The effect of swimming volume and intensity on changes in supraspinatus tendon thickness.

OBJECTIVES: To compare the change in supraspinatus tendon thickness (STT) following a high volume (HV) and high intensity (HI) swimming practice in shoulders of elite swimmers. DESIGN: Cohort Study. SETTING: Non-clinical, state swim team training facility. PARTICIPANTS: A convenience sample of eight non-injured state and national level swimmers from a regional swim team were recruited for this study. MAIN OUTCOME MEASURES: Ultrasound measures of STT were collected in response to the two swimming practice sessions. Measures were taken prior to each swim practice; immediately after practice; 6-hours post practice and 24-hours post practice. RESULTS: A significant increase in STT resulted from both the HI and HV (p < 0.05) practice immediately post practice. For the HI practice, the STT remained significantly thicker than pre-practice measures at the 6-hour post practice test (p < 0.05) however no longer significant 24-hours post practice. The difference in the change in STT between the HI and HV practice was significantly different immediately post practice and 6-hours post practice (p < 0.05) however no longer significant 24-hour post practice. CONCLUSION: Ultrasound measures of STT following different swimming volumes and intensities may provide information on shoulder tendon loads.

Match High-Speed Running Distances Are Often Suppressed After Return From Hamstring Strain Injury in Professional Footballers.

BACKGROUND: High-speed running is commonly implicated in the genesis of hamstring injury. The success of hamstring injury management is typically quantified by the duration of time loss or reinjury rate. These metrics do not consider any loss in performance after returning to play from hamstring injury. It is not known to what extent high-speed running is altered on return to play after such injury. HYPOTHESIS: Match high-speed running distance will change after returning from hamstring injury. STUDY DESIGN: Non-randomized cohort. LEVEL OF EVIDENCE: Level 3. METHODS: Match high-speed running distance in highest level professional football (soccer, Rugby League, Rugby Union, and Australian Rules) were examined for a minimum of 5 games prior and subsequent to hamstring strain injury for individual differences using a linear regression models approach. A total of 22 injuries in 15 players were available for analysis. RESULTS: Preinjury cumulative high-speed running distances were strongly correlated for each individual (r2 = 0.92-1.0; P < 0.0001). Pre- and postinjury high-speed running data were available for a median of 15 matches (range, 6-15). Variance from the preinjury high-speed running distance was significantly less (P = 0.0005) than the post injury values suggesting a suppression of high-speed running distance after returning from injury. On return to play, 7 of the 15 players showed a sustained absolute reduction in preinjury high-speed running distance, 7 showed no change, and 1 player (only) showed an increase. Analysis of subsequent (second and third injury) return to play showed no differences to return from the index injury. CONCLUSION: Return to play was not associated with return to high-speed running performance for nearly half of the players examined, although the same number showed no difference. Persisting deficits in match high-speed running may exist for many players after hamstring strain injury. CLINICAL RELEVANCE: Returning to play does not mean returning to (high-speed running) performance for nearly half of the high-level professional football players examined in this study. This suggests that successful return to play metrics should be expanded from simple time taken and recurrence to include performance.

Clinical utility of measuring the size of the lumbar multifidus and quadratus lumborum muscles in the Australian football league setting: A prospective cohort study.

OBJECTIVES: Test the odds of factors previously associated with lower limb injury (decreased size of the multifidus (MF) and increased size of the quadratus lumborum (QL) muscle) in an independent sample of Australian Rules Football (ARF) players. DESIGN: Prospective cohort study. SETTING: Professional ARF. PARTICIPANTS: Forty-three male ARF players. MAIN OUTCOME MEASURES: Cross-sectional areas (CSAs) of MF and QL muscles measured from pre-season ultrasound images. Playing season injuries were recorded by club personnel. A multivariable logistic regression model was used to evaluate the usefulness of MF and QL muscle size for predicting playing season lower limb injuries. RESULTS: Fifteen players (35%) sustained a playing season lower limb injury. The multivariable model indicated that the odds of sustaining a lower limb injury during the season was 2.38 (95% CI: 1.18, 5.00; P = 0.017) times less likely for a one cm2 increase from the mean value in MF muscle CSA at the L5 vertebral level after adjusting for CSA of the QL, age and BMI. The main effect and interaction models positively predicted 75% of players that sustained a lower limb injury during the season (sensitivity 80%, specificity 85%). CONCLUSION: Future studies could examine the efficacy, feasibility and adherence of 'at risk' players to a pre-season training program aimed at increasing MF muscle size and monitor playing season injuries.

