Criterion-Based Rehabilitation and Return to Play in Fast Bowlers Following Arthroscopic Bankart Repair: Recommendations Based on a Detailed Clinical Review

Background

Anterior shoulder instability due to labral tears in the dominant arm of cricket fast bowlers can be particularly disabling and results in significant match time loss. This often follows injuries sustained during fielding and training, although micro-instability following repetitive throwing progressing to overt anterior shoulder instability is also known. To ensure ball release speeds of over 140 km/h with different ball variations, these athletes require not only physical fitness and technical skill, but also a completely stable shoulder.

Methods

A literature search of "MEDLINE", "SPORT DISCUSS", and "GOOGLE SCHOLAR" was done to identify relevant articles published till the year 2023.

Results

A treatment approach that involves anatomic restoration of the shoulder via an arthroscopic Bankart capsulo-labral repair, followed by functional and biomechanical restoration via rehabilitation is the most predictable method to ensure a successful return to pre-injury fast-bowling status. A post-operative rehabilitation program that ensures a quick return to fast bowling without disrupting the surgical repair is crucial. Timely integration of exercises to recruit and strengthen the kinetic chain used for bowling and throwing plays a key role in this faster recovery. This current review provides a phase-wise, evidence-based rehabilitation guideline for return to competitive cricket after arthroscopic Bankart repair in a fast bowler. This review also highlights a structured return to bowling, throwing, and fielding program with a clinical decision-making process.

Conclusion

Exercise selection at an early stage that does not compromise the healing tissue, and timely integration of workouts to recruit and strengthen the kinetic chain used for bowling and throwing is the key strategy to allow faster recovery.

Supplementary Information

The online version contains supplementary material available at 10.1007/s43465-023-00931-5.

Methods of Monitoring Internal and External Loads and Their Relationships with Physical Qualities, Injury, or Illness in Adolescent Athletes: A Systematic Review and Best-Evidence Synthesis

BACKGROUND

With the increasing professionalisation of youth sports, training load monitoring is increasingly common in adolescent athletes. However, the research examining the relationship between training load and changes in physical qualities, injury, or illness in adolescent athletes is yet to be synthesised in a systematic review.

OBJECTIVE

The aim of this review was to systematically examine the research assessing internal and external methods of monitoring training load and physical qualities, injury, or illness in adolescent athletes.

METHODS

Systematic searches of SPORTDiscus, Web of Science, CINAHL and SCOPUS were undertaken from the earliest possible records to March 2022. Search terms included synonyms relevant to adolescents, athletes, physical qualities, injury, or illness. To be eligible for inclusion, articles were required to (1) be original research articles; (2) be published in a peer-reviewed journal; (3) include participants aged between 10 and 19 years and participating in competitive sport; (4) report a statistical relationship between a measure of internal and/or external load and physical qualities, injury or illness. Articles were screened and assessed for methodological quality. A best-evidence synthesis was conducted to identify trends in the relationships reported.

RESULTS

The electronic search yielded 4125 articles. Following screening and a review of references, 59 articles were included. The most commonly reported load monitoring tools were session ratings of perceived exertion (n = 29) and training duration (n = 22). Results of the best-evidence synthesis identified moderate evidence of positive relationships between resistance training volume load and improvement in strength, and between throw count and injury. However, evidence for other relationships between training load and change in physical qualities, injury, or illness were limited or inconsistent.

CONCLUSIONS

Practitioners should consider monitoring resistance training volume load for strength training. Additionally, where appropriate, monitoring throw counts may be useful in identifying injury risk. However, given the lack of clear relationships between singular measures of training load with physical qualities, injury, or illness, researchers should consider multivariate methods of analysing training load, as well as factors that may mediate the load-response relationship, such as maturation.

Is Cumulative Load Associated with Injuries in Youth Team Sport? A Systematic Review

Background

High cumulative external and internal load may predispose athletes to increased risk for injury across a variety of sports, competition levels, and age groups. However, evidence of an association between cumulative load and injury in youth sport remains inconclusive. The objective of this study was to determine the current evidence for cumulative load and injury risk relationships in youth team sport through a systematic review of the existing literature.

Methods

A systematic review of the literature was performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. Literature searches were conducted in PubMed, Web of Science, SCOPUS, and CINAHL for relevant articles published between January 2010 and April 2021. The authors conducted independent review and quality assessment of the eligible studies. Eleven articles evaluating youth (less than 18 years old) team sport were included for qualitative synthesis.

