Using Presurgical Biopsychosocial Features to Develop an Advanced Clinical Decision-Making Support Tool for Predicting Recovery Trajectories in Patients Undergoing Total Knee Arthroplasty: Protocol for a Prospective Observational Study.

BACKGROUND: Following total knee arthroplasty (TKA), 10% to 20% of patients report dissatisfaction with procedural outcomes. There is growing recognition that postsurgical satisfaction is shaped not only by the quality of surgery but also by psychological and social factors. Surprisingly, information on the psychological and social determinants of surgical outcomes is rarely collected before surgery. A comprehensive collection of biopsychosocial information could assist clinicians in making recommendations in relation to rehabilitation, particularly if there is robust evidence to support the ability of presurgical constructs to predict postsurgical outcomes. Clinical decision support tools can help identify factors influencing patient outcomes and support the provision of interventions or services that can be tailored to meet individuals' needs. However, despite their potential clinical benefit, the application of such tools remains limited. OBJECTIVE: This study aims to develop a clinical decision tool that will assist with patient stratification and more precisely targeted clinical decision-making regarding prehabilitation and rehabilitation for TKA, based on the identified individual biopsychosocial needs. METHODS: In this prospective observational study, all participants provided written or electronic consent before study commencement. Patient-completed questionnaires captured information related to a broad range of biopsychosocial parameters during the month preceding TKA. These included demographic factors (sex, age, and rurality), psychological factors (mood status, pain catastrophizing, resilience, and committed action), quality of life, social support, lifestyle factors, and knee symptoms. Physical measures assessing mobility, balance, and functional lower body strength were performed via video calls with patients in their home. Information related to preexisting health issues and concomitant medications was derived from hospital medical records. Patient recovery outcomes were assessed 3 months after the surgical procedure and included quality of life, patient-reported knee symptoms, satisfaction with the surgical procedure, and mood status. Machine learning data analysis techniques will be applied to determine which presurgery parameters have the strongest power for predicting patient recovery following total knee replacement. On the basis of these analyses, a predictive model will be developed. Predictive models will undergo internal validation, and Bayesian analysis will be applied to provide additional metrics regarding prediction accuracy. RESULTS: Patient recruitment and data collection commenced in November 2019 and was completed in June 2022. A total of 1050 patients who underwent TKA were enrolled in this study. CONCLUSIONS: Our findings will facilitate the development of the first comprehensive biopsychosocial prediction tool, which has the potential to objectively predict a patient's individual recovery outcomes following TKA once selected by an orthopedic surgeon to undergo TKA. If successful, the tool could also inform the evolution rehabilitation services, such that factors in addition to physical performance can be addressed and have the potential to further enhance patient recovery and satisfaction. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/48801.

ACTN3 (R577X) Genotype Is Associated With Australian Football League Players.

ABSTRACT: Jacob, Y, Hart, NH, Cochrane, JL, Spiteri, T, Laws, SM, Jones, A, Rogalski, B, Kenna, J, and Anderton, RS. ACTN3 (R577X) genotype is associated with Australian Football League players. J Strength Cond Res 36(2): 573-576, 2022-Genetic variants in the angiotensin-converting enzyme (ACE) and alpha actinin-3 (ACTN3) genes have been associated with elite sport athletic performance. This study aimed to investigate the frequency of each polymorphism in a cohort of elite Australian football (AF) players. To achieve this, 47 players from an Australian Football League (AFL) club and 59 healthy age matched controls with no history of elite sporting competition were recruited for this study. Each subject provided saliva samples through buccal swab for DNA extraction and genotyping, with group comparisons made using χ2 and odds ratio analysis. There was no significant difference in ACE I/D genotype between healthy control and elite AF players. The ACTN3 XX genotype was significantly underrepresented in AFL players (4.3%) compared with healthy controls (28.8%, p = 0.003). In addition, there was a greater representation of the R allele in elite AF players (70.2%) when compared with healthy controls (50%; χ2 = 8.834, p = 0.002). This is the first study to investigate genetic variants in elite AF players, with results suggesting that the ACTN3 gene may play a significant role explaining aspects of athletic performance in AF.

