Is the acute:chronic workload ratio (ACWR) associated with risk of timeloss injury in professional team sports? A systematic review of methodology, variables and injury risk in practical situations ABSTRACT Background The acute:chronic workload ratio (ACWR) is an index of the acute workload relative to the cumulative chronic workloads. The monitoring of physical workloads using the ACWR has emerged and been hypothesized as a useful tool for coaches and athletes to optimize performance while aiming to reduce the risk of potentially preventable load-driven injuries.Objectives Our goal was to describe characteristics of the ACWR and investigate the association of the ACWR with the risk of time-loss injuries in adult elite team sport athletes.Data sources Pubmed, EMBASE and grey literature databases; inception to May 2019.
Eligibility criteriaLongitudinal studies that assess the relationship of the ACWR and time-loss injury risk in adult professional or elite team sports.
MethodsWe summarized the population characteristics, workload metrics and ACWR calculation methods. For each workload metric, we plotted the risk estimates for the ACWR in isolation, or when combined with chronic workloads. Methodological quality was assessed using a modified version of the Downs and Black scale.Results Twenty studies comprising 2375 injuries from 1234 athletes (all male and mean age of 24 years old) from different sports were included. Internal (65%) and external loads (70%) were collected in more than half of the studies and the sRPE and total distance were the most commonly collected metrics. The ACWR was commonly calculated using the coupled method (95%), 1:4 weekly blocks (95%) and subsequent week injury lag (80%). There were 14 different binning methods with almost none of the studies using the same binning categories.
ConclusionThe majority of studies suggest that athletes are at greater risk of sustaining a timeloss injury when the ACWR is higher relative to a lower or moderate ACWR. The heterogenous 4 methodological approaches reflects the wide range of sports studied and the differing demands of these activities, but also limits the strength of recommendations.
PROSPERO registration number CRD42017067585
Key Points• A higher acute:chronic workload ratio in relation to a lower or moderate acute:chronic workload ratio suggests a greater risk of sustaining a time-loss injury. No clear association was observed for a low acute:chronic workload ratio in terms of injury risk.• A low chronic load combined with a high acute:chronic workload ratio may increase the risk of injury, although the number of studies addressing these combinations are limited.• The review highlighted a wide variation in methodologies, especially in regard the definitions for workload categories. Researchers should clearly report and justify the methods they use for data structuring and analysis. Practitioners should be aware of the methodological divergence associated with research on ACWR and injuries when interpreting published studies and adapting to the...