Artificial Soccer Turf What Shoes to Wear? Thorsten Sterzing, Clemens Müller, Thomas L. Milani thorsten.sterzing@hsw.tu-chemnitz.de Chemnitz University of Technology
Development of Artificial Soccer Turf (AT) 1 st Generation 1960 concrete layer no infill 2 nd Generation 1980 elastic layer sand infill 3 rd Generation 1990 elastic layer sand/rubber infill
AT included in FIFA Rules of The Game (2004) U 17 World Cup Peru 2005 U 20 World Cup Canada 2007 Young Boys Bern Switzerland Red Bull Salzburg Austria
FIFA 1-Star and 2-Star Installations Continent 1-Star 2-Star UEFA 109 121 AFC 35 12 CONCACAF 29 6 CAF 29 4 CONMEBOL 10 1 OFC 1 0 www.fifa.com (18. April 2010)
Game Characteristics 3 rd Generation - Only slight changes depending on playing level - Discrepancy of objective and subjective data - FIFA 2007 - Anderson et al. 2008 - Müller et al. 2009 Exception: Sliding Tacking
Injury Observations 3 rd Generation - No major differences in injury incidences - Ekstrand et al. 2006 - Fuller et al. 2007a - Fuller et al. 2007b - Steffen et al. 2007 Prospective Studies Critical Improvement compared to 1 st and 2 nd Generations of Artificial Turf
New Artificial Surface 3 rd Generation elastic layer sand infill rubber infill (traction) Traditional Natural Grass Shoes!? Purpose: Development of an AT Soccer Shoe Outsole - A Three Phases Project -
Project Chronology Phase I 2007 Status Quo Evaluation Phase II 2008 Prototype Modification Phase III 2009 Market Comparison
Comprehensive Evaluation of Athletic Footwear Performance Perception Biomechanical Mechanical Hennig & Milani 1996, Lafortune 2001, Sterzing et al. 2007
Performance Slalom Parcours Start/ Finish 2.00 m 2.20 m 72 3 repetitive runs per shoe condition 2 minutes rest between runs Shoe change between each run Variables - Running time - Running time perception Pylon Double Light Barrier Running Direction Krahenbuhl 1974, Sterzing et al. 2009
Perception Traction Several rapid cutting movements Questionnaire: 9-point perception scale Variable - Traction suitability
Biomechanical Cutting 45 cutting movement, two step approach 5 repetitive trials Variable - Force ratio: m-l shear/vertical 45 Force plate (Kistler,1 khz) Running direction high shear forces during cutting movements in soccer (Valiant, 1987)
Testing Protocol subject pool of 37 experienced soccer players (23.0 ± 3.4 years, 177.4 cm ± 4.3, 71.4 ± 6.1 kg) 4 different shoe models in each phase Randomization of shoe models FIFA 2-Star Liga Turf 240 22/4 RPU brown (Polytan) Mean and standard deviation Statistics Repeated measures ANOVA (p < 0.05) Post-hoc test: Bonferroni (p < 0.05)
Phase I Status Quo Evaluation Natural Grass Outsole Designs first prototype hard ground (HG) firm ground (FG) soft ground (SG) innovative design (ID) currently used on artificial turf DuoCell technology at forefoot
[s] 12 Slalom running time p<0.0001 Perception: Slalom running time p<0.0001 slower 5 11 4 10 3 9 2 8 HG [-] 0,6 FG SG ID Biomechanical force ratio Fx/Fz p=0.0012 0,5 0,4 0,3 0,2 0,1 0 HG FG SG ID faster 1 HG FG SG ID Traction suitability p<0.0001 very bad 9 8 7 6 5 4 3 2 very good 1 HG FG SG ID
Findings: Phase I Status Quo Evaluation first prototype Natural Grass Outsole Designs hard ground (HG) firm ground (FG) better suited soft ground (SG) innovative design (ID) less suited better suited Phase II prototypes based on the innovative design
Fong et al. 2009 Traction Concept Availability Mechanics Utilization Biomechanics Athlete Anatomy Anthropometrics Body Composition Motor Performance Skills Training Status Interface Material Geometry Loading Optimization of Traction for Maximization of Performance
Phase II Modified Prototypes innovative design Phase I (ID) DC-FG DuoCell only at forefoot FG design at rearfoot DC 85 DC 90 DuoCell at forefoot and rearfoot Slightly different TPU hardness
Slalom running time p=0.04 [s] 13 Perception: Slalom running time p=0.02 slower 4 12 3 11 2 10 1 9 8 ID DC-FG DC 85 DC 90 Biomechanical force ratio Fx/Fz p=0.70 0,6 faster 0 bad 0,4 5 0,3 4 0,2 3 0,1 2 ID DC-FG DC 85 DC 90 DC 90 7 6 very good DC-FG DC 85 Traction suitability p=0.10 0,5 0 ID 1 ID DC-FG DC 85 DC 90
Findings: Phase II Modified Prototypes innovative design Phase I (ID) DC-FG DC 85 DC 90 no negative effect of rearfoot DuoCell compared to rearfoot FG no effect of TPU hardness Phase III prototype based on DC 90 design
Phase III Market Comparison Predator Absolion PS TRX AG (AP) Tiempo Mystic II MG (NT) King XL Synthetic Grass HG (PK) final Prototype (DC 90) commercially available artificial turf designs
Slalom running time p=0.0035 12 Perception: Slalom running time p=0.0051 slower 5 11 4 10 3 9 8 0,6 2 AP NT PK DC 90 Biomechanical force ratio Fx/Fz p<0.0500 faster 1 bad 7 0,5 6 0,4 5 0,3 4 0,2 3 0,1 2 0 very good 1 AP NT PK DC 90 AP NT PK DC 90 Traction suitability p=0.0006 AP NT PK DC 90
Findings: Phase III Market Comparison Predator Absolion PS TRX AG (AP) Tiempo Mystic II MG (NT) King XL Synthetic Grass HG (PK) final Prototype (DC 90) Final prototype outperformed three commercially available shoes. Relatively short and evenly distributed stud configurations were identified to provide good functional traction to players. Comprehensive approach was shown to be successful for the development process of an artificial soccer turf outsole.
Thank you very much for your attention! This research was supported by