Clinical Application of Skeletal Muscle Quantity and Quality Assessment Using Bioelectrical Impedance and Ultrasound Images.

A decline in muscle strength is a key factor responsible for physical dysfunction in older individuals. Both loss of muscle quantity and quality are associated with muscle strength decline. While the gold standard method for evaluating muscle mass and quality is magnetic resonance imaging, it is not suitable for clinical settings because of the measurement and analysis costs. Bioelectrical impedance analysis (BIA) and B-mode ultrasonography are clinically useful alternatives for skeletal muscle assessment owing to their feasibility and noninvasiveness. The recent advancements in the techniques for BIA and ultrasonography have improved their accuracy in assessing skeletal muscle quantity and quality, making them useful in detecting age-related and disease-specific alterations. This review comprehensively analyzes the advantages of using BIA and ultrasound imaging for assessing skeletal muscle quantity and quality and detecting muscle degeneration. We summarize the recent findings regarding age-related changes in muscle characteristics and the associations of muscle degeneration with physical dysfunction in patients with knee osteoarthritis. Furthermore, we discuss the clinical application of skeletal muscle assessment using BIA and ultrasound for evaluating training effects and exercise prescription.