Fibrotic interstitial lungs diseases (ILD) are a group of chronic and rare diseases characterized by an altered blood oxygenation in the lung, leading to dyspnea and physical limitation. Physical training is efficient to fight vicious circle of physical deconditioning observed in ILD. Eccentric cycling is an interesting modality of endurance training, allowing better exercise tolerance and adherence while developing cardiorespiratory function. Feasibility and efficacity of eccentric cycling were shown in chronic obstructive pulmonary disease but never in ILD. The primary aim of our work is to compare concentric and eccentric cycling training on physical capacities in ILD. Moreover, we will study the effects of training on the different steps of oxygen transport at exercise, from the lung to the muscles through the blood transport. Our second goal is then to characterize the physiological mechanisms underlying the benefits of exercising in ILD patients. Evaluations will be led during one year to study the long-term effects of training