Postural control impairment in chronic obstructive pulmonary disease (COPD): The role of respiratory muscle weakness and spinal curvature

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is associated with respiratory muscle dysfunction, postural alterations and balance impairment. However, the impact of respiratory muscle weakness on postural control and its relationship with spinal curvature and mobility remain insufficiently clarified. OBJECTIVES: The objectives of this study were to compare postural control in individuals with COPD with and without respiratory muscle weakness; to examine the relationship among spinal curvature, spinal mobility, postural control and respiratory muscle strength; and to determine the effect of respiratory muscle strength on postural control. METHODS: This cross-sectional study included 41 clinically stable individuals with COPD aged 40–75 years. Respiratory muscle strength was assessed using a mouth pressure measurement device. Postural control and balance were evaluated with the Biodex Balance System and functional tests. Higher stability index values indicate greater postural sway and poorer balance performance, whereas lower values reflect better postural stability. Spinal curvature and mobility were assessed using the Spinal Mouse®. RESULTS: Individuals with respiratory muscle weakness showed significantly higher overall, anterior–posterior and medial–lateral stability indices, as well as worse eyes-open and eyes-closed firm-surface indices compared to those without weakness (p < 0.05). In participants with severe and very severe COPD, thoracic kyphosis angle was significantly associated with MIP, MIP% and multiple balance indices under different surface and visual conditions (p < 0.05). CONCLUSIONS: Respiratory muscle weakness is associated with impaired postural control and balance performance in individuals with COPD, and thoracic spinal curvature appears to be linked to both respiratory muscle strength and balance outcomes.