[Bioimpedance analysis in sports and clinical practice: the influence of alternative measurement conditions on body composition indicators].

There is a number of standard conditions that must be followed during preparation and during the procedure of bioelectrical impedance analysis (BIA) for the results of body composition estimating to be correct. This is because many biological and non-biological factors influence the accuracy of the results. In the conditions of sports camps, fitness centers and in some groups of patients, it is impossible to carry out measurements in compliance with all standard conditions. Practicing researchers and clinicians should be aware of exactly what changes occur in body composition indicators under alternative measurement conditions. The purpose of the research was to identify which indicators change in the body composition protocol when certain standard conditions of bioimpedance measurement are not met and whether measurements taken in violation of one of the standard measurement conditions can be considered correct, i.e. in alternative conditions. Material and methods. 35 literature sources were analyzed, keyword searches were carried out in the PubMed, Scopus, Web of Science, Elsevier and eLibrary databases. Results. After aerobic and anaerobic exercise, when changing the standard position of the electrode on the lower limb [the measuring (sensor) electrode is moved from the articulation line of the tarsal joint (ventral position) to the Achilles tendon (dorsal position)], when changing the body position from «lying» to «standing», as well as after 1000 ml saline intravenous administration, the indicators of body resistance and the proportion of body fat significantly decrease, and the indicators of total body water, lean, active cellular and skeletal muscle mass significantly increase. Opposite trends in the change in indicators were obtained after drinking water, food intake, donating blood in a volume of 480 ml, when using bioadhesive electrodes with a small contact surface (adjacent area), during a long-term (60-240 min) study on an empty stomach, as well as after consuming anhydrous caffeine in capsules (200 mg, without dissolution in water, 60 min), caffeine as a drink, and black tea with sugar: body resistance and the proportion of body fat increased significantly, while total body water, lean, active cellular and skeletal muscle mass decreased significantly. All the obtained changes in body resistance and body composition indicators observed after violating one of the standard measurement conditions (except for studies assessing the effect of physical activity) were equated to the error of the BIA, as well as to the differences obtained when measuring on different devices. Conclusion. It is considered acceptable to perform BIA with a violation of one of the standard measurement conditions if another measurement is impossible, with the exception of performing BIA after physical exercise.