Background: Specific respiratory muscle training can improve respiratory muscle function in
patients with COPD, but the magnitude of improvement appears dependent on the magnitude of
the training load. High training loads are difficult to achieve using conventional, constant loading
techniques, but may be possible using interval-based training techniques.
Methods: To assess the feasibility of high-intensity respiratory muscle training, nine subjects with
moderate-to-severe COPD (FEV1 34 12% predicted [mean SD]) completed 8 weeks of
interval-based respiratory muscle training combined with a general exercise program. This
involved three 20-min sessions per week, each session comprising seven 2-min bouts of breathing
against a constant inspiratory threshold load, each bout separated by 1 min of unloaded recovery.
Inspiratory load was progressively incremented. Respiratory muscle strength (maximum inspiratory
pressure generated against an occluded airway [PImax]) and endurance (maximum pressure
generated against a progressively increasing inspiratory threshold load [Pthmax]) were measured
before and immediately after the 8-week training period.
Results: By the third training session (week 1), subjects breathed against a threshold that required
generation of pressures equivalent to 68 5% of the pretraining PImax. By week 8, this had
increased to 95 12% of the pretraining PImax. On completion of training, PImax had increased
by 32 27% (p < 0.05), Pthmax had increased by 56 33% (p < 0.05), and Pthmax/PImax had
increased by 20 20% (p < 0.05).
Conclusions: This study has demonstrated that high-intensity, interval-based respiratory muscle
training is feasible in patients with moderate-to-severe COPD, resulting in significant improvements
in respiratory muscle strength and endurance when performed three times a week for 8
weeks.