Results

Fifty-nine percent (n = 39/66) of the relationships assessed revealed an association between cumulative load and injury across the team sports studied, including the presence of load–injury associations in 84% (n = 16/19) of assessments in youth soccer. Of those relationships where an association was present, 79% (n = 31/39) were positive associations between cumulative load and injury. Risk of bias assessment scores ranged from three to six out of seven possible (median = 5) for cohort studies and from four to seven out of 10 possible (median = 5.5) for cross-sectional studies.

Conclusions

There is some evidence for a positive association between load and injury in youth team sport. Youth soccer was the most studied team sport, and a substantial number of positive load–injury associations were reported. Current evidence lacks consistency in the measures and metrics used in defining load–injury relationships.

Trial Registration PRISMA ID - CRD42020203622.

Upper respiratory tract symptom risk in elite field hockey players during a dry run for the Tokyo Olympics

ABSTRACTThe primary aim of this study was to examine if biomarker and/or self-reported data could predict upper respiratory tract symptom (URTS) risk in elite field hockey players. The secondary aim was to investigate the effect of the additional stressor 'repeated heat exposure' on measures of thermoregulation and immunity. A prospective cohort repeated measures study design was used to collect URTS, household illness, self-reported wellness, biomarker and thermoregulatory data from elite male field hockey players (n = 19), during an 8-week training and competition period that simulated the preparatory and competition phases of the 2020 Tokyo Olympics. Heat response testing (HRT) was performed at the beginning of the study period, following heat acclimation (HA) and following an intensified competition period (ICP) played in hot and humid conditions (27-37°C and 53-80% relative humidity). Univariate frailty analysis demonstrated that illness in players' households (Hazard ratio (HR: 4.90; p < 0.001)) and self-reported stress (HR: 0.63; p = 0.043) predicted players' risk for URTS. Additionally, low baseline resting salivary secretory immunoglobulin A (SIgA) concentration predicted players' "potential" URTS risk (p = 0.021). The additional stressor "repeated heat exposure" was found to facilitate partial thermoregulatory adaptation without attenuating resting immune functions. In conclusion, lifestyle and behavioural factors (i.e. household illness and stress) influenced players risk for URTS more so than sport-related stressors. Furthermore, repeated heat exposure did not appear to compromise players resting immunity. To assess athletes' risk for URTS, baseline screening of SIgA concentration and regular monitoring of self-reported lifestyle and behavioural data are recommended.

Injury incidence within male elite New Zealand cricket from the early T20 era: 2009-2015

Objectives

This study aimed to describe the injury epidemiology of domestic and international level male New Zealand cricketers from seasons 2009–2010 to 2014–2015 across all match formats given the increasing popularity of T20 cricket.

Methods

Match exposure and injury surveillance data collected prospectively by New Zealand Cricket was analysed using international consensus recommendations for injury surveillance and reporting in cricket. Relationships between playing level, role and injury were statistically analysed.

Results

A total of 268 elite male New Zealand cricketers from seasons 2009–2010 to 2014–2015 were analysed from the New Zealand Cricket injury surveillance system. Total new match injury incidence rates were 37.0 and 58.0 injuries per 10 000 player hours in domestic and international cricket, respectively. Total new and recurrent match injury incidence in international cricket was approximately 1.7 times higher than domestic cricket (277.6 vs 162.8 injuries per 1000 player days). Injury prevalence rates were 7.6% and 10.0% in domestic and international cricket. The hamstring (8.2%) in domestic cricket and the groin (13.5%) in international cricket were the most injured body sites. Most match days lost in domestic cricket were to the lumbar spine (417 days), and groin in international cricket (152 days). There were statistically significant differences in injury between domestic and international level cricketers (χ²=4.39, p=0.036), and playing role (χ²=42.29, p<0.0001).

Conclusions

Total injury incidence rates in elite New Zealand cricket increased in 2009–2015 compared with previous data. International-level players and pace bowlers were the most injured individuals.

