Respiratory Muscle Strength and Endurance Cut-Offs in Multiple Sclerosis

Multiple sclerosis (MS) is a chronic and progressive autoimmune disease of the central nervous system characterized by inflammation, demyelination, and axonal degeneration. Depending on lesion localization and disease severity, individuals with MS may develop a wide range of neurological manifestations affecting motor and sensory functions. Current evidence indicates that pulmonary function impairments may occur in individuals with MS even in the absence of overt respiratory symptoms. Compared with healthy individuals, people with MS have been reported to exhibit significantly reduced values in several respiratory parameters, particularly respiratory muscle strength. Moreover, these reductions appear to become more pronounced in parallel with increasing Expanded Disability Status Scale (EDSS) scores, regardless of disease duration. Indeed, previous studies have demonstrated that even individuals with MS who have mild disability levels (EDSS 0-4.5) experience significant declines in respiratory muscle strength, pulmonary function, and functional exercise capacity compared with healthy controls. These findings suggest that the respiratory system may be affected not only in the advanced stages of MS but also during the early phases of the disease, with functional impairments emerging before clinically evident respiratory complaints arise. Despite this, the existing literature lacks studies that define clear, clinically applicable cut-off values for respiratory muscle strength and endurance that can discriminate disability levels in individuals with MS. This gap highlights the absence of objective criteria that clinicians can rely on for early detection and for planning targeted rehabilitation interventions. The present study aims to address this gap by identifying optimal cut-off points for respiratory muscle strength and endurance in individuals with MS to facilitate early and accurate discrimination of disability status. By doing so, this research seeks to make an