Autonomic nervous system and viscera-related responses to manual therapy: A narrative overview

Background: Manual therapy (MT) has long-held that it physiologically impacts autonomic nervous system (ANS) and viscera-related function. This narrative review is intended to serve as a consolidated interdisciplinary resource of original studies related to physiological effects of MT as it relates to the ANS for MT clinicians and researchers new to this MT-related topic.
Objective: This review seeks to identify ANS and viscera-related physiological responses to MT interventions using search terms commonly used by chiropractic, massage, osteopathic, physical therapy, and structural integration clinicians and to provide a quick reference resource of original MT-related studies investigating ANS effects. Methods: For this interdisciplinary review, the search was limited to the largest and most commonly used database (PubMed) between years 2000 and 2024, with a focus on direct ANS-related physiological outcomes. Unlike systematic reviews, assessment of scientific rigor and potential bias of included articles was beyond the scope and purpose of the current work.
Results: Original MT-related studies provide mixed evidence with regards to immediate and/or short term ANS and/or viscera-related responses on blood pressure, heart rate variability, skin conductance/temperature, respiratory and lymphatic changes.
Conclusions: This review identified a large number of MT and ANS-related original research in PubMed. Careful study of original MT-related research is needed with particular attention focused on the standardization of MT methodological approaches, appropriate controls, study design, appropriate populations, MT techniques, and anatomical site delivery so as to design more rigorous studies in order to arrive at definitive conclusions regarding direct effects of MT on the ANS.