External workload intensity in cricket fast bowlers across maximal and submaximal intensities: Modifying PlayerLoad and IMU location

Workload is a commonly accepted risk factor for injury among fast bowlers, however many methods exist to characterise workload. Recently, automated intensity-sensitive measures like PlayerLoad have been used to improve the estimation of workload in fast bowlers. The purpose of this study was to determine whether similar variables could be extracted from a single inertial measurement unit (IMU) that highly correlate with intensity, according to release speed. Eight elite and pre-elite bowlers participated in the study, with each bowler bowling one over each at 60%, 80% and 100% intensity and repeating this across two sessions (36 balls per participant). IMUs were placed on the upper-back and non-bowling wrist and maximum PlayerLoad from each delivery (PL_max) was compared to the accumulated value across each delivery (PL_acc). The strongest correlation with release speed was with PL_acc from the non-bowling wrist (R = 0.74), followed by PL_acc from the upper-back (R = 0.65) and PL_max from the upper back (R = 0.60). Consequently, an improved estimation of the intensity at which bowlers are working at could be gained by examining accumulated PlayerLoad values from an IMU on the non-bowling wrist.

The relationship between cricket participation, health and wellbeing: A scoping review

Summarising and synthesising the evidence on cricket health and wellbeing can help inform cricket stakeholders and navigate future research directions. The purpose of this study was to investigate the relationship between cricket participation, health and wellbeing at all ages and playing standards, and identify research gaps in the existing literature. A scoping review was performed from inception to March, 2020. Studies were included if they assessed a construct related to health and/or wellbeing in cricketers, available in English. 219 articles were eligible. Injury incidence per 1,000 player exposures ranged from 1.8-5.7 injuries. 48% of former cricketers experienced persistent joint pain. However, former cricketers reported greater physical activity levels and mental-components of quality of life compared to the general population. Heat injury/illness and skin cancer are concerns and require further research. Cricket participation is associated with an inherent injury risk, which may have negative implications for musculoskeletal health in later life. However, cricket participation is associated with high quality of life which can persist after retirement. Gaps in the literature include prospective studies on health and wellbeing of cricketers, female cricketers, injury prevention strategies, and the impact of cricket participation on metabolic health and lifetime physical activity.

Workload Management System for Cricketers

Cricketers are dynamic players in the field and hence more vulnerable to injuries. The injury rate of Sri Lankan cricketers is very high, resulting in their careers being shortened. Therefore, we established a workload management system for cricketers to resolve this issue with wearable Inertial Measurement Unit (IMU) sensors mounted on their bodies. In order to mitigate their accidents, we evaluated kinds of the activities performed by an athlete using Convolutional Neural Network (CNN) and computed the workload parameters after the session. The expected results of our project were to develop a system to collect and analyze the critical workload parameters of cricketers and showcase results in a user-friendly manner.

Not straightforward: modelling non-linearity in training load and injury research

OBJECTIVES

To determine whether the relationship between training load and injury risk is non-linear and investigate ways of handling non-linearity.

METHODS

We analysed daily training load and injury data from three cohorts: Norwegian elite U-19 football (n=81, 55% male, mean age 17 years (SD 1)), Norwegian Premier League football (n=36, 100% male, mean age 26 years (SD 4)) and elite youth handball (n=205, 36% male, mean age 17 years (SD 1)). The relationship between session rating of perceived exertion (sRPE) and probability of injury was estimated with restricted cubic splines in mixed-effects logistic regression models. Simulations were carried out to compare the ability of seven methods to model non-linear relationships, using visualisations, root-mean-squared error and coverage of prediction intervals as performance metrics.

RESULTS

No relationships were identified in the football cohorts; however, a J-shaped relationship was found between sRPE and the probability of injury on the same day for elite youth handball players (p<0.001). In the simulations, the only methods capable of non-linear modelling relationships were the quadratic model, fractional polynomials and restricted cubic splines.

CONCLUSION

The relationship between training load and injury risk should be assumed to be non-linear. Future research should apply appropriate methods to account for non-linearity, such as fractional polynomials or restricted cubic splines. We propose a guide for which method(s) to use in a range of different situations.

A Cherry, Ripe for Picking: The Relationship Between the Acute-Chronic Workload Ratio and Health Problems

OBJECTIVE

To investigate whether the relationship between the acute-chronic workload ratio (ACWR) and health problems varies when different methodological approaches are used to quantify it.

DESIGN

Prospective cohort study.

METHODS

An online questionnaire was used to collect daily health and training information from 86 elite youth footballers for 105 days. The relationship between players' training load and health was analyzed using a range of different definitions of ACWR and health problems. We used 21-day and 28-day chronic periods, coupled and uncoupled calculations, and the exponentially weighted moving average and rolling average. Acute-chronic workload ratio data were categorized as low, medium, or high, using predefined categories and z scores. We compared medium to high, medium to low, and low to high categories. The outcome was defined in 3 ways: "all health problems," "all injuries," and "new noncontact injuries." We performed random-effects logistic regression analyses of all combinations, for a total of 108 analyses.

