Within-day variability of whole-body and segmental bioelectrical impedance in a standing position

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Abstract

Objective:

To assess the variation in whole-body and segmental bioelectrical impedance measured in the standing position over the course of a day.

Subjects:

Sixteen healthy men aged 29.6 ± 3.1 years participated in this study.

Measurement:

Impedance between the hands (ZH-H), the feet (ZF-F), and the both hands and feet (ZH-F) was measured using a bioelectrical impedance analysis (BIA) data acquisition system at 500 μA and 50 kHz. Body weight, ZH-H, ZF-F and ZH-F were measured every 3 h from 0900 to 1800.

Results:

Body weight was slightly, but significantly, changed at 1200 (−0.4 ± 0.4 kg, P < 0.05), 1500 (+04 ± 0.3 kg, P < 0.05) and 1800 (−0.2 ± 0.2 kg, P < 0.05) compared to their respective previous measurement values. ZH-H significantly increased (P < 0.05) and ZF-F significantly decreased (P < 0.05) over the course of a day. The mean changes in impedance from 0900 to 1800 were +27.2 Ω (ZH-H) and −31.8 Ω (ZF-F), respectively. There were no changes in ZH-H at 1500 and in ZF-F at 1800 compared to their respective previous measurement values. The ZH-F value did not change significantly between 0900 and 1800.

Conclusion:

Although changes in standing whole-body impedance during the day are small, arm and leg segmental impedance measurements change significantly. Therefore, it is necessary to measure the impedance at regularly scheduled times when evaluating whole-body %fat or body water content using the segmental BIA method.

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