Powering Exercise-induced Hypoalgesia and Functional Recovery in Chronic Nonspecific Neck Pain by Hybrid Muscle Conditioning: a Comparative Effectiveness Randomised Controlled Trial With Mechanistic Analysis

Chronic nonspecific neck pain is a prevalent and recurrent condition frequently characterised by persistent impairments in cervical-scapular neuromuscular function. Deep cervical flexor motor-control deficits and reduced upper trapezius endurance represent two clinically relevant but distinct manifestations of neuromuscular dysfunction. Deep cervical flexor motor-control exercise targets cervical segmental control and movement coordination, while upper trapezius endurance exercise targets at the mechanical capacity of the cervical-scapular system. Although both exercise approaches have demonstrated clinical benefit when used independently, it remains unknown whether combining these two exercises as compared to single-exercise approach would provide additional or synergistic effects on the clinical recovery for individuals with chronic nonspecific neck pain.

This three-arm comparative randomised controlled trial will investigate a 5-week hybrid programme combining deep cervical flexor motor-control and upper trapezius endurance exercise as compared to their single-exercise comparator programme (i.e., deep cervical flexor motor-control exercise alone or upper trapezius endurance exercise alone) in managing the clinical recovery of adults with chronic nonspecific neck pain. Two hundred and ten participants will be randomly allocated to one of the three groups (70 participants per group) upon the completion of the baseline evaluation of the study outcomes. All programmes will use standardised exercise procedures, individualised progression, supervised instruction, and structured home exercise format. Study outcomes will be assessed at baseline, immediately after the 5-week intervention, and 6 months after programme completion in order to enable the evaluation of the exercise programme effectiveness at immediate and longer-term.

The primary objective is to determine the effectiveness of hybrid exercise programme as compared to the two single-component exercise programmes on the primary outcomes namely neck pain intensity, neck-related disability and upper-extremity physical function, and general health status (as secondary outcome) at immediate (change between pre- and post-programme of the 5-week programme) and longer-term reassessments (change between pre-programme and 6-month after the 5-week programme).

The secondary objective aims to study the mechanisms underpinning the observed effectiveness produced by the exercise programmes by evaluating the changes in neuromuscular and muscle-mechanical function, including deep cervical flexor performance, upper trapezius endurance, joint position error, muscle mechanical properties and vascularity, together with changes in pain sensitivity, exercise-induced hypoalgesia, and pain-related and exercise-specific self-efficacy, at both the immediate and longer-term reassessments.

Findings this trial will provide evidence if differential effectiveness on clinical outcomes present when rehabilitating adults with chronic nonspecific neck pain using combined and single-component exercise approaches. Furthermore, findings of the mechanism-mediation analysis will provide a scientific basis for more targeted, mechanism-informed exercise prescription for chronic nonspecific neck pain. Overall, results to be obtained from this trial will help refine the therapeutic exercise prescription and promote the outcome recovery for conservative management of this highly prevalent spinal condition.