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

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

TAKE-OFF TECHNIQUE IN THE HIGH JUMP

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

BIOMECHANICAL ANALYSIS OF TWO LONG JUMP TAKE-OFF TECHNIQUES

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

THE EFFECT OF RUN-UP SPEED ON LONG JUMP PERFORMANCE

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

Optimum take-off angle in the standing long jump

The aim of this study was to identify and explain the optimum projection angle that maximises the distance achieved in a standing long jump. Five physically active males performed maximum-effort jumps over a wide range of take-off angles, and the jumps were recorded and analysed using a 2-D video analysis procedure. The total jump distance achieved was considered as the sum of three component distances (take-off, flight, and landing), and the dependence of each component distance on the take-off angle was systematically investigated. The flight distance was strongly affected by a decrease in the jumper’s take-off speed with increasing take-off angle, and the take-off distance and landing distance steadily decreased with increasing take-off angle due to changes in the jumper’s body configuration. The optimum take-off angle for the jumper was the angle at which the three component distances combined to produce the greatest jump distance. Although the calculated optimum take-off angles (19–27º) were lower than the jumpers’ preferred take-off angles (31–39º), the loss in jump distance through using a sub-optimum take-off angle was relatively small

Optimum take-off angle in the long jump

In this study, we found that the optimum take-off angle for a long jumper may be predicted by combining the equation for the range of a projectile in free flight with the measured relations between take-off speed, take-off height and take-off angle for the athlete. The prediction method was evaluated using video measurements of three experienced male long jumpers who performed maximum-effort jumps over a wide range of take-off angles. To produce low take-off angles the athletes used a long and fast run-up, whereas higher take-off angles were produced using a progressively shorter and slower run-up. For all three athletes, the take-off speed decreased and the take-off height increased as the athlete jumped with a higher take-off angle. The calculated optimum take-off angles were in good agreement with the athletes' competition take-off angles

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

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