Changes in the Viscoelastic Properties of Accessory Respiratory and Peripheral Muscles in Patients with Stable Chronic Obstructive Pulmonary Disease

Objective: Muscle viscoelastic properties remain incompletely investigated in patients with chronic obstructive pulmonary disease (COPD). This study aimed to compare the viscoelastic properties of the accessory respiratory muscles and peripheral muscles between COPD patients and healthy individuals. Method: Sixty males were included in the study: patients with stable COPD and healthy adults (n=30 each). Pulmonary function was assessed using spirometry. Muscle viscoelastic properties, including tone (Hz), stiffness (N/m) and elasticity (E, inverse of logarithmic decrement), were quantified using MyotonPRO®. Result: Compared to the healthy group, the tone values of sternocleidomastoid muscles (SCM), left deltoid muscle (D), and left biceps brachii (BB) muscles were higher in the COPD group (bilateral SCMs; p < 0.001, left D; p = 0.014, left BB; p = 0.006). The stiffness values of SCMs (p < 0.001), as well as the left D (p = 0.008), and left BB muscles (p = 0.044) were also higher in the COPD group. The logarithmic decrements for the SCM, upper trapezius (UT), pectoralis major (PM), and D muscles bilaterally were higher in the COPD group (p = 0.031/p = 0.009; p < 0.01/p < 0.01; p = 0.006/p = 0.018; p = 0.005/p = 0.014, respectively, right/left side). Conclusion: Reduced elasticity of the respiratory muscles, particularly the SCM muscle, along with increased tone and stiffness, reflects a change in muscle viscoelastic properties in patients with COPD. Further studies are needed to assess the impact of COPD on the viscoelastic properties of lower extremity muscles.