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Barefoot vs. shod kicking in soccer — what's faster?
6.4 Sports Activity
Track 6. Sport Biomechanics - Joint ISB Track
The application of the lining must substantially contribute to the heat exchange reduction with the environment and simultaneously separate the moisture produced by the sweating foot. Both, the materials and the fabric structure will affect the overall performance of the lining. Three structures which combine different raw materials (soybean fibre, bamboo fibre, corn fibre, cotton, polypropylene and polyester) were studied. They have been tested in laboratory for their water vapour absorption and air permeability amongst other physical parameters. Tests with a thermal manikin have been used to measure its thermal insulation. However, in order to study moisture disposal, the present manikin can not be used which led to the development of a foot prototype. The goal was to construct a low cost and easy to use breathable prototype of the foot, capable of simulating the foot perspiration and temperature. As the number of soporiferous sweat glands per unit area along the foot varies strongly, it becomes important to differentiate the levels of regulation for various regions. With that propose several leathers and fabrics have been tested for permeability to be used as the material prototype. A model of the foot with at least three independent sections has been developed and it has been constructed. 4190 Mo-Tu, no. 34 (P61) Barefoot vs. shod kicking in soccer - what's faster? T. Sterzing, J. Kroiher & E. Hennig. Biemechanics Laboratory, University ef
Duisburg Essen, Essen, Germany Objective: Different soccer shoes evoke different ball velocities during full instep kicking [1]. This study investigates whether, in general, the artificial interface between foot and ball, the soccer shoe, acts as a rather enhancing, reducing or neutral piece of equipment for ball velocity during kicking. Methods: In a laboratory study 19 soccer players performed six full instep kicks in three shod, one sock and one barefoot kicking conditions. The unshod conditions exhibit no mechanical influence to the kicking, however the sock reduces skin pain. Ball velocity was measured by a radar gun. GRFs of the final stance leg step were obtained. Subjects gave a pain rating and a ball velocity ranking for all conditions. Results and Discussion: Subjects kicked faster being barefoot compared to being shod (p=0.05). This is especially remarkable as peak resultant shear force (p < 0.05) and time to peak resultant shear force (p < 0.05) of the stance leg indicate a more cautious approach to the kick when being unshod. This would rather suggest lower ball velocities due to kinetic chain theories. Here, the more cautious approach is overcompensated by superior collision mechanics. The unshod conditions were perceived most painfully (p<0.01). Despite perceiving highest pain when being barefoot subjects kicked fastest in this condition. The more painful kicking conditions were ranked lower with regard to ball velocity (p < 0.01). Conclusions: Soccer shoes do not naturally provide beneficial mechanical support for ball velocity. Anatomical structures perform better during full instep kicking than the functional unit of foot and shoe does. This mechanism is explained by a more plantarflexed ankle angle at initial ball contact in the barefoot condition as detected by high speed video. This leads to higher foot rigidity and less give during the kicking collision. Therefore, good soccer shoes should permit the full anatomical range of plantarflexion. Acknowledgement: This study was supported by Nike Inc., USA. References [1] Sterzing T., Hennig E., unpublished data.
4869 Mo-Tu, no. 35 (P61) Roll-over characteristics of prosthetic feet used in developing nations R.V. Gonzalez, M. Vaughan, S. Ayers. Biomedical and Mechanical
Engineering, LeToumeau University, Longview, Texas, USA The roll-over shapes of six prosthetic feet commonly used in third-world countries was performed in an attempt to quantify the degree of human foot functionality these feet provide amputees. Roll-over shape allows for the comparison of prosthetic feet to a biological foot by measuring the location of the center-of-pressure of the foot with respect to a fixed axis between the ankle and knee in the saggital plane. Six prosthetic feet were tested. Testing utilized a motion capture system and a force plate. Data for each prosthetic foot was recorded while mounted to a quasi-static foot tester and manually "walked" by applying a uniform vertical force measured by a force plate while infrared cameras captured positional data from reflective markers placed on the simulated ankle and knee. For comparison, a subject was similarly fitted with reflective markers and walked across the force plate to record a biological foot roll-over shape. Changing center-of-pressure of each foot was plotted with respect to a fixed line. Roll-over data of each foot was summarized and each prosthetic foot compared to the biological foot. Radii of curvature of the rollover shapes were also obtained for comparison. Results showed varying levels
$551
of imitation between the biological and each prosthetic roll-over shape. We believe the deviation of the prosthetic feet from the biological foot ideal is often a result of stiffness, misalignment, and/or poor design. Roll-over shape testing allows for a quantitative method in which to compare prosthetic feet to a biological foot. As a result of these tests, we believe we can use roll-over shape testing to develop a prosthetic foot that better mimics a biological foot thereby increasing comfort and mobility in the rehabilitation of lower-limb amputees in developing nations.
