibrating materials. As a consequence, both absolute and relative values can differ substantially between manufacturers, between instruments and the ad hoc software used (10,27). Despite the multitude of DXA validation studies and despite the related controversy of its measuring quality, it is being reaffirmed that there have been comparatively few validation experiments of accuracy, and precision of either bone or BC measurements by cadaver and/or carcass analysis. More of these validations against direct values are necessary before we can be confident about the accuracy of absorptiometry (27). A review of the state of the art of carcass studies related to DXA (28) reveals validation attempts with rhesus monkeys (30), mice (31,32), piglets (9,33–37), pigs (38–40), pig hindlegs (21), chickens (41), and with dogs and cats (42). The majority of these validation studies were based on chemical analysis and only a few on direct dissection comparison. Almost all studies indicated perfect correlations for all variables with DXA, but approximately half of the results of the various variables were found to be significantly different (P < 0.001 and P < 0.05). In approximately a third of these studies, DXA was suggested to be valid and accurate for all its variables, whereas two studies indicated significant differences and/or erroneous data at all levels and for all variables. However, two important statements resulting from these studies are retained: (i) dissection and direct comparison combined with bone ashing are considered the most accurate and direct validation technique (9) and (ii) further research with direct dissection and ashing is needed (27), in particular, with focus on the influence of abdominal and thoracic organs associated with

How Well do Skinfold Equations Predict Percent Body Fat in Elite Soccer Players

The use of generic equations for estimating percent body fat from skinfold thicknesses can be criticised when applied to specific sports. The present aims were to compare existing methods of using skinfold data and to derive an equation for predicting body fat values in professional soccer players. Forty-five professional soccer players (24.2 +/- 5.0 years; 82.0 +/- 8.5 kg; 1.82 +/- 0.07 m) participated. Skinfold thicknesses were assessed at eight sites for the application of existing prediction equations. Skinfold data were also utilised to determine a novel soccer-specific equation. All players had a reference estimate of percent fat by dual-energy x-ray absorptiometry (DXA). The existing skinfold equations differed from the DXA-referenced values by varying degrees, the equation of Withers et al. (1987) demonstrating the lowest bias and highest relationship and agreement with DXA. Regression analysis resulted in an equation incorporating anterior thigh, abdominal, triceps and medial calf sites, accounting for 78.4% variance in DXA criterion values.

Whole Body Composition by Hologic QDR 4500/A DXA: System Reliability versus User Accuracy and Precision

Accurate and precise measurement of human tissue composition is both important and imperative in individual health assessment. Although body composition (BC) data acquisition and analysis are both popular and important, selecting an appropriate method or technique for accurate and/or precise assessment of individuals and/or groups remains a challenging task within various sectors of public health. Since 1950s and 1960s, with the pioneer work of Keys & Brozek (1953), Forbes et al. (1956), Siri (1956), Brozek et al. (1963), Behnke (1963), Durnin & Rahaman (1967), BC almost became a scientific discipline profiling itself with the development of many methods, techniques, and equipments. Popular approaches have been criticized over the years because they are subject to measurement errors and/or violation of basic assumptions underlying their use such as hydrodensitometry (Clarys et al., 2010c; Clasey et al., 1999; Elowsson et al., 1998; Heyward, 1996; Johansson et al., 1993; Prior et al., 1997) or anthropometry, e.g., skinfolds (Beddoe, 1998; Clarys et al., 1987, 2005, 2010a; Martin et al., 1985, 1992; Scafoglieri et al., 2010a) and the universally accepted new method of choice, the dual energy X-ray absorptiometry (DXA) (Bolotin, 1998, 2007; Bolotin & Sievanen, 2001; Bolotin et al., 2001; Clarys et al., 2010b; Provyn et al., 2008; Scafoglieri et al., 2010c).

The Measurement of Body Composition in an Athletic Population: The Importance of DXA

The assessment of an athletes physiology is a key skill for the applied exercise physiologist as it allows for the planning of training and competition strategy. One key aspect of this assessment is the analysis of his/her body composition. The present article examines issues related to measuring body composition in an athletic population. Numerous methods are currently employed; however Dual-energy X-ray Absorptiometry (DXA) should be considered the most valid in an athletic population. This article will examine some of the shortcomings in other methods as well as identify some of the theory underpinning the measurement of body composition and the use of DXA.

A macro-quality field control of dual energy X-ray absorptiometry with anatomical, chemical and computed tomographical variables

Dual-energy X-ray absorptiometry (DXA) studies both in humans and animals one cannot avoid obtaining a controversial impression concerning its use. The pro’s and contra’s however are dictated by the model DXA was verified with. This study will cross-validate and compare fan beam data with both dissection and computed tomography (CT) scanning data.