Acute:chronic Workload Ratio Research Articles

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

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. Scoping review. PubMed, SPORTDiscus, and Scopus were systematically searched on March 13, 2020. Two reviewers independently screened the retrieved literature and selected articles for inclusion. Prospective cohort studies using workload-related variables as the primary exposure to sports injury were eligible for inclusion. 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. 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. 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.

Does a greater training load increase the risk of injury and illness in ultramarathon runners? : A prospective, descriptive, longitudinal design.

Ultramarathon running has become extremely popular over the years. Despite the numerous health benefits of running, there are also many negative effects of running, such as increased risk of musculoskeletal injury and illness. Monitoring of an athlete's training load has become extremely important in terms of injury prevention. Currently, the relationship between training loads and injury and illness incidence is uncertain. To determine if there are any associations between injury and illness incidences and training loads among ultramarathon runners in the 12 week period preceding an ultramarathon event and the four week period after the event. This prospective, descriptive, longitudinal study design was conducted in 119 runners who were training for the 2019 Two Oceans ultramarathon event. Data were collected once a week via an online logbook over 16 weeks. Training parameters measured included weekly average running distance, average duration, average frequency and average sessional RPE. Injury data included injury counts, the structure injured, the main anatomical location and the time-loss as a result of injury. Illness data included illness counts, the main illness-related symptoms and the time-loss as a result of illness. The overall injury incidence was five per 1000 training hours and the overall illness incidence was 16 per 1000 training days. There was a significant relationship between external training load and injury and illness incidence for those who ran less than 30 km per week. There was also a significant relationship between the ACWR (Acute Chronic Workload Ratio) and injury incidence when the ACWR was >1.5 and for illness incidence when the ACWR was <0.5. The use of both absolute and relative workloads in the monitoring of an athlete's training load with the aim of minimising injury and illness risk and maximising performance in ultramarathon runners is recommended.

Does an Optimal Relationship Between Injury Risk and Workload Represented by the "Sweet Spot" Really Exist? An Example From Elite French Soccer Players and Pentathletes.

ObjectiveTo examine the relationships between the occurrence and severity of injuries using three workload ratios (ACWR, EWMA, REDI) in elite female soccer players and international male and female pentathletes.Materials and MethodsFemale soccer players in the U16 to U18 national French teams (n = 24) and international athletes (n = 12, 4 women and 8 men) in the French modern pentathlon team were monitored throughout an entire season. The Acute Chronic Workload Ratio (ACWR), the Exponentially Weighted Moving Averages (EWMA), and the Robust Exponential Decreasing Index (REDI) were calculated for internal load by the ROE method in soccer and external load in pentathlon. The occurrence and severity of injuries (determined according to time-loss) were quantified in the sweet spot zone [0.8; 1.3] and compared to the other zones of load variation: [0; 0.8], [1.3; 1.5], [1.5; +8], using the three ratios.ResultsOver the study period, a total of sixty-six injuries (2.75 per athlete) were reported in the soccer players and twelve in pentathletes (1 per athlete). The cumulative severity of all injuries was 788 days lost in soccer and 36 in pentathlon: respectively, 11.9 days lost per injury in soccer player and 3.0 per pentathlete. The mean values across the three methods in soccer showed a higher number of injuries detected in the [0; 0.8] workload ratio zone: 22.3 ± 6.4. They were 17.3 ± 3.5 in the sweet spot ([0.8–1.3] zone) and 17.6 ± 5.5 in the [1.5; +8] zone. In comparison to the [1.5; +8] zone, soccer players reported a higher number of days lost to injuries in the presumed sweet spot and in the [0–0.8] zone: 204.7 ± 28.7 and 275.0 ± 120.7 days, respectively. In pentathletes, ten of the twelve injuries (83.3%) occurred in the presumed sweet spot. REDI was the only method capable of tracking workloads over all-time series.ConclusionIn the present cohort of elite soccer players and pentathletes, acute chronic workload calculations showed an association with injury occurrence and severity but did not provide evidence supporting existence of a sweet spot diminishing injury risk.

