Acute:chronic workload ratio and load management for team sports: a multilevel meta-analysis.

OBJECTIVE: The acute:chronic workload ratio (ACWR) has been widely used to monitor training load and injury risk in team-sport athletes. However, its practical utility remains debated because of methodological heterogeneity across load metrics, calculation methods, time-window definitions, sport types, and injury definitions. This systematic review and multilevel meta-analysis aimed to quantify the association between ACWR and injury risk in team-sport athletes and to examine potential moderators. METHODS: Four electronic databases were searched from inception through October 2024. Prospective cohort studies or trials were eligible if they included team-sport athletes, reported associations between ACWR and injury outcomes, and provided sufficient data for effect size extraction or conversion. Study characteristics, participant information, injury definition, load metric, ACWR calculation method, time window, sport type, and effect estimates were extracted. Effect sizes were converted to Hedges' g and pooled using a three-level random-effects model. RESULTS: 41 studies met the inclusion criteria, and 16 studies involving 797 athletes were included in the meta-analysis. Elevated ACWR showed a small-to-moderate association with higher injury risk (g = 0.35; 95% CI, 0.16-0.54), with substantial heterogeneity (I2 = 95.8%). Stronger associations were observed for contact and non-contact injuries, whereas effects were not significant for time-loss injuries or other moderators. CONCLUSION: Elevated ACWR may be associated with increased injury risk in specific contexts, but current evidence does not support its use as a stand-alone causal or predictive model. ACWR should be interpreted as a contextual monitoring indicator within individualized, multi-marker load-management systems. SYSTEMATIC REVIEW REGISTRATION: The systematic review was registered in PROSPERO under the unique identifier CRD420245127618.