You are in Home » Bioimpedance » Contributions The contributions by doctors in the making of Cube.Bioelectrical impedance analysis ( BIA). Impedance describes a measure of opposition to a sinusoidal alternating current. The symbol for impedance is usually Z and it is measured in ohms. Impedance represented as a complex quantity and the term complex impedance may be used interchangeably: The polar form conveniently captures magnitude and phase characteristics. The real port of impedance is the resistance R and the imaginary part is the reactance Xc (known also as capacitance and resistance) that is also associated with accumulated energy phenomenon’s. (Foster and Lukaski 1996 ; Grimnes and Martinsen, 2000 ). Impedance is an electrical property of materials and for this reason it is used in predictive equations that allows us to obtain an evaluation of the body composition in healthy subjects. By means of this method, you can estimate for example the total amount of water in your body and its intracellular and extracellular distribution. ( De Lorenzo and others 1997; Matthie and others 1998, Ellis 2000 ). We can simply say that the impedance technique measures the body’s impedance by introducing a small alternating electrical current so mild that its below the threshold of perception ( 800 micro amps ). This current passes through the fluids and the electrical components of the non-fatty tissues related to the volume of body liquids. In general, all biological structures pose a resistance( RZ ) with the alternative electrical current, keeping in mind that it represents the force that a conductor resists as the current passes through it. In relation to this, we can ascertain that fat-free body tissues are good conductors due to the fact that they are rich in body fluids therefore posing a low resistance. Different instead is the behaviour off adipose tissues and of the bones that are bad conductors which are lacking in fluids and electrolytes becoming a highly resistant electric current ( Khaled and others, 1988 ). Reactance (Xc) ,also known as capacity resistance is the force that a condenser opposes when electrical current passes through. The cells that are present in the organism behave like condensers that oppose to the alternating current a capacitive resistance. The reactance is therefore an indirect measure of the entire cellular membrane and is in proportion to the body cellular mass. BRIEFLY As previously mentioned, we can ascertain that not all tissues conduct energy in the same manner. As a matter of fact, there are tissues that are good conductors and others that are not. The force that contrasts the alternating current is called IMPEDANCE, which consists of two components :RESISTANCE (RZ) and REACTANCE (Xc).The first one is the force opposed by fluids and the second one is the force opposed by cells. The capacity is the property of the condenser to accumulate electric changes. |
|
|
|||||||||||
