Are there differences in muscular activation to maintain balance between individuals with chronic obstructive pulmonary disease and controls?

Background: The mechanisms underlying impaired balance in chronic obstructive pulmonary disease (COPD) are poorly understood, which makes it difficult to choose the best therapeutic approaches. Therefore, this study aimed to investigate patterns of muscular activation to maintain balance and its determinants in this population. Methods: Thirty-three subjects with COPD and 33 controls were assessed by a force platform in four tasks: standing with eyes opened (FHEO) and closed (FHEC); standing on unstable surface (SUS) and one-legged stance (OLS). Electromyographic activity of lower limb, trunk and neck muscles was concomitantly recorded. To asses functional balance, Brief-balance evaluation systems and timed up & go (TUG) tests were applied. Lung function, exercise capacity and muscle force were also assessed. Results: Subjects with COPD presented worse balance and higher scalene activation than controls in OLS (mean difference 23.0 [95%CI 1.7–44.3] _%Δ μV_RMS; P = 0.034), besides presenting also higher activation of gluteus medius during FHEC task (mean difference 1.5 [95%CI 0.2–2.8] _%Δ μV_RMS; P = 0.023) and taking longer to complete the TUG (mean difference 0.6 [95%CI 0.1–1.2] seconds; P = 0.042). Exercise capacity and peripheral muscle force were determinants of functional balance (r² = 0.505), whereas age (OR = 1.24; 95%CI 1.02–1.52) and total lung capacity (OR = 2.42; 95%CI 1.05–5.56) were determinants of static balance. Conclusion: Individuals with COPD have worse static and functional balance in comparison with controls, besides presenting higher activation of scalene and gluteus medius during static balance tasks. Exercise capacity and peripheral muscle force emerged as determinants of functional balance, whereas age and lung hyperinflation contributed to poor static balance.