The usefulness and limitations of muscle quality assessment for sarcopenia diagnosis

This article discusses the concept of muscle quality, a relatively new term in physiological and medical research that has gained prominence since 2006. Initially defined as specific tension (muscle strength per unit muscle mass), the concept has expanded with technological advancements. Early research in 1990’s defined muscle quality as the ratio of muscle strength to lean mass. The relationship between aging and muscle quality is complex, with studies showing inconsistent results across genders and measurement methods. Since 2000, advanced imaging techniques (MRI, CT, ultrasound) have expanded muscle quality assessment to include muscle composition, particularly intramuscular fat infiltration and extracellular matrix changes. Muscle quality can be evaluated through various methods including MRI/MRS, CT, ultrasound imaging, dilution methods, bioelectrical impedance, and specific tension measurements. Each method has advantages and limitations regarding accessibility, cost, and reproducibility. In sarcopenia guidelines, the Global Leadership Initiative on Sarcopenia (GLIS) recently proposed that specific tension (force-to-size ratio) should be included in sarcopenia’s conceptual definition, while morphological features like fat infiltration should not. However, standardized measurement protocols and cutoff values remain challenging to establish.