Background: Pulmonary involvement and fibrosis are prevalent in patients with post-COVID-19. Pulmonary function abnormalities and impaired exercise capacity occur in patients. Information about the

effects of inspiratory muscle strength training (IMST) on peak oxygen consumption (VO2peak), pulmonary function, and quality of life in patients post-COVID-19 syndrome is limited.

Aim: To investigate the effects of IMST on VO2peak, pulmonary function, and quality of life in patients post- COVID-19 syndrome with pulmonary involvement.

Methods: A randomized, controlled, triple blinded study. 20 patients in each; IMST group (50% of MIP) and control group (breathing exercises) for 7days/8weeks, were compared. Pulmonary involvement (CT), pulmonary function (spirometry), maximal inspiratory and expiratory muscle strength (MIP and MEP) (mouth pressure device), exercise capacity (CPET), and quality of life (Saint George’s Respiratory Questionnaire (SGRQ)) were evaluated.

Results: The MIP (Δ:48.78 vs. -3.88 cmH2O, p=0.003), MEP (Δ:42.49 vs. -3.09 cmH2O, p<0.001), peak- VO2kg (Δ:2.43 vs. -0.39 ml/min/kg, p=0.004), peak-VO2kg(%) (Δ:9.04% vs. -3.02%, p=0.003), VCO2

(p=0,009), VO2/HR (p=0,001), VO2/HR(%) (p=0,022) and SGRQ total scores (p<0.001) were significantly improved in IMST group compared with controls. Static, dynamic lung volumes and DLCO(%) were similar in groups after (p>0.05).

Conclusions: IMST improves oxygen consumption, respiratory muscle strength, and quality of life in patients with pulmonary involvement post-COVID-19 syndrome. It is important to determine the optimal duration and frequency to maintain the long-term positive effects of IMST.