Complex systems approach for sports injuries: moving from risk factor identification to injury pattern recognition-narrative review and new concept.

Injury prediction is one of the most challenging issues in sports and a key component for injury prevention. Sports injuries aetiology investigations have assumed a reductionist view in which a phenomenon has been simplified into units and analysed as the sum of its basic parts and causality has been seen in a linear and unidirectional way. This reductionist approach relies on correlation and regression analyses and, despite the vast effort to predict sports injuries, it has been limited in its ability to successfully identify predictive factors. The majority of human health conditions are complex. In this sense, the multifactorial complex nature of sports injuries arises not from the linear interaction between isolated and predictive factors, but from the complex interaction among a web of determinants. Thus, the aim of this conceptual paper was to propose a complex system model for sports injuries and to demonstrate how the implementation of complex system thinking may allow us to better address the complex nature of the sports injuries aetiology. According to this model, we should identify features that are hallmarks of complex systems, such as the pattern of relationships (interactions) among determinants, the regularities (profiles) that simultaneously characterise and constrain the phenomenon and the emerging pattern that arises from the complex web of determinants. In sports practice, this emerging pattern may be related to injury occurrence or adaptation. This novel view of preventive intervention relies on the identification of regularities or risk profile, moving from risk factors to risk pattern recognition.

Examining the effect of the injury definition on risk factor analysis in circus artists.

A secondary data analysis of a prospective cohort study was conducted to explore how different definitions of injury affect the results of risk factor analyses. Modern circus artists (n=1281) were followed for 828,547 performances over a period of 49 months (2004-2008). A univariate risk factor analysis (age, sex, nationality, artist role) estimating incidence rate ratios (IRR) with 95% confidence intervals (95% CI) was conducted using three injury definitions: (1) medical attention injuries, (2) time-loss injuries resulting in ≥1 missed performances (TL-1) and (3) time-loss injuries resulting in >15 missed performances (TL-15). Results of the risk factor analysis were dependent on the injury definition. Sex (females to male; IRR=1.13, 95% CI; 1.02-1.25) and age over 30 (<20 years to >30 years; IRR=1.37, 95% CI; 1.07-1.79) were risk factors for medical attention injuries only. Risk of injury for Europeans compared with North Americans was higher for TL-1 and TL-15 injuries compared with medical attention injuries. Finally, non-sudden load artists (low-impact acts) were less likely than sudden load artists (high-impact acts) to have TL-1 injuries, but the risk of medical attention injuries was similar. The choice of injury definition can have effects on the magnitude and direction of risk factor analyses.

The effectiveness of a neuromuscular prevention strategy to reduce injuries in youth soccer: a cluster-randomised controlled trial.

BACKGROUND: Soccer is a leading sport for participation and injury in youth. OBJECTIVE: To examine the effectiveness of a neuromuscular prevention strategy in reducing injury in youth soccer players. DESIGN: Cluster-randomised controlled trial. SETTING: Calgary soccer clubs (male or female, U13-U18, tier 1-2, indoor soccer). PARTICIPANTS: Eighty-two soccer teams were approached for recruitment. Players from 60 teams completed the study (32 training (n=380), 28 control (n=364)). INTERVENTION: The training programme was a soccer-specific neuromuscular training programme including dynamic stretching, eccentric strength, agility, jumping and balance (including a home-based balance training programme using a wobble board). The control programme was a standardised warm-up (static and dynamic stretching and aerobic components) and a home-based stretching programme. MAIN OUTCOME MEASURES: Previously validated injury surveillance included injury assessment by a study therapist. The injury definition was soccer injury resulting in medical attention and/or removal from a session and/or time loss. RESULTS: The injury rate in the training group was 2.08 injuries/1000 player-hours, and in the control group 3.35 injuries/1000 player-hours. Based on Poisson regression analysis, adjusted for clustering by team and covariates, the incidence rate ratios (IRR) for all injuries and acute onset injury were 0.62 (95% CI 0.39 to 0.99) and 0.57 (95% CI 0.35 to 0.91). Point estimates also suggest protection of lower extremity, ankle and knee sprain injuries (IRR=0.68 (95% CI 0.42 to 1.11), IRR=0.5 (95% CI 0.24 to 1.04) and IRR=0.38 (95% CI 0.08 to 1.75)). CONCLUSIONS: A neuromuscular training programme is protective of all injuries and acute onset injury in youth soccer players.

