Cricket bowling: A two-segment Lagrangian model

In this study, a Lagrangian forward solution of the bowling arm in cricket is made using a two-segment rigid body model, coupled with projectile equations for the free flight of the ball. For given initial arm positions and constant joint torques, the equations are solved numerically to determine the ball speed and arm angle at release so that the ball can land on a predetermined position on the pitch. The model was driven with kinematic data from video obtained from an elite bowler. The model can be analysed in order to study the biomechanics of the bowling arm as well as to quantify the effects of changing input parameters on the trajectory and speed of the ball

Three-dimensional biomechanical analysis of fast bowling in cricket

A three-dimensional (3-D) dynamics model of the human body has been developed to provide a mechanical basis for evaluating fast bowling technique. Thirty-four fast bowlers were selected for study and divided into four groups according to ball release speed. A five camera 240 Hz motion analysis system (Motion Analysis Corp.) was used to track markers on the bowler delivering a series of balls at a target in line with the wickets, and a Bertec force plate was used to measure ground reaction forces. The marker arrangement allowed for the 3-D motion tracking of all major body segments. The resulting kinematic and force plate data of a typical ball were fed into a computer model using Mathematica's Mechanical Systems Pack. This is a set of packages designed for the analysis of spatial rigid body mechanisms by implementing a dynamics formulation with Lagrangian multipliers. The computer model gives a 3-D representation of the human body as a system of fifteen rigid body segments with mass and inertia properties. The model can output the kinematics, inverse solution dynamics, kinetics and powers for each body segment of a bowler delivering a ball. Bowling in cricket is a unique method of propelling a ball at high speed so that it reaches a batter 20 m away after having bounced once off the pitch. Fast bowlers reduce the time available for the batsman to execute the correct stroke, and therefore increase the chance of error. There are a number of coaching texts available that propose various hypotheses on the correct technique of fast bowling, which have been mostly based on the experiences of successful fast bowlers. However, dynamics has not played any meaningful role in the development of fast bowling technique. In this thesis, the synthesis of a 3-D rigid body model of bowling was used to calculate the inverse solution dynamics, kinematics, kinetics and segment power flows to test certain established hypotheses on the mechanics of bowling technique. The analysis also probed for mechanical differences in technique between bowling speed groups. It was found that lower trunk, upper trunk, bowling arm, front arm, front leg, and rear leg interacted in such a way that each segmental motion was subject to a kinematic sequencing pattern and a dynamics actuation pattern determined by the calculation of muscle powers. Also, it was possible to differentiate between the consequential motion of a segment, and the actuation of a segment motion. This information provides a perspective of how the body needs to move in order to achieve correct technical form. The results show that that certain established concepts of bowling technique, such as front arm 'sweeping' and 'pull down', lower trunk flexion, and rear leg action have only been partially specified. Also, in certain technical and sequencing aspects there are differences between the bowling speed groups

Optimising the front foot contact phase of the cricket fast bowling action

Cricket fast bowling is a dynamic activity in which a bowler runs up and repeatedly delivers the ball at high speeds. Experimental studies have previously linked ball release speed and several technique parameters with conflicting results. As a result, computer simulation models are increasingly being used to understand the effects of technique on performance. This study evaluates a planar 16-segment whole-body torque-driven simulation model of the front foot contact phase of fast bowling by comparing simulation output with the actual performance of an elite fast bowler. The model was customised to the bowler by determining subject-specific inertia and torque parameters. Good agreement was found between actual and simulated performances with a 4.0% RMS difference. Varying the activation timings of the torque generators resulted in an optimised simulation with a ball release speed 3.5 m/s faster than the evaluation simulation. The optimised technique used more extended front ankle and knee kinematics, increased trunk flexion and a longer delay in the onset of arm circumduction. These simulations suggest the model provides a realistic representation of the front foot contact phase of fast bowling and is suitable to investigate the limitations of other kinematic or kinetic variables on fast bowling performance

Study of Healthcare Personnel with Influenza and other Respiratory Viruses in Israel (SHIRI): study protocol