RESULTS

We recorded 6250 athlete-days and 196 health problems. Of the 108 analyses performed, 23 (21%) identified a statistically significant (P<.05) association between the ACWR and health problems. A greater proportion of significant associations were identified when using an exponentially weighted moving average (44% of analyses), when comparing low to high categories (33%), and when using the "all health problems" definition (33%).

CONCLUSION

The relationship between the ACWR and health problems was dependent on methodological approach. J Orthop Sports Phys Ther 2021;51(4):162-173. Epub 20 Jan 2021. doi:10.2519/jospt.2021.9893.

Predictors of upper respiratory tract symptom risk: Differences between elite rugby union and league players

This study examined possible predictors of upper respiratory tract symptom (URTS) episodes in elite rugby union and league players (n = 51) during intensive pre-season training. Baseline saliva and blood samples were collected in the first week of pre-season training for analysis of salivary secretory immunoglobulin A (SIgA) and cytomegalovirus. Thereafter, SIgA, URTS, internal training load and self-reported wellness data were repeatedly measured throughout a 10-week pre-season training period. Univariate frailty model analysis, which included 502 observations, was performed for each rugby code for the following independent predictor variables: SIgA concentration, internal training load, total wellness, sleep quantity, sleep quality and stress. Rugby union and league players experienced a similar number of URTS episodes; however, predictors of URTS episodes differed between the codes. No biomarkers or self-reported measures significantly predicted URTS risk in rugby union players, while reductions in self-reported total wellness (HR: 0.731, p = 0.004) and sleep quality (HR: 0.345, p = 0.001) predicted increased URTS risk in rugby league players. The findings from this study highlight that factors influencing URTS risk are perhaps sport specific and this may be attributed to different sporting demands and/or different management of players by team-practitioners.

Training Load and Its Role in Injury Prevention, Part 2: Conceptual and Methodologic Pitfalls

In part 2 of this clinical commentary, we highlight the conceptual and methodologic pitfalls evident in current training-load-injury research. These limitations make these studies unsuitable for determining how to use new metrics such as acute workload, chronic workload, and their ratio for reducing injury risk. The main overarching concerns are the lack of a conceptual framework and reference models that do not allow for appropriate interpretation of the results to define a causal structure. The lack of any conceptual framework also gives investigators too many degrees of freedom, which can dramatically increase the risk of false discoveries and confirmation bias by forcing the interpretation of results toward common beliefs and accepted training principles. Specifically, we underline methodologic concerns relating to (1) measure of exposures, (2) pitfalls of using ratios, (3) training-load measures, (4) time windows, (5) discretization and reference category, (6) injury definitions, (7) unclear analyses, (8) sample size and generalizability, (9) missing data, and (10) standards and quality of reporting. Given the pitfalls of previous studies, we need to return to our practices before this research influx began, when practitioners relied on traditional training principles (eg, overload progression) and adjusted training loads based on athletes' responses. Training-load measures cannot tell us whether the variations are increasing or decreasing the injury risk; we recommend that practitioners still rely on their expert knowledge and experience.

Global Positioning System-Derived Workload Metrics and Injury Risk in Team-Based Field Sports: A Systematic Review

OBJECTIVE

To evaluate the current literature regarding the utility of global positioning system (GPS)-derived workload metrics in determining musculoskeletal injury risk in team-based field-sport athletes.

DATA SOURCES

PubMed entries from January 2009 through May 2019 were searched using terms related to GPS, player workload, injury risk, and team-based field sports.

STUDY SELECTION

Only studies that used GPS metrics and had injury as the main outcome variable were included.

DATA EXTRACTION

Total distance, high-speed running, and acute : chronic workload ratios were the most common GPS metrics analyzed, with the most frequent sports being soccer, rugby, and Australian rules football.

DATA SYNTHESIS

Many distinct workload metrics were associated with increased injury risk in individual studies performed in particular sport circumstances; however, the body of evidence was inconclusive as to whether any specific metrics could consistently predict injury risk across multiple team-based field sports.

CONCLUSIONS

Our results were inconclusive in determining if any GPS-derived workload metrics were associated with an increased injury risk. This conclusion is due to a myriad of factors, including differences in injury definitions, workload metrics, and statistical analyses across individual studies.

