Accessory Inspiratory Muscles in Chronic Neck Pain

Ultrasonographic Characteristics of Accessory Inspiratory Muscles and Their Relationship With Respiratory Function in Individuals With Chronic Non-Specific Neck Pain: A Cross-Sectional Case-Control Study

This cross-sectional case-control study aims to investigate the ultrasonographic structural and functional characteristics of accessory inspiratory muscles in individuals with chronic non-specific neck pain and compare them with healthy controls. In addition, the relationships between accessory inspiratory muscle characteristics, diaphragm function, respiratory muscle strength, and pulmonary function parameters will be examined. The findings may improve understanding of the respiratory involvement associated with chronic neck pain and contribute to more comprehensive assessment strategies.

Chronic non-specific neck pain is a prevalent musculoskeletal disorder associated with pain, disability, and reduced quality of life. Emerging evidence suggests that its effects may extend beyond the cervical region and involve respiratory dysfunction. Previous studies have reported reductions in respiratory muscle strength, pulmonary function, and diaphragm function in individuals with chronic neck pain.

The diaphragm plays an important role not only in respiration but also in postural control and spinal stabilization. Ultrasonographic studies have demonstrated alterations in diaphragm thickness and mobility in individuals with chronic neck pain. However, little is known about potential compensatory adaptations occurring in accessory inspiratory muscles, including the sternocleidomastoid, anterior scalene, and upper trapezius muscles.

The purpose of this observational case-control study is to investigate the ultrasonographic characteristics of accessory inspiratory muscles in individuals with chronic non-specific neck pain and to compare these characteristics with those of healthy controls. Additionally, the relationships between accessory inspiratory muscle characteristics, diaphragm function, respiratory muscle strength, and pulmonary function will be examined.

Participants with chronic non-specific neck pain and age-matched healthy controls will undergo ultrasonographic assessment of the diaphragm and accessory inspiratory muscles, pulmonary function testing, and respiratory muscle strength evaluation. Associations among ultrasonographic, respiratory, and functional variables will be analyzed to improve understanding of respiratory involvement in chronic neck pain and to identify potential clinical assessment targets.

Inclusion Criteria

Chronic Non-Specific Neck Pain Group:

• Age between 18 and 65 years
• Presence of chronic non-specific neck pain for at least 3 months
• Non-traumatic origin of neck pain
• Pain intensity ≥ 3 on the Numeric Pain Rating Scale (NPRS) or Visual Analog Scale (VAS)
• Neck Disability Index (NDI) score ≥ 15
• Willingness to participate and provide informed consent

Healthy Control Group:

• Age between 18 and 65 years
• No neck pain during the previous 3 months
• Not receiving any treatment related to the cervical region
• Willingness to participate and provide informed consent

Exclusion Criteria (Both Groups):

• History of whiplash injury or cervical trauma
• Previous cervical spine surgery
• Cervical radiculopathy or neurological deficits
• Chronic respiratory diseases (e.g., COPD, asthma)
• Active respiratory tract infection
• Thoracic or abdominal surgery within the previous 6 months
• Rheumatologic, neuromuscular, or systemic inflammatory disorders
• Pregnancy
• Physiotherapy treatment for neck pain within the previous 3 months
• Regular respiratory muscle training or breathing exercises within the previous 3 months
• Inability to comply with study procedures or assessments