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.