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). Fat-free 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 fat-free mass, body cell mass, total body water, and intracellular water. Studies of large populations have produced equations that yield fat-free 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 high-frequency meter, a microprocessor and a printer. This meter, called an impedance meter, measures resistance and reactance. The microprocessor computes the size of the fat-free mass and body cell mass compartments in kilograms and performs all secondary calculations. The printer provides a printout of the results. test protocol Test Position Subjects lie face up on an examination table, bench or carpet in a supine position. Sensor Pads Two pairs of sensor electrodes (ecg pads) are placed on the subject's right hand and wrist, and right foot and ankle. Connecting Subject A cable is connected between the analyzer and the sensor electrodes. Subject Data Using the analyzer's keypad, the subject's gender, age, height, and weight are entered. A test is performed and a printout is generated by pressing a button. Testing Time About three minutes are required to set up and test a subject.