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.

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 CRITERIA: Longitudinal studies that assess the relationship of the ACWR and time-loss injury risk in adult professional or elite team sports. METHODS: 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. RESULTS: Twenty studies comprising 2375 injuries from 1234 athletes (all males and mean age of 24 years) 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. CONCLUSION: 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. PROSPERO REGISTRATION NUMBER: CRD42017067585.

The effect of previous shoulder pain on supraspinatus tendon thickness changes following swimming practice.

OBJECTIVES: To assess if swimming practice results in changes in supraspinatus tendon thickness, acromiohumeral distance, and occupational ratio in shoulders of elite swimmers with and without a history of shoulder pain. DESIGN: Case-Control study. METHODS: A convenience sample of fifty elite swimmers (14-22 years) were recruited for this study. Groups were defined by the presence (history of pain, N = 37) or absence (pain free, N = 63) of significant interfering shoulder pain within the previous 6 months. The current study analyzed supraspinatus tendon thickness, acromiohumeral distance, and the occupational ratio, through the use of ultrasound. Measures were taken prior to swim practice; immediately after practice; and 6 hours post-practice. RESULTS: No statistically significant difference in supraspinatus tendon thickness, acromiohumeral distance or ratio between shoulders with and without a history of pain were found at rest. Following a swimming practice, both shoulders with and without a history of pain had a significant increase in tendon thickness (0.27 & 0.17 mm; P ≤ .001 & <.001). The increase in thickness was significantly greater in the history of pain shoulders compared to pain-free shoulders (P = .003). At 6-hour post-practice, the history of pain shoulders was still significantly thicker than their pre-practice (rested) levels (P = .007). Despite changes in tendon thickness, the occupational ratio remained non-significant between groups. CONCLUSION: Shoulders with a history of pain show an altered response to swimming practice. The results of the current study have implications for training load and injury management. It should prompt investigation into how the tendon reacts under varying load conditions.

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.

Comparison of the Physical and Technical Demands of Cricket Players During Training and Match-Play.

Vickery, W, Duffield, R, Crowther, R, Beakley, D, Blanch, P, and Dascombe, BJ. Comparison of the physical and technical demands of cricket players during training and match-play. J Strength Cond Res 32(3): 821-829, 2018-This study aimed to determine which training method (net-based sessions or center-wicket simulations) currently used in national level and U19 male players cricket provided a more physical and technical match-specific training response. The heart rate, rating of perceived exertion, and movement patterns of 42 male cricket players were measured across the various training and match formats. Video analysis was coded retrospectively to quantify technical loads based on the cricket skills performed. Magnitude-based inferences were based on the standardization of effect and presented with ±90% confidence intervals. Regardless of playing position, differences in physiological demands between training modes and match-play were unclear, with the exception of higher heart rates in fielders during traditional net sessions (mean heart rate: d = -2.7 [-4.7 to -0.7]; 75% of maximum heart rate: d = -1.7 [-3.2 to -0.2]). Typically, the movement demands of center-wicket simulations were similar or greater than match-play, which was most evident in the distance traveled at a high intensity within each playing position (batsmen: d = 6.4 [3.7-9.2]; medium-fast bowlers: d = 1.71 [0.1-3.3]; spin bowlers: d = 6.5 [0.01-13.0]; fielders: d = 0.8 [-0.2 to 1.7]). The technical demands of traditional net cricket training exceeded that of a typical match for each playing position. Specifically, fast bowlers delivered a greater number of balls during net-bowling compared with a match (d = -2.2 [-3.6 to 0.9]). In conclusion, center-wicket simulations more closely matched the physical demands of a One-Day match within batsmen and spin bowlers, whereas traditional cricket training often exceeded match-specific demands.

