INTRODUCTION: Inspiratory muscle training (IMT) has been applied during pulmonary rehabilitation in patients with chronic obstructive pulmonary disease (COPD). However, it remains unclear if the addition of IMT to a general exercise training programme leads to additional clinically relevant improvements in patients with COPD. In this study, we will investigate whether the addition of IMT to a general exercise training programme improves 6 min walking distance, health-related quality of life, daily physical activity and inspiratory muscle function in patients with COPD with inspiratory muscle weakness. METHODS AND ANALYSIS: Patients with COPD (n=170) with inspiratory muscle weakness (Pi,max /=50% of their Pi,max), whereas the placebo group (n=85) will undertake IMT at a low training intensity (=10% of Pi,max). Total daily IMT time for both groups will be 21 min (6 cycles of 30 breaths). Improvement in the 6 min walking distance will be the primary outcome. Inspiratory muscle function, health-related quality of life and daily physical activity will be assessed as secondary outcomes. ETHICS AND DISSEMINATION: Ethics approval has been obtained from relevant centre committees and the study has been registered in a publicly accessible clinical trial database. The results will be easily interpretable and should immediately be communicated to healthcare providers, patients and the general public. RESULTS: This can be incorporated into evidence-based treatment recommendations for clinical practice. CLINICALTRIALSGOV: NCT01397396.