Effects of therapeutic exercise on pain processing in people with chronic non-specific neck pain - A systematic review and meta-analysis

Background: Emerging evidence suggests that individuals with chronic non-specific neck pain may experience altered sensory processing, potentially contributing to the modest response to therapeutic exercise treatments. Objective: This systematic review aims to explore the effect of therapeutic exercise on pain processing among patients with chronic non-specific neck pain. Methods: A systematic search was conducted in multiple databases (PubMed, EMBASE, CINAHL, PEDro, SportDiscus, and Cochrane CENTRAL) from inception to June 2023. Inclusion criteria included randomized controlled trials (RCT) comparing therapeutic exercise to non-exercise treatments or no treatment. The screening and data extraction was conducted by two reviewers. The methodological quality was evaluated using the PEDro scale and the certainty of evidence using GRADE. The primary outcomes assessed were pressure pain threshold (PPT), temporal summation, and conditioned pain modulation. Results: Thirteen trials included a total of 948 participants, with 586 in the exercise therapy group and 362 in the non-exercise group. The therapeutic exercise was not superior to non-exercise treatments for both local and PPT in the immediate (MD = 0.13, 95%CI = -0.18 to 0.43), and short-term follow-up (MD = 0.17, 95%CI = -0.27 to 0.61). In the medium term, therapeutic exercise demonstrated a small effect size in increasing local PPT (Kg/cm2) (MD = 0.64, 95%CI = 0.08 to 1.19) compared to non-exercise interventions. The certainty of evidence for these outcomes was very low. Conclusions: There is very low certainty of evidence that therapeutic exercise is not superior than non-exercise treatment on pain processing in patients with chronic non-specific neck pain.