Multi-Frequency Bioimpedance Reliability and Validity for Assessing Total and Segmental Body Composition in College-Aged Males

Abstract

Bioimpedance analysis (BIA), which may be affected by hydration status, is frequently used to assess total and segmental body composition for research purposes. However, the reliability and validity of BIA in determining body composition in all populations including well hydrated college aged males has not been determined. PURPOSE: To determine the reliability of direct segmental multi-frequency BIA and its validity against dual energy x-ray absorptiometry (DXA) in a population of normally hydrated college-aged males. METHODS: Body composition was measured in the early morning 3 times in the following order: 1) BIA, 2) DXA, and 3) BIA, all in the same session lasting < 30 minutes. Immediately prior to body composition measurement, a urine sample was collected and analyzed for urine specific gravity (USG). To ensure normal hydration, a USG of 1.022-1.028 encompassing slightly dehydrated, euhydrated, and well hydrated statuses was required for study participation. RESULTS: A total of 102 males (mean age = 20.35 ± 1.38 years) were included in the analyses. Intra-class correlations between the two BIA determined fat free mass (FFM) of total body, right arm, left arm, trunk, right leg and left leg were .974, .961, .965, .963, .994, and .994, respectively. Two-tailed paired samples t-tests showed all comparisons of DXA FFM (bone mineral content [BMC] + lean mass) compared to the average of the two BIA FFM (comparable to DXA BMC + lean mass) to be significantly different (p <. 001) except for the trunk (p = .242). Segmental BIA FFM underestimated segmental DXA FFM by ≤ 1.05kg, while total body BIA FFM overestimated total body DXA FFM by 2.2kg. CONCLUSIONS: Multi-frequency BIA is reliable in determining total and segmental FFM. The significant differences between DXA and BIA in determining segmental FFM may be due to body composition derived from DXA is based on attenuation of x-ray to determine BMC, lean tissue, and fat mass while; body composition derived from BIA is based on impedance of body water content.