RESUMO
This report provides a systematic review of the literature to analyze the effects of transcutaneous electrical nerve stimulation (TENS) on analgesia on sensitization measures, in studies with chronic musculoskeletal pain and in studies with acute experimental pain. The protocol was registered at PROSPERO (CRD42020213473). The authors searched Cochrane Central Register of Controlled Trials, Cumulative Index to Nursing and Allied Health Literature, EMBASE, Latin American and Caribbean Health Sciences Literature via Biblioteca Virtual de Saúde, Physiotherapy Evidence Database, PubMed, ScienceDirect, Web of Science, Google Scholar, and hand-searched reference lists were also conducted. Among 22,252 manuscripts found, 58 studies were included in the systematic review and 35 in the meta-analysis. Thirty-four studies assessed pain intensity; 24 studies investigated hyperalgesia; temporal summation was only evaluated in 2 studies; and conditioned pain modulation was not observed in the included studies. Meta-analyses favored TENS, despite its limitations and heterogeneity. Primary hyperalgesia in studies with musculoskeletal pain presented a high level of evidence, while other outcomes presented moderate evidence in the studies that were included. It is not possible to infer results about both temporal summation and conditioned pain modulation. Moderate evidence suggests that TENS promotes analgesia by reducing both central and peripheral sensitization, as shown by the reduction in primary and secondary hyperalgesia, pain intensity at rest, and during movement in experimental acute pain and chronic musculoskeletal pain. Overall, both types of studies analyzed in this review presented meta-analyses favorable to the use of TENS (compared to placebo TENS), showing reductions in both primary and secondary hyperalgesia, as well as decreases in pain intensity at rest and in motion. PERSPECTIVE: This article presents data from the literature on the effect of TENS through sensitization assessments in individuals with chronic musculoskeletal pain, or acute experimental pain. These data contribute to knowledge about pain neuroscience research, using TENS technology.
