



overview



Bioimpedance analysis (BIA) is the analysis of resistance and reactance in the human body.
The characteristics and composition of a material can be
determined by analyzing their effect on an electrical current conducted in the material.
The effect due to energy dissipation is called resistance (R). The effect due to energy storage is called reactance (X). Units of resistance and reactance are called ohms. Resistance and reactance taken together are called the impedance (Z).
Fatfree mass in the human body is proportional to the resistance. Body cell mass is proportional to the reactance.
A bioimpedance analyzer measures resistance and reactance and computes fatfree mass, body cell mass, total body water, and intracellular water.
Studies of large populations have produced equations that yield fatfree mass and body cell mass in kilograms, and water compartments in liters for any combination of resistance and reactance measurements.
These studies also establish normal values for populations, and establish the relationship between body composition and health.
To measure resistance and reactance, a bioimpedance analyzer applies a small electrical current to the body via electrodes.
A bioimpedance analyzer is an electronic device containing a precision
highfrequency meter, a microprocessor and a printer. This meter, called
an impedance meter, measures resistance and reactance. The microprocessor
computes the size of the fatfree mass and body cell mass compartments in
kilograms and performs all secondary calculations. The printer provides a
printout of the results.






