Linking Physiological Responses to Clinical Outcomes Following Cervical Spine Manipulation

The investigators aim to investigate the relationship between delivery kinetics, physiological responses and clinical outcomes following spinal manipulation.

Neck pain participants will be randomised to attend two intervention sessions and will receive either a single cervical spine manipulation or mobilization (one set of central posterior-anterior mobilizations applied with either a crossed-thumb or pisiform contact) at the most painful level.

Participants without neck pain will attend a single experimental session, where all measurement procedures will be the same as for neck pain participants with the exception that no treatment will be delivered.

For participants with neck pain, physiological responses \& clinical outcomes associated with cervical spine manipulation and mobilization will be recorded. Both treatments will be delivered by several registered, practicing and experienced clinicians. A targeted history \& physical examination will be conducted at the beginning of each experimental session to ensure it is ethical to proceed. Pre-treatment questionnaires regarding pain and treatment expectation will be completed. The participant will be instrumented with electromyographic and galvanic skin response sensors and required to wear a chest strap to measure heart rate variability. The participant will then lie in a quiet room for 10-15 minutes while baseline data is recorded. Following this, the treatment will be delivered \& responses measured. After the treatment, the participant will again lie in a quiet room for 10-15 minutes while post-treatment data is recorded. Before leaving, all sensors will be removed and post-treatment questionnaires will be completed. The participant will return after 72 hours, at the same time of day, for the second session with the alternate treatment.

Participants without neck pain will attend a single experimental session, where all procedures will be the same as described above with the exception of treatment delivery and questionnaires describing neck pain changes following treatment.

Each visit will take approximately 2-3 hours and will be performed at the Balgrist University Hospital.

Eligibility Criteria:
Inclusion criteria:

All participants:

* 18-65 years of age
* English and/or French and/or German proficiency (to guarantee proper understanding of instructions and informed consent)
* Provision of informed consent

People with neck pain:

* Mechanical neck pain located inferior to the superior nuchal line and inferior border of the mandible and superior to the superior border of the clavicle, suprasternal notch and scapular spines bilaterally
* Neck pain of ≥ 12 weeks duration
* Neck pain not associated with an identified pathological cause
* Who have not received treatment for their neck pain (e.g. spinal manipulation, spinal mobilization, massage etc) in the previous 2 weeks

Exclusion criteria:

All participants:

* Unable to provide informed consent (e.g. due to language difficulties)
* Any neurological condition
* Any major medical or psychiatric condition (e.g. cardiovascular disease, diabetes, autoimmune disorders, major depressive disorder)
* Conditions and/or medications that could affect heart rate variability signals (e.g. hypertension, obesity (body mass index \> 30), the current use of pain medications, steroids, antidepressants and/or β-blockers)
* Any chronic pain condition other than neck pain (e.g. low back pain)
* Pregnancy (all females will be asked verbally if there is a chance they are pregnant during screening)

People without neck pain:

* Acute pain
* Neck pain (\> 3 consecutive days) in the last year

People with neck pain:

* Neck pain that does not originate from the cervical spine
* Who have received treatment for their neck pain (e.g. spinal manipulation, spinal mobilization, massage etc) in the previous 2 weeks
* Who have taken medication within the past 24 hours prior to the first visit and during their participation in the study
* All contraindications to the application of spinal manipulation and mobilization (e.g. personal or family history of a connective tissue disorder, current use of anticoagulant therapy, history of recent surgery and/or neck trauma, facial or intra-oral anesthesia or paresthesia, visual disturbances, dizziness and/or vertigo). Such contraindications will be screened during the medical history and physical examination performed by a registered health care clinician (e.g. chiropractor). Any participant not meeting the inclusion and exclusion criteria will be excluded from the study. As in routine daily clinical practice at the Balgrist University Hospital Chiropractic Polyclinic, the ultimate decision whether it is appropriate to deliver an intervention to the participant (spinal manipulation and/or mobilization) will be determined by the clinician delivering the treatment. The investigator is responsible for coordinating adequate medical care if complications occur. Possible subsequent medical care is contingent on the nature of the complication and could range from referral to the on-site Chiropractic Department Polyclinic for follow-up treatment of muscle soreness to referral to the Emergency Department of the Balgrist University Hospital (not expected).