Is protective equipment useful in preventing concussion? A systematic review of the literature.

OBJECTIVE: To determine if there is evidence that equipment use reduces sport concussion risk and/or severity. DATA SOURCES: 12 electronic databases were searched using a combination of Medical Subject Headings and text words to identify relevant articles. REVIEW METHODS: Specific inclusion and exclusion criteria were used to select studies for review. Data extracted included design, study population, exposure/outcome measures and results. The quality of evidence was assessed based on epidemiologic criteria regarding internal and external validity (ie, strength of design, sample size/power calculation, selection bias, misclassification bias, control of potential confounding and effect modification). RESULTS: In total, 51 studies were selected for review. A comparison between studies was difficult due to the variability in research designs, definition of concussion, mouthguard/helmet/headgear/face shield types, measurements used to assess exposure and outcomes, and variety of sports assessed. The majority of studies were observational, with 23 analytical epidemiologic designs related to the subject area. Selection bias was a concern in the reviewed studies, as was the lack of measurement and control for potentially confounding variables. CONCLUSIONS: There is evidence that helmet use reduces head injury risk in skiing, snowboarding and bicycling, but the effect on concussion risk is inconclusive. No strong evidence exists for the use of mouthguards or face shields to reduce concussion risk. Evidence is provided to suggest that full facial protection in ice hockey may reduce concussion severity, as measured by time loss from competition.

Sport concussion assessment tool: baseline values for varsity collision sport athletes.

OBJECTIVE: To determine baseline symptom and neurocognitive norms for non-concussed and previously concussed varsity athletes using the sport concussion assessment tool (SCAT). STUDY DESIGN: Descriptive cohort study. SETTING: University of Calgary. SUBJECTS: 260 male and female university football, ice hockey and wrestling athletes over three seasons (2005-7). METHODS: A baseline SCAT was completed during preseason medical evaluation. Subjects were grouped as follows: all participants, men, women, never concussed (NC) and previously concussed (PC). MAIN RESULTS: The mean age of participants was 20.5 years (range 17-32). In total, 41.2% of all athletes had a total post-concussion symptom scale (PCSS) score of 0. The mean baseline PCSS scores were as follows: all participants 4.29; men 3.52; women 6.39; NC 3.75 and PC 5.25. The five most frequently reported symptoms for all athletes were fatigue/low energy (37% of subjects), drowsiness (23%), neck pain (20%), difficulty concentrating (18%) and difficulty remembering (18%). The median immediate recall score was 5/5 for all groups. Women scored a median of 5/5 on delayed recall, whereas all remaining groups scored a median of 4/5. Months in reverse order were successfully completed by 91.6% of subjects. All participants, women and PC scored a median of 6 on reverse digits, whereas men and NC scored a median of 5. CONCLUSIONS: The mean SCAT baseline PCSS score was approximately 5, although just under half of the athletes scored 0. Female athletes scored better on tests of neurocognitive function. PC athletes scored better than NC athletes on all neurocognitive tests except delayed five-word recall.

Consensus statement on injury definitions and data collection procedures in studies of football (soccer) injuries.

Variations in definitions and methodologies have created differences in the results and conclusions obtained from studies of football (soccer) injuries, making interstudy comparisons difficult. Therefore an Injury Consensus Group was established under the auspices of Fédération Internationale de Football Association Medical Assessment and Research Centre. A nominal group consensus model approach was used. A working document on definitions, methodology, and implementation was discussed by the group. Iterative draft statements were prepared and circulated to members of the group for comment before the final consensus statement was produced. Definitions of injury, recurrent injury, severity, and training and match exposures in football together with criteria for classifying injuries in terms of location, type, diagnosis, and causation are proposed. Proforma for recording players' baseline information, injuries, and training and match exposures are presented. Recommendations are made on how the incidence of match and training injuries should be reported and a checklist of issues and information that should be included in published reports of studies of football injuries is presented.

