Placement effects of inertial measurement units on contact identification in wheelchair racing.

Inertial measurement units (IMUs) provide a practical solution for attaining key performance data for wheelchair sports. The effects of IMU placement position on the identification of propulsion characteristics are unknown. The aim of this study was to determine the variability in the reliability of cycle time measurements (time between hand contacts) across IMU locations on the chair frame (axle housings), and wheels (axle, push rim, outer rim), on both the left and right sides (n = 8). Contacts were defined by spikes in the resultant acceleration data, corresponding to impact between the hands and push rim, and verified against motion capture. Five elite wheelchair racing athletes propelled at racing speeds on a treadmill. Excellent inter-rater Intraclass Correlation Coefficient values indicated high reliability and repeatability for both motion capture and IMU signal analysis approaches (R = 0.997, p < 0.001 and R = 0.990, p < 0.001, respectively). The best results were (as determined by the best between method agreement) were observed for IMUs located on the frame. Detection reliability was positively associated with signal-to-noise ratio of the acceleration data. The IMU assessment approach facilitates an automated processing capability, which is an improvement to the currently used video analysis.

A practical assessment of wheelchair racing performance kinetics using accelerometers.

Due to the detrimental influence of unnecessary mass on performance, racing wheelchair instrumentation used in both competition assessment and research is currently limited. Attaining key kinetic parameters of propulsion can enhance technique and provide athletes with a competitive advantage. This research examined the plausibility of inertial measurement units (IMUs) to estimate propulsion forces, during a simulated wheelchair race start and training. Start propulsion data calculated from an IMU system was compared to reference force plate data; steady state motion data was compared with existing literature. Some agreement in kinetic parameters between IMU data was observed under steady state motion, with data from athletes following a linear force-velocity relationship. In this context, it is important to identify that this cannot be directly compared to the existing literature due to the different methods of force measurement and the lack of data for similar force measurements using IMUs. IMUs were ineffective when used with wheelchairs having spoked wheels. Performance was best for measurements in the direction of motion. Although exact agreement was not observed, the IMU can provide an effective tool in the in-field assessment of propulsion kinetics.

The influence of upper-body mechanics, anthropometry and isokinetic strength on performance in wrist-spin cricket bowling.

Delivering a cricket ball with a wrist-spin (WS) bowling technique is considered one of the game's most difficult skills. Limited biomechanical information exists for WS bowlers across skill levels. The purpose of this study was to compare biomechanical, isokinetic strength and anthropometric measures between elite (12) and pathway bowlers (eight). Data were collected using a motion analysis system, dynamometer and a level-two anthropometrist. A regression analysis identified that performance was best explained by increased wrist radial deviation torque and longitudinal axis rotational moments at the shoulder and wrist. From back foot impact (BFI) to ball release (BR), elite bowlers rotated their trunks less, experienced less trunk deceleration resulting in a more front-on position and increased pelvis rotation angular velocity. They also displayed an increased shoulder internal rotation moment as the upper arm moved from external into internal rotation and was a major contributor in the subsequent differences observed in the distal segments of the bowling limb. Anthropometric differences were observed at the wrist and finger joints and may be used to form the basis for talent identification programmes. This study highlights the important contribution to bowling performance of the musculature responsible for producing long axis rotations of the bowling limb.

Estimating the Maximum Isometric Force Generating Capacity of Wheelchair Racing Athletes for Simulation Purposes.

