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

Coaches and sports medicine teams have long used the acute:chronic workload ratio, a way of comparing recent training load to an athlete's longer-term training habits, as a tool for flagging injury risk in team sports. But the approach has been debated because studies calculate and define things so differently. This review pooled data from studies of team-sport athletes to ask whether a higher ratio is genuinely linked to more injuries, and whether that link holds up across different ways of measuring load, injury, and time windows. Across the pooled data, a higher ratio was associated with a small-to-moderate increase in injury risk, and this link appeared stronger for contact and non-contact injuries specifically, but not for injuries that caused time away from sport.

The results varied enormously between studies, and the evidence pool feeding the actual pooled analysis was modest, only 16 studies and fewer than 800 athletes. The authors conclude the ratio may be a useful contextual signal but should not be used alone to predict or explain injury.

If you play a team sport, you may have heard trainers talk about balancing how much you're training right now against what your body has been used to over recent weeks, sometimes described using a workload ratio. This review looked at whether that ratio actually predicts injury risk across many studies of team-sport athletes. The findings suggest a real but modest link, athletes with a higher ratio did tend to have somewhat more injuries, and this connection looked stronger for injuries from contact (like collisions) and for other non-contact injuries.

However, it wasn't so clearly linked to more serious injuries that cause a person to miss playing time. Importantly, the number of studies that could be combined for the pooled analysis was fairly small, and results differed a lot between individual studies, so this tool doesn't reliably predict injury on its own.

The researchers describe it as one piece of information among several that might be considered when monitoring training, rather than a stand-alone measure of risk.

This is a summary of research, not medical advice. Talk to your own healthcare provider about anything affecting your care.

This multilevel meta-analysis pooled 16 of 41 identified studies (797 athletes total) examining associations between acute:chronic workload ratio (ACWR) and injury in team-sport athletes, using a three-level random-effects model given nested effect sizes. The pooled effect was small-to-moderate (Hedges' g = 0.35, 95% CI 0.16 to 0.54), indicating higher ACWR was associated with increased injury risk, but heterogeneity was extremely high (I² = 95.8%), limiting confidence in a single summary estimate. Moderator analyses showed stronger associations for contact and non-contact injury subtypes, while associations with time-loss injuries and other examined moderators were not statistically significant, suggesting the relationship is context-dependent rather than uniform across load metrics, calculation methods, time windows, or sport types.

The authors explicitly caution against treating ACWR as a stand-alone causal or predictive model given this heterogeneity and the modest, methodologically diverse evidence base. Clinically, this supports interpreting ACWR as one contextual input within a broader, individualized, multi-marker load-monitoring approach rather than a definitive risk threshold. The substantial unexplained heterogeneity and reliance on observational cohort designs mean causal inference is not warranted, and further harmonization of ACWR calculation and injury definitions would be needed to strengthen confidence in these associations.