Modelling the relationships between volume,intensity and injury-risk in professional rugby league players

ObjectiveThis study aimed to: (a) identify the association between external-workloads and injury-risk in the subsequent week; and (b) understand the effectiveness of workload variables in establishing injury-risk.DesignRetrospective cohort study.MethodsWorkload and injury data (soft-tissue) were collected from forty-eight professional male rugby league players. Load variables included duration (min), total distance (m), relative distance (m min⁻¹), high speed distance ([m]>20 km h⁻¹), very-high speed distance ([m]>25 km h⁻¹), acceleration and deceleration efforts (count) and PlayerLoad (Arbitrary Unit: AU). Cumulative two-, three- and four-weekly loads; Acute:Chronic Workload Ratio (ACWR); Mean-Standard Deviation Workload Ratio (MSWR) and strain values were calculated and divided into three equally-sized bins (low, moderate and high). Generalised Estimating Equations analysed relationships between workload variables and injury probability in the subsequent week.ResultsInjury-risk increased alongside increases in the ACWR for duration, total distance and PlayerLoad. Conversely, injury-risk decreased (Area Under Curve: 0.569–0.585) with increases in the four-weekly duration, total distance, accelerations, decelerations and PlayerLoad. For relative distance, high four-weekly workloads (high: >60 m min⁻¹) demonstrated a positive association with injury-risk, whilst high two-weekly loads (high: >82 m min⁻¹) were negatively associated.ConclusionsA range of external workload metrics and summary statistics demonstrate either positive or negative associations with injury-risk status. Such findings provide the framework for the development of decision-support systems in which external workload metrics (e.g. total or high speed distance) can be uniquely and routinely monitored across a range of summary statistics (i.e. cumulative weekly loads and ACWR) in order to optimise player performance and welfare.     

Tackle technique of rugby union players during head impact tackles compared to injury free tackles

Objectives

The majority of head injuries in rugby union occur during tackles in which the head receives an impact. Head impacted tackles may be a result of poor tackle technique. Therefore, the purpose of this study was to analyse ball-carrier and tackler technique proficiency in head impacted tackles and compare the technique proficiency to successfully completed tackles in real-match situations.

Motor performance is not related to injury risk in growing elite-level male youth football players. A causal inference approach to injury risk assessment

ObjectiveTo identify the causal relation between growth velocity and injury in elite-level youth football players, and to assess the mediating effects of motor performance in this causal pathway.DesignProspective cohort study.MethodsWe measured the body height of 378 male elite-level football players of the U13 to U15 age categories three to four months before and at the start of the competitive season. At the start of the season, players also performed a motor performance test battery, including motor coordination (Körperkoordinationstest für Kinder), muscular performance (standing broad jump, counter movement jump), flexibility (sit and reach), and endurance measures (YoYo intermittent recovery test). Injuries were continuously registered by the academies’ medical staff during the first two months of the season. Based on the causal directed acyclic graph (DAG) that identified our assumptions about causal relations between growth velocity (standardized to cm/y), injuries, and motor performance, the causal effect of growth velocity on injury was obtained by conditioning on maturity offset. We determined the natural indirect effects of growth velocity on injury mediated through motor performance.ResultsIn total, 105 players sustained an injury. Odds ratios (OR) showed a 15% increase in injury risk per centimetre/year of growth velocity (1.15, 95%CI: 1.05–1.26). There was no causal effect of growth on injury through the motor performance mediated pathways (all ORs were close to 1.0 with narrow 95%CIs).ConclusionsGrowth velocity is causally related to injury risk in elite-level youth football players, but motor performance does not mediate this relation.     

