Exercise intolerance is one of the key disabling factors in patients with chronic obstructive pulmonary disease (COPD). Although multifactorial, exercise intolerance involves physiological interactions between respiratory and locomotor muscles that may contribute to further reducing exercise tolerance in COPD. The respiratory muscle work during exercise is closely related to breathing and could induce respiratory muscle fatigue in patients with COPD.

Respiratory muscle training is an intervention strategy that is sometimes proposed for some patients with COPD, especially whose with inspiratory muscle weakness. It was reported that inspiratory muscle training improves inspiratory muscle endurance and strength, dyspnea and exercise tolerance. There are two types of inspiratory muscle training, inspiratory muscle training against a resistive loading and normocapnic hyperpnoea. The advantage of normocapnic hyperpnoea compared to resistive training is the possibility to simulate the exercise ventilation level while maintaining stable the partial pressure of arterial carbon dioxide and end-tidal pressure of carbon dioxide and to solicit the inspiratory and expiratory muscles together, which could increase respiratory muscle tolerance and avoid their fatigue during whole-body exercise.

Therefore, the aim of this project is to study the effect of normocapnic hyperpnoea training on exercise tolerance in patients with COPD.

We hypothesize that greater improvement in cycling exercise tolerance will be observed following 6-weeks normocapnic hyperpnoea training compared to a sham intervention in patients with COPD.

Inclusion Criteria:

• Age ≥ 40 years;
• Chronic airflow obstruction : FEV1/FVC < 0.7, FEV1 of 30 to 80% predicted, after bronchodilation;

Exclusion Criteria:

• Inability to perform a cycling exercise;
• Diagnosed of one of more comorbidities that may limit exercise tolerance : cardiovascular, metabolic, endocrine, gastrointestinal, renal, neurological or rheumatologically disease;
• Recent COPD exacerbation (< 3 months);
• Recent cancer;
• A daily dose of Prednisone > 10 mg;
• Hypoxemia at rest or during exercise: PaO2 < 60 mmHg or SpO2 ≤ 88%;
• Body mass index > 30 kg/m²;
• Pregnancy;
• Skinfold at intercostal or vastus lateralis muscle > 1.5 cm.

Patients will be randomized to training group or sham group.