RESUMO
BACKGROUND: The efficacy of interval exercise (IE) compared to constant-load exercise (CLE) training remains unsettled in adults with Cystic Fibrosis (CF). METHODS: Twenty-four adults with CF were randomised to 30-min IE (100 % peak work capacity (WRpeak) for 30-s alternated with 40 % WRpeak for 30-s; nâ¯=â¯12) or 30-min CLE (70 % WRpeak; nâ¯=â¯12) training, 3 times weekly, for 12 weeks. Isometric quadriceps muscle strength was assessed using a strain gauge Myometer. RESULTS: The magnitude of improvement in quadriceps muscle strength was greater (pâ¯=â¯0.037) in the IE (by 32⯱â¯13 Nm) compared to the CLE (by 23⯱â¯12 Nm) groups. Maximum inspiratory and expiratory mouth pressures were significantly improved only in the IE group (by 30⯱â¯10 cmH2O; pâ¯=â¯0.009 and 13⯱â¯4 cmH2O; pâ¯=â¯0.007, respectively). Arterial oxygen saturation during training was higher (pâ¯=â¯0.002) for IE (94⯱â¯1%) compared to CLE (91⯱â¯1%), whereas dyspnoea scores were lower (pâ¯=â¯0.001) for IE (3.8⯱â¯0.7) compared to CLE (5.9⯱â¯0.8) CONCLUSIONS: IE is superior to CLE in improving peripheral and respiratory muscle strength and preferable to CLE because it is associated with lower exercise-induced arterial oxygen desaturation and breathlessness.