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 (cmH₂O): 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 cmH₂O, 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.