Abstract Background The Study of Healthcare Personnel with Influenza and other Respiratory Viruses in Israel (SHIRI) prospectively follows a cohort of healthcare personnel (HCP) in two hospitals in Israel. SHIRI will describe the frequency of influenza virus infections among HCP, identify predictors of vaccine acceptance, examine how repeated influenza vaccination may modify immunogenicity, and evaluate influenza vaccine effectiveness in preventing influenza illness and missed work. Methods Cohort enrollment began in October, 2016; a second year of the study and a second wave of cohort enrollment began in June 2017. The study will run for at least 3 years and will follow approximately 2000 HCP (who are both employees and members of Clalit Health Services [CHS]) with routine direct patient contact. Eligible HCP are recruited using a stratified sampling strategy. After informed consent, participants complete a brief enrollment survey with questions about occupational responsibilities and knowledge, attitudes, and practices about influenza vaccines. Blood samples are collected at enrollment and at the end of influenza season; HCP who choose to be vaccinated contribute additional blood one month after vaccination. During the influenza season, participants receive twice-weekly short message service (SMS) messages asking them if they have acute respiratory illness or febrile illness (ARFI) symptoms. Ill participants receive follow-up SMS messages to confirm illness symptoms and duration and are asked to self-collect a nasal swab. Information on socio-economic characteristics, current and past medical conditions, medical care utilization and vaccination history is extracted from the CHS database. Information about missed work due to illness is obtained by self-report and from employee records. Respiratory specimens from self-collected nasal swabs are tested for influenza A and B viruses, respiratory syncytial virus, human metapneumovirus, and coronaviruses using validated multiplex quantitative real-time reverse transcription polymerase chain reaction assays. The hemagglutination inhibition assay will be used to detect the presence of neutralizing influenza antibodies in serum. Discussion SHIRI will expand our knowledge of the burden of respiratory viral infections among HCP and the effectiveness of current and repeated annual influenza vaccination in preventing influenza illness, medical utilization, and missed workdays among HCP who are in direct contact with patients. Trial registration NCT03331991 . Registered on November 6, 2017.https://deepblue.lib.umich.edu/bitstream/2027.42/146186/1/12879_2018_Article_3444.pd

A preliminary forward solution model of cricket bowling

Abstract. In order to produce high ball release speeds, fast bowlers in cricket require high run-up speeds, generate large ground reaction forces, and produce high joint torques. Extensive magnitudes of external loading in combination with kinematic factors such as counter-rotation experienced during fast bowling have been associated with a high incidence of lower lumbar injury. A full mechanical analysis of the technique is lacking such that attempts to modify techniques remain on a trial and error basis. The purpose of this study was to develop a forward solution model to predict the causal factors associated with counter-rotation of fast bowlers. It was shown that a reduction of the shoulder-hip torque differential lead to a minimisation of counter-rotation. This approach potentially gives the cricket coach a scientific means of modifying the technique of high-risk action bowlers to reduce their susceptibility to lower lumbar injury

Biomechanics of lumbar spine injury in young Australian fast bowlers

Cricket fast bowlers have a high incidence of serious lumbar injuries, such as lesions in the pars interarticularis. As lumbar loading is the causal mechanism of such injuries, the purpose of this study was to find relationships between lumbar spine kinetics, selected kinematic variables and the subsequent development of lumbar spine injury. At the beginning of the cricket season, the bowling techniques of 13 young fast bowlers (17.4 ± 1.9 years) from the Cricket New South Wales development squad were assessed using a three-dimensional motion analysis system (200 Hz). Using Kintrak software, kinematics and lumbar spine kinetics (forces and moments) were calculated about the L5/S1 joint during the arm acceleration phase. Towards the end of that season, each bowler underwent an MRI scan that took sagittal and axial sequences (T1 and T2) from T12 to S1. The largest kinetic values were lumbar compression forces and lumbar flexion moments. Maximum lumbar spine moments were associated with several kinematic variables such as front knee angle, pelvic and thoracic rotation at ball release and shoulder counter-rotation. There was an increased incidence of S1, L4 and L5 stress fractures and responses when shoulder counter-rotation exceeded 44°, lumbar compression force exceeded 8 time body weight (BW) and compression multiplied by flexion torque exceeded 20 BW2 m. This study suggests that lumbar spine forces and moments are dependent on a number of fundamental kinematic descriptors of bowling technique. By modifying the technique, bowlers may be able to reduce lumbar loads to reduce the risk of lumbar injury