Athletic injury reporting. Development of universal systems.

There are numerous athletic injury reporting systems currently in place. In order for our understanding of athletic injury epidemiology to advance, we must be able to compare data from divergent sources. This paper provides a review of existing athletic injury reporting systems in North America. The epidemiological designs employed in these systems are outlined, along with a description of the strengths and weaknesses of each approach to reporting. The differences between the case-series and cohort methods are delineated and the importance of injury definition, sources of error, denominator data and exposure estimation are discussed within this context. Four recommendations are then offered to assist in moving toward more universal systems for athletic injury reporting. First, comparability of data between systems should be maximised through clear indication of the reporting system design and the methods of data collection. Secondly, an exact definition should be given as to what constitutes a reportable event ('injury'). Thirdly, whenever possible, outcome information should be collected on each reported event so that an injury definition may be applied at the time of data analysis. Lastly, any limitations or sources of error should be acknowledged.

Injuries in cross-country skiing: a critical appraisal of the literature.

This study comprehensively reviews and critically appraises recent literature on cross-country skiing injuries. Particular attention was paid to the study design when reviewing the literature, thereby producing a measure of internal and external validity. From these data, the factors associated with the aetiology, frequency, site distribution and types of cross-country skiing injuries are examined. The incidence of injury in cross-country skiing is estimated to be between 0.49 and 5.63 per 1000 skier days. The most common injuries are medial collateral ligament sprains of the knee, and ulnar collateral ligament sprains of the thumb. Overuse and cold injuries (e.g. hypothermia and frostbite) appear to be common as well, although the data do not provide an estimate of incidence. Comments in the literature on prevention of these injuries are mainly empirical: they recommend safer equipment, wise choice of terrain and a general increase in skier awareness of ways to prevent injury. However, rigorous studies that adequately evaluate preventive intervention strategies have yet to be conducted. Cross-country skiing is relatively safe and a suitable activity for physical fitness and rehabilitation. In the future, studies employing an analytical design will be required to evaluate the effectiveness of injury prevention intervention strategies.

Risk factors for groin injuries in hockey.

PURPOSE: The objective of this cohort study was to determine the level of off-season sport specific activity, peak isometric adductor torque, and hip abduction flexibility that are predictive of groin or abdominal strain injury in the National Hockey League (NHL). METHODS: The subjects were 1292 consenting NHL players. Estimated relative risks of injury are reported using the following exposures: 1) level of sport specific training in the off-season, 2) peak isometric adductor torque, 3) total hip abduction flexibility, 4) previous injury, 5) years of NHL experience, and 6) skate blade hollow measurement. Estimates of probability of injury are predicted for various levels of exposures on the basis of logistic regression analysis. RESULTS: During training camp, players who reported less than 18 sessions sport specific training in the off-season were at greater than three times the risk of injury than those who did not (relative risk (RR); 3.38 95% confidence interval (CI), 1.45-7.92). Players who reported previous history of this injury were at more than two times the risk of injury than those who did not (RR, 2.88; 95% CI, 1.33-6.26). Veterans were at greater than five times the risk of injury than rookies (RR, 5.69; 95% CI, 2.05-15.85). Peak isometric adductor torque, total abduction flexibility, and skate blade hollow measurement were not predictive of injury. There is evidence of a dose-response gradient as predicted probability of injury decreases with increasing levels of sport specific training. In the regular season, sport specific training was not as strong a risk factor (RR, 2.32; 95% CI, 1.0-5.39). CONCLUSION: Low levels of off-season sport specific training and previous injury are clearly risks for groin injury at an elite level of hockey. Future research is required to investigate prevention strategies for this injury in hockey.

The effect of salbutamol on performance in elite nonasthmatic athletes.

