The dose-response relationship of aquatic exercise for musculoskeletal pain relief: a systematic review and meta-analysis of randomized controlled trials.

Musculoskeletal pain constitutes a pervasive global health burden and represents a primary driver of disability worldwide. While aquatic exercise (AQE) is a promising intervention, its clinical application remains limited by the lack of quantitative dose guidance and standardized exercise prescription parameters. Therefore, this systematic review and meta-analysis aimed to evaluate the independent analgesic effect of AQE compared with passive controls and to explore the dose-response relationship between exercise dose and pain relief. Four major databases were searched from inception to January 2026 for randomized controlled trials (RCTs) comparing AQE with passive controls in adults with musculoskeletal pain. Standardized mean differences (SMDs) were calculated using random-effects models. A model-based network meta-analysis using Metabolic Equivalents of Task (METs) was conducted to model the dose-response relationship. Twenty-nine RCTs involving 2,210 participants were included. AQE yielded a moderate, statistically significant reduction in pain compared to passive controls (SMD = -0.55; 95% CI: -0.69 to -0.42; p < 0.001), with benefits persisting during the follow-up period (SMD = -0.51; 95% CI: -0.80 to -0.23; P < 0.001). Subgroup analyses indicated that middle-aged patients (45–59 years) and those with chronic disease durations (> 10 years) demonstrated larger pooled effect sizes. Among intervention modalities, pool-based multicomponent exercise yielded the largest effect size, followed by resistance and aerobic training. Regarding protocols, a frequency of 3 sessions/week, session duration > 60 min, and intervention periods ≥ 13 weeks were associated with more pronounced improvements. Crucially, dose-response analysis revealed an inverted U-shaped relationship, suggesting an effective therapeutic window of 450–1700 METs-min/week, with the peak analgesic effect observed at approximately 1200 METs-min/week. AQE appears to provide meaningful pain relief for musculoskeletal disorders, with benefits that may persist during follow-up. By identifying a peak therapeutic effect at approximately 1200 METs-min/week, this study aims to advance AQE from a qualitative recommendation toward quantitative, evidence-based guidance. These findings provide rigorous evidence base for understanding the physiological adaptations to aquatic therapy, informing tailored clinical management and optimized rehabilitation strategies. The review protocol was registered in PROSPERO (CRD420261303731).