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Heterogenous treatment effects following inspiratory muscle training during recovery from post-acute COVID-19 syndrome.

Metcalfe, Richard S.; Swinton, Paul A.; Mackintosh, Kelly A.; Berg, Ronan M.G.; Shelley, James; Saynor, Zoe L.; Hudson, Joanne; Duckers, Jamie; Lewis, Keir; Davies, Gwyneth A.; McNarry, Melitta A.


Richard S. Metcalfe

Kelly A. Mackintosh

Ronan M.G. Berg

James Shelley

Zoe L. Saynor

Joanne Hudson

Jamie Duckers

Keir Lewis

Gwyneth A. Davies

Melitta A. McNarry


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.


METCALFE, R.S., SWINTON, P.A., MACKINTOSH, K.A., BERG, R.M.G., SHELLEY, J., SAYNOR, Z.L., HUDSON, J., DUCKERS, J., LEWIS, K., DAVIES, G.A. and MCNARRY, M.A. 2023. Heterogenous treatment effects following inspiratory muscle training during recovery from post-acute COVID-19 syndrome. Medicine and science in sports and exercise [online], 55(10), pages 1761-1769. Available from:

Journal Article Type Article
Acceptance Date Apr 26, 2023
Online Publication Date May 12, 2023
Publication Date Oct 31, 2023
Deposit Date May 4, 2023
Publicly Available Date May 13, 2024
Journal Medicine and science in sports and exercise
Print ISSN 0195-9131
Electronic ISSN 1530-0315
Publisher Lippincott, Williams & Wilkins
Peer Reviewed Peer Reviewed
Volume 55
Issue 10
Pages 1761-1769
Keywords Long COVID; Post-acute COVID-19 syndrome; Rehabilitation; Breathlessness; Breathing; Respiratory system
Public URL