For the wheelchair racing population, it is uncertain whether musculoskeletal models using the maximum isometric force generating capacity of non-athletic, able-bodied individuals, are appropriate, as few anthropometric parameters for wheelchair athletes are reported in the literature. In this study, a sensitivity analysis was performed in OpenSim, whereby the maximum isometric force generating capacity of muscles was adjusted in 25% increments to literature defined values between scaling factors of 0.25x to 4.0x for two elite athletes, at three speeds representative of race conditions. Convergence of the solution was used to assess the results. Artificially weakening a model presented unrealistic values, and artificially strengthening a model excessively (4.0x) demonstrated physiologically invalid muscle force values. The ideal scaling factors were 1.5x and 1.75x for each of the athletes, respectively, as was assessed through convergence of the solution. This was similar to the relative difference in limb masses between dual energy X-Ray absorptiometry (DXA) data and anthropometric data in the literature (1.49x and 1.70x), suggesting that DXA may be used to estimate the required scaling factors. The reliability of simulations for elite wheelchair racing athletes can be improved by appropriately increasing the maximum isometric force generating capacity of muscles.

The Effects of Personalized Versus Generic Scaling of Body Segment Masses on Joint Torques During Stationary Wheelchair Racing.

The anthropometries of elite wheelchair racing athletes differ from the generic, able-bodied anthropometries commonly used in computational biomechanical simulations. The impact of using able-bodied parameters on the accuracy of simulations involving wheelchair racing is currently unknown. In this study, athlete-specific mass segment inertial parameters of the head and neck, torso, upper arm, forearm, hand, thigh, shank, and feet for five elite wheelchair athletes were calculated using dual-energy X-ray absorptiometry (DXA) scans. These were compared against commonly used anthropometrics parameters of data presented in the literature. A computational biomechanical simulation of wheelchair propulsion using the upper extremity dynamic model in opensim assessed the sensitivity of athlete-specific mass parameters using Kruskal-Wallis analysis and Spearman correlations. Substantial between-athlete body mass distribution variances (thigh mass between 7.8% and 22.4% total body mass) and between-limb asymmetries (<62.4% segment mass; 3.1 kg) were observed. Compared to nonathletic able-bodied anthropometric data, wheelchair racing athletes demonstrated greater mass in the upper extremities (up to 3.8% total body mass) and less in the lower extremities (up to 9.8% total body mass). Computational simulations were sensitive to individual body mass distribution, with joint torques increasing by up to 31.5% when the scaling of segment masses (measured or generic) differed by up to 2.3% total body mass. These data suggest that nonathletic, able-bodied mass segment inertial parameters are inappropriate for analyzing elite wheelchair racing motion.

Modified perceptual training in sport: A new classification framework.

OBJECTIVES: To overview a framework that provides a theoretically-grounded approach to predicting the types of modified perceptual training tasks that will stimulate transfer of improved perceptual skills to sport performance environments. Modified perceptual training (MPT) collectively describes on- or off-field sports training tasks that are specifically designed to develop visual and perceptual-cognitive skill. Traditional training approaches in sport include sports vision training and perceptual-cognitive training, while recently, new technologies have enabled a broad range of additional MPT tools to become available to coaches and athletes. DESIGN: Short literature review and opinion article. METHODS: Literature in the fields of sports vision training and perceptual-cognitive training are summarised and contrasted. A selection of emerging MPT technologies are then overviewed. This leads to the identification of three interacting factors of MPT task design that may influence the task's capacity to transfer improved training performance to actual competition: (i) the targeted perceptual function, (ii) stimulus correspondence, and (iii) response correspondence, which are assimilated with key tenets of representative learning design. RESULTS: These three theoretically-grounded differences are adopted to support and justify the structure of the Modified Perceptual Training Framework which sets out predictions for future research to test in order to clarify the transfer effect of MPT tools. CONCLUSIONS: The application of the Modified Perceptual Training Framework may assist in future testing, design and selection of beneficial training tools in sport and as such, is predicted to have significant impact in empirical and practical settings.

Illegal bowling actions contribute to performance in cricket finger-spin bowlers.