Influence of Baseball Training Load on Clinical Reach Tests and Grip Strength in Collegiate Baseball Players.

A baseball-specific training load may influence strength or glenohumeral range of motion, which are related to baseball injuries. Glenohumeral reach tests and grip strength are clinical assessments of shoulder range of motion and upper extremity strength, respectively. To examine changes in glenohumeral reach test performance and grip strength between dominant and nondominant limbs and high, moderate, and low baseball-specific training-load groups. Repeated-measures study. University laboratory and satellite clinic. Collegiate baseball athletes (n = 18, age = 20.1 ± 1.3 years, height = 185.0 ± 6.5 cm, mass = 90.9 ± 10.2 kg). Participants performed overhead reach tests (OHRTs), behind-the-back reach tests (BBRTs), and grip strength assessments using the dominant and nondominant limbs every 4 weeks for 16 weeks. Percentage change scores were calculated between testing times. After each training session, participants provided their duration of baseball activity, throw count, and body-specific and arm-specific ratings of perceived exertion. We classified them in the high, moderate, or low training-load group based on each training-load variable: body-specific acute:chronic workload ratio (ACWR), arm-specific ACWR, body-specific cumulative load, and arm-specific cumulative load. Mixed models were used to compare training-load groups and limbs. The arm-specific ACWR group demonstrated as main effect for OHRT (F = 7.70, P = .001), BBRT (F = 4.01, P = .029), and grip strength (F = 8.89, P < .001). For the OHRT, the moderate training-load group demonstrated a 10.8% greater increase than the high group (P = .004) and a 13.2% greater increase than the low group (P < .001). For the BBRT, the low training-load group had a 10.1% greater increase than the moderate group (P = .011). For grip strength, the low training-load group demonstrated a 12.1% greater increase than the high group (P = .006) and a 17.7% greater increase than the moderate group (P < .001). Arm-specific ACWR was related to changes in clinical assessments of range of motion and strength. Clinicians may use arm-specific ACWR to indicate when a baseball athlete's physical health is changing.

Is There a Relationship Between Workload and Occurrence of Back Pain and Back Injuries in Athletes?

The back is subjected to a great deal of strain in many sports. Up to 20% of all sports injuries involve an injury to the lower back or neck. Repetitive or high impact loads (e.g., running, gymnastics, skiing) and weight loading (e.g., weightlifting) affect the lower back. Rotation of the torso (e.g., golf, tennis) causes damage to both, the lumbar and thoracic spine. The cervical spine is most commonly injured in contact sports (e.g., boxing, football). One of the factors that increases the odds of injuries in athletes is excessive and rapid increases in training loads. In spite of currently emerging evidence on this issue, little is known about the balance between physiological loading on the spine and athletic performance, versus overloading and back pain and/or injury in athletes. This scoping review aims (i) to map the literature that addresses the association between the training load and the occurrence of back pain and/or injury, especially between the Acute:Chronic Workload Ratio (ACWR) and back problems in athletes of individual and team sports, and (ii) to identify gaps in existing literature and propose future research on this topic. A literature search of six electronic databases (i.e., MEDLINE, PubMed, Web of Science, SCOPUS, SportDiscus, and CINAHL) was conducted. A total of 48 research articles met the inclusion criteria. Findings identified that fatigue of the trunk muscles induced by excessive loading of the spine is one of the sources of back problems in athletes. In particular, high training volume and repetitive motions are responsible for the high prevalence rates. The most influential are biomechanical and physiological variations underlying the spine, though stress-related psychological factors should also be considered. However, limited evidence exists on the relationship between the ACWR and back pain or non-contact back injuries in athletes from individual and team sports. This may be due to insufficiently specified the acute and chronic time window that varies according to sport-specific schedule of competition and training. More research is therefore warranted to elucidate whether ACWR, among other factors, is able to identify workloads that could increase the risk of back problems in athletes.

Player Monitoring in Professional Soccer: Spikes in Acute:Chronic Workload Are Dissociated From Injury Occurrence.

