A comparison between two methods for measuring limb resistances with wrist and ankle electrodes

Segmental measurements of limb resistances permit to evaluate the regional distribution of fat-free-mass (FFM). As shown by Organ et al. (J Appl Physiol 1994;77:98-112) "virtual" limb resistances can be measured with only peripheral electrodes at ankle and wrist, which is faster and does not require undressing. This paper presents a different method for obtaining "virtual" limb resistances from peripheral electrodes and compares it with that of Organ et al. and with segmental measurements using same protocol. It is found that virtual arm resistances of both methods were overestimated as compared to segmental values, by 6.8% in men and 5.8% in women for our method and by 7.4% and 8% for Organ et al. one. Virtual leg resistances were found, for both methods, to be slightly lower than segmental leg resistances measured with proximal waist electrodes, which were a little overestimated. But after correcting this overestimation using Organ et al. data, we evaluated the overestimation of virtual leg resistances to be 2.3% in men and 2.8% in women by our method versus 4.4% and 5.9%, respectively, for Organ et al. one. An important finding was the strong correlation between virtual resistances of both methods and segmental ones, as their ratio had a small standard deviation between 0.019 and 0.024 for arms and legs. Thus, the overestimation of limb resistance is automatically corrected when FFM is determined by an equation calibrated with DXA segmental measurements.