With advances in technology, scientists are now able to more accurately measure elbow displacement changes during the cricket bowling action. This has led to the realization that the majority of bowlers undergo some degree of elbow extension during the forward swing phase of bowling. Consequently, the International Cricket Council were obliged to revise the once zero tolerance for elbow extension threshold to a 15° range. However, it is still not understood if bowling with >15° of elbow extension aids performance or alters other kinematic movements. The purpose of this study was to compare performance and technique measures between legal and illegal finger-spin bowlers. Data were collected from 48 pathway and elite bowlers using a 22-camera motion analysis system. Results indicated that the ball velocity and revolutions at ball release of pathway bowlers with illegal actions showed no significant difference and were similar to elite legal bowlers. Technique differences were also identified, with illegal bowlers being more front-on, forcing a reliance on increased elbow flexion and supination to impart effective ball kinematics at ball release. The performance benefit of greater ball velocity and revolutions is obtained when finger-spin bowlers deliver the ball with more than the allowable 15° of elbow extension, thus reinforcing the validity of the current bowling laws. To counteract bowling with an illegal action, it is recommended that a more side-on technique at back foot impact and rotating the trunk through to the point of ball release will assist bowlers in reducing undesirable elbow extension levels.

Does performance level affect initial ball flight kinematics in finger and wrist-spin cricket bowlers?

Spin bowling plays a fundamental role within the game of cricket yet little is known about the initial ball kinematics in elite and pathway spin bowlers or their relationship to performance. Therefore, the purpose of this study was to record three-dimensional ball kinematics in a large and truly high level cohort of elite and pathway finger-spin (FS) and wrist-spin (WS) bowlers, identifying potential performance measures that can be subsequently used in future research. A 22-camera Vicon motion analysis system captured retro-reflective markers placed on the seam (static) and ball (dynamic) to quantify ball kinematics in 36 FS (12 elite and 24 pathway) and 20 WS (eight elite and 12 pathway) bowlers. Results indicated that FS bowlers delivered the ball with an increased axis of rotation elevation, while wrist-spin bowlers placed greater amounts of revolutions on the ball. It also highlighted that ball release (BR) velocity, revolutions and velocity/revolution index scores for both groups and seam stability for FS bowlers, and seam azimuth angle and spin axis elevation angle for WS bowlers, were discriminators of playing level. As such these variables could be used as indicators of performance (i.e. performance measures) in future research.

Peak outward acceleration and ball release in cricket.

The purpose of this study was to investigate the utility of peak outward acceleration (POA) measured from an inertial sensor worn at the wrist as an indicator of the critical end point of the bowling action ­ ball release, a critical element when assessing illegal actions. Twenty-one finger-spin and fast bowlers from nine countries were recruited from the ICC under-19 Cricket World Cup to take part in this research. Bowlers delivered a cross section of their standard deliveries while wearing an inertial sensor placed on their wrists. Ball release was determined by a validated motional analysis ball release (MABR) protocol and compared to the simultaneously collected POA. POA was shown to be highly correlated with MABR (R(2) = 0.98) and a Bland-Altman plot indicated that all 148 trials were within the 3.42 frame (0.014 s) limits of agreement. POA when measured by an inertial sensor worn on the wrist during bowling had a close relationship with an established method of identifying ball release in a biomechanical laboratory regardless of bowler and delivery type. Further, accuracy can be achieved with the adoption of a simple regression equation applied to the POA and as such is a valid measure of ball release in cricket bowlers.

Acquisition of expertise in cricket fast bowling: perceptions of expert players and coaches.

OBJECTIVES: Experiential knowledge of elite athletes and coaches was investigated to reveal insights on expertise acquisition in cricket fast bowling. DESIGN: Twenty-one past or present elite cricket fast bowlers and coaches of national or international level were interviewed using an in-depth, open-ended, semi-structured approach. METHODS: Participants were asked about specific factors which they believed were markers of fast bowling expertise potential. Of specific interest was the relative importance of each potential component of fast bowling expertise and how components interacted or developed over time. RESULTS: The importance of intrinsic motivation early in development was highlighted, along with physical, psychological and technical attributes. Results supported a multiplicative and interactive complex systems model of talent development in fast bowling, in which component weightings were varied due to individual differences in potential experts. Dropout rates in potential experts were attributed to misconceived current talent identification programmes and coaching practices, early maturation and physical attributes, injuries and lack of key psychological attributes and skills. CONCLUSIONS: Data are consistent with a dynamical systems model of expertise acquisition in fast bowling, with numerous trajectories available for talent development. Further work is needed to relate experiential and theoretical knowledge on expertise in other sports.

