20 research outputs found

    EFFECT OF THE LOCATION OF THE FOOT IMPACT POINT ON BALL VELOCITY IN A SOCCER PENALTY KICK

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    The aim of this study was to identify the impact point on the foot that maximizes ball velocity in a soccer instep penalty kick. One male player performed 23 maximum-effort penalty kicks using a wide range of impact points along the length of his foot. The kicks were recorded by a video camera at 100 Hz and a biomechanical analysis was conducted to obtain measures of impact point, ball projection velocity, and kinematics of the kicking leg. We found that ball velocity was insensitive to the location of the impact point (at least for positions between the ankle joint and the base of the toes). This result suggests that players should consider other factors (such as shot accuracy, shot reliability, and foot comfort) when selecting the impact point

    ADDING MASS TO THE SHOE DOES NOT AFFECT BALL VELOCITY IN A SOCCER PENALTY KICK

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    The aim of this study was to identify the optimum shoe mass that maximizes ball velocity in a soccer instep penalty kick. Two players performed 20–30 maximum-effort penalty kicks while wearing football shoes with lead weights attached to the base of the shoe (total mass: 0.26 – 0.81 kg). The kicks were recorded by a video camera at 100 Hz and a biomechanical analysis was conducted to obtain measures of ball projection velocity and kinematics of the kicking leg. We found that ball velocity was insensitive to shoe mass (at least for the range of shoe mass tested). An important contributing factor to the observed relationship was that the velocity of the kicking foot at ball impact decreased as the mass of the shoe increased. Our result indicates that players should not change their shoes before taking a penalty kick

    A mathematical modelling study of an athlete's sprint time when towing a weighted sled

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    This is the author's accepted manuscript. The final publication is available at Springer via http://dx.doi.org/10.1007/s12283-013-0114-2.This study used a mathematical model to examine the effects of the sled, the running surface, and the athlete on sprint time when towing a weighted sled. Simulations showed that ratio scaling is an appropriate method of normalising the weight of the sled for athletes of different body size. The relationship between sprint time and the weight of the sled was almost linear, as long as the sled was not excessively heavy. The athlete’s sprint time and rate of increase in sprint time were greater on running surfaces with a greater coefficient of friction, and on any given running surface an athlete with a greater power-to-weight ratio had a lower rate of increase in sprint time. The angle of the tow cord did not have a substantial effect on an athlete’s sprint time. This greater understanding should help coaches set the training intensity experienced by an athlete when performing a sled-towing exercise

    TAKE-OFF FORCES AND IMPULSES IN THE LONG JUMP

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    A series of jumps by an experienced female athlete were recorded with a force platform and a high-speed video camera. We obtained a wide range of run-up velocities by using direct intervention to set the length of the athlete’s run-up. In all jumps the horizontal take-off force was predominantly a backwards braking force and so the athlete’s horizontal velocity was substantially reduced during the take-off. The athlete’s breaking impulse increased with increasing run-up velocity, but not so much as to negate the increase in run-up velocity. The optimum long jump take-off technique is a compromise between the conflicting desires of generating vertical impulse and minimising the horizontal braking impulse. We currently have no firm recommendation as to the usefulness of a force platform in improving an athlete’s take-off technique

    THE EFFECT OF RUN-UP SPEED ON LONG JUMP PERFORMANCE

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    The effect of run-up speed on long jump performance was systematically examined using a technique intervention study. The results from the study were in good agreement with theoretical models and confirmed the accepted wisdom that the faster your run-up, the farther you will jump. However. the strength of the relation between jump distance and run-up speed (8 cm per 0.1 m/s) was less than that suggested by a cross-sectional study (13 cm per 0.1 m/s). We propose that the trend line from the technique intervention study indicates the improvement to be expected from better running technique, whereas the trend line from the cross-sectional study indicates the improvement to be expected from increased muscular strength

    TAKE-OFF TECHNIQUE IN THE HIGH JUMP

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    INTRODUCTION: Alexander (1990) produced a model of jumping that predicts optimum techniques that are in good agreement with those used by high jumpers and long jumpers. We have refined Alexander’s model and used it to more closely examine the take-off technique in the high jump. In particular, we examined the sensitivity of the athlete’s performance to deviations from the optimum technique, and the dependence of the optimum technique on the athlete’s leg strength and leg length. The results from this work are to be incorporated into a biomechanical analysis program conducted for Athletics Australia. The aim is to improve the performance of Australian high jumpers through relevant and timely biomechanical analysis. Similar work investigating the take-off in the long jump is also in progress. METHODS: The mathematical model incorporates the geometry of the athlete’s legs and the properties of the leg extensor muscles. In this model, the leg angle is the angle between the ground and the line joining the foot to the hip; and the knee angle is the angle included between the thigh and the shank. The model’s anthropometric values were adjusted to be representative of elite male and elite female athletes, and many jumps were then simulated with various run-up speeds and angles of the leg and knee at touchdown. RESULTS: The simulations predict the observed differences between male and female athletes in their optimum take-off technique (Dapena et al., 1990). Because of their longer legs and greater leg strength, male athletes should use a faster run-up and have a greater leg angle at touchdown than female athletes. For an individual athlete, jumping performance is only moderately sensitive to deviations from the optimum take-off technique. As training increases the athlete’s leg strength, the optimum jump performance improves, but the run-up speed must be faster, and the leg angle at touchdown must be increased. The simulations also predict the observed changes in jump performance, leg angle, and knee angle as an athlete uses a progressively faster run-up (Greig and Yeadon, 1997). It is planned to use the model to investigate the effect on jump performance of the athlete’s crural index, and of the design of the jumper’s shoe. CONCLUSIONS: This relatively simple model accurately predicts the observed relationships between the performance parameters in elite high jumpers. REFERENCES: Alexander, R. (1990). Optimum Take-Off Techniques for High and Long Jumps. Philosophical Transactions of the Royal Society of London, Series B 329, 3-10. Dapena, J., McDonald, C., Cappaert, J. (1990). A Regression Analysis of High Jumping Technique. International Journal of Sport Biomechanics 6, 246-260. Greig, M. P., Yeadon, M. R. (1997). The Influence of the Approach on High Jump Performance. Athletics Coach 30, 10-13

    THE OPTIMUM TAKEOFF ANGLE IN THE LONG JUMP

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    This study showed that the optimum takeoff angle for a long jumper may be predicted by combining the equation for the range of a projectile in free flight with the relations between takeoff speed, takeoff height, and takeoff angle for the athlete. The prediction method was evaluated using measurements of three experienced male long jumpers who performed maximum-effort jumps over a wide range of take-off angles. The calculated optimum takeoff angles (about 23°) were in good agreement with the athletes' competition takeoff angles

    BIOMECHANICAL ANALYSIS OF TWO LONG JUMP TAKE-OFF TECHNIQUES

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    A technique intervention strategy was used whereby the run-up velocities of two long jumpers were systematically varied. The take-off parameters that define the athlete's take-off technique showed reproducible changes in response to changes in run-up speed. The two athletes in the study used slightly different take-off techniques to achieve their performances
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