Raymond Lloyd

The relative economy of two different rucksack designs

A comparison of power output recorded by an SRM powercrank and Kingcycle test rig.

The kinematics of the wrist in fast bowling in cricket

Soccer instep kick kinematics has been examined in the literature through 2D analysis and more recently 3D analysis (Levanon and Dapena, 1998: Medicine and Science in Sports and Exercise, 30, 917–927). The importance of ball approach prior to kick execution has been recognised in other sports such as rugby (Jackson and Baker, 2001: The Sport Psychologist, 15, 48–65). However, there is limited research on the relationship between ball approach, shot accuracy and kick kinematics in soccer. The objective of this case study was to establish the effect of altering the ball approach, on kick kinematics and shot accuracy, when performing instep penalty kicks.Annual Conference of the British Association of Sport and Exercise Sciences Liverpool, 7th – 9th September 2004 PART I. BIOMECHANICS 20. Parameter determination for a torque-driven model of springboard diving takeoff P.W. Kong, M.R. Yeadon and M.A. King School of Sport and Exercise Sciences, Loughborough University, Ashby Road, Loughborough, LE11 3TU In order to develop a planar computer simulation model of a springboard and a 8-segment diver suitable for investigating diving takeoffs (Fig. 1), it is necessary to determine subject-specific model parameters. These include: 1) springboard, 2) segmental inertia, 3) strength, 4) wobbling mass, and 5) foot-springboard interface parameters. The aim of this study was to determine such parameters either directly from measurements or indirectly using an angle-driven model. Subject-specific parameters were determined from an elite female diver who provided informed consent. Testing procedures were approved by the University Ethical Advisory Committee. The vertical behaviour of the springboard was modelled as a linear mass-spring system with no damping and with stiffness as a linear function of foot placement. The stiffness and effective board mass were measured using a dynamic board loading method (Miller and Jones, 1999: Research Quarterly for Exercise and Sport, 70, 395–400). The horizontal deflection was a quadratic function of the vertical deflection and the board angle was a linear function of the vertical deflection. Body segmental inertias were calculated from 95 anthropometric measurements of the diver using a mathematical model of the human body (Yeadon, 1990: Journal of Biomechanics, 23, 67–74). To ensure that the torque generators produced realistic joint torques, maximum isometric and isovelocity torques of the diver were obtained using an isokinetic dynamometer. Movements measured included flexion and extension of shoulder, hip, knee and ankle. A 10parameter fit was used to express torque as a function of joint angle and angular velocity. Wobbling masses were included in the shank, thigh and trunk segments to model the movement of soft tissues during impact. The wobbling mass inertias were calculated from body composition and density reported in the literature and scaled to the diver. Each wobbling mass was attached to the body segment through two pairs of non-linear damped springs. Initial estimates of stiffness and damping were chosen so as to produce appropriate displacement and oscillation frequency. The elastic properties of the foot-springboard interface were represented by three pairs of spring-dampers acting on the heel, ball and toes. The stiffness and damping of these elastic elements, along with the refined estimation ofwobblingmass parameters and springboard stiffness, were determined using an angle-driven model. This was achieved by driving the model with joint angle time histories obtained from 200 Hz video recordings of diving performance from a one-metre springboard and minimising the difference in orientation and linear and angular momentum between simulation and performance using the Simulated Annealing optimisation algorithm (Corana et al., 1987: ACM Transactions on Mathematical Software, 13, 262–280). Four dives with minimum and maximum angular momentum in the Fig. 1. Simulation model of a springboard and a diver. Journal of Sports Sciences, 2005, 23, 93–223 Journal of Sports Sciences ISSN 0264-0414 print/ISSN 1466-447X online # 2005 Taylor & Francis Group Ltd DOI: 10.1080/02640410512331334413 forward and reverse groups were used to obtain a common set of parameters. The mean difference between simulation and performance was 8.3%. This paper described how subject-specific parameters could be measured experimentally or determined indirectly using an angle-driven model. These model parameters will then be used in a torque-driven model which, after satisfactory evaluation, will be used to investigate diving takeoff techniques and to optimise performance. Acknowledgment: This study was supported by the International Society of Biomechanics. 21. Strategies for maximum velocity movements in relation to reaction time and performance