METHODOLOGY: Study design and setting: It will be a randomized double-blind trial during which 34 patients with moderate to severe COPD will complete 2 Glittre ADL-tests 15 minutes following nebulization of a placebo or of ipratropium bromide/salbutamol sulfate combination. Patients receiving bronchodilators before the beginning of the study will be asked to withdraw from their medication 8h in the case of short-acting bronchodilators and/or 72 h in the case of long-acting bronchodilators before visits. Those treated with tiotropium will have a 4-week washout period during which this therapy will be replaced by ipratropium bromide. The study will require 3 visits to the research center of Institut Universitaire de Cardiologie et de Pneumologie de Québec-Université Laval (IUCPQ). The 1st visit will be devoted to verify the eligibility to the study, obtain informed consent, and measure baseline characteristic including anthropometric measurements, pulmonary, and lower limb muscle function, as well maximal exercise capacity and participation in activities of daily life. In addition, participants will be familiarized with the Glittre test. During the following visits, subjects will complete two Glittre tests (1/visit) preceded by administration of nebulized placebo or ipratropium bromide/salbutamol sulfate (500 mg/2.5 mg) administrated in a randomized and double-blind fashion. Study visits will be separated by \>72 h and \<7 days. Subjects will be scheduled to attend at the same time of day throughout the study. Ethics approval will be obtained before starting the project and all subjects will provide written informed consent prior to testing. Procedure and measurements: Anthropometric measurements: Weight and height will be measured on a standing scale. Pulmonary function: Complete pulmonary function tests including spirometry, lung volumes and diffusing capacity for carbon monoxide will be obtained according to standardized technique and expressed as a percent of predicted9. In addition, during visit 2 and 3, a spirometry (FEV1 and FVC) will be obtained before and after bronchodilation to determine bronchodilator-induced change in FEV1 and baseline respiratory condition before functional tests. Muscle function: Quadriceps muscle function (force, endurance and fatigue) will be quantified during a knee extension test. The test will consist of one set of 30 repetitions at an angular velocity of 90°/s. Amplitude and angular velocity will be controlled using a dynamometric isokinetic system (Biodex, system pro 4, Biodex Medical System, Shirley, NY, USA). Maximal exercise capacity: Maximal exercise capacity will be assessed using a symptom-limited incremental cycling test. Subjects will be seating on an electrically braked ergocycle (Quinton Corival 400; A-H Robins, Seattle, WA) and connected to a portable a gas analysis system (Oxycon Mobile, Viasys Healthcare, Jaeger, Germany). After 5 minutes of rest, a progressive stepwise exercise test will be performed up to the individual maximal capacity. Each exercise step lasts 1 minute and increments of 10 watts will be applied. Minute ventilation (VE), oxygen uptake (VO2), and CO2 excretion (VCO2) respiratory exchange ratio (RER), respiratory rate (RR) inspiratory capacity (IC) and heart rate (HR) will be measured at rest and during exercise on a breath-by-breath basis. In addition, pulsed oxygen saturation (SpO2) will be measured at rest, continuously during the tests, and at end-exercise by pulse oximetry (OSM2 Hemoximeter; Radiometer,Copenhagen, Denmark). Dyspnea and leg fatigue perception will be measured by a modified Borg scale at rest, each 2 minutes and at the end of exercise. Participation in activities of daily life: Participation in activities of daily life will be measured with an accelerometer-based activity monitor (DynaPort Minimod, McRoberts BV, The Hague, The Netherlands). Patients will be instructed to wear the monitor on the waist for 7 consecutive days. They will also fill a diary of activities through the week they are wearing the physical activity monitor. Self-efficacy: Patients' perceived walking and climbing stairs confidence (on flat ground, with and without handrail) will be assessed with the 10-item self-report modified Gait Efficacy Scale. Functional tests: The Glittre ADL tests will be completed according to the original procedure described by Skumlien5. Briefly, patient carrying a weighted backpack (2.5 kg for women, 5.0 kg for men) will be instructed to stand up and walk along a flat 10-m long course. In the middle of the course, there will be a 2-step staircase (each step 17 cm high×27 cm deep) to get across. After completing the second 5 m, the subject will be facing a shelf containing 3 objects, each weighing 1 kg, positioned on the top shelf (shoulder height). Participants will then move objects, 1 by 1, to the bottom shelf (waist height) and then to the floor. Once completed, participants will then have to return the objects, always 1 by 1, to the bottom shelf and finally to the top shelf again. Participants will then walk back along the circuit, climbing and descending the stairs, until reaching the starting point (chair); sitting down and immediately beginning the next lap. Patients will be instructed to complete 5 laps on this circuit as quickly as possible. The 1-minute STST will be completed according to the procedure described by Ozalevli and al. Patients will be instructed to fully stand up from a chair, arms across the chest, sit back down and repeat as often as possible during one minute. Physiological measures as well as dyspnea and leg fatigue perception will be acquired with the same methodology used for the maximal exercise capacity. The order of functional tests will be randomized for each patient. Patients will also fill the Multidimensional Dyspnea Profile questionnaire. Global rating of change: Patients' perception of change in their performance, dyspnea and leg fatigue induced by the functional tests will be ascertain with a 7-point Likert Scale ranging from -3 (large deterioration) to +3 (large improvement) immediately after each functional test. No feedback from the evaluator will be given to patients before patients' own rating.