This project aims to quantify accessory movements that occur during cervical range of motion (ROM) assessment in young adults and to examine their relationship with functional and psychological factors. Although cervical ROM is widely used in clinical practice, accurate measurement is challenged by the complex anatomy of the cervical spine and coupled movements, which may alter true motion values. Despite their clinical relevance, accessory movements have been largely overlooked in both research and routine assessment.

This cross-sectional observational study will include volunteers aged 18-30 years, recruited between January and August 2025 following ethical approval. Individuals with cervical trauma or surgery, neurological disease, recent treatment, musculoskeletal injury, or medications affecting movement will be excluded. Accessory movements will be measured using the CROM device while participants perform flexion-extension, lateral flexion, and rotation, maintaining end-range for 20 seconds to record primary and accessory motions.

Clinical outcomes will include cervical disability (Neck Disability Index), pain intensity (Visual Analog Scale), cervical mechanosensitivity (pressure algometry at the upper trapezius and C2-C7 regions), psychological status (Depression, Anxiety, Stress Scale-21), and sleep quality (Pittsburgh Sleep Quality Index).

Range of motion (ROM) is a routinely accepted parameter used by physiotherapists and other health professionals in the evaluation of spinal movements, serving as both a baseline and outcome measure for documenting disability and the effects of interventions, as well as for adjusting physiotherapy treatment plans. However, due to the complex anatomy of the cervical spine and its associated movements, accurate measurement of cervical ROM remains challenging.

A variety of tools have been developed to assess cervical mobility, ranging from simple visual inspection to advanced three-dimensional motion analysis systems, including goniometers, inclinometers, CROM devices, Optotrak and Vicon systems, radiographic techniques, and smartphone applications.

The anatomy of the cervical spine and the presence of "coupled movements" make the measurement of cervical ROM particularly difficult. Coupled movements refer to accessory motions that accompany a primary target movement. For example, when an individual flexes the head forward while simultaneously rotating it laterally, flexion is considered the primary movement, whereas the accompanying lateral flexion and axial rotation are accessory movements. The complex structure of the functional units of the cervical spine permits the combination of multi-axial movements rather than isolated single-axis motions. Movements of adjacent vertebrae are guided by the geometry of the articular surfaces, which allows the combination of ipsilateral rotation with lateral flexion. At the lower cervical levels, the orientation of the apophyseal joints and the presence of cervical lordosis may lead lateral flexion to be accompanied by ipsilateral rotation and slight extension. Other studies have emphasized the variability in movement patterns that arise due to the presence of these coupled motions, even during simple tasks. Additionally, research has demonstrated that accessory movements can cause substantial variation in the magnitude of the primary movement.

At the structural level of the cervical spine, multiple movement strategies may be used to achieve a specific functional goal. The number of studies describing accessory movements as involuntary patterns developed in the presence of cervical pain is limited, and those that exist vary depending on the measurement technique and participant characteristics. By revealing the impact of often-neglected accessory movements during the assessment of active cervical ROM, the present project aims to introduce conceptual and methodological innovations to cervical mobility evaluation methods. Considering the scarcity of research on this topic, the proposed project will provide a unique contribution to clinical assessment and treatment strategies.

To the best of our knowledge, although there are a limited number of studies investigating the presence of accessory movements during cervical ROM measurement, no research has explored the factors associated with these movements. A better understanding of the characteristics of ROM impairments may help clarify the clinical significance of these relationships. However, in both the literature and clinical practice, the magnitude of accessory movements occurring during cervical ROM has generally been overlooked. The present project addresses this important gap by quantifying accessory movements and, for the first time, comprehensively examining their relationship with both physical and psychological limitations in young individuals. In this context, the project is expected to contribute to the development of more specific and individualized treatment algorithms for individuals with cervical spine dysfunction.

Inclusion Criteria:Participants will be included if they:

Are between 18 and 30 years of age

Volunteer to participate in the study

Provide written informed consent.

Exclusion Criteria:Participants will be excluded if they have:

A history of cervical trauma

A history of cervical spine surgery

Any neurological disorder

Received treatment related to the cervical region within the past 6 months

Any musculoskeletal injury that may affect cervical movement

Use of medications that could influence movement or neuromuscular function.

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The study population will consist of young adults aged 18-30 years who volunteer to participate and meet the inclusion criteria. Only individuals without cervical trauma, surgery, neurological disorders, recent treatment, musculoskeletal injuries, or medication use affecting cervical movement will be included, ensuring a homogeneous non-clinical sample suitable for accurately evaluating accessory cervical movements.