Noninvasive brain stimulation combined with exercise in chronic pain: a systematic review and meta-analysis

Background: The use of noninvasive brain stimulation (NIBS) combined with exercise could produce synergistic effects on chronic pain conditions. This study aims to evaluate the efficacy and safety of NIBS combined with exercise to treat chronic pain as well as to describe the parameters used to date in this combination. Methods: The search was carried out in Medline, Central, Scopus, Embase, and Pedro until November 2019. Randomized clinical trials (RCTs) and quasi-experimental studies reporting the use of noninvasive brain stimulation and exercise on patients with chronic pain were selected and revised. Results: The authors included eight studies (RCTs), reporting eight comparisons (219 participants). Authors found a significant and homogeneous pain decrease (ES: −0.62, 95% CI:-0.89 to −0.34; I2 = 0.0%) in favor of the combined intervention compared to sham NIBS + exercise, predominantly by excitatory (anodal tDCS/rTMS) motor cortex stimulation. Regarding NIBS techniques, the pooled effect sizes were significant for both tDCS (ES: −0.59, 95% CI: −0.89 to −0.29, I2 = 0.0%) and rTMS (ES: −0.76, 95% CI: −1.41 to −0.11, I2 = 0.0%). Conclusions: This meta-analysis suggests a significant moderate to large effects of the NIBS and exercise combination in chronic pain. The authors discuss the potential theoretical framework for this synergistic effect.