Annual appendicular skeletal muscle mass and quality changes in adults over 50 years of age, assessed using bioelectrical impedance analysis

Abstract Objective: It is essential to monitor changes in skeletal muscles in order to control healthy ageing. The aim of this study was to assess changes in muscle mass, strength and functional quality taking place in the course of ageing and to analyse their correlations with the recorded changes in impedance. Research Methods & Procedures: The study, carried out in two stages at a one-year interval, covered 313 subjectively healthy adults aged 50-83 years. Hand grip strength and knee extensor strength were measured. Impedance parameters were measured using the bioelectrical impedance analysis method and body composition components, including appendicular skeletal muscle mass, were estimated. The rates of annual changes in the analysed parameters and their correlations with changes in impedance were calculated. Results: The annual losses in muscle strength and functional quality were found to be considerably larger than the losses in appendicular skeletal muscle mass. Larger decreases in leg muscle strength were recorded in the women than in the men. The decline in reactance and phase angle was positively correlated with the decrease in the muscle condition evaluating indices. Conclusion: Muscle mass deficits are not the main cause of the decline in muscle functional quality in older adults. Changes in muscle condition, impairing muscle functions, can be identified by changes in impedance components. An analysis of changes in phase angle and reactance would facilitate the assessment of muscle quality in geriatric prophylaxis and in screening, but it is necessary to establish their normalized reference values for older adults.