The purpose of this study was to investigate whether heterogeneous treatment effects occur for changes in inspiratory muscle strength, perceived dyspnoea and health-related quality of life (QoL), following eight-weeks unsupervised home-based inspiratory muscle training (IMT) in adults with post-acute COVID-19 syndrome. In total, 147 adults with self-reported prior COVID-19 either completed an eight-week home-based IMT intervention (n=111; 92 females; 48±11 years; 9.3±3.6 months post-acute COVID-19 infection) or acted as "usual care" wait-list controls (n=36; 34 females; 49±12 years; 9.4±3.2 months post-acute COVID-19 infection). Applying a Bayesian framework, we found clear evidence of heterogeneity of treatment response for inspiratory muscle strength: the estimated difference between standard deviations (SDs) of the IMT and control groups was 22.8 cmH2O (75% Credible Interval (CrI): 4.7-37.7) for changes in maximal inspiratory pressure (MIP), and 86.8 pressure time-units (PTUs; 75% CrI: 55.7-116.7) for sustained MIP (SMIP). Conversely, there were minimal differences in the SDs between the IMT and the control group for changes in perceived dyspnoea and health-related QoL, providing no evidence of heterogeneous treatment effects. Higher cumulative power during the IMT intervention was related to changes in MIP (ß=10.9 [95% CrI: 5.3-16.8] cmH2O per 1SD) and SMIP (ß=63.7 [32.2-95.3] PTUs per 1SD), clearly indicating an IMT dose response for changes in inspiratory muscle strength. Older age (>50 years), a longer time post-acute COVID-19 (>3 months), and greater severity of dyspnoea at baseline were also associated with smaller improvements in inspiratory muscle strength. The study therefore concluded that heterogenous individual responses occurred following an eight-week home-based IMT programme in people with post-acute COVID-19 syndrome. Consistent with standard exercise theory, larger improvements in inspiratory muscle strength are strongly related to a greater cumulative dose of IMT.


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Metcalfe, R., Swinton, P., Mackintosh, K., Berg, R., Shelley, J., Saynor, Z., Hudson, J., Duckers, J., Lewis, K., Davies, G. & McNarry, M. 2023, 'Heterogenous treatment effects following inspiratory muscle training during recovery from post-acute COVID-19 syndrome', Medicine and Science in Sports and Exercise. https://rgu-repository.worktribe.com/output/1952736

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Last updated: 05 May 2023
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