It is expected that different physical therapy treatments influence outcomes in many different ways. Each treatment is assumed to have a "specific" treatment mechanism, which explains how that specific treatment works. Different treatments also have "shared" mechanisms, which are similar across many different types of interventions (e.g., exercise, cognitive treatments or manual therapy). In this study, the study team will investigate the several types of specific treatment mechanisms of a manual therapy-based approach and an exercise-based approach and the study team will compare these to see if they are different. The patient population will include individuals with chronic neck pain, which is a condition that leads to notable disability and pain. The study team will also evaluate several shared treatment mechanisms to see if these are similar across the two treatments (e.g., manual therapy versus exercise). The study team expects to find that there are some specific treatment mechanisms with each approach (manual therapy versus exercise) but also several "shared" mechanisms that are similar across the two seemingly different approaches. These will likely influence the outcomes and may help explain why clinicians see similar outcomes across both treatment groups for chronic neck pain. This study is important because no one has investigated whether the outcomes that occur with chronic neck pain are mostly influenced by specific or shared treatment mechanisms. Interestingly, in the psychological literature, shared treatment mechanisms demonstrate the strongest influence (more than specific treatment mechanisms).

Treatment mechanisms involve the steps or processes through which an intervention unfolds and produces the change in an outcome variable. In other words, a treatment mechanism is "how a treatment works". Treatment mechanisms can be specific to the intervention provided (i.e., fiber size increase and neuro adaptation occur with resistance exercise) or shared with other treatments (i.e., theoretically, increased therapeutic alliance and reduced fear of movement occur with almost all forms of interventions). In this proposal, the study team plans to investigate specific and shared treatment mechanisms of a manual therapy approach and a resistance exercise approach for treatment of chronic neck pain. The study team is targeting chronic neck pain because it is a common problem that is second only to low back pain for years lived with disability. Routinely, chronic neck pain management includes manual therapy and resistance exercise, as both approaches are included in clinical practice guidelines. The study plans to answer two research questions: 1) what are the specific mechanisms associated with manual therapy and resistance exercise interventions (and are these different), and 2) what are the shared mechanisms associated with these interventions, and do both mechanisms mediate clinical outcomes? The study team hypothesized that manual therapy and resistance exercise approaches will exhibit different specific treatment mechanisms. Further, the team hypothesizes that both approaches will lead to shared treatment mechanisms, which will notably influence outcomes at both 4 weeks and 6-month follow-up. This study is important because it will help identify how different treatment mechanisms influence clinical outcomes. There are several studies in the psychological literature that demonstrate the role of both specific and shared treatment mechanisms but this form of investigation is mostly absent for general musculoskeletal rehabilitation interventions. It will be the first study involving manual therapy in which specific and shared mechanisms are evaluated and explored against clinical outcomes.

Inclusion Criteria:

• Individuals with chronic neck pain (chronic pain is defined using the International Association of the Study of Pain (IASP) pragmatic criteria of pain lasting for 3 months or more that cannot be attributed to another diagnosis or condition.)
• 18 years of age and older
• experience ongoing neck pain of ≥3 on a 10-point scale for most days of the previous 3-months.

Exclusion Criteria:

• Individuals with cervical pain and suspected radicular symptoms
• a history of neck surgery within 1 year
• current or suspected red flags
• unable to speak or write in English.

The proposal will follow the data sharing guidelines set forth for the NIH HEAL Initiative®. As with the HEAL initiative, we plan to create an infrastructure that addresses the need for researchers, clinicians, and patients to collaborate on sharing their collective data. Our Data Sharing Plan that (1) will make the two projected Publications Open Access and, to the extent possible, and (2) will make the Underlying Primary Data immediately and broadly available to the public. Underlying Primary Data should be made as widely and freely available as possible while safeguarding the privacy of participants and protecting confidential and proprietary data.

Protocol when published. SAP within the protocol when published. Informed consent once approval of IRB.

Subjects are told they will be randomized into two forms of treatment for chronic neck pain and that the study team is interested in learning the mechanisms associated with that treatment