Inspiratory muscle conditioning using a threshold loading device.

We demonstrate the effectiveness of a new conditioning technique for increasing the strength and endurance of the inspiratory muscles. The technique employs a threshold loading device which allows for maximization of exercise intensity with a minimum of exercise duration. After ten weeks, with approximately 25 minutes of exercise time per week, four test subjects showed an average increase in maximum inspiratory pressure (PImax) of 50 (+/- 9 SD) cm H2O (p less than 0.02), whereas four control subjects undergoing submaximal inspiratory muscle exercise showed no significant change. The time the test subjects could endure 65 percent of their prestudy PImax increased from an average of 3.58 +/- 1.65 SD min to over 10 min in all four subjects. No significant change was seen in control subjects. Further testing showed the test subjects could endure 100 percent of their prestudy PImax after conditioning for an average duration 5.15 +/- 1.65 min. This technique should be useful for conditioning the inspiratory muscles in subjects with pulmonary disease.