Exercise Improves Autonomic Function in Chronic Pain Patients, HRV Data Shows

Chronic musculoskeletal pain (CMP) affects hundreds of millions globally and is associated with substantial disability, healthcare costs, and reduced quality of life. Beyond its well-known sensory and functional consequences, CMP is increasingly recognized as a condition involving autonomic nervous system dysregulation — particularly reduced parasympathetic (vagal) activity as reflected by heart rate variability (HRV). Lower HRV in CMP patients suggests diminished organism adaptability and is linked to altered central pain processing via pathways connecting the prefrontal cortex, amygdala, and vagus nerve.

This systematic review, registered in PROSPERO and conducted following PRISMA guidelines, searched PubMed, Web of Science, Scopus, and the Cochrane Library through June 2024. Ten controlled trials — five randomized (RCTs) and five non-randomized — met inclusion criteria, collectively enrolling 277 adults aged 18–65 with diagnoses including fibromyalgia, chronic low back pain, neck pain, and other musculoskeletal conditions. Exercise interventions ranged from 4 to 24 weeks in duration and encompassed aerobic training, resistance training, and multi-component programs (e.g., yoga, combined aerobic-resistance protocols). HRV was assessed at rest before and after each intervention using both linear (time- and frequency-domain) and non-linear analytic methods.

The primary finding was that exercise interventions produced significant within-group improvements in multiple HRV indices, especially those associated with vagal modulation — including RMSSD, HF power, and related parasympathetic markers. These improvements suggest that exercise can meaningfully restore autonomic balance in CMP patients, potentially contributing to improved pain modulation and overall health adaptability. Effect sizes were calculated where data permitted, though the heterogeneity of HRV measurement protocols — varying devices, recording durations, body positions, and preprocessing steps — complicated direct cross-study comparisons.

Risk of bias was assessed using the Cochrane RoB-2 tool for RCTs and ROBINS-I for non-randomized studies. Most studies showed moderate to serious risk of bias, driven by lack of blinding, small sample sizes, inadequate reporting of exercise intervention details per the Consensus on Exercise Reporting Template (CERT), and inconsistent HRV acquisition standards. GRADE-based certainty of evidence was accordingly low to very low across outcomes. Between-group differences (exercise vs. control) were less consistently significant than within-group changes, further limiting causal conclusions.

The authors emphasize two critical gaps: first, published international standards for HRV measurement (covering data acquisition, artifact correction, and analysis) are widely available but inconsistently applied in clinical research; second, exercise intervention reporting frequently omits key details on dosage, intensity, supervision, and tailoring. Both gaps undermine reproducibility and limit clinical translation. Future trials should adopt standardized HRV protocols, adhere strictly to CERT reporting, include larger and more diverse CMP populations, and systematically compare exercise modalities — particularly investigating whether high-intensity training confers superior HRV benefits in CMP as it does in healthy and athletic populations.