Comparison of two inspiratory muscle training protocols in people with spinal cord injury: a secondary analysis

STUDY DESIGN/SETTING: Secondary analysis. OBJECTIVES: To compare the change in maximal inspiratory pressure (PI(max)) over the first 4 weeks of two different inspiratory muscle training (IMT) protocols and explore if either method is more effective for people with spinal cord injury. METHODS: Data originated from two published studies. Participants completed flow-resistive IMT (F-IMT) at 80% daily PI(max,) 7 days/week (supervised weekly), or threshold IMT (T-IMT) at 30–80% weekly PI(max,) twice-daily, 5 days/week (supervised every session). Seven participants from each trial were matched by training adherence, level of spinal cord injury, impairment grade (A–C), and height. Differences between F-IMT and T-IMT groups in training intensity, breaths taken, inspiratory work, and the change in the PI(max) from baseline at the end of week four were analysed. RESULTS: Over 4 weeks, there was no difference in the change in PI(max) between groups (Absolute change in PI(max) (cmH(2)O): p = 0.456, Percent change in PI(max) relative to baseline: p = 0.128). F-IMT participants trained at a higher intensity (median: 77 vs 22 cmH(2)O, p = 0.001 and 80% baseline vs 61% baseline, p = 0.038) but took fewer breaths (840 vs 1404 breaths, p = 0.017) than T-IMT participants. Inspiratory work was similar between groups (64,789 vs 65,910 (% PI(max) × number of breaths), p = 0.535). CONCLUSIONS: Our findings support both methods of IMT as the change in PI(max) and inspiratory work were similar between groups. However, daily high-intensity F-IMT with intermittent supervision, required fewer breaths and less participant and therapist time. Future studies should examine optimal dosage and supervision required to achieve increased PI(max).