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

Secondary analysis.

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.

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.

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).

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.