Clinimetric Properties of Muscle Mass and Stiffness Measurements of the Quadriceps in Patients With COPD

This study is measuring muscle mass and stiffness in the thigh muscles (quadriceps) of patients with chronic obstructive pulmonary disease (COPD) who are starting a pulmonary rehabilitation program. COPD causes the lungs to work poorly, and over time many patients lose significant muscle strength and mass — which affects their ability to exercise and recover. Researchers want to know how reliable these measurements are and whether they improve after the rehabilitation program, which could help doctors better track patient progress. **You may be eligible if...** - You have been diagnosed with COPD - You are an adult over 18 years old - You are starting a pulmonary rehabilitation program **You may NOT be eligible if...** - You are already enrolled in another research study - You are a minor or under legal guardianship - You are pregnant - You have had a leg amputation or have a neuromuscular disease - You have heart conditions that make pulmonary rehabilitation medically unsafe Talk to your doctor to see if this trial is right for you.