A SIMULATION STUDY OF THE INTERNAL TWISTING TORQUE IN THE FOUETTÉ TURN

The purpose of this study was to investigate the effects of the magnitude of the twisting torque for one revolution of a Fouetté turn. Simulations were performed using a simple model comprising the supporting leg and the remainder of the body. It is shown that when the dancer turns more than one revolution with a small twisting torque, the turn will be decelerated and will finally stop. A large twisting torque is required at the start of each turn in order to increase the angular momentum which will subsequently decrease during the turn due to friction

Optimised performance of the backward longswing on rings

Many elite gymnasts perform the straight arm backward longswing on rings in competition. Since points are deducted if gymnasts possess motion on completion of the movement, the ability to successfully perform the longswing to a stationary final handstand is of great importance. Sprigings et al. (1998) found that for a longswing initiated from a still handstand the optimum performance of an inelastic planar simulation model resulted in a residual swing of more than 3° in the final handstand. For the present study, a three-dimensional simulation model of a gymnast swinging on rings, incorporating lateral arm movements used by gymnasts and mandatory apparatus elasticity, was used to investigate the possibility of performing a backward longswing initiated and completed in handstands with minimal swing. Root mean square differences between the actual and simulated performances for the orientations of the gymnast and rings cables, the combined cable tension and the extension of the gymnast were 3.2°, 1.0°, 270 N and 0.05 m respectively. The optimised simulated performance initiated from a handstand with 2.1° of swing and using realistic changes to the gymnast's technique resulted in 0.6° of residual swing in the final handstand. The sensitivity of the backward longswing to perturbations in the technique used for the optimised performance was determined. For a final handstand with minimal residual swing (2°) the changes in body configuration must be timed to within 15 m s while a delay of 30 m s will result in considerable residual swing (7°)

PERFORMANCE SENSITIVITY TO PERTURBATIONS IN ACTIVATION TIMING

This study investigated the sensitivity of optimum jumping performances to perturbations in activation timing. A planar eight-segment computer simulation model was used to simulate the takeoff phase in a high jumping performance. The model was evaluated and subsequently used to produce an optimum performance with a jump height of 2.63 m. The mLJscle activation onset timings at the knee were then varied by ± 5 ms and the effect on the simulated performance was determined. By simply varying the knee activation onset timings the performance did not change in terms of jump height, but the simulations included penalties which indicated that anatomical constraints had been violated. Reoptimisation with a measure of robustness included resulted in an optimum simulated jump of 2.32 m with no penalties which was unaffected by 5 ms perturbations

DNA sequence of histidine-3 from two Neurospora wild-types.

We report sequence differences between laboratory strains of Neurospora within his-3,and corrections to published sequence for this locus for ST74A strains, of possible significance to experiments using histidine mutants for gene replacement and gene targeting

COORDINATION IN DYNAMIC JUMPING

This study investigated coordination in dynamic jumping using a forward dynamics computer simulation model. A planar eight-segment torque-driven model was used to match the takeoff phase in a recorded running jump for height and recorded jump for distance by varying the torque generator activation timings. Two optimisations were then carried out to maximise height reached and distance travelled for each set of initial conditions used in the matching simulations. Although for each set of initial conditions, the order of activation onset timing was different for the two optimisations, the timing of activation onset in the optimisations for height and distance using the same initial conditions was very similar. This study has shown that the optimal activations are more a function of the initial conditions than the selection of maximal height or maximal distance

OPTIMISATION OF PERFORMANCE IN RUNNING JUMPS FOR HEIGHT

This study investigates the effect of approach conditions and takeoff technique on optimum performance. A planar eight-segment computer simulation model was used to simulate the takeoff phase in high jumping. Optimisations based on performances in the laboratory and at an athletics track were carried out to maximise the height reached by the mass centre in the flight phase. Three pairs of optimisations were performed: (i) optimisation of technique, (ii) optimisation of technique and initial conditions, (iii) optimisation of technique, initial conditions and approach velocity. In the first pair of optimisations the increases in height were 0.12 m and 0.17 m respectively. In the second pair of optimisations the additional increases in height were 0.09 m and 0.19 m and in the third pair further increases of 0.42 m and 0.02 m were obtained

THE INFLUENCE OF CRICKET PITCH LENGTH ON BALL RELEASE BY JUNIOR BOWLERS

Most junior cricket is played on pitches not much shorter than the 22 yards that adults play on. Young bowlers often struggle to bowl with good technique on these relatively long pitches, having to release the ball almost horizontally to achieve the distance, while adults typically bowl downwards at around 7° below horizontal. In this study ball release by 20 junior seam bowlers was analysed when they bowled on two different pitch lengths. It was found that the ball release angle was 3.4° lower on a 16 yard compared to a 19 yard pitch, while other release measures, including ball speed, were not substantially changed. Maintaining ball speed while bowling into the pitch more should enable players to achieve greater success and develop more variety in their bowling

CONSTRAINTS AND ROBUSTNESS CONSIDERATIONS IN THE OPTIMISATION OF SPRINGBOARD DIVING TAKEOFF TECHNIQUE: A SIMULATION STUDY

The aim of this study was to investigate the effects of imposing anatomical constraints and robustness requirements on the optimisation of springboard diving takeoff technique. A planar eight-segment model of a diver with torque generators together with a springboard model was used to optimise takeoff techniques for maximum rotational potential in the forward dive group by varying the activation timings of the torque-generators. Optimisation 1 imposed no constraints or robustness requirements. Optimisation 2 imposed anatomical constraints. Optimisation 3 imposed anatomical constraints and a requirement of robustness to perturbations in activation timing. The results showed that imposing both anatomical constraints and robustness requirements have a substantial effect on optimum simulated performance

A NEW MODEL OF THE SPRINGBOARD IN DIVING

This paper presents a model which describes the vertical, horizontal and rotational movement of a diving springboard. Model parameters were determined from experimental data. The springboard model was used in conjunction with a diver model to simulate a diving takeoff. Diving performance of an elite female diver was recorded at 200 Hz and was digitised to obtain kinematic data used to drive the simulation. There was good agreement in terms ot linear and angular takeoff conditions between the performance and the simulation. It is concluded that the proposed model is an improved representation of the springboard as a simple mass-spring system. This model will be used in conjunction with a diver model to investigate takeoff techniques and optimise diving performance