Preliminary results suggest that the activation and differentiation processes of satellite cells isolated from the VL of patients with COPD could be altered. The investigators propose to compare the regenerative potential of the VL and the diaphragm in 15 patients with COPD and 15 individuals with normal lung function undergoing a thoracic surgery. From muscle biopsies, satellite cells will be isolated and cultured to assess their proliferation and differentiation rates, and the expression level of myogenic effectors (MyoD, Myf5, myogenin, and MRF4). Alterations in these measurements will confirm the hypotheses that the regenerative potential is lower in both muscle groups in patients with COPD compared to controls and that in COPD, the regenerative potential is lower in VL compared to the diaphragm.