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

The study was much smaller than planned, with 44 participants randomized instead of 90, so it had low power and wide confidence intervals. Recruitment stopped when the planned sample could not be reached within a reasonable timeframe. Many people who were eligible could not manage the testing or intervention, and others declined because of severe fatigue or PESE, so the sample was selected for tolerability. Ten of the 44 participants withdrew, and those who withdrew had lower baseline function, which may overestimate effects among completers. Participants and therapists could not be blinded, and maximal inspiratory pressure testing depends on voluntary effort. Secondary outcomes were exploratory and not corrected for multiple testing, so the cough finding and within-group functional changes need caution. Adherence was moderate and not adjusted for, and the programme included exercise, breathing instructions and physiotherapy follow-up, so component contributions cannot be separated. The study had only 8 weeks of follow-up and no long-term data.

The work was supported by grants from the Swedish Heart Lung Foundation, Swedish Heart and Lung Association, Swedish Research Council, Strategic Research Area Health Care Science Karolinska Institutet, Odd Fellows, and Bygg-Göta Foundation. The funders were not involved in any part of the study or its publication. No other conflicts of interest are stated.

Do not conclude that inspiratory muscle training works for all adults with post-COVID symptoms. The trial was smaller than planned, many people with severe fatigue or PESE did not join or withdrew, and only inspiratory strength and cough differed between groups.