GOLD Stage I Chronic Obstructive Pulmonary Disease (COPD)

The study will be conducted among three subgroups: symptomatic GOLD stage I patients with COPD, asymptomatic patients GOLD stage I COPD and healthy control subjects with normal lung function. Subjects will be paired for age, sex and smoking history. The project will require three visits. In the initial visit, assessment of the pulmonary function with respiratory symptoms quantification will allow to classify subjects in the proper subgroup. The Medical Research Council (MRC) dyspnea scale will serve as the reference outcome to determine whether COPD patients are symptomatic or not. Patients with an MRC dyspnea score \< 2 will be considered asymptomatic. A second questionnaire (ATS-DLD-78) will serve to document cough, expectorations, wheezing and smoking history in every subjects. Body composition will be measured by bioimpedance and by waist circumference after a blood sample taken in the morning, in a fasting state. A six-minute walk test (6MWT) will be performed by all subjects. After a one-hour resting period, a maximal incremental shuttle walking test will be realized in the same visit to quantify maximal exercise capacity. Measures of force and endurance of the quadriceps will be taken by magnetic stimulation of the femoral nerve before the maximal walking test. Finally, subjects will receive a portable device to monitor physical activity for a period of 7 days. In the 2nd and 3rd visits, subjects will realize an endurance walking test at 85 % of their predetermined maximal capacity. Before each endurance test, a bronchodilator or a placebo will be administered following a randomized double-blind design. Measures of force and endurance of the quadriceps will be taken by magnetic stimulation of the femoral nerve before and 10-min after endurance exercise tests. A needle biopsy of the vastus lateralis will be performed at the end of the third visit.