6.4 Sports Activity 6059 Mo-Tu, no. 36 (P61) Differences of standing vertical jump with different arm action X. Wei, Z. Du. Shanghai University of Sports, Shanghai, China Introduction: There were few studies to evaluate and explain the effects of different arm motions on standing vertical jump previously. The aim of present study was to analyse the performance of standing vertical jump with different arm swing motions (a beeline or arc line from the side of body to the top) and to compare the effects on standing vertical jumps between the two arm motion ways. Methods: Ten adult males were arranged to perform a series of maximal vertical jump, with their arms banded (one arm puts on the bosom and the other on the back), a beeline arm swing and arc line arm swing.The force, velocity, acceleration and height data were recorded during each performance by Vicon system, Kistler force platform and visual 3D. Results: Participant jumped significantly higher in the both arm swing conditions compared to the no-arm swing condition (P <0.05).The mean increased squat heights of beeline and arc line arm swing were 0.040m and 0.033m respectively. Additionally, the height of the center of mass and velocity at takeoff in beeline arm swing condition were 8% and 22% higher than those of arc line condition respectively (P <0.05). Conclusions: The results of our study showed the differences of standing vertical jump with different arm swing, and jump with beeline arm swing motion might be more superior than arc line. The mechanism may be due to the former store energy more than the latter, though it exhausts more than latter, and need the further investigation. References [1] Blake M., Ashby, et al. Role of arm motion in the standing long jump. J Biomech 2002; 35(12): 1631-1637. [2] Yoon Y.S., et al. Optimization of the standing vertical jump. J Biomech 1979; 12(8): 637. [3] Marcus G., et al. Optimal muscular coordination strategies for jumping. J Biomech 1991; 24(1): 1-10.
5566 Mo-Tu, no. 37 (P61) Complex biomechanical analysis of sports technique on the example of long jumps A. Egoyan, M. Mirtskhulava, D. Chitashvili, C. Moistrapishvili, R. Salukvadze, G. Piranashvili, T. Kotorashvili, I. Khipashvili, E. Korinteli, G. Eradze, Z. Pkhaladze. Physiology lab., State Academy of Physical Education and
Sport of Georgia, Tbilisi, Georgia In the present research we are trying to study sport technique of long jumps in order to make recommendations to athletes to improve their results. We have performed a complex mathematical analysis of long jump technique and obtained optimal values for the main parameters the results depend on. We have made a few recommendations to athletes. 1. The result depends basically on the sportsman's start speed V0 and ~J,,the angle between OX and V0. The result increases as V0, ~J,increase. The most important parameter is V0: its change is more effective than the change of ~J,.V0 depends mainly on the sportsman's physical fitness and qualification; 2. Losses of energy during the take-off phase must be minimal, to save his speed a sportsman must have good technique ("scissors"): he should be able to keep balance and hold his trunk upright as long as it is possible; 3. When pushing off, the angle 15 between r-radius-vector of the center of gravity and OX must be between 500 and 70°; 4. The result depends on the physical characteristics of the sportsman such as his height and body proportions, more perspective are tall thin sportsmen with long legs; 5. When jumping, a sportsman must take into account air drag and move his body in accordance with the rules of aerodynamics (decreasing caused by air drag is about 3-4%). The main advantage of this research is its complexity; we have studied how the result depends on the main parameters taking into account complex correlations between these parameters. The theoretical curves are in good agreement with the experimental data obtained by means of video-computer modeling [1]. A theoretical model considering air drag has been also provided.
