Classification of outcome measures and Cochrane Collaboration Back Review Group (CCBRG) Levels of evidence for evaluating interventions [95, 101]
Outcome measures	Validated assessment tools
Pain	Visual analogue scale (VAS) and numerical-pain-rating-scale (NPRS) pressure pain thresholds (PPT)
Functional disabilities	Neck-Disability-Index (NDI), Fear-Avoidance-Belief-Questionnaire (FABQ), the Northwick-Neck-Pain-Questionnaire (NPQ), the cervical-Range-Of-Motion (CROM)
Overall-health improvement	Short-form-health-survey (SF-36)
Quality of life	Adverse events
Overall level of evidence	Conditions description
Strong	Consistent findings from multiple high quality trials (level A) ($n⩾$ 3)
Moderate	Consistent findings among multiple moderate quality (level B) and/or one level A
Limited	One level B
Conflicting	Inconsistent findings among multiple trials
No evidence	No trials
Search strategy in MEDLINE	“Manual-Therapy” was used as a free-term in MeSH (MEDLINE). “Musculoskeletal-Manipulations” was the result of the MeSH heading terms, we added “Neck-Pain” to the MEDLINE search box as follows: “Musculoskeletal-Manipulation” [Mesh] and “Neck-Pain” [Mesh] and (“human” [MeSH-Terms] and (“male” [MeSH-Terms] or “female” [MeSH-Terms]) and Randomized-Controlled-Trial [ptyp] and English [lang] and “adult” [MeSH-Terms] and “2000/01/01” [PDat]: “2015/12/31”[PDat])