Kinetic analysis of push-up exercises: a systematic review with practical recommendations.

Push-ups represent one of the simplest and most popular strengthening exercise. The aim of this study was to systematically review and critically appraise the literature on the kinetics-related characteristics of different types of push-ups, with the objective of optimising training prescription and exercise-related load. A systematic search was conducted in the electronic databases PubMed, Google Scholar and Science Direct up to April 2018. Studies that reported kinetic data (e.g. initial and peak-force supported by the upper-limbs, impact-force, peak-flexion-moment of the elbow-joint, rate of propulsive- and impact-, and vertebral-joint compressive-forces) related to push-ups and included trained, recreational and untrained participants, were considered. The risk of bias in the included studies was assessed using the Critical Appraisal Skills Programme scale. From 5290 articles retrieved in the initial search, only 26 studies were included in this review. Kinetic data for 46 push-up variants were assessed. A limitation of the current review is that the relationship between our findings and actual clinical or practical consequences is not statistically proven but can only be inferred from our critical descriptive approach. Overall, this review provides detailed data on specific characteristics and intensities of push-up variations, in order to optimise exercise prescription for training and rehabilitation purposes.

Clinical Decision Support Tools for Predicting Outcomes in Patients Undergoing Total Knee Arthroplasty: A Systematic Review.

BACKGROUND: Total knee arthroplasty is the standard surgical treatment for end-stage osteoarthritis. Although widely accepted as a successful procedure, approximately 30% of patients are not satisfied due to non-optimal postoperative outcomes. Clinical decision support tools that are able to accurately predict post-surgery outcomes would assist in providing individualized advice or services to help alleviate possible issues, resulting in significant benefits to both the healthcare system and individuals. METHODS: Five databases (Ovid Medline, Ovid EMBASE, CINAHL complete, Cochrane Library, and Scopus) were searched for the key phrases "knee replacement" or "knee arthroplasty" and "decision support tool," "decision tool," "predict∗ tool," "predict∗ model," "algorithm" or "nomogram." Searches were limited to peer-reviewed journal articles published between January 2000 and June 2019. Reference lists of included articles were examined. Authors came to a consensus on the final list of included articles. RESULTS: Eighteen articles were included for review. Most models reported low predictive success and inability to externally validate. Both candidate and final predictor variables were inconsistent between studies. Only 1 model was considered strongly predictive (AUROC >0.8), and only 2 studies were able to externally validate their developed model. In general, models that performed well used large patient numbers, were tested on similar demographics, and used either nonlinear input transformations or a completely nonlinear model. CONCLUSION: Some models do show promise; however, there remains the question of whether the reported predictive success can continue to be replicated. Furthermore, clinical applicability and interpretation of predictive tools should be considered during development.

The effect of isokinetic dynamometer deceleration phase on maximum ankle joint range of motion and plantar flexor mechanical properties tested at different angular velocities.

During range of motion (max-ROM) tests performed on an isokinetic dynamometer, the mechanical delay between the button press (by the participant to signal their max-ROM) and the stopping of joint rotation resulting from system inertia induces errors in both max-ROM and maximum passive joint moment. The present study aimed to quantify these errors by comparing data when max-ROM was obtained from the joint position data, as usual (max-ROMPOS), to data where max-ROM was defined as the first point of dynamometer arm deceleration (max-ROMACC). Fifteen participants performed isokinetic ankle joint max-ROM tests at 5, 30 and 60° s-1. Max-ROM, peak passive joint moment, end-range musculo-articular (MAC) stiffness and area under the joint moment-position curve were calculated. Greater max-ROM was observed in max-ROMPOS than max-ROMACC (P < 0.01) at 5 (0.2 ±â€¯0.15%), 30 (1.8 ±â€¯1.0%) and 60° s-1 (5.9 ±â€¯2.3%), with the greatest error at the fastest velocity. Peak passive moment was greater and end-range MAC stiffness lower in max-ROMPOS than in max-ROMACC only at 60° s-1 (P < 0.01), whilst greater elastic energy storage was found at all velocities. Max-ROM and peak passive moment are affected by the delay between button press and eventual stopping of joint rotation in an angular velocity-dependent manner. This affects other variables calculated from the data. When high data accuracy is required, especially at fast joint rotation velocities (≥30° s-1), max-ROM (and associated measures calculated from joint moment data) should be taken at the point of first change in acceleration rather than at the dynamometer's ultimate joint position.

