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.

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.

Comparison of player movement patterns between 1-day and test cricket.

Physical demands of cricket presumably vary by both game format and performance level. Differences in player movement patterns between 2 game formats (1 day and multiday) and 2 levels of elite performance (state and international) were quantified with global positioning system technology. Five movement categories were established, and 15 movement pattern variables were reported. Data from state (n = 42, 200 files) and international (n = 12, 63 files) cricketers were scaled to hourly values to compare movement demands. Cricketers generally covered similar distances in both formats, except for state 1-day fielders who covered moderately greater distance (~0.7 km·h⁻¹ more; 21 ± 8%; mean ± 90% confidence interval) than state multiday (first-class) fielders. State 1-day cricketers also covered small to moderately greater distances (running 41 ± 13%; striding 38 ± 16%; sprinting 39 ± 36%) in the faster movement patterns and consequently had moderately less recovery time (13-67%) between high-intensity efforts as first-class cricketers. Comparisons of movements between performance levels revealed similar total distances between state and international cricketers. However, Test fielders covered moderately greater (29-48%) distances at the higher-intensity movement patterns (running, striding, and sprinting) than first-class fielders. In summary, although movement patterns were broadly similar between formats and levels, it appears that one day cricket (compared with multiday games) and test matches (compared with state-level competition) require more higher-intensity running. Conditioning coaches should train state and international 1-day cricket players similarly, but should account for the higher physical demands of international multiday cricket.

Comparison of training and game demands of national level cricketers.

Although the physiological demands of cricket match play are emerging, the demands of contemporary training practices have not been reported. The aim of this study was to quantify the physiological demands of selected cricket training activities and compare these to known match demands. Twenty-eight different training activities were monitored in national academy level cricketers (n = 42) using global positioning system units during a 14-week residential training program. The training activities were classified into 3 categories: conditioning sessions (n = 8), skill sessions (n = 9), and game simulations (n = 11). Conditioning sessions were further classified into high- (n = 4) and low- (n = 4) intensity drills. Time-motion measures included movement patterns (walk, jog, run, stride, and sprint distances), total distance covered, number of sprints, number of high-intensity efforts, maximum speed, and recovery time between high-intensity efforts. Inferential statistics were used to quantify magnitudes of difference between various training drills. Movement patterns were then compared to recently published game data (Twenty20, One-Day, and Multiday games) from the same sample group of cricketers. Conditioning drills were twice as long in duration as skill drills and twice as intense as both the skill and game simulation drills. Exercising heart rates were 9-26% and lactate levels up to 3.5 times higher in conditioning compared to other training drills. Conditioning drills matched or exceeded (up to 10 b·min⁻¹; 5%) peak game heart rates. Conversely, skill and simulation drills replicated mean game heart rates for some, but not all positions. In conclusion, training replicates or exceeds cricket match demands in conditioning-type drills but not in simulation or skill-based drills. Modification of skill and simulation training drill practices will ensure closer replication of match and training demands.

Enhancing cricket batting skill: implications for biomechanics and skill acquisition research and practice.

This review synthesises the biomechanical and skill acquisition/sport expertise literature focused on the skill of cricket batting. The literature is briefly reviewed and the major limitations, challenges, and suggested future research directions are outlined. This is designed to stimulate researchers to enhance the understanding of cricket batting biomechanics and skill acquisition and in turn assist cricket coaches develop efficacious batting skill development programmes. An interdisciplinary approach between biomechanists and skill acquisition specialists is advocated to further knowledge of the underlying processes and mechanisms of cricket batting expertise. Issues such as skill measurement, practice design, ball machines, skill transfer, the impact of Twenty/20 cricket, video simulation, and skill decomposition are discussed. The ProBatter ball machine systems are introduced along with suggestions for best practice approaches for coaches when designing batting skill development programmes.

Partial heat acclimation in cricketers using a 4-day high intensity cycling protocol.

