Body Impedance Analyzer (BIA)

BIA is used to estimate body composition such as fat, water and muscle. A tiny electrical current is sent to the body via several electrodes and the body “opposition” to the flow of this current is measured (called Impedance) as the current travels more easily through body compartments with more water (such as blood, urine and muscle mass) than the ones with less water (such as fat, bones and air). When current goes through water containing compartments it faces only an electrical Resistance R but when trying to go through less watery compartments it has to go through cell membranes which (due to their chemical structure) act like a capacitor with a unique resistance called Reactance (in fact it is a time delay caused by current trying hard to go through the medium). We call the sum of simple Resistance (example water) and Reactance (example cell membrane) Impedance. If our electrical current is an A/C (alternating current), its particular frequency acts differently when passing through water and non-water body compartments: it travels easier through cell membrane than watery parts (causing a “phase” shift) which is also used to determine body (total)cell mass to fat free mass: this “phase angle” is proportional to to the ratio of Reactance and Resistance. Monitoring body compartments contents over time (such as phase angle, impedance etc) gives us valuable information about general health state or recovery progress.