The effect of inspiratory muscle training in individuals with post-COVID-19 condition

Impaired inspiratory muscle strength is a respiratory complication in post-COVID-19 condition (PCC). Interventions that improve inspiratory muscle strength are warranted. The aim of this study was to evaluate the effect of inspiratory muscle training (IMT) in adults with PCC and impaired inspiratory muscle strength. A two-armed, randomized controlled trial was conducted (Sept 2021-Dec 2023) at Karolinska University Hospital and primary care units in Stockholm, Sweden, with an 8-week intervention period. Both intervention and control group performed individualized physical exercise twice weekly. Additionally, the intervention group performed IMT twice daily. Primary outcome was change in inspiratory muscle strength, measured with maximal inspiratory pressure (MIP), presented as percent of reference mean value (Sclauser Pessoa et al. Can Respir J 2014; 21:43–50). Preliminary, per protocol analyzes included 32 adults with PCC and impaired inspiratory muscle strength, randomized to intervention (n=16) or control group (n=16). Mean age was 51 years (SD=13) and 26 (81 %) were women. Median MIP at baseline was 51 % (IQR=46-65) and time from COVID-19 was 22 months (IQR=17-26). There was no significant difference in MIP between the groups at baseline. The intervention group had a significantly higher increase in MIP compared to control group after the intervention period (27 vs 11 %, U= 73.5, p=0.042, r_B=0.43). Both groups significantly increased MIP compared to baseline (intervention: M=27, SD=5.5, p<0.001; control: M=11, SD=3.1, p=0.004). Preliminary findings indicate that IMT in addition to individualized physical exercise may further improve MIP in adults with PCC and impaired inspiratory muscle strength.