Track 6. Sport Biomechanics - Joint ISB Track
The application of the lining must substantially contribute to the heat exchange reduction with the environment and simultaneously separate the moisture produced by the sweating foot. Both, the materials and the fabric structure will affect the overall performance of the lining. Three structures which combine different raw materials (soybean fibre, bamboo fibre, corn fibre, cotton, polypropylene and polyester) were studied. They have been tested in laboratory for their water vapour absorption and air permeability amongst other physical parameters. Tests with a thermal manikin have been used to measure its thermal insulation. However, in order to study moisture disposal, the present manikin can not be used which led to the development of a foot prototype. The goal was to construct a low cost and easy to use breathable prototype of the foot, capable of simulating the foot perspiration and temperature. As the number of soporiferous sweat glands per unit area along the foot varies strongly, it becomes important to differentiate the levels of regulation for various regions. With that propose several leathers and fabrics have been tested for permeability to be used as the material prototype. A model of the foot with at least three independent sections has been developed and it has been constructed. 4190 Mo-Tu, no. 34 (P61) Barefoot vs. shod kicking in soccer - what's faster? T. Sterzing, J. Kroiher & E. Hennig. Biemechanics Laboratory, University ef
Duisburg Essen, Essen, Germany Objective: Different soccer shoes evoke different ball velocities during full instep kicking [1]. This study investigates whether, in general, the artificial interface between foot and ball, the soccer shoe, acts as a rather enhancing, reducing or neutral piece of equipment for ball velocity during kicking. Methods: In a laboratory study 19 soccer players performed six full instep kicks in three shod, one sock and one barefoot kicking conditions. The unshod conditions exhibit no mechanical influence to the kicking, however the sock reduces skin pain. Ball velocity was measured by a radar gun. GRFs of the final stance leg step were obtained. Subjects gave a pain rating and a ball velocity ranking for all conditions. Results and Discussion: Subjects kicked faster being barefoot compared to being shod (p=0.05). This is especially remarkable as peak resultant shear force (p < 0.05) and time to peak resultant shear force (p < 0.05) of the stance leg indicate a more cautious approach to the kick when being unshod. This would rather suggest lower ball velocities due to kinetic chain theories. Here, the more cautious approach is overcompensated by superior collision mechanics. The unshod conditions were perceived most painfully (p<0.01). Despite perceiving highest pain when being barefoot subjects kicked fastest in this condition. The more painful kicking conditions were ranked lower with regard to ball velocity (p < 0.01). Conclusions: Soccer shoes do not naturally provide beneficial mechanical support for ball velocity. Anatomical structures perform better during full instep kicking than the functional unit of foot and shoe does. This mechanism is explained by a more plantarflexed ankle angle at initial ball contact in the barefoot condition as detected by high speed video. This leads to higher foot rigidity and less give during the kicking collision. Therefore, good soccer shoes should permit the full anatomical range of plantarflexion. Acknowledgement: This study was supported by Nike Inc., USA. References [1] Sterzing T., Hennig E., unpublished data.
4869 Mo-Tu, no. 35 (P61) Roll-over characteristics of prosthetic feet used in developing nations R.V. Gonzalez, M. Vaughan, S. Ayers. Biomedical and Mechanical
Engineering, LeToumeau University, Longview, Texas, USA The roll-over shapes of six prosthetic feet commonly used in third-world countries was performed in an attempt to quantify the degree of human foot functionality these feet provide amputees. Roll-over shape allows for the comparison of prosthetic feet to a biological foot by measuring the location of the center-of-pressure of the foot with respect to a fixed axis between the ankle and knee in the saggital plane. Six prosthetic feet were tested. Testing utilized a motion capture system and a force plate. Data for each prosthetic foot was recorded while mounted to a quasi-static foot tester and manually "walked" by applying a uniform vertical force measured by a force plate while infrared cameras captured positional data from reflective markers placed on the simulated ankle and knee. For comparison, a subject was similarly fitted with reflective markers and walked across the force plate to record a biological foot roll-over shape. Changing center-of-pressure of each foot was plotted with respect to a fixed line. Roll-over data of each foot was summarized and each prosthetic foot compared to the biological foot. Radii of curvature of the rollover shapes were also obtained for comparison. Results showed varying levels
$551
of imitation between the biological and each prosthetic roll-over shape. We believe the deviation of the prosthetic feet from the biological foot ideal is often a result of stiffness, misalignment, and/or poor design. Roll-over shape testing allows for a quantitative method in which to compare prosthetic feet to a biological foot. As a result of these tests, we believe we can use roll-over shape testing to develop a prosthetic foot that better mimics a biological foot thereby increasing comfort and mobility in the rehabilitation of lower-limb amputees in developing nations.