UNLABELLED: Cricketers are often required to play in hot/humid environments with little time for heat adaptation. PURPOSE: We examined the effect of a short 4-d hot/humid acclimation program on classical physiological indicators of heat acclimation. METHODS: Male club cricketers were randomly assigned into heat acclimation (ACC, n = 6) or control (CON, n = 6) groups, and 30 min treadmill trials (10 km/h, approx. 30 ± 1.0°C, approx. 65 ± 6% RH) were conducted at baseline and postacclimation. The ACC group completed four high intensity (30-45 min) acclimation sessions on consecutive days at approx. 30°C and approx. 60% RH using a cycle ergometer. The CON group completed matched cycle training in moderate conditions (approx. 20°C, approx. 60% RH). Physiological measures during each treadmill trial included heart rate; core and skin temperatures; sweat Na+, K+ and Cl- electrolyte concentrations; and sweat rate. RESULTS: After the 4-d intervention, the ACC group had a moderate decrease of -11 (3 to -24 beats/min; mean and 90% CI) in the 30 min heart rate, and moderate to large reductions in electrolyte concentrations: Na+ -18% (-4 to -31%), K+ -15% (0 to -27%), Cl- -22% (-9 to -33%). Both ACC and CON groups had only trivial changes in core and skin temperatures and sweat rate. After the intervention, both groups perceived they were more comfortable exercising in the heat. The 4-d heat intervention had no detrimental effect on performance. CONCLUSIONS: Four 30-45 min high intensity cycle sessions in hot/humid conditions elicited partial heat acclimation. For full heat acclimation a more intensive and extensive (and modality-specific) acclimation intervention is needed for cricket players.

Variability in movement patterns during One Day Internationals by a cricket fast bowler.

PURPOSE: The time-motion characteristics and the within-athlete variability in movement patterns were quantified for the same male fast bowler playing One Day International (ODI) cricket matches (n=12). METHODS: A number of different time motion characteristics were monitored using a portable 5-Hz global positioning system (GPS) unit (Catapult, Melbourne, Australia). RESULTS: The bowler's mean workload per ODI was 8+/-2 overs (mean+/-SD). He covered a total distance of 15.9+/-2.5 km per game; 12+/-3% or 1.9+/-0.2 km was striding (0.8+/-0.2 km) or sprinting (1.1+/-0.2 km), whereas 10.9+/-2.1 km was spent walking. One high-intensity (running, striding, or sprinting) repetition (HIR) occurred every 68+/-12 s, and the average duration of a HI effort was 2.7+/-0.1 s. The player also completed 66+/-11 sprints per game; mean sprint distance was 18+/-3 m and maximum sprinting speed 8.3+/-0.9 m.s(-1). CONCLUSIONS: The movement patterns of this fast bowler were a combination of highly intermittent activities of variable intensity on the base of approximately 16 km per game. This information provides insight for conditioning coaches to determine the physical demands and to adapt the training and recovery processes of ODI fast bowlers.

The associations between fast bowling technique and ball release speed: a pilot study of the within-bowler and between-bowler approaches.

The inability of the between-bowlers methodology to control parameters external to technique could lead to erroneous significant and non-significant associations being reported between fast-bowling technique and ball release speed. Using Pearson's product - moment correlation, we first examined the effectiveness of a within-bowler methodology to identify associations between technique and ball release speed of an elite semi-open fast bowler over 20 deliveries. These results were compared with associations identified from a between-bowlers methodology in which 20 single-performance trials bowled by elite fast bowlers adopting a semi-open shoulder alignment were collated. Sufficient variation was observed in within-bowler ball release speed to allow f relationships to be identified between technique and ball release speed. Although greater variation in bowling technique parameters was observed in the between-bowlers methodology, no associations were identified between technique and ball release speed. Multiple stepwise regression analysis showed that 87.5% of the within-bowler variation in ball release speed can be attributed to run-up velocity, angular velocity of the bowling arm, vertical velocity of the non-bowling arm, and stride length. The within-bowler methodology provided significant detailed information about the individual bowler that the between-bowlers methodology overlooked, forming the basis of a performance enhancement programme. It is recommended that within-bowler methodology be used in future investigation of technique relationships.

Fast bowling arm actions and the illegal delivery law in men's high performance cricket matches.

