Ye X, et al. - This study tested the ability of ultrasound-measured echo intensity of the rectus femoris for distinguishing muscles affected by COPD compared with healthy non-COPD affected muscles. It was also investigated if the severity of ultrasonic abnormalities was related to health-related quality of life (HRQoL). Findings demonstrated that quantitative ultrasound served as a tool to distinguish healthy muscles from those affected by COPD grade I–IV. Furthermore, it was observed that quality and quantity of muscles were related to HRQoL and forced expiratory volume in 1 second. Overall, as a tool to examine disease severity in COPD and to monitor skeletal muscle changes attributable to disease progression or clinical intervention, ultrasonic echo intensity of the rectus femoris may prove to be useful.