Persistent pain and disability in whiplash-associated disorders (WAD) grade II and III are common. Randomized controlled studies (RCTs) have shown promising result for neck-specific exercise (NSE) programmes in chronic WAD with clinically and statistically significant improvement in pain and disability. Neck-specific exercise with internet support (NSEIT) and four visits to a physiotherapist was non-inferior to NSE at a physiotherapist clinic 2 times a week in 12 weeks (24 visits). The aims of the proposed study are to evaluate an implementation strategy for NSE and NSEIT in primary health care and to evaluate the effectiveness of NSE and NSEIT in clinical practice.

The study is a prospective cluster-randomized study with hybrid II trial design.

In total will 20 physiotherapy clinics in primary health care be recruited. Reg. physiotherapists working in the twenty physiotherapy clinics will be included. The clinics will be randomised to two groups with different implementation strategy: (A, intervention) three theoretical on-line lectures and the three hours' practical training with additional support; (B, control) the same education and practical training as A but with no additional support. Twenty-five patients with neck pain will be consecutively recruited from each clinic, a total of 500 patients. Outcome measurements will be conducted at baseline, 3- and 12-months.

This trial will evaluate the implementation strategy in terms of adoption of and adherence to NSEIT and NSE in clinical primary health care, also measuring diffusion of the method to other neck pain patients. In parallel, effectiveness of the exercises are evaluated.

All analyses will be conducted in collaboration with a statistician using parametric or non-parametric statistics depending on the type of data.

1. The implementation strategy will be analyzed using parametric t-test and a linear mixed model Analysis of Variance (ANOVA) or non-parametric Mann-Whitney U test and Kruskal-Wallis to evaluate differences between group A and B and change in variables over time.

   To further evaluate the implementation strategy will two focus group studies be conducted, with a purposeful sample of physiotherapists included in the cluster-randomized mixed-design study. The overall aim of these qualitative studies is to deepen the knowledge on the uptake of the new method, i.e., the NSEIT/NSE programme (adoption), the implementation in clinical practice (implementation), and how it continues to be used (maintenance).

2. The effectiveness of NSEIT and NSE will be analysed with a linear mixed model Analysis of Variance (ANOVA) or Kruskal-Wallis depending on the data.

The effect of neck-specific exercises in the present study will also be evaluated and compared to the results in our former RCT-studies.

Sample size and power regarding group differences were calculated by a statistician. Sample size calculation was based on the assumption that 15% more patients will receive neck-specific exercises in the intervention group (40% in the intervention group and 25% in the control group). The required sample size under individual randomization will be 150 patients in each arm. With ten physiotherapy clinics (clusters) in each arm (a total of 20 clusters), intra-cluster correlation of 0.02 and a cluster size of 21 patients, a total of 420 patients are recruited for 80% power and a significance level of 0.05. To ensure that enough people are in each group after dropouts, a total of 500 patients will be included, 25 patients from each cluster. The patients will be consecutively recruited.

Patients who are included in both the intervention and control groups and received neck-specific exercises will be treated as one group in terms of the effect of the intervention. The sample size calculation to evaluate effectiveness was based on a clinically relevant improvement of 7% on the Neck Disability Index (NDI), effect size 0.2 (Cohen's f) or 0.4 (Cohen's d), and correlation among repeated measures of 0.3, resulting in a total of 56 participants for 80% power and a significance level of 0.05. With an expected dropout rate of 20%, a total of 70 participating patients are needed.

The patients will be analysed as one group and the total number of patients may be more than 70 because patients will be included at each clinic. All analyses will be conducted in collaboration with a statistician using parametric or non-parametric statistics depending on the type of data. Data will be analysed according to intention to treat and supplemented with per protocol analysis.

Inclusion criteria implementation

- Reg. physiotherapists working in twenty physiotherapy clinics in primary health care.

Exclusion criteria implementation

- No exclusion criterta

Inclusion criteria to evaluate the effectiveness of neck-specific exercise

• The physiotherapists will include patients ≥ 18 years with neck pain.
• Patients are required to have internet access by phone, tablet, or computer
• Be able to read and understand Swedish

Exclusion criteria:

• Physiotherapists should exclude patients with "red flags"i.e., symptoms that suggest a serious illness or spinal abnormality.
• Serious trauma to the neck and no X-ray
• Preceding neck surgery
• Osteoporosis
• Myelopathy
• History of cancer
• Unexplained weight loss
• Present fever, history of infections
• Constant and progressive non-mechanical pain
• Insidious progression of pain
• Signs of spinal cord compression (neurological examination to exclude spinal cord or cervical myelopathy such as clumsy hands, altered gait, or disturbances of sexual, bladder or sphincter function).