Cricket fast bowlers without low back pain have larger quadratus lumborum asymmetry than injured bowlers.

OBJECTIVE: The objective of the study was to determine the magnitude and side of quadratus lumborum (QL) asymmetries in elite, adult, cricket fast bowlers and the relationship with lumbar spine injury. DESIGN: Cohort study. SETTING: Cricket fast bowers had magnetic resonance (MR) scans at the start of a cricket season and their injury characteristics over the next cricket season were compared with the amount of QL asymmetry. PARTICIPANTS: Twenty-three elite, asymptomatic, adult, cricket fast bowlers. ASSESSMENT OF RISK FACTORS: The cross-sectional area (CSA) of QL was measured using MR imaging. The association between side-to-side differences in CSA (asymmetry) was evaluated as a possible risk factor for development of lumbar spine injury. MAIN OUTCOME MEASURES: The main outcome measurements were QL CSA and asymmetry in relation to lumbar spine injury in cricket fast bowlers. RESULTS: There were a greater proportion of dominant- (bowling arm) side asymmetries (65%). Asymmetry magnitudes that favored the dominant side were not significantly larger than those on the nondominant side. Four participants who had bone oedema on MR imaging preseason went on to develop symptomatic lumbar stress fractures. Participants with no lumbar spine injury had significantly larger QL asymmetries than those who sustained lumbar spine injury. CONCLUSIONS: Cricket fast bowlers demonstrated asymmetrical QL development, which may be related to the trunk positions adopted in the fast bowling technique. Uninjured bowlers had larger asymmetries than those who developed lumbar spine injury, which is contrary to some previous research.

Battlezone: An examination of the physiological responses, movement demands and reproducibility of small-sided cricket games.

As cricket training typically involves separate skill and conditioning sessions, this study reported on the movement demands, physiological responses and reproducibility of the demands of small-sided cricket games. Thirteen amateur, male cricket players (age: 22.8 ± 3.5 years, height: 1.78 ± 0.06 m, body mass: 78.6 ± 7.1 kg) completed two sessions of a generic small-sided cricket game, termed Battlezone; consisting of six repeat 8-over bouts. Heart rate and movement demands were continuously recorded, whilst blood lactate concentration and perceived exertion were recorded after each respective bout. Batsmen covered the greatest distance (1147 ± 175 m) and demonstrated the greatest mean movement speed (63 ± 9 m · min⁻¹) during each bout. The majority of time (65-86%) was spent with a heart rate of between 51-85% HR(max) and a blood lactate concentration of 1.1-2.0 mmol · L⁻¹. Rating of perceived exertion ranged between 4.2-6.0. Movement demands and physiological responses did not differ between standardised sessions within respective playing positions (P > 0.05). The reliability for the majority of movement demands and physiological responses were moderate to high (CV: 5-17%; ICC: 0.48-1.00) within all playing positions. These results suggest that the physiological responses and movement characteristics of generic small-sided cricket games were consistent between sessions within respective playing positions.

The influence of field size, player number and rule changes on the physiological responses and movement demands of small-sided games for cricket training.

