The association between inspiratory muscle strength and walking performance among people with post covid-19 condition; an observational study.

<bold>Background:</bold> Physical performance is often lowered among people with persistent symptoms after a SARS COV-2 infection (Post Covid-19 condition). Inspiratory muscle strength is a known component in physical performance and exertional tolerance among other pulmonary diseases, however not yet described among people with Post COVID-19 condition. <bold>Aim:</bold> The association between lung function and inspiratory muscle strength on the walking performance of people with Post COVID-19 condition. <bold>Methods:</bold> A retrospective cohort with pre/post-measurements of people with Post COVID-19 condition where we compared lung function, lung X-ray imaging and inspiratory muscle strength measured by maximal inspiratory pressure (MIP) with walking performance measured by the six-minute walking test (6MWT). Secondarily a correlation analysis was conducted between the change in MIP scores and the change in walked distance of the 6 MWT after eight weeks of rehabilitation. <bold>Results:</bold> 140 patients were eligible for the first analysis. Inspiratory muscle strength showed a poor to fair association with walking distance (r=0,25, 95% CI [0,09 – 0,40]) followed by lung function (Diffusion capacity (r = 0,18, 95% CI [0,01 – 0,34])) and x-ray findings (r = −0,17, 95% CI [−0,33 – −0,01]). Second analysis among 35 patients showed no significant association. <bold>Conclusion</bold> Inspiratory muscle strength shows a poor to fair association with walking distance and surpasses the role of lung function and findings on lung imaging. The results complement previous research findings and further address the impact of respiratory muscle function among people with Post COVID-19 condition.