Optimizing Preseason Training Loads in Australian Football.

PURPOSE: To investigate whether preseason training plans for Australian football can be computer generated using current training-load guidelines to optimize injury-risk reduction and performance improvement. METHODS: A constrained optimization problem was defined for daily total and sprint distance, using the preseason schedule of an elite Australian football team as a template. Maximizing total training volume and maximizing Banister-model-projected performance were both considered optimization objectives. Cumulative workload and acute:chronic workload-ratio constraints were placed on training programs to reflect current guidelines on relative and absolute training loads for injury-risk reduction. Optimization software was then used to generate preseason training plans. RESULTS: The optimization framework was able to generate training plans that satisfied relative and absolute workload constraints. Increasing the off-season chronic training loads enabled the optimization algorithm to prescribe higher amounts of "safe" training and attain higher projected performance levels. Simulations showed that using a Banister-model objective led to plans that included a taper in training load prior to competition to minimize fatigue and maximize projected performance. In contrast, when the objective was to maximize total training volume, more frequent training was prescribed to accumulate as much load as possible. CONCLUSIONS: Feasible training plans that maximize projected performance and satisfy injury-risk constraints can be automatically generated by an optimization problem for Australian football. The optimization methods allow for individualized training-plan design and the ability to adapt to changing training objectives and different training-load metrics.

The Relationship Between Variables in Wearable Microtechnology Devices and Cricket Fast-Bowling Intensity.

To date, the monitoring of fast-bowling workloads across training and competition environments has been limited to counting total balls bowled. However, bowling at faster velocities is likely to require greater effort while also placing greater load on the bowler. This study investigated the relationship between prescribed effort and microtechnology outputs in fast bowlers to ascertain whether the technology could provide a more refined measure of workload. Twelve high-performing fast bowlers (mean ± SD age 20.3 ± 2.2 y) participated in the study. Each bowler bowled 6 balls at prescribed bowling intensities of 60%, 70%, 85%, and 100%. The relationships between microtechnology outputs, prescribed intensity, and ball velocity were determined using polynomial regression. Very large relationships were observed between prescribed effort and ball velocity for peak PlayerLoad™ (R = .83 ± .19 and .82 ± .20). The PlayerLoad across lower ranges of prescribed effort exhibited a higher coefficient of variation (CV) (60% = 19.0% [17.0-23.0%]), while the CV at higher ranges of prescribed effort was lower (100% = 7.3% [6.4-8.5%]). Routinely used wearable microtechnology devices offer opportunities to examine workload and intensity in cricket fast bowlers outside the normal metrics reported. They offer a useful tool for prescribing and monitoring bowling intensity and workload in elite fast bowlers.

Hardness and posting of foot orthoses modify plantar contact area, plantar pressure, and perceived comfort when cycling.