This study aimed to determine whether spikes in acute:chronic workload ratio (ACWR) are associated with injury incidence, and to examine the differences in external load due to greater or lesser exposure to matches and the long-term effects of the load during a chronic seasonal period. Fifteen professional soccer players belonging to the squad of a European Champions League club were enrolled in this study. External training and match load were assessed from all athletes using a global positioning system (GPS). We calculated the uncoupled ACWR for 10 consecutive competitive microcycles. Injuries were identified and determined by the days of absence. The differences in external load were determined using a linear mixed-model approach. In addition to the null hypothesis testing, the effect size was calculated. Thirteen athletes who did not suffer an injury exceeded several times the critical threshold of an ACWR > 1.5. This is equivalent to 1 player exceeding the critical threshold for ACWR in total distance (TD), 2 players for ACWR at distance covered above moderate speed (MSD), 2 players for ACWR at distance covered above high speed (HSD), 2 players for ACWR at distance covered above very high speed (VHSD), and 2 players for ACWR in DC at sprint per week. One athlete experienced a non-contact muscle strain injury and another a contact -injury manifested as a concussion; both athletes document an ACWR <1.5 within the 4 weeks prior to the injury event. Players with lesser participation in official games covered lower TD (−19.6%, very-large ES), MSD (−24.8%, very-large ES), HSD (−25.1%, moderate ES), VHSD (−25.5%, moderate ES), and DC at sprint (−30.6%, moderate ES) over the course of the 10-weeks period in comparison with the players with greater participation in official games. The present study demonstrated that spikes in the ACWR were not related to a subsequent injury occurrence in professional soccer players. Differences in participation in official games caused significant imbalances in the chronic external loads between players in a squad, which should be minimized in training sessions in order to prevent substantial changes in workload for those who usually do not play.

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.

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. 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. PubMed, EMBASE and grey literature databases; inception to May 2019. Longitudinal studies that assess the relationship of the ACWR and time-loss injury risk in adult professional or elite team sports. We 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. Twenty studies comprising 2375 injuries from 1234 athletes (all males and mean age of 24years) from different sports were included. Internal (65%) and external loads (70%) were collected in more than half of the studies and the session-rating of perceived exertion 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. The majority of studies suggest that athletes are at greater risk of sustaining a time-loss injury when the ACWR is higher relative to a lower or moderate ACWR. The heterogenous methodological approaches not only reflect the wide range of sports studied and the differing demands of these activities, but also limit the strength of recommendations. CRD42017067585.

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.

Variations of Workload Indices Prior to Injuries: A Study in Trail Runners.

The purpose of this study was to compare the variations of weekly workload indices of internal and external load measures across the three weeks prior to injury occurrences in trail runners. Twenty-five trail runners (age: 36.23 ± 8.30 years old; body mass: 67.24 ± 5.97 kg; height: 172.12 ± 5.12 cm) were monitored daily for 52 weeks using global positioning systems (GPSs) to determine the total distance covered. Additionally, a rate of perceived exertion (RPE) scale was applied to determine session-RPE (sRPE: RPE multiplied by training time). The accumulated load (AL), acute: chronic workload ratio (ACWR), training monotony (TM), and training strain (TS) indices were calculated weekly for each runner. During the period of analysis, the injury occurrences were recorded. The differences were observed in AL and ACWR for sRPE and training time were significantly greater during the injury week when compared to the previous weeks. Similar evidence was found in TM and TS indices for sRPE, training time, and total distance. Furthermore, no meaningful differences were observed in AL and ACWR for total distance in the weeks prior to injury occurrence. Nevertheless, significant between-subjects variability was found, and this should be carefully considered. For that reason, an individualized analysis of the workload dynamics is recommended, avoiding greater spikes in load by aiming to keep a progressive increment of load without consequences for injury risk.

Training Load Monitoring in Amateur Rugby Union: A Survey of Current Practices.

