Interval versus constant-load exercise training in adults with Cystic Fibrosis

•Interval improves more than continuous training peripheral and respiratory muscle strength in adults with CF.•Improvements in aerobic capacity are comparable following interval and continuous training in adults with CF.•There is less oxygen desaturation and breathlessness with interval than continuous exercise in adults with CF.•Application of interval is preferable to continuous exercise for rehabilitation in adults with CF. The efficacy of interval exercise (IE) compared to constant-load exercise (CLE) training remains unsettled in adults with Cystic Fibrosis (CF). 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; n = 12) or 30-min CLE (70 % WRpeak; n = 12) training, 3 times weekly, for 12 weeks. Isometric quadriceps muscle strength was assessed using a strain gauge Myometer. The magnitude of improvement in quadriceps muscle strength was greater (p = 0.037) in the IE (by 32 ± 13 Nm) compared to the CLE (by 23 ± 12 Nm) groups. Maximum inspiratory and expiratory mouth pressures were significantly improved only in the IE group (by 30 ± 10 cmH2O; p = 0.009 and 13 ± 4 cmH2O; p = 0.007, respectively). Arterial oxygen saturation during training was higher (p = 0.002) for IE (94 ± 1%) compared to CLE (91 ± 1%), whereas dyspnoea scores were lower (p = 0.001) for IE (3.8 ± 0.7) compared to CLE (5.9 ± 0.8) 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.