The Effect of Variation of Plyometric Push-Ups on Force-Application Kinetics and Perception of Intensity.

PURPOSE: To examine differences between ground-reaction-force (GRF)-based parameters collected from 5 types of plyometric push-ups. Between-trials reliability and the relationships between parameters were also assessed. METHODS: Thirty-seven highly active commando soldiers performed 3 trials of 5 variations of the plyometric push-up in a counterbalanced order: standard countermovement push-up (SCPu), standard squat push-up (SSPu), kneeling countermovement push-up (KCPu), kneeling squat push-up (KSPu), and drop-fall push-up (DFPu). Vertical GRF was measured during these exercises using a portable Kistler force plate. The GRF applied by the hands in the starting position (initial force supported), peak GRF and rate of force development during takeoff, flight time, impact force, and rate of force development impact on landing were determined. RESULTS: During standard-position exercises (SCPu and SSPu) the initial force supported and impact force were higher (P < .001) than with kneeling exercises (KCPu, KSPu, and DFPu). The peak GRF and rate of force development during takeoff were higher (P < .001) in the countermovement push-up exercises ([CMP] SCPu, KCPu, and DFPu) than squat push-up exercises ([SP] SSPu and KSPu). Furthermore, the flight time was greater (P < .001) during kneeling exercises than during standard-position exercises. A significant relationship (P < .01) between impact force and the rate of force development impact was observed for CMP and SP exercises (r = .83 and r = .62, respectively). The initial force supported was also negatively related (P < .01) to the flight time for both CMP and SP (r = -.74 and r = -.80, respectively). It was revealed that the initial force supported and the peak GRF during takeoff had excellent reliability; however, other parameters had poor absolute reliability. CONCLUSIONS: It is possible to adjust the intensity of plyometric push-up exercises and train athletes' muscle power by correctly interpreting GRF-based parameters. However, caution is required as some parameters had marginal absolute reliability.

Relationship between Leg Mass, Leg Composition and Foot Velocity on Kicking Accuracy in Australian Football.

Kicking a ball accurately over a desired distance to an intended target is arguably the most important skill to acquire in Australian Football. Therefore, understanding the potential mechanisms which underpin kicking accuracy is warranted. The aim of this study was to examine the relationship between leg mass, leg composition and foot velocity on kicking accuracy in Australian Football. Thirty-one Australian Footballers (n = 31; age: 22.1 ± 2.8 years; height: 1.81 ± 0.07 m; weight: 85.1 ± 13.0 kg; BMI: 25.9 ± 3.2) each performed ten drop punt kicks over twenty metres to a player target. Athletes were separated into accurate (n = 15) and inaccurate (n = 16) kicking groups. Leg mass characteristics were assessed using whole body DXA scans. Foot velocity was determined using a ten-camera optoelectronic, three-dimensional motion capture system. Interactions between leg mass and foot velocity evident within accurate kickers only (r = -0.670 to -0.701). Relative lean mass was positively correlated with kicking accuracy (r = 0.631), while no relationship between foot velocity and kicking accuracy was evident in isolation (r = -0.047 to -0.083). Given the evident importance of lean mass, and its interaction with foot velocity for accurate kickers; future research should explore speed-accuracy, impulse-variability, limb co-ordination and foot-ball interaction constructs in kicking using controlled with-in subject studies to examine the effects of resistance training and skill acquisition programs on the development of kicking accuracy. Key pointsAccurate kickers expressed a very strong inverse relationship between leg mass and foot velocity. Inaccurate kickers were unable to replicate this, with greater volatility in their performance, indicating an ability of accurate kickers to mediate foot velocity to compensate for leg mass in order to deliver the ball over the required distance.Accurate kickers exhibited larger quantities of relative lean mass and lower quantities of relative fat mass in their kicking leg. Higher relative lean mass reduces the relative muscular impulses required to produce a given action, allowing greater limb control with proportionately reduced volitional effort.Kicking accuracy was unable to be explained by either foot velocity or leg mass in isolation; rather, it was the co-contribution and interrelation of these characteristics which were the discriminatory factors between accurate and inaccurate kickers.

