Table 1 Inclusion and exclusion criteria

- 18 years of age and older

- History of CGH ≥ 3 months at Baseline 1, ≥5 days of CGH per month

- CGH intensity ≥3 (0–10 scale)

- Cervical spine dysfunction (cervical joint tenderness and/or restricted segmental motion)

- Clear temporal sequence linking the source of CGH to the neck: headache preceded by neck pain, stiffness, movement and/or awkward postures

- English literate

- Independent ambulation

- Other headaches within one year of enrollment (e.g. migraine occurring on >1 day per month in the last year, medication overuse, daily, cluster, temporomandibular joint dysfunction related headaches, sinus, posttraumatic, tumor and glaucoma related, occipital neuralgia, metabolic/toxic/substance abuse related).

- Spinal manipulative therapy, massage or exercise therapy for neck pain or headaches in the previous 3 months. Any other types of care by a licensed provider in the previous month for headaches or neck pain

- Contraindications to study treatments (e.g., inflammatory arthropathies, cervical instability, severe osteoporosis, vertigo, dizziness)

- Daily prescription or nonprescription pain medication; corticosteroid use in previous month

- Cancer in the past five years

- Cardiovascular comorbidities (e.g., history of stroke, transient ischemic attacks, stage 2 hypertension, taking anticoagulant medication, syncope, myocardial infarction, hemophilia)

- Neurological comorbidities (e.g., multiple sclerosis, ALS, Parkinson’s, myelopathy, seizures, cervical radiculopathy, herniated disc, thoracic outlet syndrome, brachial plexus neuropathy)

- Spinal pathology (e.g., infection, tumor, fracture, diffuse idiopathic skeletal hyperostosis, degenerative joint disease, stenosis)

- Involved in a research study about pain

- Active or pending medical litigation, personal injury, workers compensation; disability compensation

- Noncompliance with headache diary at baseline (<24/28 days completed); pre-randomization noncompliance

- Pregnancy, trying to get pregnant, 3 months post-partum

- Brain or cervical spine surgery in previous 5 years; trauma to head or neck requiring hospitalization in previous year

- Severe, unmanaged depression