Body Fat Percentage in College-Age Female Athletes as Estimated Via Four Selected Skinfold Equations: A Dual-Energy X-Ray Absorptiometry Validation

Abstract

Body composition is a health-related component of physical fitness that describes the relative percentage of all the different tissues that comprise the body and is generally assessed by estimating one's body fat percentage (BF%). An optimal body composition in an athletic population can have imperative health and performance implications. The skinfold method has been shown to provide a valid means for estimating BF% when compared to hydrostatic weighing in the overall population. However, there is limited data available to determine the accuracy of estimating BF% via the skinfold technique in college-age female athletes. PURPOSE: The purpose of this investigation was to validate or cross-validate body fat percentage (BF%) estimated via four different skinfold models to the criterion dual-energy x-ray absorptiometry (DEXA) in a cohort of college-age female athletes. METHODS: Forty college-age female athletes from the National Association for Intercollegiate Athletics volunteered to participate in this study. For each participant, total BF% was obtained via DEXA. In addition, skinfold thickness measurements were assessed at the following seven sites: chest, tricep, suprailliac, mid-axillary region, subscapularis, abdomen, and thigh. The criterion DEXA measurement was used to compare the accuracy of four skinfold equations as follows: 7-site skinfold equation (7SF), 4-site skinfold equation (4SF), 3-site skinfold equation (3SF), and a 2-site skinfold equation (2SF). RESULTS: The results indicated significant correlations between each skinfold equation and the DEXA (correlation coefficients ranged from r = 0.79 to 0.87, p < 0.01). However, all four skinfold equations significantly underestimated BF% by 7.7% to 8.6% (p < 0.05). Furthermore, the standard error of estimate ranged from 4.61 to 5.30 and total error ranged from 7.75 to 8.69 for each skinfold model. Last, compared to the DEXA, the limits of agreement (95% CI) for each skinfold model ranged as follows: SF7 = 1.0% to 13.8%; SF4 = 0.0% to 13.3%; SF3 = 0.1% to 14.9%; SF2 = 0.0% to 15.2%. CONCLUSIONS: In contrast to DEXA, the skinfold technique is relatively easy to obtain in a large group. Although this method has been widely used in field settings to assess BF%, the four equations in this study significantly underestimated BF% in the female athletic sample when compared to the criterion DEXA. Even though each skinfold model held strong correlations to the DEXA measure, there were significant mean differences between the DEXA and the skinfold models. Furthermore, the SEE and TE were rather large. PRACTICAL APPLICATIONS: Female athletes have been shown to be at an increased risk of eating disorders and body image concerns. Coaches, strength and conditioning professionals, athletic trainers, and exercise physiologist should be aware that over- or under-predicting BF% in this population could have potential health hazards. Doing so could place an apparently healthy subject in an “at risk” category. Therefore, future research is needed in a female athletic population to develop accurate skinfold techniques that are comparable to the criterion DEXA.