New equation to estimate body fat mass in international-elite soccer referees

In soccer referees, body fat mass (FM) is commonly estimated by skinfolds or dual-energy X-ray absorptiometry (DXA). The main aim was to crossvalidate the skinfolds for quantifying body fat against a recent model of DXA and to develop a specific equation for this population. This study involved a group of 43 international-level, elite male soccer referees (age 39±4 y) to participate inWorld Cup in Russia 2018. Methodology used for the assessment of body composition was made with the integration of anthropometry, skinfold thickness and DXA. Anthropometric measurements were taken following ISAK protocol. Percentage of FM from skinfold thicknesswas then calculated from themain eight equationsmost commonly used: 1. Yushaz (Yuhasz 1962), 2. Faulkner (Faulkner 1968); 3. Eston et al. (Eston et al. 2005); 4. Durnin & Womersley (Durnin andWomersley 1974); 5. Reilly et al. (Reilly et al. 2009), 6. Deuremberg et al. (Deurenberg et al. 1991), 7. Suarez et al. (Suarez-Arrones et al. 2018) and 8. the mean of all of these equations as suggestedMascherini et al. (2015). All skinfold equations (with the exception of Eston) showed large-to-very large positive correlations (r from 0.71 to 0.78, p ≤ 0.01) with DXA. All the sum of skinfolds showed moderate-to-very large positive correlations with DXA (r from 0.41 to 0.76, p ≤ 0.01). The best equation found was FM% = 8.5 + (0.572 × supraspinal skinfold) + (0.252 × abdominal skinfold) based on significance, coefficient of determination, and sample size, included supraspinal skinfold and abdominal skinfold (P < .001; R2adj = .589; df = 40). Almost all the equations showed positive correlations, but with different values in comparison with a recentmodel of DXA. Finally, the sum of skinfolds appears to be a good alternative when limited time and budget is available.