Injury epidemiology in Australian male professional soccer

ObjectivesTo describe the injury epidemiology of the Australian male professional soccer league (A-League) over 6 consecutive seasons.DesignProspective observational cohort study.MethodsMatch-loss injury data was collected from each A-League club (n = 10) for each competition match (n = 27/season) over 6 seasons (2012/13–2017/18). Injuries were collected weekly through a standardised protocol and were classified by setting, mechanism, severity, the type and location on the body. Generalised Linear Models were used to estimate the injury incidences (injury/round/season), whilst rate ratios were reported for total injuries and within abovementioned injury classifications.ResultsOverall injury incidence was not significantly different ranging from 4.8 (95%CI:4.1–5.8) to 6.7 (95%CI:5.8–7.8) between seasons 2012/13 to 2017/18 (p > 0.05). Match injuries remained stable whilst training injuries decreased across the 6 seasons (exp(β) 0.59[95%CI:0.36–1.0]; p = 0.04). Respectively, contact and non-contact injuries were not significantly different across the 6 seasons, although non-contact injuries were more common than contact injuries (p > 0.05). Mild severity injuries decreased (exp(β) 0.64 [95%CI:0.4–0.9];p = 0.02), whilst moderate severity injuries increased (exp(β) 1.7 [95%CI:1.0–2.8];p = 0.04) in season 2017/18 compared to 2012/13. The most common injuries were at thigh (23–36%), of which the majority were hamstring injuries (54%–65%) of muscle/tendon type (50–60% of total injuries/season). Injuries remained stable across the seasons by type and location (p > 0.05 and p > 0.05, respectively).ConclusionsInjury rates, mechanisms, locations and types have remained relatively stable over recent seasons of the A-League. Current Australian professional soccer league medical practices may have contributed to the stability of injury rates.     

Association between lower extremity muscle strength and acute ankle injury in youth team-sports athletes

ObjectivesTo investigate lower extremity muscle strength as risk factor for an acute ankle injury in youth athletes.DesignCohort study.SettingBasketball and floorball clubs.Participants188 youth (≤21) male and 174 female athletes.Main outcome measures1RM leg press, maximal concentric isokinetic quadriceps and hamstrings as well as maximal isometric hip abductor strength were measured and athletes were followed for an acute ankle injury up to three years. Cox regression models were used in statistical analyses.ResultsIn males, greater 1RM leg press and maximal quadriceps strength increased the risk of any type of acute ankle injury (Hazard ratio [HR] for 1 SD increase, 1.63 [95% CI, 1.12–2.39] and 1.43 [95% CI, 1.01–2.01], respectively). In females, greater 1RM leg press and difference between legs in hip abduction strength increased the risk of acute non-contact ankle injury (HR for 1 SD increase, 1.44 [95% CI, 1.03–2.02] and 1.44 [95% CI, 1.03–2.00], respectively). However, ROC curve analyses showed AUC:s of 0.57–0.64 indicating “fail” to “poor” combined sensitivity and specifity of these tests.ConclusionGreater strength in both sexes along with asymmetry in hip abductor strength in females increased the risk of acute ankle injury.     

The effectiveness of the nationwide BokSmart rugby injury prevention program on catastrophic injury rates

Rugby Union (“rugby”) participants have a higher than average risk of injury compared with participants of other popular team sports. BokSmart, a nationwide injury prevention program was launched in South Africa in mid‐2009, with the goal of reducing catastrophic head/neck (serious) injuries in players. The program provides injury prevention information to coaches and referees. This study investigated if BokSmart has been associated with a reduction in these injuries. The BokSmart program collected data on all South African rugby‐related serious injuries since 2008. Using a Poisson regression, injury numbers were compared pre‐BokSmart (2008–2009) to the years post‐implementation (2010–2013). Player numbers were assumed to be constant throughout this evaluation: junior = 529 483; senior = 121 663. In junior players, the “post‐BokSmart” period had 2.5 less annual serious injuries than “pre‐BokSmart” (incidence rate ratio: 0.6, 95% confidence interval: 0.5–0.7, P < 0.000). In contrast, there was no significant difference in these periods in seniors. The absence of effect in seniors may be a result of fewer players or of differences in effectiveness of BokSmart in this group – future studies should investigate these questions.     