A preliminary investigation of trunk and wrist kinematics when using drivers with different shaft properties.

It is unknown whether skilled golfers will modify their kinematics when using drivers of different shaft properties. This study aimed to firstly determine if golf swing kinematics and swing parameters and related launch conditions differed when using modified drivers, then secondly, determine which kinematics were associated with clubhead speed. Twenty high level amateur male golfers (M ± SD: handicap = 1.9 ± 1.9 score) had their three-dimensional (3D) trunk and wrist kinematics collected for two driver trials. Swing parameters and related launch conditions were collected using a launch monitor. A one-way repeated measures ANOVA revealed significant (p ≤ 0.003) between driver differences; specifically, faster trunk axial rotation velocity and an early wrist release for the low kick point driver. Launch angle was shown to be 2° lower for the high kick point driver. Regression models for both drivers explained a significant amount of variance (60-67%) in clubhead speed. Wrist kinematics were most associated with clubhead speed, indicating the importance of the wrists in producing clubhead speed regardless of driver shaft properties.

Segmental Musculoskeletal Examinations using Dual-Energy X-Ray Absorptiometry (DXA): Positioning and Analysis Considerations.

Musculoskeletal examinations provide informative and valuable quantitative insight into muscle and bone health. DXA is one mainstream tool used to accurately and reliably determine body composition components and bone mass characteristics in-vivo. Presently, whole body scan models separate the body into axial and appendicular regions, however there is a need for localised appendicular segmentation models to further examine regions of interest within the upper and lower extremities. Similarly, inconsistencies pertaining to patient positioning exist in the literature which influence measurement precision and analysis outcomes highlighting a need for standardised procedure. This paper provides standardised and reproducible: 1) positioning and analysis procedures using DXA and 2) reliable segmental examinations through descriptive appendicular boundaries. Whole-body scans were performed on forty-six (n = 46) football athletes (age: 22.9 ± 4.3 yrs; height: 1.85 ± 0.07 cm; weight: 87.4 ± 10.3 kg; body fat: 11.4 ± 4.5 %) using DXA. All segments across all scans were analysed three times by the main investigator on three separate days, and by three independent investigators a week following the original analysis. To examine intra-rater and inter-rater, between day and researcher reliability, coefficients of variation (CV) and intraclass correlation coefficients (ICC) were determined. Positioning and segmental analysis procedures presented in this study produced very high, nearly perfect intra-tester (CV ≤ 2.0%; ICC ≥ 0.988) and inter-tester (CV ≤ 2.4%; ICC ≥ 0.980) reliability, demonstrating excellent reproducibility within and between practitioners. Standardised examinations of axial and appendicular segments are necessary. Future studies aiming to quantify and report segmental analyses of the upper- and lower-body musculoskeletal properties using whole-body DXA scans are encouraged to use the patient positioning and image analysis procedures outlined in this paper. Key pointsMusculoskeletal examinations using DXA technology require highly standardised and reproducible patient positioning and image analysis procedures to accurately measure and monitor axial, appendicular and segmental regions of interest.Internal rotation and fixation of the lower-limbs is strongly recommended during whole-body DXA scans to prevent undesired movement, improve frontal mass accessibility and enhance ankle joint visibility during scan performance and analysis.Appendicular segmental analyses using whole-body DXA scans are highly reliable for all regional upper-body and lower-body segmentations, with hard-tissue (CV ≤ 1.5%; R ≥ 0.990) achieving greater reliability and lower error than soft-tissue (CV ≤ 2.4%; R ≥ 0.980) masses when using our appendicular segmental boundaries.

Tests examining skill outcomes in sport: a systematic review of measurement properties and feasibility.

