Relationship Between Bioelectrical Impedance Parameters and Appendicular Muscle Functional Quality in Older Adults from South-Western Poland

Purpose: The aim of this research was to assess the correlations between the impedance components and the appendicular skeletal muscle strength and functional quality indices in older adults. The use of the impedance parameters as potential identifiers characterizing the functional state of muscles could improve methods of monitoring "healthy ageing". Patients and Methods: A total of 346 subjectively healthy adults aged 50-83 years were subjected to tests. Body mass and height, hand grip strength and knee extensor strength were measured. Resistance, reactance and phase angle were measured using the bioelectrical impedance method. The relationship between the impedance parameters and the appendicular skeletal muscle strength and quality indices was evaluated using stepwise multiple regression. Results: Participants aged >= 65 years were found to be characterized by lower values of the impedance parameters and the appendicular skeletal muscle strength and functional quality indices than participants 10 years younger. In both groups of sexes, the relative percentage differences in limb strength between the age groups were 3-6 times greater than the differences in appendicular skeletal muscle mass. Significant regression models for muscle strength and quality, with strong age, sex and reactance prediction and a weaker phase angle effect, were obtained. Conclusion: The impedance components explain the part of changes in muscle strength which is independent of the decline in skeletal muscle mass. Phase angle and reactance can be suitable for diagnosing and preventing dangers connected with the decline in muscle quality, but it is necessary to establish their normalized reference values for older adults.