Objective: To investigate the physiological and structural adaptations of peripheral muscle function at a cellular level in response to EBV treatment. Study design: A single center, prospective clinical trial with a single-arm pretest-posttest design. Patients with severe emphysema who will receive a bronchoscopic lung volume reduction treatment are asked to undergo additional in-magnet exercise testing and muscle biopsies before and after placement of EBVs. Study population: Patients with severe emphysema who are scheduled to undergo EBV treatment. Main study parameters/endpoints: The difference in quadriceps phosphocreatine concentration (PCr), quadriceps inorganic phosphorus concentration (Pi), and quadriceps pH at rest, during progressive exercise, and recovery rate will be measured by 31P-MRS to assess the physiological effect of EBV treatment on skeletal muscle function and its bioenergetics. Furthermore, we will perform a detailed histological and biochemical analysis of muscle fiber type composition, mitochondrial density, master regulators of muscle oxidative programming, and mitochondrial respiration before and after EBV treatment.