Effects of inspiratory muscle training in advanced multiple sclerosis

Abstract

Background: Respiratory training using Threshold Inspiratory Muscle Trainer (IMT) has not been examined adequately in multiple sclerosis (MS). The primary objective in this study of persons with advanced MS was to investigate the training effect of IMT. The secondary objective was to evaluate the retention of IMT benefits. Methods: This study was a repeated measures within-subject design (before-after trial). Participants were recruited from a long-term care facility specialized in progressive neurologic conditions. Thirty-six non-ambulatory persons with advanced MS volunteered. Inspiratory muscle exercise using the threshold IMT were performed daily for 10 weeks at 3 sets of 15 repetitions per day. Resistance was progressed weekly based on perceived rate of exertion and symptoms. Primary outcome measures were maximum inspiratory pressure (MIP) and maximum expiratory pressure (MEP) that were measured at baseline, after 5 and 10 weeks of IMT exercises (training period), and at 4 and 8 weeks after the IMT training ended (retention). Linear mixed-effect regression models with time (i.e. weeks from baseline) as the fixed factor and participants as the random effect factor were applied separately to test each hypothesis. Effect size was calculated using partial eta square (η2p). Two-tailed significance level was p < 0.05. Results: Participants were 60.5 ± 8.6 years old. Expanded Disability Status Scale was 8.5 ± 0.4. Baseline MIP were 25.9 ± 16.4 cmH2O (33.2% %± 19.8% of predicted values) and MEP were 23.5 ± 15.7 cmH2O (25.8% %± 14.4% of predicted values). Compared to the baseline, MIP increased significantly to 30.1 ± 17.9 cmH2O (38.9% %± 22.4% of predicted values) and 30.6 ± 17.6 cmH2O (39.6% %± 22.3% of predicted values) after 5 (p < 0.05) and 10 weeks (p < 0.05) of IMT exercises. MIP improvements were retained in an 8-week washout period. MEP did not differ significantly by time. Conclusion: In persons with advanced MS, 10-week IMT training increased inspiratory muscle strength. This study is the first to demonstrate the retention of benefits following daily IMT exercises at 8 weeks after training ended.