RATIONALE: Exercise limitation is frequent in patients with pulmonary hypertension (PH). In view of the marked exacerbated ventilatory responses, activation of metaboreceptors and increased sympathetic activity, we hypothesize that inspiratory muscle training (IMT) is a useful strategy in improving exercise tolerance. OBJECTIVES:To evaluate the effects of IMT on the strength and endurance of the respiratory muscles on exercise capacity, assessed through cardiorespiratory exercise test (CPET) with constant load on a cycle ergometer and the distance walked in the 6-minute walk test (6MWD). METHODS: 25 patients were included in the study (68% CTEPH and 32% PAH, 80% female, 4112 yrs). The IMT consisted of 2 daily training sessions of 30 breaths (~50% maximal inspiratory pressure - MIP; 3-5 minutes per session), for 8 weeks (12 patients). The SHAM group (13 patients) performed 2 daily sessions of 30 breaths, with a load of 5cmH2O during the entire study period. Patients perfomed pulmonary function tests, measurements of maximal inspiratory and expiratory pressures, 6MWD, incremental and constant load CPET with non-invasive hemodynamic and peripheral oxygenation assessment. RESULTS: A greater improvement of MIP was achieved in the IMT group (U=23,500, p=0,009) as well as the 6MWTD compared to Sham group (t(30)= -2,467; p=0,021).CONCLUSIONS: IMT is a useful strategy in improving MIP and exercise tolerance of PH patients.