Risk of acute and overuse injuries in youth elite soccer players: Body size and growth matter

ObjectivesThis study investigated anthropometric measures and growth as risk factors for overuse and acute injuries in younger (U10–U12) and older (U13–U15) elite level soccer players.DesignProspective cohort study.MethodsHeight, weight, and sitting height were measured at the start and the end of the 2016–2017 competitive season and growth velocities were calculated. Throughout the season, injuries were registered continuously by the (para-)medical staff of the included clubs. We analyzed the injury risk using multilevel Poisson regression models, accounting for club and team clustering.ResultsOf the included 314 players (11.7 ± 1.7 years of age), 160 players sustained 133 overuse and 163 acute injuries (i.e. 106 injuries in 69 players of the younger group, 190 in 91 players of the older group). In the younger group, risk of overuse injuries was associated with an increase in leg length over the season (incidence rate ratio (IRR) 1.620 [95% CI 1.230–2.117]) and risk of acute injuries with relatively younger age (IRR 1.003 [95% CI 1.000–1.006]). In the older group, a higher leg length was associated with an increased risk of overuse injuries (IRR 1.055 [95% CI 1.011–1.108]), and a higher weight and a lower growth rate with an increased risk of acute injuries (IRR 1.043 [95% CI 1.021–1.067] and 0.903 [95% CI 0.831–0.981], respectively).ConclusionsInjury risk factors differ by age group and type of injury. The age-specific anthropometric and growth-related risk factors should be monitored and these risk profiles should be considered to manage injury risk effectively.     

Incidence of injury in junior rugby league players over four competitive seasons

While several studies have documented the incidence of injury in senior rugby league players, information on the injury rates of junior rugby league players is limited. In addition, all of the injury surveillance studies performed on junior rugby league players have been performed over a limited time frame (typically one season). The purpose of this study was to document the incidence of injury in junior rugby league players over four competitive seasons. Injury data were collected from 84 matches. An injury was defined as one that occurred in a match and resulted in the player missing a subsequent match. The overall incidence of injury was 56.8 (95% CI, 42.6–70.9) per 1000 playing hours. The majority of injuries were sustained to the shoulder (15.6 [95% CI, 8.2–23.0] per 1000 playing hours). Sprains were the most common type of injury (24.7 [95% CI, 15.4–34.1] per 1000 playing hours). Injuries were most commonly sustained while being tackled (19.2 [95% CI, 11.0–27.5] per 1000 playing hours) and while tackling (10.1 [95% CI, 4.1–16.0] per 1000 playing hours). While there was a tendency towards differing injury rates over the four competitive seasons (χ² = 6.3, d.f. = 3), the differences were not statistically significant (p = 0.10). These findings demonstrate that the incidence of junior rugby league injuries is similar to previously reported for senior competitors. A long-term collaborative effort to reduce the incidence of injury in junior rugby league players is warranted.     

Injuries according to the percentage of adult height in an elite soccer academy

ObjectivesThis study aimed to ascertain if there is a defined pattern of injury related to the percentage of attained adult height and classify injuries according to maturity status bands.DesignProspective cohort study.MethodsFrom 1998–2019, 63 elite male soccer players of at least the U12 category from a Spanish LaLiga club’s academy were followed until reaching their final height. Medical staff recorded injuries following the FIFA consensus and measured height 2–3 times per season. The percentage of adult height at which each injury occurred was calculated using the player’s closest height to the injury and his final adult height. Injuries were classified in maturity bands, pre-peak-height-velocity (PHV) <88%, circa-PHV 88%–96%, and post-PHV >96%.ResultsThere were 509 injuries among the 63 players. Growth-related injuries occurred at a median (IQR) of 91.2% (86.7%–95.2%) of adult height, predominating in pre-PHV and PHV bands. Muscle injuries predominantly occurred at post-PHV, with 77.78% of those conditions occurring within that time frame and at 98.7% (96%–99.5%) of adult height. Likewise, knee and ankle joint/ligament injuries predominated at post-PHV (87% and 65% of total cases, respectively) occurring at 99.0% (97.9%–99.9%) and 98.4% (89.2%–99.4%) of adult height, respectively.ConclusionsInjuries follow a specific pattern according to the percentage of adult height.     