This study investigated the physiological responses and movement demands associated with modified versions of small-sided games for cricket training, termed 'Battlezone'. Eleven (22.2 ± 3.6 years; 1.80 ± 0.06 m; 81.7 ± 11.4 kg) male, cricket players volunteered to perform each of four modified 8-over scenarios of Battlezone. Modifications to Battlezone included reducing the field size, removal of a fielder, a combination of these modifications and additional rule changes. Heart rate, blood lactate concentration, rating of perceived exertion (RPE) and the movement patterns of participants were measured during each scenario. The total distances covered per 8-over bout ranged from 626 ± 335 m for wicketkeepers to 1795 ± 457 m for medium-fast bowlers; although similar distances (P > 0.05) were covered within positions between the four different scenarios. Between scenarios, the greatest mean speed, heart rate and blood lactate responses occurred when the rules were changed, resulting in increased movement patterns (P < 0.05), most notably for batsmen and wicketkeepers. In contrast, altering the playing field size or player number did not significantly influence (P > 0.05) these responses. These results suggest that the physical demands of cricket-specific training can be increased via rule variations including hit-and-run activities, more so than field size or player number.

Effects of mixed-method cooling on recovery of medium-fast bowling performance in hot conditions on consecutive days.

This investigation examined physiological and performance effects of cooling on recovery of medium-fast bowlers in the heat. Eight, medium-fast bowlers completed two randomised trials, involving two sessions completed on consecutive days (Session 1: 10-overs and Session 2: 4-overs) in 31 ± 3°C and 55 ± 17% relative humidity. Recovery interventions were administered for 20 min (mixed-method cooling vs. control) after Session 1. Measures included bowling performance (ball speed, accuracy, run-up speeds), physical demands (global positioning system, counter-movement jump), physiological (heart rate, core temperature, skin temperature, sweat loss), biochemical (creatine kinase, C-reactive protein) and perceptual variables (perceived exertion, thermal sensation, muscle soreness). Mean ball speed was higher after cooling in Session 2 (118.9 ± 8.1 vs. 115.5 ± 8.6 km · h⁻¹; P = 0.001; d = 0.67), reducing declines in ball speed between sessions (0.24 vs. -3.18 km · h⁻¹; P = 0.03; d = 1.80). Large effects indicated higher accuracy in Session 2 after cooling (46.0 ± 11.2 vs. 39.4 ± 8.6 arbitrary units [AU]; P = 0.13; d = 0.93) without affecting total run-up speed (19.0 ± 3.1 vs. 19.0 ± 2.5 km · h⁻¹; P = 0.97; d = 0.01). Cooling reduced core temperature, skin temperature and thermal sensation throughout the intervention (P = 0.001-0.05; d = 1.31-5.78) and attenuated creatine kinase (P = 0.04; d = 0.56) and muscle soreness at 24-h (P = 0.03; d = 2.05). Accordingly, mixed-method cooling can reduce thermal strain after a 10-over spell and improve markers of muscular damage and discomfort alongside maintained medium-fast bowling performance on consecutive days in hot conditions.

Quadratus lumborum asymmetry and lumbar spine injury in cricket fast bowlers.

OBJECTIVES: Previous studies have demonstrated quadratus lumborum asymmetry in cricket fast bowlers, but there has been conflicting evidence regarding the relationship to lumbar spine injury, particularly vertebral bone stress injuries. This study investigated the relationship between quadratus lumborum asymmetry and lumbar spine injury in adolescent cricket fast bowlers. DESIGN: The study was a prospective cohort design. METHODS: Magnetic resonance imaging of 38 adolescent cricket fast bowlers was completed prior to a cricket season, and the cross sectional area of the quadratus lumborum muscle was measured at each lumbar spinal level. The bowlers were followed through the cricket season and those that reported lumbar spine injuries were investigated and classified as either having a soft tissue injury or a bone stress injury. The pre-season cross sectional area of quadratus lumborum was associated with injury status at the conclusion of the cricket season. RESULTS: Twenty-one percent of the cohort developed lumbar bone stress injuries during the cricket season. There was no significant relationship between lumbar spine injury and quadratus lumborum cross sectional area. CONCLUSIONS: A high incidence of lumbar bone stress injuries was demonstrated in adolescent fast bowlers. Unlike previous research that demonstrated a link between lumbar spine bone stress injuries and quadratus lumborum cross-sectional area, no such relationship was found.