The effect of salbutamol on performance was studied in seven male nonasthmatic highly trained (VO2max > or = 60 ml.kg-1 x min-1) cyclists. Salbutamol (S = 2 puffs = 200 micrograms) or placebo (P) was administered by metered-dose inhaler, through a spacer device, 20 min prior to testing in a double-blind, randomized cross-over design. Testing sessions on a cycle ergometer included the measurement of maximal oxygen uptake (VO2max), peak power, maximal heart rate, and pulmonary function. A timed sprint to exhaustion was performed after 45 min of exercise at 70% of VO2max, and a Wingate anaerobic test was used to measure total work and peak power. There was a nonsignificant decrease in VO2max (P = 63.5 +/- 3.2; S = 62.6 +/- 3.3 ml.kg-1 x min-1). No difference was found in peak power, maximum heart rate, endurance sprint time, Wingate peak power, or total work. After an anticipated baseline increase was taken into account, the pattern of change in FEV1 over time did not differ between salbutamol and placebo. It was concluded that a therapeutic dose of aerosol salbutamol does not have an ergogenic effect in elite nonasthmatic athletes, and it is therefore recommended that inhaled salbutamol continue to be permitted in international competition for individuals with exercise induced bronchospasm.

The distribution of injuries in men's Canada West university football. A 5-year analysis.

We conducted a prospective cohort study from 1993 to 1997 to determine the frequency and severity of injury in men's Canada West university football. The Canadian Intercollegiate Sport Injury Registry was used to document baseline preseason data, daily athlete participation, and subsequent injury from five varsity football teams. An injury was defined as "any injury resulting in one or more complete or partial sessions of time loss" or "any concussion or transient neck neurologic injury." The annual proportion of injured athletes ranged from 53.5% to 60.4%, with a 5-year total of 1,811 injuries. Regression analysis indicated that the rate of nonconcussion, nonneck neurologic injuries increased. Concussion (N = 110), hamstring strain (N = 88), and brachial plexus (N = 84) injuries were the most common, specific injury diagnoses. Knee injuries resulted in the highest rate of severe (greater than or equal to 7 sessions of time loss) injury and resulted in the most time loss (3,350.5 sessions). Ligament sprains and muscle strains and spasms accounted for approximately half of all injury diagnoses. A total of 1,173 injuries (65%) were related to contact between players or between players and other obstacles. Future studies should be conducted to identify risk factors for the ultimate purpose of implementing injury prevention strategies.

Relation between running injury and static lower limb alignment in recreational runners.

OBJECTIVES: To determine if measurements of static lower limb alignment are related to lower limb injury in recreational runners. METHODS: Static lower limb alignment was prospectively measured in 87 recreational runners. They were observed for the following six months for any running related musculoskeletal injuries of the lower limb. Injuries were defined according to six types: R1, R2, and R3 injuries caused a reduction in running mileage for one day, two to seven days, or more than seven days respectively; S1, S2, and S3 injuries caused stoppage of running for one day, two to seven days, or more than seven days respectively. RESULTS: At least one lower limb injury was suffered by 79% of the runners during the observation period. When the data for all runners were pooled, 95% confidence intervals calculated for the differences in the measurements of lower limb alignment between the injured and non-injured runners suggested that there were no differences. However, when only runners diagnosed with patellofemoral pain syndrome (n = 6) were compared with non-injured runners, differences were found in right ankle dorsiflexion (0.3 to 6.1), right knee genu varum (-0.9 to -0.3), and left forefoot varus (-0.5 to -0.4). CONCLUSIONS: In recreational runners, there is no evidence that static biomechanical alignment measurements of the lower limbs are related to lower limb injury except patellofemoral pain syndrome. However, the effect of static lower limb alignment may be injury specific.

Lumbosacral dysfunctions in elite cross-country skiers.

While the incidence of injury in cross-country skiing remains relatively low, overuse problems affecting the lumbosacral region may be on the rise, particularly among elite athletes. In this study, a certified "Part A" (Canadian Physiotherapy Association) manual therapist performed lumbosacral physical assessments on 18 elite cross-country skiers and 15 normal subjects. Results indicated sacroiliac (SI) joint dysfunction occurred significantly more often in the skier population (p < 0.007). Incidences of SI joint asymmetry and lumbar spine dysfunction did not differ between groups. The predominant use of asymmetrical ski-skating techniques may play an influential role in the pathogenesis of SI joint dysfunction in elite cross-country skiers.

Consensus statement on injury definitions and data collection procedures for studies of injuries in rugby union.

