Is the Acute: Chronic Workload Ratio (ACWR) Associated with Risk of Time-Loss Injury in Professional Team Sports? A Systematic Review of Methodology, Variables and Injury Risk in Practical Situations

Abstract

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...

Training Load and Injury Risk in Elite Rugby Union: The Largest Investigation to Date

“…The training load dataset file was imported into Matlab (Matlab 2018b, MathWorks) to programmatically produce the data combinations required for analysis. For each daily load value per player, each possible ACWR calculation method was produced, including RA and EWMA [14], coupled and uncoupled [7,36] and each time frame (3,5,7,9,14,21,28,35). This procedure resulted in the following ACWR measure for each player each day (▶ Fig 1).…”

Do you Play or Do you Train? Insights From Individual Sports for Training Load and Injury Risk Management in Team Sports Based on Individualization

“…In team sports, it is more complicated because of the influence of contextual factors (Brito et al, 2016;Oliva-Lozano et al, 2020) affecting both internal and external load parameters in a different manner (Fox et al, 2020). The picture is even more complex if we consider that the current ACWR literature has found different relationships between ACWR indices generated with different internal [e.g., session rating of perceived exertion (sRPE)] and external (e.g., accelerations) load parameters in team sports characterized by different psycho-physiological demands (Andrade et al, 2020;Griffin et al, 2020). This means that the relationships found between ACWR and injury risk are not interchangeable among team sports, therefore suggesting the greater weight of extrinsic factors within this relationship, as it has been also suggested that the strength of the relationships between internal and external load parameters in team sports depends upon the training mode (McLaren et al, 2018).…”

“…The ACWR is currently in the spot light of sport sciences (Griffin et al, 2020;Maupin et al, 2020). While some emerging evidence suggests that it is a valid method to identify an increased injury risk (Andrade et al, 2020), other authors have pointed out its methodological limitations and even questioned its validity (Impellizzeri et al, 2020;Wang et al, 2020). Proponents of the ACWR approach argue that athletes are at greater risk of sustaining a time-loss injury when the ACWR is higher relative to a lower or moderate ACWR (Andrade et al, 2020).…”

“…While some emerging evidence suggests that it is a valid method to identify an increased injury risk (Andrade et al, 2020), other authors have pointed out its methodological limitations and even questioned its validity (Impellizzeri et al, 2020;Wang et al, 2020). Proponents of the ACWR approach argue that athletes are at greater risk of sustaining a time-loss injury when the ACWR is higher relative to a lower or moderate ACWR (Andrade et al, 2020). In other words, the ACWR helps to identify critical windows in terms of elevated injury risk based on imbalanced training loading as for example sudden spike loads (Bowen et al, 2020).…”

More than a Metric: How Training Load is Used in Elite Sport for Athlete Management

“…While early introductory research concentrated on the relationship between load parameters and injury, this may have led to the belief that these were the only measures of importance, however it has since been stated that these measures should only be a component of a wide variety of measures [9][10][11]. We agree that no single metric can clearly state the risk of injury or state of preparedness of an athlete and therefore review why load monitoring is far more than any individual metric, and how it can play a vital role in informing performance-related decisions.…”