Mixed-method pre-cooling reduces physiological demand without improving performance of medium-fast bowling in the heat.

This study examined physiological and performance effects of pre-cooling on medium-fast bowling in the heat. Ten, medium-fast bowlers completed two randomised trials involving either cooling (mixed-methods) or control (no cooling) interventions before a 6-over bowling spell in 31.9±2.1°C and 63.5±9.3% relative humidity. Measures included bowling performance (ball speed, accuracy and run-up speeds), physical characteristics (global positioning system monitoring and counter-movement jump height), physiological (heart rate, core temperature, skin temperature and sweat loss), biochemical (serum concentrations of damage, stress and inflammation) and perceptual variables (perceived exertion and thermal sensation). Mean ball speed (114.5±7.1 vs. 114.1±7.2 km · h(-1); P = 0.63; d = 0.09), accuracy (43.1±10.6 vs. 44.2±12.5 AU; P = 0.76; d = 0.14) and total run-up speed (19.1±4.1 vs. 19.3±3.8 km · h(-1); P = 0.66; d = 0.06) did not differ between pre-cooling and control respectively; however 20-m sprint speed between overs was 5.9±7.3% greater at Over 4 after pre-cooling (P = 0.03; d = 0.75). Pre-cooling reduced skin temperature after the intervention period (P = 0.006; d = 2.28), core temperature and pre-over heart rates throughout (P = 0.01-0.04; d = 0.96-1.74) and sweat loss by 0.4±0.3 kg (P = 0.01; d = 0.34). Mean rating of perceived exertion and thermal sensation were lower during pre-cooling trials (P = 0.004-0.03; d = 0.77-3.13). Despite no observed improvement in bowling performance, pre-cooling maintained between-over sprint speeds and blunted physiological and perceptual demands to ease the thermoregulatory demands of medium-fast bowling in hot conditions.

Duration-dependant response of mixed-method pre-cooling for intermittent-sprint exercise in the heat.

This study examined the effects of pre-cooling duration on performance and neuromuscular function for self-paced intermittent-sprint shuttle running in the heat. Eight male, team-sport athletes completed two 35-min bouts of intermittent-sprint shuttle running separated by a 15-min recovery on three separate occasions (33°C, 34% relative humidity). Mixed-method pre-cooling was completed for 20 min (COOL20), 10-min (COOL10) or no cooling (CONT) and reapplied for 5-min mid-exercise. Performance was assessed via sprint times, percentage decline and shuttle-running distance covered. Maximal voluntary contractions (MVC), voluntary activation (VA) and evoked twitch properties were recorded pre- and post-intervention and mid- and post-exercise. Core temperature (T (c)), skin temperature, heart rate, capillary blood metabolites, sweat losses, perceptual exertion and thermal stress were monitored throughout. Venous blood draws pre- and post-exercise were analyzed for muscle damage and inflammation markers. Shuttle-running distances covered were increased 5.2 ± 3.3% following COOL20 (P < 0.05), with no differences observed between COOL10 and CONT (P > 0.05). COOL20 aided in the maintenance of mid- and post-exercise MVC (P < 0.05; d > 0.80), despite no conditional differences in VA (P > 0.05). Pre-exercise T (c) was reduced by 0.15 ± 0.13°C with COOL20 (P < 0.05; d > 1.10), and remained lower throughout both COOL20 and COOL10 compared to CONT (P < 0.05; d > 0.80). Pre-cooling reduced sweat losses by 0.4 ± 0.3 kg (P < 0.02; d > 1.15), with COOL20 0.2 ± 0.4 kg less than COOL10 (P = 0.19; d = 1.01). Increased pre-cooling duration lowered physiological demands during exercise heat stress and facilitated the maintenance of self-paced intermittent-sprint performance in the heat. Importantly, the dose-response interaction of pre-cooling and sustained neuromuscular responses may explain the improved exercise performance in hot conditions.

