This study is designed to evaluate the reproductibility and the performance of the 3 minutes sit-to-stand test in patients with idiopathic pulmonary fibrosis.

To do this, the investigators are recruiting 40 patients with idiopathic pulmonary fibrosis in 2 centers (Grenoble university hospital and Lyon university hospital).

Patients had to achieve an effort test on a cycle ergometer. 2 visits are planned in the hospital. During each visit, patients will perform a 3 minutes sit-to-stand test, a 1 minute sit-to-stand test and a 6 minutes walk test. During the second visit, patients will also perform a 3 minutes sit-to-stand test with measurement of oxygen uptake.

The investigators will then analyse the results by comparing numbers of cycle, functional response and symptoms during the 3 minutes sit-to-stand test of the 2 visits. The investigators will also compare the functional response obtained during the 3 minutes sit-to-stand test, the 1 minute sit-to-stand test and the 6 minutes walk test.

Finally, the investigators will compare the maximal values of oxygen uptake, respiration rate and expired volume obtained during the 3 minutes sit-to-stand test to the effort test on cycle ergometer.

Inclusion Criteria:

• man or woman aged less than 85 years
• patients with Idiopathic Pulmonary Fibrosis without any acute exacerbation during 4 months before the inclusion
• Non-opposition to participation in research
• Patient with 6 minutes walk test > 200 meters (with or without oxygen therapy)

Exclusion Criteria:

• Patient with reduced locomotor activity, or joint pain that compromises the performance of the tests
• Patient with 6 minutes walk test < 200 meters
• Patient with an other etiology of pulmonary fibrosis
• Other significant pulmonary diseases
• Patient with unstable cardiac disease
• Patient who may be, according to the investigator's assessment, not cooperating or respecting the obligations inherent in participating to the study.
• Opposition to participation in research