6.4 Sports Activity 6059 Mo-Tu, no. 36 (P61) Differences of standing vertical jump with different arm action X. Wei, Z. Du. Shanghai University of Sports, Shanghai, China Introduction: There were few studies to evaluate and explain the effects of different arm motions on standing vertical jump previously. The aim of present study was to analyse the performance of standing vertical jump with different arm swing motions (a beeline or arc line from the side of body to the top) and to compare the effects on standing vertical jumps between the two arm motion ways. Methods: Ten adult males were arranged to perform a series of maximal vertical jump, with their arms banded (one arm puts on the bosom and the other on the back), a beeline arm swing and arc line arm swing.The force, velocity, acceleration and height data were recorded during each performance by Vicon system, Kistler force platform and visual 3D. Results: Participant jumped significantly higher in the both arm swing conditions compared to the no-arm swing condition (P <0.05).The mean increased squat heights of beeline and arc line arm swing were 0.040m and 0.033m respectively. Additionally, the height of the center of mass and velocity at takeoff in beeline arm swing condition were 8% and 22% higher than those of arc line condition respectively (P <0.05). Conclusions: The results of our study showed the differences of standing vertical jump with different arm swing, and jump with beeline arm swing motion might be more superior than arc line. The mechanism may be due to the former store energy more than the latter, though it exhausts more than latter, and need the further investigation. References [1] Blake M., Ashby, et al. Role of arm motion in the standing long jump. J Biomech 2002; 35(12): 1631-1637. [2] Yoon Y.S., et al. Optimization of the standing vertical jump. J Biomech 1979; 12(8): 637. [3] Marcus G., et al. Optimal muscular coordination strategies for jumping. J Biomech 1991; 24(1): 1-10.
5566 Mo-Tu, no. 37 (P61) Complex biomechanical analysis of sports technique on the example of long jumps A. Egoyan, M. Mirtskhulava, D. Chitashvili, C. Moistrapishvili, R. Salukvadze, G. Piranashvili, T. Kotorashvili, I. Khipashvili, E. Korinteli, G. Eradze, Z. Pkhaladze. Physiology lab., State Academy of Physical Education and
Sport of Georgia, Tbilisi, Georgia In the present research we are trying to study sport technique of long jumps in order to make recommendations to athletes to improve their results. We have performed a complex mathematical analysis of long jump technique and obtained optimal values for the main parameters the results depend on. We have made a few recommendations to athletes. 1. The result depends basically on the sportsman's start speed V0 and ~J,,the angle between OX and V0. The result increases as V0, ~J,increase. The most important parameter is V0: its change is more effective than the change of ~J,.V0 depends mainly on the sportsman's physical fitness and qualification; 2. Losses of energy during the take-off phase must be minimal, to save his speed a sportsman must have good technique ("scissors"): he should be able to keep balance and hold his trunk upright as long as it is possible; 3. When pushing off, the angle 15 between r-radius-vector of the center of gravity and OX must be between 500 and 70°; 4. The result depends on the physical characteristics of the sportsman such as his height and body proportions, more perspective are tall thin sportsmen with long legs; 5. When jumping, a sportsman must take into account air drag and move his body in accordance with the rules of aerodynamics (decreasing caused by air drag is about 3-4%). The main advantage of this research is its complexity; we have studied how the result depends on the main parameters taking into account complex correlations between these parameters. The theoretical curves are in good agreement with the experimental data obtained by means of video-computer modeling [1]. A theoretical model considering air drag has been also provided.