This study investigated the bowling arm kinematics of 21 elite fast bowlers (mean +/- SD; age = 27.8 +/- 3.9 years) while performing in test, tour and one day international matches. Thirty-one of the 34 deliveries analysed exhibited straightening at the elbow joint (straightening min = 3 degrees, max = 22 degrees, mean +/- SD = 9 +/- 5 degrees), which by strict definition in the 2000 laws of cricket made them illegal. Five deliveries from three bowlers exhibited hyperextension of the bowling elbow (19 +/- 5 degrees). When assessed against an arbitrary threshold of 15 degrees for elbow straightening, ball speeds for deliveries above this threshold (39.5 +/- 2.0 m/s) were significantly faster (effect size = 1.4; p = 0.006) than deliveries below it (37.1 +/- 1.4 m/s). When grouped by delivery length, the bouncers and short deliveries recorded more elbow straightening (12 +/- 6.6 degrees) than the good length deliveries (9 +/- 4.4 degrees) and the full deliveries (8 +/- 5.7 degrees), although these were not statistically significant differences. The results of this study support the implementation of a tolerance threshold for assessing the legality of fast bowling actions. Further research is recommended into in-match kinematic modelling, laboratory based assessments of illegal bowling actions, perceptual aspects of bowling actions and remedial methods to reduce elbow straightening in bowling actions.

Anthropometric and strength correlates of fast bowling speed in junior and senior cricketers.

The aim of this study was to characterize relationships between anthropometric and isoinertial strength characteristics and bowling speed in junior and senior cricket fast bowlers. Subjects were first-class senior (n = 24; mean +/- SD age = 23.9 +/- 4.8 years, height = 187.4 +/- 4.8 cm, mass = 87.8 +/- 8.4 kg) and junior representative (n = 48; mean +/- SD age = 14.8 +/- 1.3 years, height = 175.7 +/- 9.8 cm, mass = 65.8 +/- 12.9 kg) male fast bowlers. A full anthropometric profile, upper- and lower-body isoinertial strength tests, and peak bowling speed (Vpeak) were assessed on the same day. The senior bowlers had a substantially faster Vpeak (126.7 km.h(-1)) than the juniors (99.6 km.h(-1)), a larger estimated muscle mass (seniors 40.0 +/- 3.9 kg, juniors 28.3 +/- 5.6 kg), and a greater bench press throw and deltoid throw (all p < 0.01). The best multiple predictors of Vpeak for the junior bowlers were the static jump, bench throw, body mass, percentage muscle mass, and height (multiple-correlation r = 0.86). For the senior bowlers, static jump and arm length correlated positively with Vpeak (multiple-correlation r = 0.74). The 1-legged countermovement jump was negatively correlated with Vpeak in both groups. We conclude that differences in Vpeak between junior and senior bowlers relate primarily to body mass and upper-body strength. However, lower body strength is a more important contributor to Vpeak in senior bowlers.

Injuries to elite male cricketers in Australia over a 10-year period.

This study analyses injuries occurring to Australian male cricketers at the state and national levels over 10 years using recently published international definitions of injury. Data was collected retrospectively for 3 years and then prospectively over the final 7 years. Injury incidence has stayed at a fairly constant level over the 10 years. Injury prevalence has gradually increased over the 10-year period but fell in season 2004-2005. Increasing match scheduling over the 10-year period has probably contributed to the increasing injury prevalence. Fast bowlers miss, through injury, about 16% of all potential playing time, whereas the prevalence rate for all other positions is less than 5%. Some match and schedule-related risks for bowling injury have been noted, including a greater risk of injury in the second innings of first class matches (compared to the first innings), a greater risk of injury in the second game of back-to-back matches and an increased risk of injury in the rare situation of enforcing the follow-on in a test match. The introduction of a boundary rope at all grounds has successfully eliminated the mechanism of injury from collision with fences whilst fielding. Cricket is a much safer sport to play at the elite level for batsmen, fieldsmen, wicketkeepers, and spin bowlers than the football codes, which are the other most popular professional sports in Australia.