Effect of high-intensity inspiratory muscle training on lung volumes, diaphragm thickness, and exercise capacity in subjects who are healthy

Background and Purpose. Previous investigations have demonstrated that a regimen of high-intensity inspiratory muscle training (IMT) resulted in changes in ventilatory function and exercise capacity in patients with chronic lung disease, although the effect of high-intensity IMT in subjects who are healthy is yet to be determined. The purpose of this study, therefore, was to examine whether high-intensity IMT resulted in changes in ventilatory function and exercise capacity in subjects who were healthy. Subjects. Twenty subjects were randomly assigned to 2 groups. Methods. The training group completed an, 8-week program of IMT set at 80% of maximal effort. The control group did not participate in any form of training. Baseline and posttraining measures of body composition, pulmonary function, inspiratory muscle function (including maximal and sustained maximal inspiratory pressures [MIP and SMIP]), relaxed and contracted diaphragm thickness and thickening ratio (Tdi.rel, Tdi.cont, and TR), and exercise capacity were determined. Results. The training group demonstrated significant increases in MIP, SMIP, Tdi.cont, TR, VC, total lung capacity, and exercise capacity compared with the control group, which demonstrated no change from baseline measurements at 8 weeks. Discussion and Conclusion. The findings of this study suggest that high-intensity IMT results in increased contracted diaphragm thickness and increased lung volumes and exercise capacity in people who are healthy.