Can glenohumeral joint isokinetic strength and range of movement predict injury in professional rugby league

ObjectiveTo isokinetically record shoulder strength scores and range of motion in a professional rugby league squad. To prospectively monitor injuries over a season looking for associations between measured variables and injury.DesignA cohort study design involving prospective screening of risk factors with subsequent injury surveillance.SettingUniversity Sports Science Laboratory and Professional Rugby League Club.ParticipantsAll players participating in the clubs reserve team squad for the 2011 season (n = 20).Main outcome measuresConcentric (Con) and eccentric (Ecc) peak torque values; ratio of Ecc internal rotation IR to Con external rotation ER, also known as the dynamic control ratio (DCR), shoulder range of IR and ER.ResultsEight players (36%) received a total of eleven injuries over the season. There were no statistically significant differences between injured and non-injured shoulders. IR range of movement was significantly lower in injured versus non-injured groups with left (p = 0.022) and right (p = 0.024). Left IR range of movement was predictive of injury using binary logistic regression (p = 0.046). No isokinetic strength parameters reached statistical significance (p > 0.05) for prediction of injury; however size effects were apparent for reduced con IR of the left shoulder and Ecc IR of both shoulders.ConclusionReduced shoulder IR range appears predictive of future shoulder injury although caution is drawn due to small participant numbers. Injury prevention strategies for rugby league players should include exercises to improve shoulder IR and possibly Ecc IR strength.     

Automatic detection of one-on-one tackles and ruck events using microtechnology in rugby union

ObjectivesTo automate the detection of ruck and tackle events in rugby union using a specifically-designed algorithm based on microsensor data.DesignCross-sectional study.MethodsElite rugby union players wore microtechnology devices (Catapult, S5) during match-play. Ruck (n = 125) and tackle (n = 125) event data was synchronised with video footage compiled from international rugby union match-play ruck and tackle events. A specifically-designed algorithm to detect ruck and tackle events was developed using a random forest classification model. This algorithm was then validated using 8 additional international match-play datasets and video footage, with each ruck and tackle manually coded and verified if the event was correctly identified by the algorithm.ResultsThe classification algorithm’s results indicated that all rucks and tackles were correctly identified during match-play when 79.4 ± 9.2% and 81.0 ± 9.3% of the random forest decision trees agreed with the video-based determination of these events. Sub-group analyses of backs and forwards yielded similar optimal confidence percentages of 79.7% and 79.1% respectively for rucks. Sub-analysis revealed backs (85.3 ± 7.2%) produced a higher algorithm cut-off for tackles than forwards (77.7 ± 12.2%).ConclusionsThe specifically-designed algorithm was able to detect rucks and tackles for all positions involved. For optimal results, it is recommended that practitioners use the recommended cut-off (80%) to limit false positives for match-play and training. Although this algorithm provides an improved insight into the number and type of collisions in which rugby players engage, this algorithm does not provide impact forces of these events.     

Sport specialization and sport participation opportunities and their association with injury history in female high school volleyball athletes

ObjectiveDetermine the association of sport specialization in female volleyball athletes with previous injury history and determine the association of sport specialization with volleyball participation opportunities.DesignCross-sectional.SettingRecruitment occurred from 83 Wisconsin high schools during the 2018 volleyball season.ParticipantsFemale volleyball athletes (N = 1,588, grades 9–12, age = 15.6 ± 1.1 years).Main outcomesParticipants completed a pre-season questionnaire soliciting information regarding 1) demographics, 2) sport specialization, 3) sport participation, and 4) sport-related injuries in the previous 12 months. Univariable logistic regression models were used to identify associations with previous injury. Chi-square analyses were used to investigate associations between sport specialization classification and other sport participation opportunities.ResultsBoth moderately and highly specialized athletes were more likely to report a previous injury compared to low specialized athletes (moderate OR: 1.84 [1.29–2.62]; p < 0.001 and high OR: 2.30 [1.64–3.24]; p < 0.001). Highly specialized athletes were more likely to report participating in club volleyball, summer tournaments, and training camps in the past 12 months. Participants who reported participating in club volleyball, summer competitions, and training camps last year were more likely to report an injury.ConclusionsSpecialization was associated with injury history and year-round volleyball opportunities among female adolescent volleyball athletes.     

Non-sanctioning of illegal tackles in South African youth community rugby

Objectives

The tackle event in rugby union (‘rugby’) contributes to the majority of players’ injuries. Referees can reduce this risk by sanctioning dangerous tackles. A study in elite adult rugby suggests that referees only sanction a minority of illegal tackles. The aim of this study was to assess if this finding was similar in youth community rugby.

