The effect of different body positions on anthropometric measurements and derived estimates of body composition

Abstract

Purpose: Measurement of cross-sectional lean limb area using physical anthropometry is usually performed in the standing position, but sometimes this may be impractical. Our aim was to determine the effect of different positions on cross-sectional lean area of the upper arm, calf and thigh derived from girth and skin-fold measurements. Methods: Twenty healthy volunteers participated. Girth and skin-fold thickness of the upper arm, calf and thigh were measured in the standing, sitting and supine positions. We derived lean cross-sectional area (cm2), and calculated the mean difference, its 95% confidence intervals (CI), and the 95% limits of agreement (LOA) between standing and the other two positions. Results: For the upper arm, mean differences in lean cross-sectional area for the supine-standing and sitting-standing positions were 0.7cm2, (95% CI -0.6 to 2.0) and -0.6cm2, (95% CI -1.4 to 0.3) respectively. Mean differences for thigh were 3.9cm2 (95% CI -2.3 to 10.1) and -4.3cm2 (95% CI -8.6 to 0.0) for supine-standing and sitting-standing respectively. For the calf, mean difference for supine-standing was -3.1cm2 (95% CI -5.3 to -0.9), while for sitting-standing it was 0.3cm2 (95% CI -1.8 to 2.4). The range of values expected to cover agreement for 95% of subjects (LOA) was widest for the thigh and narrowest for the upper arm. Conclusion: In young healthy subjects, lean cross-sectional area differs according to measurement position, particularly for the lower limb. The same measurement method should be used in any one individual when monitoring change.