OBJECTIVES: To evaluate the effects of hardness and posting of orthoses on plantar profile and perceived comfort and support during cycling. DESIGN: A repeated measures study with randomised order of orthoses, hardness, and posting conditions. METHODS: Twenty-three cyclists cycled at a cadence of 90rpm and a perceived exertion rating of twelve. Contoured soft and hard orthoses with or without a medial forefoot or lateral forefoot post were evaluated. Plantar contact area, mean pressure and peak pressure were measured for nine plantar regions using the pedar®-X system and represented as a percentage of the total (CA%, MP%, and PP% respectively). Perceived comfort and support was rated on a visual analogue scale. RESULTS: The softer orthosis significantly increased CA% (p=0.014) across the midfoot and heel with a decrease in the toe region and forefoot. MP% (p=0.034) and PP% (p=0.012) were significantly increased at the mid and lateral forefoot with reductions in MP% at the midfoot and in PP% at the hallux and toes. Forefoot posting significantly increased CA% (p=0.018) at the toes and forefoot and decreased it at the heel. PP% was significantly altered (p=0.013) based on posting position. Lateral forefoot posting significantly decreased heel comfort (p=0.036). CONCLUSION: When cycling, a soft, contoured orthosis increased contact across the midfoot and heel, modulating forefoot and midfoot plantar pressures but not altering comfort or support. Forefoot postings significantly modified contact areas and plantar pressures and reduced comfort at the heel.

Autologous tenocyte implantation into shoulder tendon pathology in an elite swimmer.

INTRODUCTION: The use of novel bioengineer treatment techniques such as Autologous Tenocyte Implantation (ATI) have shown promising improvements in both pain ratings and functional outcomes in elbow, gluteal and shoulder tendon pathology. This case will review the injury timeline of ATI intervention in an elite male swimmer with subscapularis tendon pathology and investigate whether ATI has a concomitant healing effect associated with improved functional outcomes. METHODS: A palmaris longus tendon biopsy was performed and cells were expanded by in-vitro culture. Autologous tenocytes were injected into the subscapularis site identified. Three blinded radiologists reported on pre and post shoulder MRIs using the same 3T MRI protocol. A validated rating scale for severity of tendinopathy (0-3) and degree of tear (0-3) was used and hand-held Dynamometry (HHD) strength was recorded. RESULTS: Independent blinded radiology review demonstrated a significant reduction in tear size and improved tendon morphology. IR strength on HHD returned to baseline strength levels post ATI (231-253N) 6 weeks post intervention. The athlete returned to full training (volume and intensity) pain free and international level competition at 4 months post ATI. CONCLUSION: An athlete who had previously undergone unsuccessful conservative management demonstrated significant improvement in function and in tendon morphology post intervention.

Training loads and injury risk in Australian football-differing acute: chronic workload ratios influence match injury risk.

AIMS: (1) To investigate whether a daily acute:chronic workload ratio informs injury risk in Australian football players; (2) to identify which combination of workload variable, acute and chronic time window best explains injury likelihood. METHODS: Workload and injury data were collected from 53 athletes over 2 seasons in a professional Australian football club. Acute:chronic workload ratios were calculated daily for each athlete, and modelled against non-contact injury likelihood using a quadratic relationship. 6 workload variables, 8 acute time windows (2-9 days) and 7 chronic time windows (14-35 days) were considered (336 combinations). Each parameter combination was compared for injury likelihood fit (using R2). RESULTS: The ratio of moderate speed running workload (18-24 km/h) in the previous 3 days (acute time window) compared with the previous 21 days (chronic time window) best explained the injury likelihood in matches (R2=0.79) and in the immediate 2 or 5 days following matches (R2=0.76-0.82). The 3:21 acute:chronic workload ratio discriminated between high-risk and low-risk athletes (relative risk=1.98-2.43). Using the previous 6 days to calculate the acute workload time window yielded similar results. The choice of acute time window significantly influenced model performance and appeared to reflect the competition and training schedule. CONCLUSIONS: Daily workload ratios can inform injury risk in Australian football. Clinicians and conditioning coaches should consider the sport-specific schedule of competition and training when choosing acute and chronic time windows. For Australian football, the ratio of moderate speed running in a 3-day or 6-day acute time window and a 21-day chronic time window best explained injury risk.

Calculating acute:chronic workload ratios using exponentially weighted moving averages provides a more sensitive indicator of injury likelihood than rolling averages.

