Background: The use of exercise is a potential treatment option to modulate pain (exercise-induced hypoalgesia). The pain threshold (PT) response is a measure of pain sensitivity that may be a useful marker to assess the effect of physical exercise on pain modulation.
Aim: The aim of this systematic review and meta-analysis is to evaluate the PT response to exercise in healthy subjects.
Methods: We searched in MEDLINE, EMBASE, Web of Science, Lilacs, and Scopus using a search strategy with the following search terms: "exercise" OR "physical activity" AND "Pain Threshold" from inception to December 2nd, 2019. As criteria for inclusion of appropriate studies: randomized controlled trials or quasi-experimental studies that enrolled healthy subjects; performed an exercise intervention; assessed PT. Hedge's effect sizes of PT response and their 95% confidence intervals were calculated, and random-effects meta-analyses were performed.
Results: For the final analysis, thirty-six studies were included (n=1326). From this we found a significant and homogenous increase in PT in healthy subjects (ES=0.19, 95% CI= 0.11 to 0.27, I2=7.5%). According to subgroup analysis the effect was higher in studies: with women (ES=0.36); performing strength exercise (ES=0.34), and with moderate intensity (ES=0.27), and no differences by age were found. Confirmed by the meta-regression analysis.
Conclusion: This meta-analysis provides evidence of small to moderate effects of exercise on PT in healthy subjects, being even higher for moderate strength exercise and in women. These results support the idea of modulation of the endogenous pain system due to exercise and highlight the need of clinical translation to chronic pain population.
Background: The analgesic effects of transcranial Direct Current Stimulation (tDCS) combined with physical therapy remain unclear.
Objective: To systematically review available evidence comparing tDCS with any physical therapy modality (PTM) to PTM alone or PTM with sham tDCS on pain relief on common musculoskeletal (MSK) conditions, namely knee osteoarthritis (KOA), chronic low back pain (CLBP), myofascial pain syndrome (MPS) and fibromyalgia.
Methods: EMBASE and MEDLINE were searched from inception to April 2019 for randomized controlled trials. Reviewers independently assessed the studies quality and extracted data according to the PRISMA protocol. The GRADE approach was used to asses quality of evidence and a "Summary of Findings" table was created. The analyses used random-effects model. The primary outcome was pain reduction after treatment.
Results: Eight articles were included. Only one study had low risk of bias. Quality of evidence was considered low or very low. Significant reduction in pain scores were found for fibromyalgia and KOA (Standardized mean difference (SMD) = -1.94 [95% CI: -3.37 to -0.49; I 2=76.4%] and SMD = -2.35 [95% CI: -3.63 to -1.06; I 2=69.7%] respectively). Subgroup analysis considering the type of PTM despite MSK condition revealed significant reduction in pain scores for exercise, SMD = -1.20 [95% CI: -1.683 to -0.717; I 2=10.8%].
Conclusions: Large heterogeneity and low quality of evidence and limited number of studies were found. Results suggest a potential analgesic effect of tDCS in combination with a PTM for fibromyalgia and KOA. Subgroup analysis suggests a stronger effect of tDCS when combined with an exercise based PTM.