Griffin, A, Kenny, IC, Comyns, TM, and Lyons, M. Training load monitoring in amateur Rugby Union: A survey of current practices. J Strength Cond Res 35(6): 1568-1575, 2021-Amateur Rugby Union has an inherent risk of injury that is associated with detrimental effects on player welfare and team performance. Training load (TL) is a modifiable risk factor that, when monitored, may provide strength and conditioning (S&C) coaches with opportunities to reduce the risk of injury. The purpose of this study was to explore TL monitoring practices used by S&C coaches working with male and female amateur adult Rugby Union teams and their rationale for using such. Thirty-three (n = 31 male and n = 2 female) S&C coaches representing 62% of the total number of male clubs and 71% of female clubs, playing at the highest national amateur level, participated in the study by completing an online survey. Seventy-three percent of respondents stated that they monitor TL. The most common method of recording TL was the session rating of perceived exertion (sRPE), used in 83% of monitoring systems. Thirty-three percent of the S&C coaches surveyed use the sRPE data to calculate the acute:chronic workload ratio (ACWR) for highlighting when players are at risk of injury. This study is the first of its kind to exclusively examine the TL monitoring practices of S&C coaches working with amateur adult Rugby Union teams. Thirteen S&C coaches responded to the open-ended question and 3 higher order themes were highlighted: (a) communication with players (b) support from other staff and (c) limiting factors.

Difference in Internal and External Workloads between Non-Injured and Injured Groups in Collegiate Female Soccer Players

Background: Effects of internal and external workloads (IL, EL) on lower limb soft-tissue injuries (LLSTI) risk in male soccer players has been described, the relationships remain unclear in collegiate female (soccer players. Objective: The purpose was to examine the mean difference in IL and EL in LLSTI between non-injured and injured groups (N-IG and IG). Method: 20 collegiate female soccer players (age: 19.2±1.2years; height: 168.2±7.3cm; body mass: 41.0±17.9kg) were included for 14 week competitive season. IL included average heart rate (Avg-HR) and high heart rate zone. EL included total distance, average speed (Avg-Spd), and high-speed running distance. Injuries were counted if (a) they were LLSTI and muscular/ligamentous strains or tears and tendon problems, and (b) the players missed more than one match or training session. Acute (7-day simple average) and chronic (21-day simple average) IL and EL were calculated in the IG while the mean of acute (7-day) and chronic (21-day) IL and EL were computed in the NIG. Acute Chronic Workload Ratio (ACWR) was calculated as the ratio of acute and chronic IL and EL. Results: Seven LLSTI occurred over 14 weeks. The acute Avg-HR and ACWR of Avg-Spd were significantly higher in the IG than the N-IG (p=0.001 and 0.024). IL and EL in the IG were placed below or above the mean of the N-IG. Conclusion: LLSTI might occur at high and low workloads in collegiate female soccer players. This may support the use of micro-technology to monitor workload based on individual player’s threshold to reduce LLSTI.

Analyzing Activity and Injury: Lessons Learned from the Acute:Chronic Workload Ratio.

Injuries occur when an athlete performs a greater amount of activity than what their body can withstand. To maximize the positive effects of training while avoiding injuries, athletes and coaches need to determine safe activity levels. The International Olympic Committee has recommended using the acute:chronic workload ratio (ACWR) to monitor injury risk and has provided thresholds to minimize risk when designing training programs. However, there are several limitations to the ACWR and how it has been analyzed which impact the validity of current recommendations and should discourage its use. This review aims to discuss previously published and novel challenges with the ACWR, and strategies to improve current analytical methods. In the first part of this review, we discuss challenges inherent to the ACWR. We explain why using a ratio to represent changes in activity may not always be appropriate. We also show that using exponentially weighted moving averages to calculate the ACWR results in an initial load problem, and discuss their inapplicability to sports where athletes taper their activity. In the second part, we discuss challenges with how the ACWR has been implemented. We cover problems with discretization, sparse data, bias in injured athletes, unmeasured and time-varying confounding, and application to subsequent injuries. In the third part, conditional on well-conceived study design, we discuss alternative causal-inference based analytical strategies that may avoid major flaws in studies on changes in activity and injury occurrence.

The Relationship Between Acute: Chronic Workload Ratios and Injury Risk in Sports: A Systematic Review.