OBJECTIVE: To determine if any differences exist between the rolling averages and exponentially weighted moving averages (EWMA) models of acute:chronic workload ratio (ACWR) calculation and subsequent injury risk. METHODS: A cohort of 59 elite Australian football players from 1 club participated in this 2-year study. Global positioning system (GPS) technology was used to quantify external workloads of players, and non-contact 'time-loss' injuries were recorded. The ACWR were calculated for a range of variables using 2 models: (1) rolling averages, and (2) EWMA. Logistic regression models were used to assess both the likelihood of sustaining an injury and the difference in injury likelihood between models. RESULTS: There were significant differences in the ACWR values between models for moderate (ACWR 1.0-1.49; p=0.021), high (ACWR 1.50-1.99; p=0.012) and very high (ACWR >2.0; p=0.001) ACWR ranges. Although both models demonstrated significant (p<0.05) associations between a very high ACWR (ie, >2.0) and an increase in injury risk for total distance ((relative risk, RR)=6.52-21.28) and high-speed distance (RR=5.87-13.43), the EWMA model was more sensitive for detecting this increased risk. The variance (R2) in injury explained by each ACWR model was significantly (p<0.05) greater using the EWMA model. CONCLUSIONS: These findings demonstrate that large spikes in workload are associated with an increased injury risk using both models, although the EWMA model is more sensitive to detect increases in injury risk with higher ACWR.

The reliability of shoulder range of motion measures in competitive swimmers.

OBJECTIVES: Investigate reliability of shoulder internal and external rotation (IR, ER), abduction in internal rotation (ABIR) and combined elevation (CE) range of motion tests in competitive swimmers. DESIGN: Within participants, inter- and intra-examiner reliability. SETTING: Physiotherapy Department, University of Melbourne, Australia. PARTICIPANTS: 17 competitive swimmers (aged 12-24 years) who participate in at least 5 weekly swimming sessions and two physiotherapy examiners. MAIN OUTCOME MEASURES: Inter- and intra-examiner reliability of IR, ER, ABIR and CE. RESULTS: Good to excellent intra-examiner reliability across tests (ICCs: 0.85-0.96) with standard error of measurement (SEM)and minimal detectable change at 90% confidence interval (MDC90) ranging from 2 to 5, and 5-12°, respectively. Good to excellent inter-examiner reliability for all tests (ICCs: 0.77-0.94) except left IR (ICC: 0.65). Inter-examiner SEM and MDC90 ranged from 2 to 5° and 5-12°, respectively. CONCLUSION: Shoulder range of motion tests were reliable when applied by the same examiner. Inter-examiner reliability was acceptable for all tests except IR, which was affected by inconsistent manual scapula stabilisation between examiners.

Has the athlete trained enough to return to play safely? The acute:chronic workload ratio permits clinicians to quantify a player's risk of subsequent injury.

The return to sport from injury is a difficult multifactorial decision, and risk of reinjury is an important component. Most protocols for ascertaining the return to play status involve assessment of the healing status of the original injury and functional tests which have little proven predictive ability. Little attention has been paid to ascertaining whether an athlete has completed sufficient training to be prepared for competition. Recently, we have completed a series of studies in cricket, rugby league and Australian rules football that have shown that when an athlete's training and playing load for a given week (acute load) spikes above what they have been doing on average over the past 4 weeks (chronic load), they are more likely to be injured. This spike in the acute:chronic workload ratio may be from an unusual week or an ebbing of the athlete's training load over a period of time as in recuperation from injury. Our findings demonstrate a strong predictive (R(2)=0.53) polynomial relationship between acute:chronic workload ratio and injury likelihood. In the elite team setting, it is possible to quantify the loads we are expecting athletes to endure when returning to sport, so assessment of the acute:chronic workload ratio should be included in the return to play decision-making process.

Cricket fast bowling workload patterns as risk factors for tendon, muscle, bone and joint injuries.

