Muscle Biomechanical Properties, Pain, and Disability in Chronic Neck Pain: The Associations With Demographic Factors.

Chronic neck pain (CNP), which ranks as the fourth leading cause of disability worldwide, negatively affects quality of life and impairs activities of daily living. This study aimed to examine the relationships between muscle biomechanical properties, pain, disability, and demographic factors in individuals with CNP. Cross-sectional study. Forty-one participants (mean age 29.63 ± 12.46 years; 78% female) were included. Muscle properties of the trapezius and sternocleidomastoid (SCM) were assessed using myotonometry, while pain intensity (NRS), multidimensional pain impact (PEG), and disability (Neck Disability Index [NDI], Bournemouth Neck Pain Questionnaire [BNPQ]) were recorded. Significant positive correlations were found between age and trapezius/SCM tone, stiffness, and decrement values (r = 0.312-.811, p < .05 to <.001), ranging from weak to very strong. Additionally, SCM decrement showed a moderate correlation with BMI (r = 0.439, p = .004). Pain measures demonstrated strong associations with disability: NRS correlated with NDI (r = 0.448, p = .003) and BNPQ (r = 0.481, p = .001), while PEG showed stronger correlations with NDI (r = 0.637, p < .001) and BNPQ (r = 0.615, p < .001). Regression analyses showed that pain measures were significantly associated with disability, with PEG explaining a greater proportion variance (NDI R²=.406, BNPQ R²=.378) compared to NRS (NDI R²=.219, BNPQ R²=.213). No direct associations were found between muscle biomechanical properties and pain. These findings indicate that muscle biomechanical properties are associated with demographic factors such as age and BMI, whereas pain-particularly when assessed using multidimensional instruments-is more strongly associated with disability in individuals with CNP.