Modern BIA views the human body as five “cylinders”: the arms, the legs, and the trunk. Accurate and independent measurements of each cylinder are essential for providing analysis not just for each cylinder, but for the entire body. InBody’s advanced technology allows all InBody devices to directly measure all five cylinders.
Direct Segmental Multi-frequency Bioelectrical Impedance Analysis (DSM-BIA), InBody’s signature technology, separately measures the impedance of the arms, legs, and trunk. Although accurate impedance measurement of each cylinder is critical for reliable results, the most important measurement is trunk impedance.
The trunk contains essential internal organs, and its metabolic characteristics are different from the other parts of the body. In terms of impedance, it is important to precisely and directly measure the trunk because resistance values in the trunk are much lower than those in the arms and legs. This means that the margin of error for trunk measurements must be controlled as much as possible.
Impedance values in the arms and legs generally range between 200~500Ω, while the values for the trunk are between 20~30Ω. Despite its low impedance, the trunk accounts for 50% of Lean Body Mass. Because the impedance values for the arms and legs range in the hundreds, an error of 1~2Ω will have a negligible effect on the final measurement. However, a 1~2Ω error in the trunk can cause significant miscalculations when determining results for the trunk. Therefore, overall body composition can only be accurately calculated when even slight changes in the impedance of the trunk can be detected. For this reason, accurate and direct trunk measurements are essential for determining body composition.
InBody’s patented design separates the current-emitting and voltage-detecting electrodes, which allows impedance to be measured in the area where current flow and voltage measurement overlap. Using DSM-BIA, InBody can determine the impedance values of the arms, legs, and trunk. This technology was first developed by InBody and is protected by patents in various countries around the world.
Conventional BIA devices, by contrast, employ the “Whole Body Impedance” measurement method, which only reports a single impedance value for the entire body. This is an imprecise and dated method because it cannot directly measure trunk impedance, which is essential for accurate measurements.