PurposeLow injury rates have previously been correlated with sporting team success, highlighting the importance of injury prevention programs. Recent methods, such as acute:chronic workload ratios (ACWR) have been developed in an attempt to predict and manage injury risk; however, the relation between these methods and injury risk is unclear. The aim of this systematic review was to identify and synthesize the key findings of studies that have investigated the relationship between ACWR and injury risk.MethodsIncluded studies were critically appraised using the Downs and Black checklist, and a level of evidence was determined. Relevant data were extracted, tabulated, and synthesized.ResultsTwenty-seven studies were included for review and ranged in percentage quality scores from 48.2% to 64.3%. Almost perfect interrater agreement (κ = 0.885) existed between raters. This review found a high variability between studies with different variables studied (total distance versus high speed running), as well as differences between ratios analyzed (1.50–1.80 versus ≥1.50), and reference groups (a reference group of 0.80–1.20 versus ≤0.85).ConclusionConsidering the high variability, it appears that utilizing ACWR for external (eg, total distance) and internal (eg, heart rate) loads may be related to injury risk. Calculating ACWR using exponentially weighted moving averages may potentially result in a more sensitive measure. There also appears to be a trend towards the ratios of 0.80–1.30 demonstrating the lowest risk of injury. However, there may be issues with the ACWR method that must be addressed before it is confidently used to mitigate injury risk. Utilizing standardized approaches will allow for more objective conclusions to be drawn across multiple populations.

Workload and Injury in Professional Soccer Players: Role of Injury Tissue Type and Injury Severity.

The purpose of the present study was to examine the influence of workload prior to injury on injury (tissue type and severity) in professional soccer players. Twenty-eight days of retrospective training data prior to non-contact injuries (n=264) were collated from 192 professional soccer players. Each injury tissue type (muscle, tendon and ligament) and severity (days missed) were categorised by medical staff. Training data were recorded using global positioning system (GPS) devices for total distance (TD), high speed distance (HSD,>5.5 m/s-1), and sprint distance (SPR,>7.0 m/s-1). Accumulated 1, 2, 3, 4-weekly loads and acute:chronic workload ratios (ACWR) (coupled, uncoupled and exponentially weighted moving average (EWMA) approaches) were calculated. Workload variables and injury tissue type were compared using a one-way ANOVA. The association between workload variables and injury severity were examined using a bivariate correlation. There were no differences in accumulated weekly loads and ACWR calculations between muscle, ligament, and tendon injuries (P>0.05). Correlations between each workload variable and injury severity highlighted no significant associations (P>0.05). The present findings suggest that the ability of accumulated weekly workload or ACWR methods to differentiate between injury type and injury severity are limited using the present variables.

Match and Training Load Exposure and Time-Loss Incidence in Elite Rugby Union Players.

ObjectiveTo investigate the impact of match and training load on time-loss incidence in elite, professional Rugby Union players.Materials and MethodsEighty-nine Rugby Union players were monitored over two seasons of training and competition. Load was measured for all training sessions and matches using subjective [session ratings of perceived exertion (sRPE) load; RPE × session duration] and objective [global positioning systems (GPS); distance and high-speed running distance] methods and quantified using multiple approaches; absolute match and training load, acute:chronic workload ratio (ACWR), exponentially weighted moving average (EWMA) and cumulative 7, 14, 21, and 28 d sums. Mixed effect models were used to assess the effect of each variable on time-loss incidence.ResultsOf the 474 time-loss incidences that occurred across the two seasons, 50.0% were contact injuries (86.5% occurred during matches and 13.5% during training), 34.8% were non-contact injuries (31.5% occurred during matches and 68.5% during training) and 15.2% were cases of illness. The absolute match and training load variables provided the best explanation of the variance in time-loss incidence occurrence [sRPE load: p < 0.001, Akaike information criterion (AIC) = 2936; distance: p < 0.001, AIC = 3004; high-speed running distance: p < 0.001, AIC = 3025]. The EWMA approach (EWMA sRPE load: p < 0.001, AIC = 2980; EWMA distance: p < 0.001, AIC = 2980; EWMA high-speed running distance: p = 0.002, AIC = 2987) also explained more of the variance in time-loss incidence occurrence than the ACWR approach (ACWR sRPE load: p = 0.091, AIC = 2993; ACWR distance: p = 0.008, AIC = 2990; ACWR high-speed running distance: p = 0.153, AIC = 2994).ConclusionOverall, the absolute sRPE load variable best explained the variance in time-loss incidence, followed by absolute distance and absolute high-speed running distance. Whilst the model fit using the EWMA approach was not as good as the absolute load variables, it was better than when the same variables were calculated using the ACWR method. Overall, these findings suggest that the absolute match and training load variables provide the best predictors of time-loss incidence rates, with sRPE load likely to be the optimal variant of those examined here.