Mechanisms of traumatic injury to the shoulder girdle in the Australian Football League

ObjectiveTo investigate mechanisms of shoulder girdle injuries and their impact on players from the Australian Football League (AFL).DesignRetrospective video analysis.MethodsTwo experienced sports physiotherapists (>10 years) examined video footage of shoulder complex injuries that occurred in the 2015 premiership season. Information obtained from video footage included activity prior to injury; mechanism of injury; arm, head and neck position and point of body contact at the time of injury. Player demographics and injury characteristics were obtained from club and media data.ResultsThe most common mechanism of injury was lateral contact (34.6%) followed by hyperflexion/ abduction of the shoulder (19.2%). Glenohumeral joint (GHJ) dislocations and subluxations were the most frequent diagnosis for all mechanisms of injury, and occurred in a variety of shoulder positions. Over 80% of injuries occurred with the arm below 100° of shoulder flexion or abduction. The most common activity prior to injury was ‘ball in dispute’ (34.6%). Lateral contact injuries had the highest overall severity (two-thirds of players missed >3 games) and over 50% of shoulder injuries required surgery. Players missed on average 5.1 season games due to shoulder injury.ConclusionThe lateral contact mechanism was the most common and severe mechanism of shoulder injury. Improved understanding of shoulder girdle injury mechanisms can help guide the use of preventative strategies and injury management programs in elite AFL players.     

Effect of an integrated functional stability program on injury rates in an international netball squad

The cost-effectiveness and efficacy of athlete profiling and injury prevention programs is influenced by procedural specificity, philosophy of athlete development within the sporting body and the dynamics within the multidisciplinary team (MDT). This article reports on the implementation of a multidisciplinary approach to injury reduction and performance development in an international netball squad. Problems with player compliance, training anxiety and injury rates sparked a decision to seek an alternative training approach. A reactive sports medicine system, poor player self-responsibility and inadequate player understanding of the anatomy and biomechanics of sound training, inadequate screening procedures and perceived conflict between sports science and sports medicine personnel were identified as causative factors. A new program was designed where common objectives were identified, and individual roles delineated. A functional profiling session was performed as a team activity and comprised player self-evaluation and netball specific movement analysis. Mechanisms of injury, training anxieties and modification of the overall program to ensure continued progression rather than a false plateau were illustrated through this process. From the above findings a strategy was outlined and comprised a foundation programme, a transitional phase, specific prophylactic programs, and sport specific sessions. A consistent approach was formulated across all disciplines in order to maximise transference of the new training program (TP). Training compliance was increased and interdisciplinary conflict prevented when dealing with different levels of training tolerance. Rate of injury in all vulnerable areas was markedly reduced. No training or overuse related injuries were sustained. Addressing fundamental functional problems and working openly and cooperatively towards a common goal, the members of the MDT were able to prevent injury, make significant gains in physiological performance and improve players' confidence and commitment to training over the defined period.     

Current injury monitoring and player education practices in Irish amateur rugby union

ObjectivesTo ascertain current injury surveillance and player education practices in Irish amateur rugby union.DesignCross-sectional survey.SettingAmateur rugby clubs in Ireland.ParticipantsMedical professionals and rugby coaches of the top 58 amateur rugby clubs in Ireland.Main outcome measuresThe survey investigated the current injury and training load monitoring practices in operation in Irish amateur rugby. It also explored whether player education sessions regarding injury prevention and concussion recognition and management were conducted in these clubs.ResultsForty-four clubs completed the survey, giving an overall response rate of 76%. Ninety-one percent of the responding clubs monitored injuries. Sixty-four percent of these clubs operated return to play protocols for all injuries, while 36% operated return to play protocols for concussion only. Injury prevention education was conducted by 71% of these clubs and 82% educated players on concussion recognition and management.ConclusionsImplementing effective injury monitoring strategies in both amateur and professional sport settings may aid in minimizing injury risk. In Ireland, 91% of the responding clubs monitored injuries and 71% educated players on injury prevention. By implementing one centralized injury surveillance system for Irish amateur rugby, injury trends can be effectively monitored and used to guide prevention strategies.     