Can an inertial measurement unit (IMU) in combination with machine learning measure fast bowling speed and perceived intensity in cricket?

This study examined whether an inertial measurement unit (IMU), in combination with machine learning, could accurately predict two indirect measures of bowling intensity through ball release speed (BRS) and perceived intensity zone (PIZ). One IMU was attached to the thoracic back of 44 fast bowlers. Each participant bowled 36 deliveries at two different PIZ zones (Zone 1 = 24 deliveries at 70% to 85% of maximum perceived bowling effort; Zone 2 = 12 deliveries at 100% of maximum perceived bowling effort) in a random order. IMU data (sampling rate = 250 Hz) were downsampled to 125 Hz, 50 Hz, and 25 Hz to determine if model accuracy was affected by the sampling frequency. Data were analysed using four machine learning models. A two-way repeated-measures ANOVA was used to compare the mean absolute error (MAE) and accuracy scores (separately) across the four models and four sampling frequencies. Gradient boosting models were shown to be the most consistent at measuring BRS (MAE = 3.61 km/h) and PIZ (F-score = 88%) across all sampling frequencies. This method could be used to measure BRS and PIZ which may contribute to a better understanding of overall bowling load which may help to reduce injuries.

Injury, Illness, and Training Load in a Professional Contemporary Dance Company: A Prospective Study

CONTEXT

Professional dance is a demanding physical activity with high injury rates. Currently, no epidemiologic data exist regarding the incidence of injury and illness together with training load (TL) over a long period of time.

OBJECTIVE

To provide a detailed description of injury, illness, and TL occurring in professional contemporary dancers.

DESIGN

Descriptive epidemiology study.

SETTING

A single professional contemporary dance company during a 1-year period.

PATIENTS OR OTHER PARTICIPANTS

A total of 16 male and female professional contemporary dancers.

MAIN OUTCOME MEASURE(S)

Injury data consisted of medical-attention injury (Med-Inj) and time-loss injury (Time-Inj). Illness was measured using the Wisconsin Upper Respiratory Tract Infection Survey. Training load was collected for each dance session using the session rating of perceived exertion and classified into 3 groups based on individual and group percentiles: low, medium, or high.

RESULTS

Reported injuries totaled 79 (86.1% new, 6.3% reinjury, and 7.6% exacerbation). The Med-Inj incidence rate was 4.6 per 1000 hours (95% confidence interval [CI] = 3.8, 5.8), and the Time-Inj rate was 1.4 per 1000 hours (95% CI = 0.8, 2.1). The median time until injury for Med-Inj and Time-Inj was 3 months. The number of days dancers experienced illness symptoms was 39.9 ± 26.9 (range = 1-96), with an incidence rate of 9.1 per 1000 hours (95% CI = 7.7, 10.7). Mean weekly TL was 6685 ± 1605 (4641-10 391; arbitrary units). Inconsistent results were found for the incidence of injury and illness based on individual and group categorizations of TL.

CONCLUSIONS

Professional dancing is associated with high injury and illness rates. This is worrying from a health perspective and underlines the need for further studies to understand how to decrease the risk. The TL is higher than in other sport disciplines, but whether the high incidence of injuries and illnesses is related to high training demands needs additional investigation, possibly conducted as international, multicenter collaborative studies.

Does load management using the acute:chronic workload ratio prevent health problems? A cluster randomised trial of 482 elite youth footballers of both sexes

BACKGROUND

The acute:chronic workload ratio (ACWR) is commonly used to manage training load in sports, particularly to reduce injury risk. However, despite its extensive application as a prevention intervention, the effectiveness of load management using ACWR has never been evaluated in an experimental study.

AIM

To evaluate the effectiveness of a load management intervention designed to reduce the prevalence of health problems among elite youth football players of both sexes.

METHODS

We cluster-randomised 34 elite youth football teams (16 females, 18 males) to an intervention group (18 teams) and a control group (16 teams). Intervention group coaches planned all training based on published ACWR load management principles using a commercially available athlete management system for a complete 10-month season. Control group coaches continued to plan training as normal. The prevalence of health problems was measured monthly in both groups using the Oslo Sports Trauma Research Centre Questionnaire on Health Problems.

RESULTS

The between-group difference in health problem prevalence (primary outcome) was 1.8%-points (-4.1 to 7.7 %-points; p=0.55) with no reduction in the likelihood of reporting a health problem in the intervention group (relative risk 1.01 (95% CI 0.91 to 1.12); p=0.84) compared with the control group.