The Association Between the Acute:Chronic Workload Ratio and Injury and its Application in Team Sports: A Systematic Review.

There has been a recent increase in research examining training load as a method of mitigating injury risk due to its known detrimental effects on player welfare and team performance. The acute:chronic workload ratio (ACWR) takes into account the current training load (acute) and the training load that an athlete has been prepared for (chronic). The ACWR can be calculated using; (1) the rolling average model (RA) and (2) the exponentially weighted moving average model (EWMA). The primary aim of this systematic review was to investigate the literature examining the association between the occurrence of injury and the ACWR and to investigate if sufficient evidence exists to determine the best method of application of the ACWR in team sports. Studies were identified through a comprehensive search of the following databases: EMBASE, Medline, SPORTDiscus, SCOPUS, AMED and CINAHL. Extensive data extraction was performed. The methodological quality of the included studies was assessed according to the Newcastle-Ottawa Scale (NOS) for Cohort Studies. A total of 22 articles met the inclusion criteria. The assessment of article quality had an overall median NOS score of 8 (range 5-9). The findings of this review support the association between the ACWR and non-contact injuries and its use as a valuable tool for monitoring training load as part of a larger scale multifaceted monitoring system that includes other proven methods. There is support for both models, but the EWMA is the more suitable measure, in part due to its greater sensitivity. The most appropriate acute and chronic time periods, and training load variables, may be dependent on the specific sport and its structure. For practitioners, it is the important to understand the intricacies of the ACWR before deciding the best method of calculation. Future research needs to focus on the more sensitive EWMA model, for both sexes, across a larger range of sports and time frames and also combinations with other injury risk factors.

To Couple or not to Couple? For Acute:Chronic Workload Ratios and Injury Risk, Does it Really Matter?

We examined the association between coupled and uncoupled acute:chronic workload ratios (ACWR) and injury risk in a cohort of 28 elite cricket fast bowlers (mean±SD age, 26±5 yr). Workloads were estimated using the session rating of perceived exertion (session-RPE). Coupled ACWRs were calculated using a 1-week acute workload and 4-week chronic workload (acute workload was included in the chronic workload calculation), whereas uncoupled ACWRs used the most recent 1-week acute workload and the prior 3-week chronic workload (acute workload was not included in the chronic workload calculation). A nearly perfect relationship (R2=0.99) was found between coupled and uncoupled ACWRs. Using a percentile rank method, no significant differences in injury risk were found between the coupled and uncoupled ACWR. Higher ACWRs were associated with increased injury likelihood for both coupled and uncoupled methods, however there were no significant differences in injury risk between coupled and uncoupled ACWRs. Our data demonstrates that both coupled and uncoupled ACWRs produce the same injury likelihoods. Furthermore, our results are consistent with previous studies: higher ACWRs are associated with greater risk, irrespective of whether acute and chronic workloads are coupled or uncoupled.