Quadratus lumborum asymmetry is not isolated to the dominant side in junior cricket fast bowlers.

BACKGROUND AND AIM: Bowling-side quadratus lumborum (QL) asymmetries have been previously reported on the dominant side in junior cricket fast bowlers using MRI. The aim of this study was to investigate QL asymmetry when measuring with two different methods; first using a small number of images with clear muscle borders and second using a larger number of images with less strict inclusion criteria. METHODS: MRI was performed on 38 junior (14.9 years) cricket fast bowlers prior to the start of a cricket season. Each MR image slice was evaluated to determine whether the QL muscle contour was visible and was assigned an image-quality rating for inclusion in the study. The cross-sectional area of each included QL image was measured and compared with the corresponding image on the other side of the spine to determine side-to-side difference (asymmetries). RESULTS: Using the main method of including only high-quality MR images, 25% of MR images, where QL was in the field of view, met the inclusion criteria. The mean QL asymmetry was 13%, while 55% of participants had asymmetries greater than 10%. There was no significant difference in the number of participants with dominant and non-dominant side QL asymmetry. However, there was a significant difference in the magnitude of asymmetry between the dominant side (10.5%) and non-dominant (16.4%) asymmetries. The intraclass correlation coefficient for repeated measurements of QL asymmetry for randomly selected images (18%) was excellent (ICC 0.966, 95% CI 0.89 to 0.99). Using the second measurement method, with less strict inclusion criteria for MR images, similar results on the distribution of QL asymmetry were found. CONCLUSION: Contrary to previous research, this study demonstrated that there was a similar distribution of QL asymmetry between the dominant and non-dominant side. The presence of only dominant side asymmetry must therefore be questioned.

Performance accuracy and functional variability in elite and developing fast bowlers.

OBJECTIVES: The relationship between performance variability and accuracy in cricket fast bowlers of different skill levels under three different task conditions was investigated. Bowlers of different skill levels were examined to observe if they could adapt movement patterns to maintain performance accuracy on a bowling skills test. DESIGN: 8 national, 12 emerging and 12 junior pace bowlers completed an adapted version of the Cricket Australia bowling skills test, in which they performed 30 trials involving short (n=10), good (n=10), and full (n=10) length deliveries. METHODS: Bowling accuracy was recorded by digitising ball position relative to the centre of a target. Performance measures were mean radial error (accuracy), variable error (consistency), centroid error (bias), bowling score and ball speed. Radial error changes across the duration of the skills test were used to record accuracy adjustment in subsequent deliveries. RESULTS: Elite fast bowlers performed better in speed, accuracy, and test scores than developing athletes. Bowlers who were less variable were also more accurate across all delivery lengths. National and emerging bowlers were able to adapt subsequent performance trials within the same bowling session for short length deliveries. CONCLUSIONS: Accuracy and adaptive variability were key components of elite performance in fast bowling which improved with skill level. In this study, only national elite bowlers showed requisite levels of adaptive variability to bowl a range of lengths to different pitch locations.

Kinematic perturbation in the flexion-extension axis for two lumbar rigs during a high impact jump task.

The measurement of lumbar spine motion is an important step for injury prevention research during complex and high impact activities, such as cricket fast bowling or javelin throwing. This study examined the performance of two designs of a lumbar rig, previously used in gait research, during a controlled high impact bench jump task. An 8-camera retro-reflective motion analysis system was used to track the lumbar rig. Eleven athletes completed the task wearing the two different lumbar rig designs. Flexion extension data were analyzed using a fast Fourier transformation to assess the signal power of these data during the impact phase of the jump. The lumbar rig featuring an increased and pliable base of support recorded moderately less signal power through the 0-60 Hz spectrum, with statistically less magnitudes at the 0-5 Hz (p = .039), 5-10 Hz (p = .005) and 10-20 Hz (p = .006) frequency bins. A lumbar rig of this design would seem likely to provide less noisy lumbar motion data during high impact tasks.