The effect of the menstrual cycle on bioimpedance reliability

Abstract

The potential influence of the menstrual cycle on percent body fat (%BF) measurements from bioimpedance analysis (BIA) was investigated on 36 female Ss (19-40 yr). Subjects were divided into 2 groups based on oral contraceptive agent (OCA) use. Those women not using an OCA were placed into the OFF group (n = 20) and those using an OCA were placed into the ON group (n = 16). The menstrual cycle was divided into 4 phases: premenstrual, menstrual, postmenstrual, and intermenstrual. All subjects were weighed and tested for %BF using BIA a minimum of 12 times, at least 3 times within each cycle phase. Subjects were also underwater weighed a single time, approximately at the middle of their respective cycles. Repeated measures ANQVAs were used to test for significance between and within groups for weight, resistance, and %BF across the 12 measurements and across the 4 phases. No significance was found for any variable tested with the exception of weight within each group across the 12 measurements (p < . 0 5 ) . Percent body fat data from hydrostatic weighing (HW) were compared to BIA values from each of the 4 phases using a repeated measures ANOVA and PPMC. No significant differences were found (p > .05) between HW and BIA for any phase. The average correlation between HW and BIA was .78, SEE = 3.3%. Overall, neither OCA use nor the menstrual cycle itself appeared to influence %BF measurements from BIA.