High-intensity respiratory muscle training improves maximal respiratory pressures, breathing endurance, dyspnoea and exercise capacity in people with Parkinson’s disease: a randomised trial

QUESTIONS: What is the effect of home-based, high-intensity, combined inspiratory and expiratory muscle training on maximal respiratory pressures, inspiratory muscle endurance, peak cough flow, dyspnoea, fatigue, exercise capacity and quality of life in people with Parkinson's disease? DESIGN: A randomised controlled trial with concealed allocation, intention-to-treat analysis and blinding of participants, assessors and statisticians. PARTICIPANTS: People with Parkinson's disease. INTERVENTION: The experimental group received high-intensity combined inspiratory and expiratory muscle training at 60% of maximal inspiratory pressure (MIP) and 60% of maximal expiratory pressure (MEP). The control group received sham training using the same protocol, but without any resistive load. Both groups trained for 20 minutes, twice per day, 7 days/week for 8 weeks. OUTCOME MEASURES: The primary outcome was respiratory muscle strength (MIP and MEP). Secondary outcomes included inspiratory muscle endurance, peak cough flow, dyspnoea (0-to-4 Medical Research Council scale, where lower scores are better), fatigue (1-to-7 Fatigue Severity, where lower scores are better), exercise capacity (6-minute walk test) and quality of life (0-to-100 Parkinson's Disease Questionnaire-39, where lower scores are better). All outcomes were measured at 0, 8 and 12 weeks. RESULTS: O, 95% CI 10 to 39) and inspiratory muscle endurance (MD 1.2 minutes, 95%CI 0.4 to 2.0). The benefits in MIP and inspiratory muscle endurance were maintained at follow-up. Benefits also occurred in dyspnoea (MD -0.71, 95% CI -1.30 to -0.12) and exercise capacity (MD 24.9 m, 95% CI 0.2 to 49.7); however, the confidence intervals spanned worthwhile and trivial effects, indicating uncertainty about whether those effects are clinically worthwhile. CONCLUSION: High-intensity combined inspiratory and expiratory muscle training improved respiratory muscle strength, inspiratory muscle endurance, dyspnoea and exercise capacity in people with Parkinson's disease. REGISTRATION NUMBER: NCT05608941.