This study determined the effect of a high vs low resistive inspiratory muscle interval training protocol on inspiratory muscle strength (PImax), incremental inspiratory threshold loading (Pitl), inspiratory muscle endurance (IE), and 12-minute distance test (12 MD) in severely impaired patients with COPD. We used a double-blind, two-group, repeated-measure design. Group 1 (n = 12) received supervised high resistive loading at approximately 52 percent PImax and group 2 (n = 8) received supervised low resistive loading at approximately 22 percent PImax. All subjects trained three times weekly (progressing from 5 min per session in week 1 to 18 min per session in week 12) for 12 weeks. After three practice sessions, measures of PImax, Pitl, IE, and 12 MD were taken at baseline, at 4-week intervals, and within 72 h of completing the protocol. Group 1 showed significant improvement in all four dependent variables while group 2 improved in Pitl, IE, and 12 MD. The results suggest there is no significant difference between high and low resistive interval training in more severely impaired patients with COPD.