Inspiratory Muscle Training with a Weighted Incentive Spirometer in Subjects with Chronic Airways Obstruction

Abstract

An incentive spirometer was modified to produce a pressure-threshold device for inspiratory muscle training designed to increase inspiratory muscle strength. METHOD AND MATERIALS: I used a quasi-randomized pretest-posttest design to determine the effectiveness of a weighted incentive spirometer (WIS) for increasing inspiratory muscle strength in subjects with moderate-to-severe chronic airways obstruction. The difference in maximal static inspiratory pressure (P_Imax) was used to reflect changes in strength in trained subjects (n = 12) and controls (n = 11) after an 8-week training period. The effectiveness of using weight to set the training load (pressure) was tested by having the treatment group train at the maximal weight tolerated, while the control group trained at a fixed weight of 0.5 pound. The fixed weight was used in the control group to maintain subject motivation and was not expected to produce a training effect. RESULTS: Although subjects (from both groups) who had low pretraining P_Imax showed a marked increase in strength after training, the mean increase in P_Imax was not significant in either the treatment (p = 0.10) or the control group (p = 0.07). CONCLUSIONS: I conclude that (1) there was no significant difference in the increase in inspiratory muscle strength between the two groups even when training weight was increased to maximal values, (2) the negative pressure generated during training inspirations from the WIS was similar in both groups regardless of the training weight, and (3) because subjects with the lowest P_Imax before training experienced the greatest improvement, their low pretraining P_Imax was probably due to inspiratory muscle weakness rather than fatigue.