The Effect Of Acute Chronic Training Load Ratio On Daily Stress, Fatigue, And Soreness Level In A Ncaa Division 1 Soccer Players

PURPOSE: To investigate the effect of acute chronic work load ratio (ACWL) on daily stress, fatigue, and soreness throughout a collegiate men’s soccer season. METHODS: Sixty-four male collegiate soccer players (mean±SD; age, 20±2y; body mass, 77.3±6.7kg; height, 179.9±6.4cm; VO2max, 53.0±5.0ml•kg-1•min-1) participated in this study, which took place during the 2016 and 2017 NCAA soccer season. During each training session and match, players donned a heart rate and GPS enabled chest strap to measure training impulse (TRIMP). Daily stress, fatigue, and soreness levels were collected using 1 to 10 Likert-scales before each training session and match. ACWL was calculated for TRIMP using the ratio of the previous 7-day average to the previous 28-day average. ACWL values were categorized into three groups: low, ACWL<0.8; medium, 0.8≦ACWL<1.5; high, ACWL≧1.5. Stress, fatigue, soreness levels were transformed to corresponding z-scores to account for individual differences. One-way ANOVA with Tukey pairwise comparison was used to assess stress, fatigue, soreness levels in different ACWL groups. Mean difference (MD), 95% confidence interval (95%CI) and effect size (ES), suggested by Cohen were calculated. RESULTS: Stress levels were significantly higher when ACWL was high compared to low (MD=0.47, 95%CI=0.34-0.60, ES=0.44) and medium (MD=0.37, 95%CI=0.25-0.48, ES=0.28) (p=0.001). Fatigue levels were significantly higher when ACWL was high (0.36±1.15) compared to low (MD=0.56, 95%CI=0.42-0.69, ES=0.55) and medium (MD=0.38, 95%CI=0.26-0.49, ES=0.36) (p=0.001). Fatigue levels were also significantly higher when ACWL was medium compared to low (MD=0.18, 95%CI=0.07-0.29, ES=0.20, p=0.001). Soreness level was significantly higher when ACWL was high compared to low (MD=0.51, 95%CI=0.37-0.64, ES=0.49) and medium (MD=0.38, 95%CI=0.26-0.50, ES=0.31) (p=0.001). CONCLUSIONS: ACWL could impact daily stress, fatigue, and soreness levels. A large change in ACWL (≧1.5) was associated with moderate to large changes in stress, fatigue, and soreness levels compared to low ACWL. Thus, ACWL may be used to manage athlete’s daily stress, fatigue, and soreness levels and optimize periodization. However, other factors should be also considered, such as sleep.

The Association Between Noncontact Injuries and the Acute-Chronic Workload Ratio in Elite-Level Athletes: A Critically Appraised Topic.

Clinical Scenario: Workload monitoring and management of an athlete is viewed by many as an essential training component to determine if an athlete is adapting to a training program and to minimize injury risk. Although training workload may be measured a variety of different ways, session rate of perceived exertion (sRPE) is often used in the literature due to its clinical ease. In recent years, sports scientists have been investigating sRPE as a measure of internal workload and its relationship to injury in elite-level athletes using a metric known as the acute:chronic workload ratio (ACWR). This critically appraised topic was conducted to determine if internal workload using the ACWR is associated with injury. Focused Clinical Question: In elite-level athletes, is there an association between the ACWR for sRPE and noncontact injuries? Summary of Search, Best Evidence Appraised, and Key Findings: The literature was searched for studies investigating the association between noncontact injuries and the sRPE ACWR in elite athletes. Three prospective cohort studies were included. Two studies found that high ACWR led to 2.0 to 4.5 times greater injury risk compared with a more balanced ACWR. One study found that low chronic workloads coupled with a low ACWR were associated with injury. Clinical Bottom Line: The majority of evidence suggests that when the acute workload exceeds the chronic workload, there is an increase in injury risk. The evidence also supports that a low chronic workload with a low ACWR should be considered as an injury risk factor. Strength of Recommendation: Based on the American Family Physician's Strength of Recommendation Taxonomy, there is level A evidence to support the sRPE ACWR as a risk factor for noncontract injuries in elite athletes.

Spikes in acute:chronic workload ratio (ACWR) associated with a 5–7 times greater injury rate in English Premier League football players: a comprehensive 3-year study

ObjectivesWe examined the relation between global positioning system (GPS)-derived workloads and injury in English Premier League football players (n=33) over three seasons.MethodsWorkload and injury data were collected over three consecutive...