Eligibility criteria

Patients who meet all the following criteria will be eligible:

1) Age range 40 to 80 years at the time of consent

2) Diagnosis of IPF confirmed at each institution by the 2011 guidelines [17]

3) 600 m > 6MWD ≥200 m

4) Exertional dyspnoea of the modified Medical Research Council (mMRC) 1 to 3 [21]

5) Without infection and/or acute exacerbation within 3 months

6) Taking nintedanib (150 mg or 100 mg twice daily) for at least 4 weeks before enrolment and expected to continue for 12 months thereafter

7)  Able to attend outpatient pulmonary rehabilitation programme twice a week for 12 weeks and subsequent maintenance programme once every 2–4 weeks for the following 40 weeks

8) Pulmonary function test within a month before the enrolment of FVC ≥50% predicted, 79% ≥ diffusing capacity of the lung for carbon monoxide (D_LCO) ≥30% predicted and forced expiratory volume in 1 s (FEV₁)/FVC ≥70%