CONCLUSIONS

We observed no between-group difference, suggesting that this specific load management intervention was not successful in preventing health problems in elite youth footballers.

TRIAL REGISTRATION NUMBER

ISRCTN18177140.

How Has Workload Been Defined and How Many Workload-Related Exposures to Injury Are Included in Published Sports Injury Articles? A Scoping Review

OBJECTIVE

To describe how workload-related exposure variables have been defined in sports injury articles, and to identify the number of workload-related exposure variables included in comparative analyses.

DESIGN

Scoping review.

LITERATURE SEARCH

PubMed, SPORTDiscus, and Scopus were systematically searched on March 13, 2020. Two reviewers independently screened the retrieved literature and selected articles for inclusion.

STUDY SELECTION CRITERIA

Prospective cohort studies using workload-related variables as the primary exposure to sports injury were eligible for inclusion.

DATA SYNTHESIS

The type (eg, distance, balls bowled) and construct of workload-related exposure variables (eg, acute-chronic workload ratio) were extracted and summarized in frequency tables.

RESULTS

A total of 648 articles were identified, and 45 were eligible for inclusion. Workload definition differed greatly, as sports- and workload-related exposure variables could be, but were not limited to, distance, balls bowled, session rating of perceived exertion, accelerations, soreness, and sleep. Within and across articles, authors used different constructs for workload-related exposure variables. For example, distance was represented as total distance, distance per week, distance per 2 weeks, and acute-chronic workload ratio. The number of workload-related exposure variables included in comparative analyses ranged from 1 to 336.

CONCLUSION

Studies used different definitions of workload-related exposure variables. The number of workload-related exposure variables in a single study ranged from 1 to 336. J Orthop Sports Phys Ther 2020;50(10):538-548. doi:10.2519/jospt.2020.9766.

Get sleep or get stumped: sleep behaviour in elite South African cricket players during competition

Despite evidence supporting the positive affect sleep has on sport performance, there is limited application of sleep research in cricket. This study investigated the sleep behaviours of 26 elite South African cricket players (28.6 ± 4.0 years) during home and away competition. Players completed an altered version of the Core Consensus Sleep Diary every morning post-travel, pre-match and post-match. Linear mixed model regression was used to compare differences in sleep between time-periods, venues and formats. Spearman's correlations (r_s) assessed the relationship of match performance and sleep. Post-match total sleep time (06:31 ± 01:09) was significantly (p < 0.05) shorter compared to post-travel (07:53 ± 01:07; g = 1.19) and pre-match (08:43 ± 01:03; g = 1.98). Post-travel sleep onset latency and sleep efficiency were significantly shorter (-20; g = 1.35) and higher (+10.4%; g = 0.74) at home than away respectively. Longer sleep onset latencies and shorter total sleep times were significantly associated with poorer One-Day International (r_s = -0.57) and Test (r_s = 0.59) batting performances respectively. The poor post-match sleep behaviour, and the sleep and performance correlations, provide motive for future interventions to focus on recovery and the use of sleep monitoring as a competitive advantage.

Acute:Chronic Workload Ratio: Conceptual Issues and Fundamental Pitfalls

The number of studies examining associations between training load and injury has increased exponentially. As a result, many new measures of exposure and training-load-based prognostic factors have been created. The acute:chronic workload ratio (ACWR) is the most popular. However, when recommending the manipulation of a prognostic factor in order to alter the likelihood of an event, one assumes a causal effect. This introduces a series of additional conceptual and methodological considerations that are problematic and should be considered. Because no studies have even tried to estimate causal effects properly, manipulating ACWR in practical settings in order to change injury rates remains a conjecture and an overinterpretation of the available data. Furthermore, there are known issues with the use of ratio data and unrecognized assumptions that negatively affect the ACWR metric for use as a causal prognostic factor. ACWR use in practical settings can lead to inappropriate recommendations, because its causal relation to injury has not been established, it is an inaccurate metric (failing to normalize the numerator by the denominator even when uncoupled), it has a lack of background rationale to support its causal role, it is an ambiguous metric, and it is not consistently and unidirectionally related to injury risk. Conclusion: There is no evidence supporting the use of ACWR in training-load-management systems or for training recommendations aimed at reducing injury risk. The statistical properties of the ratio make the ACWR an inaccurate metric and complicate its interpretation for practical applications. In addition, it adds noise and creates statistical artifacts.