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97 Injury specific orthotic therapy
WORKSHOP 97-98
Injury specific orthotic therapy P. Fleet*
Stud placement in australian football boots: Does it make a difference? S, Bartold* The University of South Australia
Sports footwear has changed enormously in appearance over the past few years. If we are to believe the manufacturers, there has also been significant change in the function of athletic footwear. Design for all the codes of football however, may have lagged behind, and strategies implemented to help reduce injury and improve performance in other sports categories, appear, to a large degree to have bypassed football. At the elite level, Australian Rules Football (ARF) places very high demands on the athlete. Not the least of these demands is the ability for the athlete to accelerate rapidly, and to make sudden, sharp changes in direction. In this regard, the grip coefficient between the outsole of the football boot and the playing surface is critical. There is however, a fine line between providing the grip an athlete needs to stay on their feet, and inducing so much grip that the boot does not release under very high loading, producing potential for injury, particularly transmission of rotary load to the knee. In 1996, Lambson et al published a three-year prospective study of football boot cleat design for grid iron, and concluded that a particular style of cleat was associated with a higher torsional resistance and concomitantly significantly higher incidence of anterior cruciate ligament injury. Whilst the direct contribution of footwear to injury remains controversial, there remains little doubt that correctly designed football boots can be protective of injury. The purpose of this study was to investigate the grip characteristics of two different football boot stud plate designs across 3 different target motions. Method: Three experienced male, Australian Rules footballers, with no injury history, mean age 24.6 years, were required to perform three separate weight bearing maneuvers, commonly experienced during the course of a game of ARF, in new football boots with different outsole cleat configuration. One design designated XL21 comprised a standard molded plastic soccer boot configuration of 9 forefoot cleats and 4 rearfoot cleats. The second design, designated Lethal, comprised a purpose built Australian Rules outsole, with asymmetrical polyethylene cleats, arranged in a concentric circular pattern, in both forefoot and rearfoot. The tasks were: a straight dash, a side step, and a plant and turn to the left. These tasks were performed on synthetic turf overlying a fourcell force plate (Kistler Instruments Corp. Grand Island. NY). x- and y-directional ground reaction force data was collected for each subject, over 5 trials of each task. The distance between each load cell and the centre of the force plate was calculated, and the torque for each subject and trial was obtained by multiplying the distance by the x- and y-directional loads. Results: The impulse measured in N.s showed no significant difference between footwear in the straight dash trial, with both designs offering acceptable levels of grip. However, for both the side step and plant and turn tasks, there was a significant increase in impulse of the Lethal compared to XL21 trial, indicating a higher grip coefficient for the Lethal during these tasks. The mean torque for all trials was also calculated with a statistically significant decrease in mean torque for the Lethal compared to the XL21. This indicates increased ease of turning. Conclusion: The results of this study indicate that stud placement and arrangement can have a significant influence on the grip characteristics of ARF boots with respect to a cutting maneuver and side step, but little effect on grip during the kick phase of a straight dash. This information may be useful in calculating the most effective outsole and cleat combination to maximize grip, and minimize potentially harmful torsional resistance. This research was funded by the Asics Research and Development Department, Kobe, Japan. 61
Injury specific orthotic therapy P. Fleet*
Stud placement in australian football boots: Does it make a difference? S, Bartold* The University of South Australia
Sports footwear has changed enormously in appearance over the past few years. If we are to believe the manufacturers, there has also been significant change in the function of athletic footwear. Design for all the codes of football however, may have lagged behind, and strategies implemented to help reduce injury and improve performance in other sports categories, appear, to a large degree to have bypassed football. At the elite level, Australian Rules Football (ARF) places very high demands on the athlete. Not the least of these demands is the ability for the athlete to accelerate rapidly, and to make sudden, sharp changes in direction. In this regard, the grip coefficient between the outsole of the football boot and the playing surface is critical. There is however, a fine line between providing the grip an athlete needs to stay on their feet, and inducing so much grip that the boot does not release under very high loading, producing potential for injury, particularly transmission of rotary load to the knee. In 1996, Lambson et al published a three-year prospective study of football boot cleat design for grid iron, and concluded that a particular style of cleat was associated with a higher torsional resistance and concomitantly significantly higher incidence of anterior cruciate ligament injury. Whilst the direct contribution of footwear to injury remains controversial, there remains little doubt that correctly designed football boots can be protective of injury. The purpose of this study was to investigate the grip characteristics of two different football boot stud plate designs across 3 different target motions. Method: Three experienced male, Australian Rules footballers, with no injury history, mean age 24.6 years, were required to perform three separate weight bearing maneuvers, commonly experienced during the course of a game of ARF, in new football boots with different outsole cleat configuration. One design designated XL21 comprised a standard molded plastic soccer boot configuration of 9 forefoot cleats and 4 rearfoot cleats. The second design, designated Lethal, comprised a purpose built Australian Rules outsole, with asymmetrical polyethylene cleats, arranged in a concentric circular pattern, in both forefoot and rearfoot. The tasks were: a straight dash, a side step, and a plant and turn to the left. These tasks were performed on synthetic turf overlying a fourcell force plate (Kistler Instruments Corp. Grand Island. NY). x- and y-directional ground reaction force data was collected for each subject, over 5 trials of each task. The distance between each load cell and the centre of the force plate was calculated, and the torque for each subject and trial was obtained by multiplying the distance by the x- and y-directional loads. Results: The impulse measured in N.s showed no significant difference between footwear in the straight dash trial, with both designs offering acceptable levels of grip. However, for both the side step and plant and turn tasks, there was a significant increase in impulse of the Lethal compared to XL21 trial, indicating a higher grip coefficient for the Lethal during these tasks. The mean torque for all trials was also calculated with a statistically significant decrease in mean torque for the Lethal compared to the XL21. This indicates increased ease of turning. Conclusion: The results of this study indicate that stud placement and arrangement can have a significant influence on the grip characteristics of ARF boots with respect to a cutting maneuver and side step, but little effect on grip during the kick phase of a straight dash. This information may be useful in calculating the most effective outsole and cleat combination to maximize grip, and minimize potentially harmful torsional resistance. This research was funded by the Asics Research and Development Department, Kobe, Japan. 61