Bioimpedance analysis: evaluation of leg-to-leg system based on pressure contact foot-pad electrodes


Medicine & Science in Sports & Exercise: April 1997 - Volume 29 - Issue 4 - pp 524-531
Applied Sciences: Biodynamics

Conventional single frequency bioimpedance analysis (BIA) systems require technician placement of arm and leg gel electrodes, a suitable location for recumbent measurements, and a separate measurement of body weight. The aim of this study was to evaluate a new single frequency 50 kHz leg-to-leg bioimpedance analysis (BIA) system combined with a digital scale that employs stainless steel pressure-contact foot pad electrodes for standing impedance and body weight measurements. Healthy adults were evaluated for 1) electrode validity and 2) potential for body component estimation. Pressure-contact foot-pad electrode measured impedance was highly correlated with (N= 9, r = 0.99, P < 0.001) impedance measured using conventional gel electrodes applied to the plantar surface of both lower extremities; mean(±SD) impedance was systematically higher by about 15 ohms for pressure contact electrodes (526 ± 56 ohms vs 511 ± 59 ohms; P< 0.001). Second, the relationship between stature-adjusted leg-to-leg impedance (H2/Z) measured by the new system and two body composition components (total body water by 3H2O dilution (N = 144); and fat-free body mass, by underwater weighing and dual x-ray absorptiometry (N = 231)) was modeled using multiple regression analysis. Correlation coefficients for H2/Z alone versus body composition components were lower for leg-to-leg BIA than for arm-to-leg BIA: correlation coefficients and SEEs became similar for the leg-to-leg and arm-to-leg BIA systems with addition of three covariates (age, gender, and waist/hip circumference ratio) to regression models. The leg-to-leg pressure contact electrode BIA system has overall performance characteristics for impedance measurement and body composition analysis similar to conventional arm-to-leg gel electrode BIA and offers the advantage of increased speed and ease of measurement.

Department of Medicine, Obesity Research Center, St. Luke's-Roosevelt Hospital, Columbia University, College of Physicians and Surgeons, New York, NY 10025; Department of Human Nutrition, Wageningen Agricultural University, Wageningen, THE NETHERLANDS

Submitted for publication October 1995.

Accepted for publication July 1996.

We would like to thank Jill Grammes, Diosdado Santos, and Dr. Richard N. Pierson Jr. for their contributions to this study.

Support for this study was provided in part by a National Institutes of Health Minority Pre-Doctoral Training Award (CN) and by Tanita Manufacturing Corporation, Tokyo, Japan.

Address for correspondence: Christopher Nuñez, Weight Control Unit, 1090 Amsterdam Avenue, 14th floor, New York, NY 10025.

©1997The American College of Sports Medicine