The goal of this clinical trial is to evaluate the effectiveness of inspiratory Muscle Training (IMT) on both objective and subjective sleep parameters in patients with OSA.Methods: A prospective, randomized, controlled clinical trial will be conducted with patients diagnosed with OSA followed at Otavio de Freitas Hospital. Participants will be evaluated for excessive daytime sleepiness (Epworth Sleepiness Scale), sleep quality (Pittsburgh Sleep Quality Index), physical activity level (IPAQ), sleep latency, total sleep time, sleep efficiency, number of nocturnal awakenings, total time in bed, total wake time during sleep (Actigraphy), hypoxic burden during sleep (Nocturnal Oximetry), disease severity (Polysomnography), respiratory muscle strength (Manovacuometry), and respiratory muscle endurance (Powerbreathe K-series) before and after 4 weeks of training, as well as perceived change in health status after IMT (PGIC).Participants will be divided into two groups and will perform IMT for 4 weeks: the experimental group will perform IMT with a progressive weekly load (50%, 60%, 75% of MIP) adjusted using the Powerbreathe® Classic device, while the control group will use the device without load. The participants will perform IMT at home under the guidance of the principal investigator.Statistical Analysis: Data will be analyzed using SPSS version 26.0 with descriptive and analytical statistical techniques. Normality will be assessed using the Shapiro-Wilk test. For intergroup and intragroup comparisons, two-way ANOVA will be used. Tukey's post-hoc test will be applied to compare pre- and post-intervention mean variances for each group. The level of significance adopted for all analyses will be 95% (p < 0.05).Expected Results: It is expected that 4 weeks of IMT in patients with OSA will reduce excessive daytime sleepiness, sleep latency, number of awakenings, and hypoxic burden, as well as increase sleep efficiency and total sleep time, leading to improved sleep quality.

Obstructive Sleep Apnea (OSA) is a prevalent sleep-related breathing disorder characterized by repeated episodes of upper airway obstruction during sleep, leading to intermittent hypoxia, sleep fragmentation, and frequent arousals. These events disrupt sleep architecture, reduce total sleep time and sleep efficiency, and result in non-restorative sleep. As a consequence, patients often present with excessive daytime sleepiness, cognitive and functional impairments, and an increased risk of occupational errors and motor vehicle accidents.

The impact of OSA extends beyond sleep, contributing to reduced quality of life and increased cardiovascular and metabolic risks. Considering the multifactorial consequences of OSA and the barriers to continuous positive airway pressure (CPAP) adherence-including cost, discomfort, and access-there is a need for alternative or adjunctive low-cost therapies that are easy to implement and have proven efficacy.

Inspiratory Muscle Training (IMT) has emerged as a promising therapeutic strategy to improve respiratory muscle strength, reduce symptoms, and potentially enhance sleep quality. However, evidence regarding its impact on objective and subjective sleep parameters in patients with OSA remains limited.

This study aims to evaluate the efficacy of a 4-week IMT protocol, following standardized training guidelines, in adults with moderate to severe OSA who have not yet initiated CPAP therapy. Validated instruments will be used to assess sleep outcomes. The findings are expected to contribute to clinical decision-making and offer evidence for non-pharmacological, non-invasive interventions to improve sleep quality and reduce daytime symptoms in this population.

Inclusion Criteria:

• Male or female participants
• Age between 18 and 70 years
• Clinical diagnosis of moderate to severe Obstructive Sleep Apnea (OSA), confirmed by polysomnography
• Not currently undergoing treatment for OSA

Exclusion Criteria:

• Presence of neuromuscular disorders, infectious diseases, immunological conditions, tumors, or any disease that prevents inspiratory muscle training (IMT), manovacuometry, or respiratory muscle performance assessment
• Unstable angina, untreated or uncontrolled systemic arterial hypertension, left ventricular dysfunction, cerebral aneurysm, or any cardiovascular condition contraindicating IMT or respiratory muscle testing
• Upper limb deformities that prevent the use of actigraphy devices or oximetry sensors
• Other sleep disorders (e.g., insomnia, hypoventilation syndrome, or need for continuous home oxygen therapy)
• Cognitive impairment that limits the participant's ability to understand or follow study procedures
• Ongoing or planned CPAP therapy during the follow-up period
• Participation in a pulmonary rehabilitation program within 6 months prior to the study
• Moderate or high physical activity level according to the IPAQ, including regular moderate or vigorous physical activity within the past 30 days
• Use of sleep-inducing medication to treat insomnia
• Grade 2 or 3 obesity (BMI ≥ 35 kg/m²)
• Residence in a geographic area with limited or no access to telephone or internet service, preventing contact or data transmission from study devices (actigraphy and/or oximetry sensors)

De-identified individual participant data (IPD) will be shared upon reasonable request for academic and research purposes, following approval by the principal investigator and compliance with ethical standards. Participants' privacy and confidentiality will be strictly maintained

Data will be available beginning 6 months after publication of the primary study results, for a period of up to 5 years.

Researchers must submit a detailed research proposal and obtain approval from the principal investigator.