Wide variations in the definitions and methodologies used for studies of injuries in rugby union have created inconsistencies in reported data and made interstudy comparisons of results difficult. The International Rugby Board established a Rugby Injury Consensus Group (RICG) to agree on appropriate definitions and methodologies to standardize the recording of injuries and reporting of studies in rugby union. The RICG reviewed the consensus definitions and methodologies previously published for football (soccer) at a meeting in Dublin to assess their suitability for and application to rugby union. Following this meeting, iterative draft statements were prepared and circulated to members of the RICG for comment; a follow-up meeting was arranged in Dublin at which time all definitions and procedures were finalized. At this stage, all authors confirmed their agreement with the consensus statement. The agreed-on document was presented to and approved by the International Rugby Board Council. Agreement was reached on definitions for injury, recurrent injury, nonfatal catastrophic injury, and training and match exposures together with criteria for classifying injuries in terms of severity, location, type, diagnosis, and causation. The definitions and methodology presented in this consensus statement for rugby union are similar to those proposed for football. Adoption of the proposals presented in this consensus statement should ensure that more consistent and comparable results will be obtained from studies of injuries within rugby union.

Consensus statement on injury definitions and data collection procedures in studies of football (soccer) injuries.

Variations in definitions and methodologies have created differences in the results and conclusions obtained from studies of football injuries; this has made inter-study comparisons difficult. An Injury Consensus Group was established under the auspices of FIFA Medical Assessment and Research Centre. Using a nominal group consensus model approach, a working document that identified the key issues related to definitions, methodology and implementation was discussed by members of the group during a 2-day meeting. Following this meeting, iterative draft statements were prepared and circulated to members of the group for comment before the final consensus statement was produced. Definitions of injury, recurrent injury, severity and training and match exposures in football together with criteria for classifying injuries in terms of location, type, diagnosis and causation are proposed. Proforma for recording players' baseline information, injuries and training and match exposures are presented. Recommendations are made on how the incidence of match and training injuries should be reported and a checklist of issues and information that should be included in published reports of studies of football injuries is presented. The definitions and methodology proposed in the consensus statement will ensure that consistent and comparable results will be obtained from studies of football injuries.

Frequency and predictability of sports injuries in intercollegiate athletes.

This study analyzes injury frequency and predictability in 712 intercollegiate athletes in 24 different male and female sports over the 1984-85 season. The injury rate was 38% for males and 32% for females, with the males suffering more acute injuries. While the men's hockey team had the highest player injury rate, the football team had the greatest absolute number of injuries. Overall, the anatomic location with the highest injury rate was the knee, while sprains were the most common type of injury. Further elaboration of these results are provided in graphic form. By comparing injury occurrence to past history and preparticipation physical findings, this study assesses the predictability of injury. With one exception, no significant relationship was found. It would appear that the preseason exam may play a role in identification, rather than prediction of sports injuries.

Exercise counselling by family physicians in Canada.

BACKGROUND: Exercise counselling is not frequently conducted by family physicians in several countries. Little is known about the exercise counselling practices of family physicians in Canada. The objective of this study was to assess physician confidence, current versus desired practice, and barriers related to the counselling of exercise by family physicians in Canada. METHODS: The study was a cross-sectional survey that included a random selection of family physicians in six provinces. A total of 330 family physicians completed the questionnaire, resulting in a response rate of 61.1%. A family physician was defined as a physician who practices family medicine at least 75% of their practice time. RESULTS: A total of 58.2% believed only 0-25% of their patients would respond to their counselling and 42.4% felt "moderately knowledgeable" to exercise counsel. Only 11.8% counselled 76-100% of their patients about exercise, but 43.3% thought they should be counselling 76-100% of their patients. Barriers to exercise counselling that rated most important included lack of time (65.7%) and lack of exercise education in medical school (64.8%). CONCLUSIONS: Family physicians indicated their current level of exercise counselling is suboptimal and confidence levels in exercise counselling were not high. Future educational opportunities for physicians may assist in improving exercise counselling.

Development, implementation, and validation of the Canadian Intercollegiate Sport Injury Registry.

