Inspiratory muscle training enhances recovery post-COVID-19: a randomised controlled trial

Background Many people recovering from coronavirus disease 2019 (COVID-19) experience prolonged symptoms, particularly breathlessness. We urgently need to identify safe and effective COVID-19 rehabilitative strategies. The aim of the current study was to investigate the potential rehabilitative role of inspiratory muscle training (IMT).Methods 281 adults (age 46.6 +/- 12.2 years; 88% female) recovering from self-reported COVID-19 (9.0 +/- 4.2 months post-acute infection) were randomised 4:1 to an 8-week IMT or a "usual care" waitlist control arm. Health-related quality-of-life and breathlessness questionnaires (King's Brief Interstitial Lung Disease (K-BILD) and Transition Dyspnoea Index (TDI)), respiratory muscle strength, and fitness (Chester Step Test) were assessed pre-and post-intervention. The primary end-point was K-BILD total score, with the K-BILD domains and TDI being key secondary outcomes.Results According to intention to treat, there was no difference between groups in K-BILD total score post-intervention (control: 59.5 +/- 12.4; IMT: 58.2 +/- 12.3; p<0.05) but IMT elicited clinically meaningful improvements in the K-BILD domains for breathlessness (control: 59.8 +/- 12.6; IMT: 62.2 +/- 16.2; p<0.05) and chest symptoms (control: 59.2 +/- 18.7; IMT: 64.5 +/- 18.2; p<0.05), along with clinically meaningful improvements in breathlessness according to TDI (control: 0.9 +/- 1.7 versus 2.0 +/- 2.0; p<0.05). IMT also improved respiratory muscle strength and estimated aerobic fitness.Conclusions IMT may represent an important home-based rehabilitation strategy for wider implementation as part of COVID-19 rehabilitative strategies. Given the diverse nature of long COVID, further research is warranted on the individual responses to rehabilitation; the withdrawal rate herein highlights that no one strategy is likely to be appropriate for all.