Phase angle can predict muscle strength in older adults: a cross-sectional study

Abstract

Muscle function is becoming increasingly vital in aging due to increased life expectancy. This study aimed to verify a relationship between phase angle (PhA) with muscle strength. We also intend to analyse the ability of PhA to predict muscle strength after adjusting for potential confounders. This cross-sectional study included fifty-six physically independent older adults (age, 70.57 ± 3.79 years; BMI, 28.09 ± 4.37 kg/m2). Bioelectrical impedance analysis was used to measure PhA at 50 KHz. Additionally, we assessed muscle strength through the handgrip test (dominant side) and maximal isokinetic strength of the dominant knee flexor and extensor during 3 repetitions of concentric actions at 60◦/s using an isokinetic dynamometer (Biodex System 3). The University of Évora Ethics Committee approved this study (approval no. 22030). There was a large correlation between PhA and knee extension (p< 0.01; r= 0.600) and there were moderate correlations between PhA and knee flexion (p< 0.01; r= 0.459) and with handgrip test (p= 0.002; r= 0.400). In addition, after adjusting for potential confounders the linear regression analysis demonstrated that PhA was a significant predictor of muscle strength in older adults: knee extension, β= 44.696; p< 0.01; R2= 0.694; knee flexion, β= 129.411; p< 0.01; R2= 0.410; and handgrip test, β= 39.915; p< 0.01; R2= 0.787. PhA can be considered a marker of muscle strength and can predict muscle strength in older adults.