PURPOSE: To outline the development and implementation of the Canadian Intercollegiate Sport Injury Registry (CISIR), to examine its validity, including the data collection forms, the recording of athlete exposure, and the mechanism of injury, and to determine the ability of the CISIR to meet its stated objectives of assessing rates and risk of injury. DESIGN: Prospective cohort study. SETTING: Canadian intercollegiate athletics. SUBJECTS: 344 varsity football players from five western Canadian universities. ASSESSMENT OF RISK FACTORS AND OUTCOME MEASURES: Three data collection instruments were developed to capture the principle types of information forming the cornerstones of the CISIR: a medical form for preseason assessment of risk factors, a weekly exposure sheet (WES) for the documentation of daily individual athlete participation, and an individual injury report form (IIRF) for collection of injury-related information. Design and implementation input was provided by therapists and physicians through initial meetings, pilot testing, site visits, questionnaire, and final consensus meeting. The completeness of injury reporting was assessed through cross-referencing with participation time loss data. An item analysis was conducted on the principal elements of the IIRF. The categorization of participation itself was also examined, as was the diagnostic agreement between the therapists and physicians involved in data collection. The recorded mechanism of injury was compared with that noted through a video analysis for game-related injuries. Lastly, a test analysis was conducted to extract data and compute rates and risks of injury. RESULTS: This developmental phase was successful, with 99.7% subject enrollment, high therapist satisfaction, and good flow of data. A relational database, incorporating dual-entry data verification, was designed and functioned well. The collection process revealed that 100% of the WESs were submitted, and the data therein was 99.7% complete. The injuries resulting in participation time loss were recorded on an IIRF 97.9% of the time. The exposure (participation) codes were thought to be overly precise, and a simplification of these categories is suggested. The diagnostic agreement between physicians and therapists was 70%. It was possible to validate game exposures, but no standard was identified to permit validation of the categories of exposure. Likewise, the mechanism of injury as recorded by the therapists was thought to be more precise than the video analysis. After two modifications in the table structure of the relational database, it was possible to extract data relating to rates and risks of injury. CONCLUSIONS: This study demonstrated a high degree of validity for many elements of the CISIR. One limitation was that no reference standard existed for some components, limiting some aspects of validity assessment. With the suggested revisions, the CISIR represents the current standard in athletic injury reporting in terms of individual injury risk assessment. This system will be used in the future to explore the prediction and prevention of sport injuries.

Test-retest reliabilty of isokinetic hip adductor and flexor muscle strength.

OBJECTIVE: To determine the test-retest reliability of eccentric hip flexor and adductor peak torque and endurance using a Cybex Norm isokinetic dynamometer and to evaluate muscle soreness after exercise as a result of the testing procedure. DESIGN: Prospective test-retest reliability study. PARTICIPANTS: A total of 19 male volunteers (21-43 years old). INTERVENTION: Tests included hip flexor and adductor peak torque strength measured at 60 degrees/s (concentric and eccentric) and endurance measurements (total work done over 20 continuous concentric/eccentric contractions at 150 degrees/s). Subjects were tested on three occasions at 1-week intervals. MAIN OUTCOME MEASURES: Repeated measures analysis of variance was performed for all dependent variables including the subject's dominant and nondominant side among the three test sessions. Intraclass correlation coefficients (ICCs) were calculated to compare the data between sessions. In addition, simple linear regression analysis was completed to determine the relationship between session measurements for all measures with ICC > 0.75. RESULTS: The main findings of this study are that eccentric peak hip adductor torque was reliably measured on a Cybex Norm isokinetic dynamometer using a continuous eccentric/ concentric cycle protocol at a speed of 60 degrees/s (ICC > 0.84). Peak concentric adductor torque and peak eccentric and concentric hip flexor torque were less reliable using the same protocol (ICC < 0.67). Endurance measurements, using total work done over 20 repetitions, were not reliable for hip flexor and adductor muscle groups using a continuous eccentric/concentric cycle protocol at a speed of 150 degrees/s (ICC < 0.55). Posttest muscle soreness was found to be of significant concern with such a protocol. CONCLUSION: The results from this test-retest reliability study confirm the reliability of eccentric peak hip adductor torque measurements for use clinically and in future research. In addition, the need to assess posttest muscle soreness after isokinetic muscle testing is confirmed.