Respiratory Rehabilitation After COVID-19: Efficacy of Inspiratory Muscle Training on Lung Function, Quality of Life and Sleep Quality: A Randomized Clinical Trial
Authors: Jose Carlos Nóbrega Júnior¹, Daniella Brandão¹, Daiara Xavier¹, Roberta Torres¹, Simone Soares Brandão², Magno Formiga³, James B. Fink⁴, Arzu Ari⁴, Shirley Campos¹, Armèle Dornelas de Andrade¹*
¹ Department of Physical Therapy, Federal University of Pernambuco, Recife 50740, Pernambuco, Brazil
² Department of Nuclear Medicine, Federal University of Pernambuco, Recife 50740, Pernambuco, Brazil
³ Department of Physical Therapy, Federal University of Ceará, Fortaleza 60440, Ceará, Brazil
⁴ Department of Respiratory Care, Texas State University, Round Rock, TX 78665, USA
*Corresponding author
Journal: COVID 2026, 6(1), 22
DOI: https://doi.org/10.3390/covid6010022
Published: 19 January 2026
Received: 18 December 2025 | Revised: 29 December 2025 | Accepted: 9 January 2026
Abstract
Background and Purpose: Post-COVID-19 syndrome significantly impacts respiratory function and quality of life. Inspiratory muscle training (IMT) has been proposed as a potential intervention to improve respiratory muscle strength and overall recovery. This study aimed to evaluate the effects of IMT on respiratory muscle performance, lung function, functional capacity, sleep quality, and quality of life in individuals with post-COVID-19 syndrome.
Methods: Nineteen individuals with post-COVID-19 syndrome were randomized into an IMT group (N = 10) or a sham group (N = 9). The IMT group performed eight weeks of training at 50% of maximal inspiratory pressure (MIP), while the sham group used a non-load device. Outcomes included MIP (cm H₂O), functional capacity (6MWT), lung function (spirometry), sleep quality (PSQI), and quality of life (SF-36).
Results: The IMT group showed significant improvements in MIP (125.50 ± 22.50 vs. 93.67 ± 20.87 cm H₂O; p = 0.036; Cohen's d = 0.50), PSQI (4.40 ± 2.50 vs. 9.00 ± 2.80; p = 0.011; Cohen's d = 0.60), and SF-36 (p = 0.030). The IMT group also increased 6MWT distance by 58.36 ± 25.10 m.
Conclusions: IMT significantly improved respiratory muscle strength, sleep quality, and quality of life in post-COVID-19 syndrome. These findings suggest that IMT may be an effective intervention, warranting further studies to confirm long-term benefits.
Introduction
Post-COVID-19 syndrome is characterized by the persistence of multiple symptoms for weeks or months after acute SARS-CoV-2 infection, which may impair the pulmonary, cardiovascular, nervous, and metabolic systems. Common symptoms include persistent fatigue, dyspnea, chest pain, palpitations, cognitive disorders, headache, sleep disturbances, anxiety, and depression. Several mechanisms have been proposed to explain the multifactorial etiology of post-COVID-19 syndrome, including persistent immunologic dysfunction, chronic low-grade inflammation, endothelial dysfunction, neuroinvasive effects, and direct or indirect tissue damage. Genetic predisposition, preexisting comorbidities, and environmental factors may also increase susceptibility to and severity of post-COVID-19 syndrome.
Previous studies have demonstrated that individuals who have recovered from COVID-19 often experience impairments in lung function and diffusion capacity, resulting in reduced functional capacity. In addition, neuromuscular and inflammatory alterations induced by viral infection may cause insomnia, sleep apnea, and daytime fatigue, thereby affecting sleep quality. These conditions reduce lung function and quality of life, hindering daily activities and psychological well-being. However, the mechanisms underlying chronic symptoms and the efficacy of different interventions remain unclear.
In this context, inspiratory muscle training (IMT) may improve lung function and functional capacity in various clinical conditions. This training increases the strength and endurance of respiratory muscles, reduces dyspnea, and improves functional capacity and quality of life. However, the benefits of IMT for individuals with post-COVID-19 syndrome remain unclear because existing studies show divergence in several factors (e.g., heterogeneity of protocols, inclusion of individuals without a diagnosis confirmed by reverse transcription polymerase chain reaction [RT-PCR], and combination of IMT with other exercise modalities), which limits adequate comparison. Therefore, this study aimed to analyze respiratory muscle performance, lung function, functional capacity, sleep quality, and quality of life in individuals with post-COVID-19 syndrome before and after an eight-week IMT program.
Results
Changes in MIP were significantly higher in the IMT group than in the sham group (mean difference: 31.83 cm H₂O; 95% CI: 2.43 to 61.32; p = 0.036, Cohen's d = 0.50). Subjective sleep quality (PSQI) was significantly higher in the IMT group (mean difference: −4.60; 95% CI: −7.99 to −1.20; p = 0.011, Cohen's d = 0.60). Although the changes in the distance walked and percentage values of the distance walked demonstrated a moderate effect size after the intervention (mean difference: 58.36 m; 95% CI: −13.08 to 129.81; p = 0.103, Cohen's d = 0.40, and mean difference: 10.23%; 95% CI: −0.37 to 20.84; p = 0.058, Cohen's d = 0.50, respectively), values were not significantly different between groups. Changes in sleep efficiency (actigraphy) showed significant differences between the groups (mean difference: 8.42; 95% CI: 2.97 to 13.88; p = 0.005, Cohen's d = 0.60).
The IMT group showed statistically significant improvements compared to the sham group in MIP (125.50 vs. 93.67 cm H₂O, p = 0.036 Cohen's d = 0.50), sleep efficacy (90.48 vs. 82.06%, p = 0.005; Cohen's d = 0.62), and PSQI scores (4.40 vs. 9.0, p = 0.011; Cohen's d = 0.60), as shown in Table 2.
The analysis revealed a significant interaction between time and group (p = 0.030), indicating that the impact of the intervention on quality of life was statistically different between groups.