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

OPTIMAL TECHNIQUE, VARIABILITY, CONTROL, AND SKILLED PERFORMANCE

Optimisation is often used in an attempt to explain technique adopted in skilled sport performance. This might take the form of minimising joint torques in an expectation that the optimum simulated technique will resemble the actual performance. If a suitable optimisation criterion can be identified then this may give some insight into the adopted technique. In all human movement there is inherent variation so that no two performances are exactly the same. As a consequence skilled technique needs to be successful in a noisy environment and so optimised technique also needs to be robust to the inherent variation in coordination. In movements in which there is sufficient time for feedback control to operate it is to be expected that there will be greater variation in technique in those phases that adjustments are made. It is also to be expected that there will be little variation in technique for those phases where accurate coordination is crucial to the success of the movement. The aspect that often governs elite technique is that of achieving consistent success rather than some biomechanical measure of movement

Optimal Technique, Variability, Control, and Skilled Performance

Optimisation is often used in an attempt to explain technique adopted in skilled sport performance. This might take the form of minimising joint torques in an expectation that the optimum simulated technique will resemble the actual performance. If a suitable optimisation criterion can be identified then this may give some insight into the adopted technique. In all human movement there is inherent variation so that no two performances are exactly the same. As a consequence skilled technique needs to be successful in a noisy environment and so optimised technique also needs to be robust to the inherent variation in coordination. In movements in which there is sufficient time for feedback control to operate it is to be expected that there will be greater variation in technique in those phases that adjustments are made. It is also to be expected that there will be little variation in technique for those phases where accurate coordination is crucial to the success of the movement. The aspect that often governs elite technique is that of achieving consistent success rather than some biomechanical measure of movement

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

FACTORS INFLUENCING VARIATION IN DIVE HEIGHT IN 1M SPRINGBOARD DIVING

The aim of this study was to determine the factors contributing to variation in dive height in performing a 1m springboard dive. 15 performances of a forward dive pike by an international diver were recorded using high speed video (250 Hz) and were digitised manually. The relationships between variables at hurdle landing, during board contact and dive height were determined. Hip extension during board contact accounted for 77% of the variance in dive height

The effect of accounting for biarticularity in hip flexor and hip extensor joint torque representations

Subject-specific torque-driven models have ignored biarticular effects at the hip. The aim of this study was to establish the contribution of monoarticular hip flexors and hip extensors to total hip flexor and total hip extensor joint torques for an individual and to investigate whether torque-driven simulation models should consider incorporating biarticular effects at the hip joint. Maximum voluntary isometric and isovelocity hip flexion and hip extension joint torques were measured for a single participant together with surface electromyography. Single-joint and two-joint representations were fitted to the collected torque data and used to determine the maximum voluntary joint torque capacity. When comparing two-joint and single-joint representations, the single-joint representation had the capacity to produce larger maximum voluntary hip flexion torque (larger by around 9% of maximum torque) and smaller maximum voluntary hip extension torque (smaller by around 33% of maximum torque) with the knee extended. Considering the range of kinematics found for jumping movements, the single-joint hip flexors had the capacity to produce around 10% additional torque, while the single joint hip extensors had about 70% of the capacity of the two-joint representation. Two-joint representations may overcome an over-simplification of single-joint representations by accounting for biarticular effects, while building on the strength of determining subject-specific parameters from measurements on the participant.N/

The effect of accounting for biarticularity in hip flexor and hip extensor joint torque representations

Subject-specific torque-driven models have ignored biarticular effects at the hip. The aim of this study was to establish the contribution of monoarticular hip flexors and hip extensors to total hip flexor and total hip extensor joint torques for an individual and to investigate whether torque-driven simulation models should consider incorporating biarticular effects at the hip joint. Maximum voluntary isometric and isovelocity hip flexion and hip extension joint torques were measured for a single participant together with surface electromyography. Single-joint and two-joint representations were fitted to the collected torque data and used to determine the maximum voluntary joint torque capacity. When comparing two-joint and single-joint representations, the single-joint representation had the capacity to produce larger maximum voluntary hip flexion torque (larger by around 9% of maximum torque) and smaller maximum voluntary hip extension torque (smaller by around 33% of maximum torque) with the knee extended. Considering the range of kinematics found for jumping movements, the single-joint hip flexors had the capacity to produce around 10% additional torque, while the single joint hip extensors had about 70% of the capacity of the two-joint representation. Two-joint representations may overcome an over-simplification of single-joint representations by accounting for biarticular effects, while building on the strength of determining subject-specific parameters from measurements on the participant