BACKGROUND: A high level of participant skill is influential in determining the outcome of many sports. Thus, tests assessing skill outcomes in sport are commonly used by coaches and researchers to estimate an athlete's ability level, to evaluate the effectiveness of interventions or for the purpose of talent identification. OBJECTIVE: The objective of this systematic review was to examine the methodological quality, measurement properties and feasibility characteristics of sporting skill outcome tests reported in the peer-reviewed literature. DATA SOURCES: A search of both SPORTDiscus and MEDLINE databases was undertaken. STUDY SELECTION: Studies that examined tests of sporting skill outcomes were reviewed. Only studies that investigated measurement properties of the test (reliability or validity) were included. A total of 22 studies met the inclusion/exclusion criteria. STUDY APPRAISAL AND SYNTHESIS METHODS: A customised checklist of assessment criteria, based on previous research, was utilised for the purpose of this review. RESULTS: A range of sports were the subject of the 22 studies included in this review, with considerations relating to methodological quality being generally well addressed by authors. A range of methods and statistical procedures were used by researchers to determine the measurement properties of their skill outcome tests. The majority (95%) of the reviewed studies investigated test-retest reliability, and where relevant, inter and intra-rater reliability was also determined. Content validity was examined in 68% of the studies, with most tests investigating multiple skill domains relevant to the sport. Only 18% of studies assessed all three reviewed forms of validity (content, construct and criterion), with just 14% investigating the predictive validity of the test. Test responsiveness was reported in only 9% of studies, whilst feasibility received varying levels of attention. LIMITATIONS: In organised sport, further tests may exist which have not been investigated in this review. This could be due to such tests firstly not being published in the peer-review literature and secondly, not having their measurement properties (i.e., reliability or validity) examined formally. CONCLUSIONS: Of the 22 studies included in this review, items relating to test methodological quality were, on the whole, well addressed. Test-retest reliability was determined in all but one of the reviewed studies, whilst most studies investigated at least two aspects of validity (i.e., content, construct or criterion-related validity). Few studies examined predictive validity or responsiveness. While feasibility was addressed in over half of the studies, practicality and test limitations were rarely addressed. Consideration of study quality, measurement properties and feasibility components assessed in this review can assist future researchers when developing or modifying tests of sporting skill outcomes.

Effect of strength on plant foot kinetics and kinematics during a change of direction task.

Understanding the magnitude of forces and lower body kinematics that occur during a change of direction (COD) task can provide information about the biomechanical demands required to improve performance. To compare the magnitude of force, impulse, lower body kinematics and post-COD stride velocity produced between athletes of different strength levels during a COD task, 12 stronger (8 males, 4 females) and 12 weaker (4 males, 8 females) recreational team sport athletes were recruited. Strength levels were determined by relative peak isometric force of the dominant and non-dominant leg. All athletes performed 10 pre-planned 45° changes of direction (5 left, 5 right) while three-dimensional motion and ground reaction force (GRF) data were collected. Differences in all variables for the dominant leg were examined using a one-way analysis of variance (ANOVA) with a level of significance set at p ≤0.05. The stronger group displayed significantly faster post-COD stride velocity and greater vertical and horizontal braking forces, vertical propulsive force, vertical braking impulse, horizontal propulsive impulse, angle of peak braking force application, hip abduction and knee flexion angle compared to the weaker group. The results suggest that individuals with greater relative lower body strength produced higher magnitude plant foot kinetics and modified lower body positioning while producing faster COD performances. Future investigations should determine if strength training to enable athletes to increase plant foot kinetics while maintaining or adopting a lower body position results in a concomitant increases in post-COD stride velocity.

Three-dimensional trunk kinematics in golf: between-club differences and relationships to clubhead speed.

The aims of this study were (i) to determine whether significant three-dimensional (3D) trunk kinematic differences existed between a driver and a five-iron during a golf swing; and (ii) to determine the anthropometric, physiological, and trunk kinematic variables associated with clubhead speed. Trunk range of motion and golf swing kinematic data were collected from 15 low-handicap male golfers (handicap = 2.5 +/- 1.9). Data were collected using a 10-camera motion capture system operating at 250 Hz. Data on clubhead speed and ball velocity were collected using a real-time launch monitor. Paired t-tests revealed nine significant (p < or = 0.0019) between-club differences for golf swing kinematics, namely trunk and lower trunk flexion/extension and lower trunk axial rotation. Multiple regression analyses explained 33.7-66.7% of the variance in clubhead speed for the driver and five-iron, respectively, with both trunk and lower trunk variables showing associations with clubhead speed. Future studies should consider the role of the upper limbs and modifiable features of the golf club in developing clubhead speed for the driver in particular.

