Inspiratory Muscle Training in Patients With Inflammatory Myopathy

Idiopathic inflammatory myopathies (IIM) are rare autoimmune disorders characterized by progressive, symmetrical proximal muscle weakness, frequently affecting the respiratory muscles. Diaphragmatic dysfunction and reduced inspiratory muscle strength contribute to impaired ventilation, fatigue, and reduced exercise tolerance. While exercise training has proven beneficial in patients with various neuromuscular conditions, evidence regarding inspiratory muscle training (IMT) in IIM is lacking.

This pilot interventional study will prospectively evaluate the impact of a 3-month IMT program on respiratory and functional outcomes in patients with IIM. The intervention consists of daily inspiratory resistance training (30 breaths/day, 7 days/week) using the Threshold IMT device (Philips Respironics, USA). Training intensity is set at 30% of maximal inspiratory pressure (MIP) and adjusted progressively based on patient-reported exertion. Participants receive individualized instruction, follow-up phone consultations every 2 weeks, and record adherence in exercise diaries.

Assessments include inspiratory muscle strength (measured with Powerbreathe KH2), spirometry (Forced Expiratory Volume in 1 Second, Forced Vital Capacity, Forced Inspiratory Vital Capacity, Inspiratory Reserve Volume), diaphragm ultrasound (mobility and thickness fraction), six-minute walk test (6MWT), fatigue assessment (Borg Rating of Perceived Exertion Scale, Fatigue Severity Scale), and quality of life (36-Item Short Form Health Survey). Outcomes will be measured 3 months before training, at baseline, after 3 months of training, and during extended follow-up (up to 6-12 months). The primary endpoint is change in MIP. Secondary endpoints include pulmonary function parameters, diaphragmatic function, exercise tolerance, fatigue, and health-related quality of life.

The study will be conducted in the Neurology Clinic of the Medical University of Warsaw (WUM). A total of 33 patients with IIM, diagnosed according to European Alliance of Associations for Rheumatology / American College of Rheumatology criteria, will be recruited. Inclusion requires age ≥18 and written informed consent. Exclusion criteria include cognitive impairment, acute respiratory infection, prior respiratory training, pneumothorax, pulmonary hypertension, or contraindications to IMT. This trial is expected to provide the first structured evidence on the role of IMT in improving functional status in patients with inflammatory myopathy, potentially guiding individualized rehabilitation strategies for this patient population.

• Change in Forced Vital Capacity (FVC) [Time frame: 3 months before training, baseline, 3 months (end of training), 6 months, 9 months, 12 months]
• Change in Forced Expiratory Volume in 1 Second (FEV1) [Time frame: 3 months before training, baseline, 3 months (end of training), 6 months, 9 months, 12 months]
• Change in diaphragm thickness [Time frame: 3 months before training, baseline, 3 months (end of training), 6 months, 9 months, 12 months]
• Change in 6-Minute Walk Distance (6-Minute Walk Test) [Time frame: 3 months before training, baseline, 3 months (end of training), 6 months, 9 months, 12 months]
• Change in perceived exertion (Borg Rating of Perceived Exertion) [Time frame: 3 months before training, baseline, 3 months (end of training), 6 months, 9 months, 12 months]
• Change in fatigue severity (Fatigue Severity Scale) [Time frame: 3 months before training, baseline, 3 months (end of training), 6 months, 9 months, 12 months]
• Change in quality of life (36-Item Short Form Health Survey) [Time frame: 3 months before training, baseline, 3 months (end of training), 6 months, 9 months, 12 months]