Body Composition Evaluation Issue among Young Elite Football Players: DXA Assessment

Abstract

Accurate assessment of body composition is an important issue among athletes. Different methodologies generate controversial results, leading to a deep uncertainty on individual exercise prescriptions. Thus, this study aims to identify the differences between field methods, such as bioelectrical impedance (BIA) and skinfold assessment, with a clinical method, highly accurate, dual-energy X-ray absorptiometry (DXA), among elite young football players. Thirty-eight male football players with a mean (sd) age of 16.7 (0.87) years, involved in the Portuguese national competition of U16 (n = 13) and U19 (n = 25), were evaluated and objective measures of body composition, muscle strength and football skills were collected by trained specialists. Body composition was assessed using BIA (Tanita BC-418, Tanita Corp., Tokyo, Japan), in agreement with all the evaluation premises. Additionally, all athletes were evaluated using the clinical method DXA (Hologic Inc., Waltham, MA, USA). Among the U19 athletes, three skinfold sites (SKF) were assessed: chest, abdomin and thigh. The Spearman correlation coefficients and the mean difference between methods were calculated. The agreement between both methods was analyzed using Bland-Altman plots. Among the evaluated athletes, lower mean values of body fat % were found using BIA as a method of body composition assessment compared with DXA (12.05 vs. 15.58 for U16; 11.97 vs. 14.16 for U19). Despite the moderate correlation between methods (r = 0.33) to estimate the percentage of total fat, the median of the difference (DXA vs. BIA) was relevant in clinical terms, with 2.90% and 1.47% for U16 and U19 athletes, respectively. Stronger correlations were found between the sum of the SKF and DXA fat estimation (r = 0.68). The Bland-Altman plots showed a clear underestimation in the evaluations using the BIA, namely among athletes with better body composition profiles (8%–12% of fat). Using BIA, an underestimation of body fat assessment was observed among 94.5% of the athletes with less than 12% body fat mass. Among the evaluated athletes, fat mass was underestimated at a median value of 2.21% using BIA in comparison with DXA. The sum of the SKF showed a stronger correlation with the reference method (DXA) (r = 0.68) than BIA.

Concurrent validity of five prediction equations to evaluate fat percentage in a sports group expected to yield high performance from Medellín, Colombia

“…The Slaughter equation showed an ICC of 0,741 (IC95%: -0,186 to 0,921), which varied very little when discerning by sex. These results are not comparable to those from other studies given that in them, the Pearson or Spearman correlation coefficients were used to assess the concurrent validity of this equation vs. DEXA (14,15). On the other hand, the average bias reached 5,6 percentage points with limits of agreement between -0,4 and 11,6, which was higher than the one reported in two Spanish studies: one among 98 soccer players of both sexes and an average age of 13,4 (SD=0.6) with a bias of 3,3 percentage points (limits of agreement: -2,9 to 9,5) (16) and the other among 88 swimmers of both sexes with an average age of 14,3 (SD=1,84) and a bias of 4,1 percentage points (limits of agreement: -2,2 to 10,4) (17).…”

Anthropometric Profile of Soccer Players as a Determinant of Position Specificity and Methodological Issues of Body Composition Estimation

“…It is assumed that the higher the level of soccer, the lower the %BF. In addition, different methods of estimating the %BF may lead to different results, and it is proven that the difference is not negligible [12]. The use of equations to calculate %BF has a good correlation with standard gold methods, such as DXA, but the different choices can increase the difference between methods [40].…”

“…Each technique presents advantages, however, also has limitations [10]. We know that there is a wide range of methods used, without standardization [11], which lead to quite different results [12], making it often impossible to make comparisons between samples from different studies. Despite the validity of using equations based on skinfolds (SKF) as a method of assessing body composition, one of the assumptions is that the choice of the formula used has been validated in a similar population [11].…”

UEFA expert group statement on nutrition in elite football. Current evidence to inform practical recommendations and guide future research

“…172 Due to several manufacturers and software, many different DXA units, while not interchangeable, showed exceptionally good precision and accuracy for FFSTM, bone mineral content and FM and may be more appropriate when assessing change in leaner athletic populations in comparison to other practical methods, namely anthropometry and bioelectrical impedance analysis. 173 Ensuring standardisation in positioning, food and hydration status will reduce errors associated with the use of DXA. 161 162 174 Practitioners must recognise that radiation exposure, although generally small, will limit the frequency of measurements, so the timing of assessments should be carefully planned.…”