Leg mass characteristics of accurate and inaccurate kickers--an Australian football perspective.

Athletic profiling provides valuable information to sport scientists, assisting in the optimal design of strength and conditioning programmes. Understanding the influence these physical characteristics may have on the generation of kicking accuracy is advantageous. The aim of this study was to profile and compare the lower limb mass characteristics of accurate and inaccurate Australian footballers. Thirty-one players were recruited from the Western Australian Football League to perform ten drop punt kicks over 20 metres to a player target. Players were separated into accurate (n = 15) and inaccurate (n = 16) groups, with leg mass characteristics assessed using whole body dual energy x-ray absorptiometry (DXA) scans. Accurate kickers demonstrated significantly greater relative lean mass (P ≤ 0.004) and significantly lower relative fat mass (P ≤ 0.024) across all segments of the kicking and support limbs, while also exhibiting significantly higher intra-limb lean-to-fat mass ratios for all segments across both limbs (P ≤ 0.009). Inaccurate kickers also produced significantly larger asymmetries between limbs than accurate kickers (P ≤ 0.028), showing considerably lower lean mass in their support leg. These results illustrate a difference in leg mass characteristics between accurate and inaccurate kickers, highlighting the potential influence these may have on technical proficiency of the drop punt.

The evaluation of a new lower-body reaction time test.

The purpose of this study was to investigate the reliability of 2 lower-body reaction time (RT) tests to determine the differences in RTs between genders and compatible and incompatible conditions. Fifteen male and female (N = 30; 22.63 ± 2.88 years; 175.31 ± 8.72 cm; 67.33 ± 9.71 kg) sport science students participated in this study. Subjects were required to complete 2 lower-body RT tests responding to an arrow during compatible (same direction) and incompatible (opposite direction) stimulus-response conditions. The "simple" foot RT test required subjects to step quickly on the appropriate mat, as directed by the stimulus, with response time being measured. The "complex" foot RT test required subjects to leap off a force plate to the appropriate mat in response to the stimulus, with RT, movement time (MT), and total movement time (TMT) being measured. Intraclass correlation coefficient, coefficient of variation, and paired samples t-test (p ≤ 0.05) were calculated for all variables. High reliability was observed for both tests between compatible and incompatible conditions. Significant differences (p ≤ 0.05) were observed between genders for RT during the simple RT test. Significant differences (p ≤ 0.05) were observed for MT and TMT during compatible and incompatible conditions for the complex RT test. In conclusion, both tests are reliable to determine lower-body RTs during both conditions. Movement time and TMT during the complex RT test were significantly different, suggesting that MT could be the discriminating factor between conditions and also genders. Examining lower-body RTs during a movement commonly observed in sports may provide coaches more details about the athletes' cognitive and athletic ability, enabling the components of RT to be trained.

Training affects knee kinematics and kinetics in cutting maneuvers in sport.

PURPOSE: The current study examined how different training affects the kinematics and applied moments at the knee during sporting maneuvers and the potential to reduce loading of the anterior cruciate ligament (ACL). The training programs were 1) machine weights, 2) free weights, 3) balance training, and 4) machine weights + balance training. METHODS: Fifty healthy male subjects were allocated either to a control group or to one of four 12-wk training programs. Subjects were tested before and after training, performing running and cutting maneuvers from which knee angle and applied knee moments were assessed. Data analyzed were peak applied flexion/extension, varus/valgus, and internal/external rotation moments, as well as knee flexion angles during specific phases of stance during the maneuvers. RESULTS: The balance training group decreased their peak valgus and peak internal rotation moments during weight acceptance in all maneuvers. This group also lowered their flexion moments during the sidestep to 60 degrees . Free weights training induced increases in the internal rotation moment and decreases in knee flexion angle in the peak push-off phase of stance. Machine weights training elicited increases in the flexion moment and reduced peak valgus moments in weight acceptance. Machine weights + balance training resulted in no changes to the variables assessed. CONCLUSIONS: Balance training produced reductions in peak valgus and internal rotation moments, which could lower ACL injury risk during sporting maneuvers. Strength training tended to increase the applied knee loading known to place strain on the ACL, with the free weights group also decreasing the amount of knee flexion. It is recommended that balance training be implemented because it may reduce the risk of ACL injury.

