What is Bioimpedance Analysis (BIA)?
Bioimpedance is the preferred method for assessing body composition in nutritional, muscular, and water-electrolyte contexts. It is a system for analyzing body composition based on the “reading” of direct electrical measurements taken with an impedance analyzer.

Why is it important to assess body composition?
Understanding your body composition is essential for maintaining health—even if you are of normal weight—or for regaining optimal fitness or improving athletic performance. A scale only tells you your weight; it doesn’t provide information on the amount of fat mass and muscle mass you have, nor does it indicate whether you are well-hydrated or, on the contrary, in a state of dehydration or water retention (edema). Bioimpedance, however, gives you detailed information on all these aspects.

How does it work?
BIA is based on the principle that different types of tissue exhibit specific electrical conductivity, making them recognizable. All biological structures oppose the flow of direct or alternating current by generating:

• Resistance: A bioelectrical parameter inversely related to the amount of bodily fluids (more water = less resistance).

• Reactance: A parameter directly related to the density of cells in tissues (with equal fluid levels, more cells = higher reactance).

• Phase Angle: The bioelectrical value that indicates the ratio between Reactance (Xc) and Resistance (Rz), essentially reflecting the balance between intracellular and extracellular volumes.

“BiaVector”
The method known as the Resistance-Reactance Graph (RXc Graph) compares the vector measured in an individual with the reference range of a normal population, expressed as percentiles of a bivariate (Gaussian) distribution.

How is the test performed?
The measurement is taken by placing one pair of electrodes on the back of the hand and another pair on the back of the foot (using the tetrapolar hand-foot technique). The electrodes are connected to the measuring instrument via clamps.
An imperceptible alternating current of very low intensity (800 µA) and high frequency (50 KHz) is passed through the electrodes. As it travels through the body, it encounters different resistances depending on the composition of various body regions. The bioimpedance device records the speed and the voltage drop (change in current) and thus provides the electrical data (resistance and reactance expressed in Ohms). The software then converts these electrical measurements into clinical data, based on algorithms that take into account the population reference values, as well as the subject’s anthropometric measurements (weight and height), age, and gender.

What information is obtained from the test?

Bioimpedance Analysis in the Athletic Field

Bioimpedance measurements, whether in power sports or endurance sports, are fundamental for:

• Training Planning: Optimizing workload and recovery times (whether for isotonic or aerobic training).

• Nutritional Programming: Tailoring dietary plans.

• Hydration Monitoring: Essential for optimizing athletic performance.

For an athlete, monitoring Body Cell Mass (BCM), more commonly known as muscle mass, is very important to prevent its decline due to overtraining—excessively intense or prolonged exercise—or an unsuitable diet for the physical demands involved. The BIA test also evaluates another critical parameter in sports, especially in endurance disciplines: hydration status. Even a slight dehydration, resulting in a 4–5% decrease in extracellular water (ECW), can lead to a significant drop in athletic performance—up to a 20–30% decrease in physical efficiency.

When extracellular hydration is optimal before a competition or training session, there is a lower risk of dehydration, muscle injuries, and a faster recovery to peak physical condition. It is therefore clear that the primary supplementation athletes need is proper hydration, applicable to both professional and amateur athletes.

Through the bioimpedance exam, you can understand an athlete’s body composition and take action to maintain proper hydration and BCM, thereby improving overall condition and athletic performance. This enables the calibration of both training and nutrition to bring the athlete to ideal conditions.

Tests are performed using devices such as the BIA 101 BIVA Akenr Pro.