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

Abstract

ObjectivesIt is essential to monitor changes in skeletal muscles to control healthy aging. The aim of this study was to assess changes in muscle mass, strength, and functional quality taking place in the course of aging and to analyze their correlations with recorded changes in impedance. MethodsThe study, carried out in two stages at a 1-y interval, covered 313 subjectively healthy adults ages 50 to 83 y. Hand grip strength and knee extensor strength were measured. Impedance parameters were measured using bioelectrical impedance analysis, and body composition components, including appendicular skeletal muscle mass, were estimated. The rates of annual changes in the analyzed parameters and their correlations with changes in impedance were calculated. ResultsThe 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 women than in men. The decline in reactance and phase angle were positively correlated with the decrease in the indices evaluating muscle condition. ConclusionsMuscle 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 normalized reference values for older adults.