OBJECTIVE: To assess workload-related risk factors for injuries to particular tissue types in cricket fast bowlers. DESIGN: 235 fast bowlers who bowled in 14600 player innings over a period of 15 years were followed in a prospective cohort risk factor study to compare overs bowled in each match (including preceding workload patterns) and injury risk in the 3-4 weeks subsequent to the match. Injuries were categorised according to the affected tissue type as either: bone stress, tendon injuries, muscle strain or joint injuries. Workload risk factors were examined using binomial logistic regression multivariate analysis, with a forward stepwise procedure requiring a significance of <0.05. RESULTS: High acute match workload and high previous season workload were risk factors for tendon injuries, but high medium term (3-month workload) was protective. For bone stress injuries, high medium term workload and low career workload were risk factors. For joint injuries, high previous season and career workload were risk factors. There was little relationship between muscle injury and workload although high previous season workload was slightly protective. CONCLUSIONS: The level of injury risk for some tissue types varies in response to preceding fast bowling workload, with tendon injuries most affected by workload patterns. Workload planning may need to be individualised, depending on individual susceptibility to various injury types. This study supports the theory that tendons are at lowest risk with consistent workloads and susceptible to injury with sudden upgrades in workload. Gradual upgrades are recommended, particularly at the start of a bowler's career to reduce the risk of bone stress injury.

Fast bowling match workloads over 5-26 days and risk of injury in the following month.

OBJECTIVES: This study examined whether high match fast bowling workloads in the short to medium term were associated with increased bowling injury rates. DESIGN: Prospective cohort study. METHODS: Over a 15 year period, workload patterns for 235 individual fast bowlers during time periods from 5 to 26 days were examined to consider whether there was an increased injury rate during the month (28 days) subsequent to the workload. RESULTS: Fast bowlers who bowled more than 50 match overs in a 5 day period had a significant increase in injury over the next month compared to bowlers who bowled 50 overs or less RR 1.54 (95% CI 1.04-2.29). For periods ranging from 12 to 26 days, there was no statistically-significant increase in injury over the next month from exceeding thresholds of certain amounts of overs, although bowlers who bowled more than 100 overs in 17 days had a non-significant increase in injury over the next month RR 1.78 (95% CI 0.90-3.50). CONCLUSION: There were no statistically-significant increases in subsequent injury risk for high workloads for periods of 12-26 days, although exceeding 100 overs in 17 days (or less) was associated with higher injury rates. Compression of cricket fixtures is likely to have only a minimal contribution to increased fast bowling injury rates being seen in the T20 era (along with sudden workload increases due to transferring between forms of the game, which has been previously established as a major contributor).

Spikes in acute workload are associated with increased injury risk in elite cricket fast bowlers.

OBJECTIVE: To determine if the comparison of acute and chronic workload is associated with increased injury risk in elite cricket fast bowlers. METHODS: Data were collected from 28 fast bowlers who completed a total of 43 individual seasons over a 6-year period. Workloads were estimated by summarising the total number of balls bowled per week (external workload), and by multiplying the session rating of perceived exertion by the session duration (internal workload). One-week data (acute workload), together with 4-week rolling average data (chronic workload), were calculated for external and internal workloads. The size of the acute workload in relation to the chronic workload provided either a negative or positive training-stress balance. RESULTS: A negative training-stress balance was associated with an increased risk of injury in the week after exposure, for internal workload (relative risk (RR)=2.2 (CI 1.91 to 2.53), p=0.009), and external workload (RR=2.1 (CI 1.81 to 2.44), p=0.01). Fast bowlers with an internal workload training-stress balance of greater than 200% had a RR of injury of 4.5 (CI 3.43 to 5.90, p=0.009) compared with those with a training-stress balance between 50% and 99%. Fast bowlers with an external workload training-stress balance of more than 200% had a RR of injury of 3.3 (CI 1.50 to 7.25, p=0.033) in comparison to fast bowlers with an external workload training-stress balance between 50% and 99%. CONCLUSIONS: These findings demonstrate that large increases in acute workload are associated with increased injury risk in elite cricket fast bowlers.