Canoe slalom competition analysis.

The aim of this study was to quantify the differences between groups of elite canoe slalom athletes based on the class they paddle in and the strategies they use in competition. Canoe and kayak footage was recorded using three cameras and analysed using lapsed-time time-motion analysis. Analysis was undertaken on the ten fastest competition runs for men's kayak and canoes and women's kayak for the 22-gate semi-final/final course at the 2005 canoe slalom world championships. Comparison between the categories of paddlers revealed that despite canoe paddlers taking significantly (P < or = 0.05) fewer strokes than kayak paddlers, they were not significantly slower than men's single kayak paddlers with respect to their run times and only significantly slower between 4 of 22 gates. Results revealed also that paddlers using different turn strategies (spin vs. pivot) had significantly (P < or = 0.05) different split times for the gates before and after the execution of the manoeuvre. For a paddler this means that their individual strategy could be analysed and compared with those of others to determine if alternate strategies would be beneficial to their performance.

Canoe slalom--competition analysis reliability.

The aim of this study was to assess intra-observer and inter-observer reliability of data gathered from a lapsed-time time-motion analysis of canoe slalom competition. The data were collected using a definition set developed in conjunction with elite canoe slalom coaches. Competition runs from four national-standard paddlers in a national selection race were analysed in random order three times by three observers. For each run, observers identified various events specific to canoe slalom, including time taken between gates, touched and missed gates, turn times, major and minor avoidance, rolls, paddle in and out of water times, and stroke classification. The error of measurement was determined for each of these variables. For time taken between gates and turn times, the error was < or = 0.21 and < or = 0.39 s for intra-observer and inter-observer analysis, respectively. The error for stroke in and out of water times was < or = 0.08 and < or = 0.13 s for intra-observer and inter-observer analysis, respectively. Analysis of stroke classification identification for intra-observer comparisons revealed that 91% of the time identical stroke identification occurred. Inter-observer analysis revealed identical stroke identification was achieved 81% of the time. These reliability data compare favourably with previous time-motion analysis in other sports using fewer variables.

Characteristics of anterior cruciate ligament injuries in Australian football.

Anterior cruciate ligament (ACL) injuries are the most costly injuries in football at both professional and amateur levels (Orchard J, Seward H, McGivern J, Hood S. Intrinsic and extrinsic risk factors for anterior cruciate ligament injury in Australian footballers. Am J Sports Med 2001;29:196-200.). In this study video analysis of 34 ACL injuries in Australian football was performed to investigate the causes of these injuries. Factors that may have contributed to the cause of the injury were analysed, rated and reported. The factors analysed were: type of manoeuvre, direction the knee 'gave way', running speed, knee angle, cutting angle and if the player was accelerating or decelerating. The majority of the injuries analysed occurred in non-contact situations (56%). Of these 37% occurred during sidestepping manoeuvres, 32% in landing, 16% land and step, 10% stopping/slowing and 5% crossover cut manoeuvres. Ninety-two percent of the non-contact injuries occurred at extended knee angles of 30 degrees or less, which is also commonly known to place stress on the ACL and reduce the protective role of hamstrings. Over half (54%) of non-contact injuries occurred whilst decelerating. It would be expected that greater speed and angle cut too would increase the frequency of ACL injury. The results could not confirm this with most injuries occurring at running speeds of slow jogging to running and equal number of injuries occurred at cutting to angles of the ranges 15-45 degrees and 45-75 degrees. These results give greater understanding into potential causes or contributors of ACL injury and information to assist in the development of knee injury prevention programs.