The relationship between physical capacity and match performance in elite Australian football: A mediation approach

The aim of this study was to verify if yo-yo intermittent recovery test (level 2) (yo-yo IR2) score is linked to Australian football (AF) performance through match exercise intensity. Six week prospective study design. Twenty-one data sets were recorded from nine individual players that completed the yo-yo IR2, and played an Australian Football League match in the first five rounds of the 2010 season wearing a global positioning system (GPS) unit. Simple mediation modelling was used to analyse the inter-relationship between yo-yo IR2 score, match exercise intensity and AF performance. Playing position and experience were also incorporated into the model to identify conditional affects. A significant direct relationship was observed between yo-yo IR2 and number of ball disposals (p < 0.1) and a significant indirect relationship was observed between yo-yo IR2 and number of ball disposals through distance travelled at high intensity (HIR m min⁻¹) (p < 0.1). Moderation analysis showed that playing position affected the relationship between of yo-yo IR2 and HIR m min⁻¹ (p < 0.1) and HIR m min⁻¹ and total ball disposals (p < 0.1). Playing experience also significantly affected the relationship between HIR m min⁻¹ and total ball disposals. This study is the first to identify the effects of yo-yo IR2 on total ball disposals through HIR m min⁻¹ performed during AF matches, and that playing position and playing experience affect these interactions.     

The financial and performance cost of injuries to teams in Australian professional soccer

ObjectivesTo determine the relationship between injury incidence, player-salary cost and team performance in the professional Australian soccer league.DesignProspective observational cohort study.MethodsInjury incidence, player-salary cost and team performance data were collected from the 10-club A-League competition (n = 27 matches/season) over 6 seasons from 2012/13. Player-salary cost of injury was calculated from the salary cap, injury-induced missed matches and player exposure, and trends were reported from Poisson regressions. Team performance was determined from ranking, points, goals (scored, conceded and difference) and match outcome (win, loss or draw) per season and analysed via a mixed-effects Poisson models to estimate association with injury.ResultsNine-hundred-and-sixteen injuries resulted in 3148 missed matches. Injury incidence remained stable apart from a decrease in 2015/16 (p = 0.01). Missed matches were significantly higher in season 2013/14 (55.1 [50.7–59.9]; p < 0.01) and 2014/15 (71.4 [66.4–76.8]; p < 0.001) compared to 2012/13, without differences between other seasons. Player-salary cost ranged between AUD$187,990–AUD$332,680/team, peaking in 2014/15 (p < 0.01). Multi-collinearity was detected for team performance variables except for matches lost. Teams who finished the season with greater positive goal differences were associated with 1% less injuries (p = 0.003). Similarly, more missed matches were associated with 1% less league points and losses (p < 0.001).ConclusionsPlayer-salary costs remained stable, concomitant with stable injury rates and missed matches. Despite injury being associated with goals difference, points and match losses; the magnitude of these relationships are small and team performance is more complex than injury occurrence alone. Injury prevention remains necessary for reducing injury-induced player-salary costs; however, additional services are required to improve team performance.     

A survey of injury knowledge and technical needs of junior Rugby Union coaches in Townsville (North Queensland)

Data of the injury knowledge and technical needs of registered coaches of junior Rugby Union teams in the Townsville district junior Rugby Union (North Queensland) were collected via a questionnaire mailed to coaches to determine the knowledge of the management, risk and protective factors of injury. A total of 35 completed self-administered questionnaires were returned in March 2003 for a response rate of 100%. Half of all coaches (54%, n=18) identified the upper limb of the tackler as the body part most likely to be injured in a tackle and one-quarter (26%, n=9) identified the lower limb of the ball carrier. Half (46%, n=16) of coaches identified rest/ice/compression/elevation as the treatment for soft tissue injury. The total injury knowledge score increased with the total number of seasons coached (Spearman's r(s)=0.401, p=0.017). Coaches with a current first aid qualification were more likely to identify rest/ice/compression/elevation as the treatment for soft tissue injury (Fishers Exact test, p=0.002). The results of this survey demonstrate that coaches of junior Rugby Union teams require education of the mechanisms of injury and procedures for the early management of minor and soft tissue in Rugby Union coaching courses.