Resistive Respiratory Muscle Training Increases Respiratory Muscle Strength and Exercise Endurance, and Reduces Fatigue in MS

Background: Respiratory muscle weakness and fatigue in normal individuals can lead to reduced exercise performance due to the diverting of blood from the peripheral muscles to the respiratory muscles during activity. Resistive Respiratory Muscle Training (RRMT) has been shown to improve respiratory and locomotor performance; however, its effects in MS patients have not been examined.

Objectives: The objective of this study was to determine the effects of 6 weeks of RRMT on respiratory muscle strength, exercise endurance and fatigue in MS patients with mild-to-moderate disability.

Methods: Twenty-one female and 8 male MS patients were randomly assigned to RRMT (13 women, 1 man) or placebo Control (8 women, 7 men) groups. All patients had EDSS scores between 1.0 and 6.0, and were able to pedal a cycle ergometer continuously for 10 minutes. They were nonsmokers, had not had a relapse or new steroid use in the last 6 weeks or had a recent respiratory infection. Ages were 51.1±13.3 years (RRMT) and 48.6±12.8 years (C). Average EDSS scores were 3.1±1.9 (RRMT) and 2.9±1.8 (C). Average years since diagnosis were 12.5±7.0 (RRMT) and 15.4±11.6 (C). The measurements of maximal inspiratory (PImax) and expiratory (PEmax) pressures (Viasys metabolic system) and self-reported fatigue (Modified Fatigue Impact Scale, MFIS), as well as exercise time to voluntary exhaustion at 60% of peak workload on a cycle ergometer were conducted before and after 6 weeks of the intervention. The RRMT and placebo control (no load) breathing were conducted 3 times/week, 30 minutes per session using a specially designed device that measured inspiratory and expiratory pressures on each breath. Resistances for RRMT progressively increased from 30-80% of the initial maximal inspiratory and expiratory pressures over the 6 weeks. The patients completed one session in the lab and then two sessions at home each week. T-tests were used to analyze the changes from before to after the intervention.

Results: The RRMT group had significant improvements in PImax (p=.0037; 77.3±31.2 to 97.5±28.0 cmH₂O), PEmax (p=.0020; 74.6±22.5 to 97.6±25.6 cmH₂O), MFIS physical fatigue (p=.0022; 16.6±8.8 to 12.5±7.2), MFIS total fatigue (p=.0125; 33.7±15.4 to 26.2±16.4), and exercise duration (p=.0295; 24.2±15.4 to 31.7±25.5 minutes) from pre to post-intervention. The placebo control group did not have significant changes in any of the physical measures.

Conclusions: A 6-week resistive respiratory muscle training program of the inspiratory and expiratory muscles improves respiratory muscle strength, exercise endurance and perceived fatigue in MS patients with mild-to-moderate disability.

This study was funded by NIDRR grant H133G120081.