Effect of inspiratory muscle training on inspiratory muscle strength in adults with post-COVID-19 condition and inspiratory muscle weakness: a randomized controlled trial.

OBJECTIVE

Evaluate the effect of inspiratory muscle training in adults with post-COVID-19 condition (PCC) and inspiratory muscle weakness.

DESIGN

Randomized controlled trial.

SUBJECTS/PATIENTS: Adults with PCC and inspiratory muscle weakness.

METHODS

Participants were randomized to inspiratory muscle training twice daily plus individualized exercise twice weekly or exercise alone, with weekly follow-ups over 8 weeks.

PRIMARY OUTCOME: inspiratory muscle strength (Maximal Inspiratory Pressure).

SECONDARY OUTCOMES: expiratory muscle strength (Maximal Expiratory Pressure); functional capacity (Six‑Minute Walk Test; One‑Minute Sit‑to‑Stand); lung function (spirometry); dyspnoea (mMRC); respiratory symptoms (chest tightness, impaired deep breathing, breathing‑related pain); cough frequency (CAAT cough item); fatigue (Fatigue Severity Scale); physical activity (Frändin-Grimby Activity Scale); activity limitations (Patient‑Specific Functional Scale); and health-related quality of life (EQ‑5D‑5L). Intention-to-treat analyses used imputed missing data. Estimated sample size: 90.

RESULTS

Forty-four participants were included (median age 47; 82% women; n = 22/group). Between‑group differences favoured the intervention for inspiratory muscle strength (mean difference: 18%; 95% CI: 5-30; OR for clinically meaningful improvement: 7.08, 95% CI: 1.31-38.32) and cough frequency. No other between-group differences were observed.

CONCLUSION

Inspiratory muscle training may improve inspiratory muscle strength and reduce cough frequency, but limited sample size and underrepresentation of the most severely affected warrant cautious interpretation.