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Article Title

BODY COMPOSITION DIFFERENCES BY ASSESSMENT METHODS SUCH AS DEXA, HYDROSTATIC, BIO-IMPEDANCE, AND SKIN FOLD

Abstract

For years the most common traditional assessment methods to determine body composition (BC) have been bio-impedance (BI), skin fold (SF), and hydrostatic weighting (HW). Bio-impedance is a non-invasive technique but has been reported to have poor validity. The new assessment in the area of anthropometric measurements is using the DEXA scan or duel x-ray absorption. This method is reported to be the most valid and reliable means of predicting an individual’s BC however the time and cost prohibit many institutions from using this method. PURPOSE: to determine if there is any significant difference in prediction of BC using DEXA, BI, HW, and 3, 4, 7, and 9 SF assessment. Also to determine if bone density significantly affects HW and BC prediction. METHODS: Forty six healthy individuals (17 males and 29 females with a mean age of 22) were recruited to participate in this study. Anthropometric measurements of height, weight, BI, 3 site, 4 site, 7 site, and 9 site SF assessments, HW, and DEXA total body scan were all collected for each participants on the same day. Each anthropometric assessment except the DEXA was repeated several times by the same researcher to insure reliability. Participants were classified as below normal, normal, and above normal in bone density based on DEXA results to determine if bone density affected hydrostatic prediction. RESULTS: Single factor ANOVA was performed to determine if there was any significant difference in BC by assessment methods (females p=.001, males p=0.001). In both genders the 9 site skin fold and DEXA results were significantly greater than the rest of the traditional BC assessments. A t-test assuming equal variance was performed by gender and results indicated that there was a significant difference between the HW and DEXA BC results (females p=0.001, males p=0.001). A correlation was performed between t-score of bone density and DEXA BC prediction and the results indicate there was no meaningful correlation in the females and a significant positive correlation in the males (females r=-0.007, males r=0.571). CONCLUSION: results from this study indicate that 3 site, 4 site and 7 site SF and BI have a significant correlation to hydrostatic BC prediction indicating that BI is a valid assessment method. DEXA results were roughly 8% higher in prediction BC when comparing HW which is similar to other research studies. Those individuals who had bone density two standard deviations greater than normal had a larger difference between predictions of DEXA BC and HW. Based on these findings, bone density should be considered a variable when assessing hydrostatic weighing for body composition prediction.

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