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Kicking in Soccer
Kicking in Soccer Thorsten Sterzing Institute for Sports Science, Chemnitz University of Technology, Germany International Society of Biomechanics in Sports 2010 Congress, Marquette, MI, USA 19.07.-23.07.2010 Kicking: Art and Sports Sculpture “Soccer Player” Renée Sintenis - Berlin, Germany 1927 Soccer Subject University of Duisburg-Essen, Germany 2005 1 Outline • Kicking Movement • Measurement Technology • Performance Criteria • Influence of Footwear • Research Perspectives Movement Measurement Technology Footwear Performance Perspective Kicking: Complex Motor Movement Bauer 1990 5 Phases: 6 Phases: − Approach − Support leg − Kicking leg − Approach angle − Plant foot forces − Swing limb loading − Hip flexion and knee extension − Foot to ball contact Barfield 1998 − Follow-through Movement Measurement Technology − Foot to ball contact − Ball flight Lees et al. 2010 Performance Footwear Perspective 2 Kicking Leg – Angular Velocity Lees 1998 Movement Measurement Technology Performance Footwear Perspective Kicking Leg – Segment Speed Lees 1998 Movement Measurement Technology Performance Footwear Perspective 3 Key Aspects for Fast and Accurate Kicking Velocity: Accuracy: − Kicking Type, Technique − Skill level, Limb Dominance − Age, Maturity, Gender − Muscle Strength & Power − Approach Speed − Kicking Velocity Reduction − Foot to Ball Contact Point − Ball Spin − Approach Speed and Angle − Energy Transfer between Body Segments Kellis & Katis 2007 Foot to ball impact characteristics Movement Measurement Technology Performance Footwear Perspective Foot to Ball Contact: Impact Phase Open - loop movement Duration: 6 - 16 ms various authors initial full final Displacement of the ball Mixture of impact-like and throwing-like aspects Tsaousidis & Zatsiorsky 1996 Movement Measurement Technology Performance Footwear Perspective 4 Impact Phase Shinkai et al. 2009 Movement Measurement Technology Performance Footwear Perspective Kicking Techniques • Full Instep p Instep Kicks: • Inner Instep • Outer Instep Other: • Side Foot • Toe Kick • Knuckle Kick Movement Measurement Technology Spin Performance Specific Techniques Footwear Perspective 5 Predominant Kicking Techniques – Purposes Full Instep Inner Instep Side Foot Women 51 88 330 Men 42 60 407 Team incidents during a 90 minute soccer game, Althoff et al. 2010 Passing, Crossing Clearance Shots on Goal Movement Measurement Technology Performance Footwear Perspective Full Instep Kick Giovanni van Bronckhorst (Netherlands) – World Cup 2010: Uruguay vs. Netherlands (2-3) Movement Measurement Technology Performance Footwear Perspective 6 Inner Instep Kick Yasuhito Endo (Japan) – World Cup 2010: Denmark vs. Japan (1-3) Movement Measurement Technology Performance Footwear Perspective Side Foot Kick Elano (Brazil) – World Cup 2010: Brazil vs. North Korea (2-1) Movement Measurement Technology Performance Footwear Perspective 7 Kicking Performance Velocity • Levanon & Dapena 1998 • Nunome et al. 2002 • Neilson & Jones 2005 •… Basic Performance Criteria Accuracy Movement Measurement Technology Performance • Kristensen et al. 2005 • Scurr & Hall 2009 • Sterzing et al. 2009 Footwear Perspective High Speed Video provided by Shinkai et al. 2009 Movement Measurement Technology Performance Footwear Perspective 8 Motion Analysis Systems Movement Measurement Technology Performance Footwear Perspective Footwear Perspective Radar Gun • 20 milliwatt Ka band dual horn microwave • • • • accuracy: speed range: acquisition time: update rate: Movement 0.1 1 to 480 0.01 100 km/h km/h seconds per second Measurement Technology Performance 9 Measurement Technology for Kicking Accuracy • Plywood wall laminated with carbon paper for impact imprints Finnoff et al. 2002 • Circular electronic target (concentric wire frame) • Ball contact generates electrostatic charges • Software based determination of ball impact location Hennig et al. 2009 • Digital camera recording (25 Hz) Scurr & Hall 2009 Movement Measurement Technology Performance Footwear Perspective Kicking Accuracy Measurement Technology - High speed video capturing of ball impact location (200 Hz) CMOS Camera HCC-1000, VDS Vosskühler, Germany - Accuracy determination: distance ball center to bull’s eye MaxTRAQ 2.06, Innovisions Systems, MI, USA Sterzing et al. 2009 Movement Measurement Technology Performance Footwear Perspective 10 Relation of velocity (VEL) and accuracy (ACC) Sterzing et al. 2009 Simultaneous quantification of VEL and ACC of full instep, inner instep and side foot kicks • Speed - accuracy trade-off • Variability of VEL and ACC Movement Measurement Technology Performance Footwear Perspective 6 Kicking Conditions 2 Performance Tasks Maximization ACC (Max ACC) 3 Kicking Techniques Movement Maximization VEL (Max VEL) Full Instep I II Inner Instep III IV Side Foot V VI Measurement Technology Performance Footwear Perspective 11 Methods - 19 soccer players (4th - 6th league) - Kicking of stationary ball – 6 m target distance - 6 repetitive trials per kicking condition (total: 36 kicks) - Mean and standard deviation (SD) - Coefficient of variability (CoV) across subjects - Repeated measures ANOVA - Post-hoc test (Bonferroni) - Coefficient of variability (CoV6 repetitive kicks) Movement Measurement Technology within subjects Performance Footwear Perspective Experimental Set-up - Radar gun for VEL measurements Stalker Pro, Applied Concepts, TX, USA - High Hi h speed d video id capturing t i off b ballll iimpactt llocation ti (200 H Hz)) CMOS Camera HCC-1000, VDS Vosskühler, Germany - ACC determination: distance ball center to bull’s eye MaxTRAQ 2.06, Innovisions Systems, MI, USA Movement Measurement Technology Performance Footwear Perspective 12 [km/h] Performance Task Kicking Velocity (p< 0,001) Max ACC Max VEL Reduction of VEL to 82-86%, independent of kicking technique Full Instep Movement Inner Instep Side Foot Technique q Full Instep Full Instep Task Max VEL Max ACC Mean 103,16 87,76 SD 6,51 11,17 CoV 0,063 0,127 Inner Instep Inner Instep Max VEL Max ACC 100,75 82,99 6,90 14,45 0,068 0,174 Side Foot Side Foot Max VEL Max ACC 89,79 77,38 5,65 11,27 0,063 0,146 Measurement Technology Performance Kicking Accuracy (p<0,001) [cm] Footwear Perspective Performance Task Max ACC Max VEL Decrease of ACC by 29-41%, dependent on kicking technique Full Instep Movement Inner Instep Side Foot Technique q Full Instep Full Instep Task Max VEL Max ACC Mean 59,51 45,93 SD 14,04 9,90 CoV 0,236 0,216 Inner Instep Inner Instep Max VEL Max ACC 50,85 39,65 12,29 11,02 0,242 0,278 Side Foot Side Foot Max VEL Max ACC 40,53 28,83 14,38 7,90 0,355 0,274 Measurement Technology Performance Footwear Perspective 13 Within Subject Variability – (CoV6 repetitive kicks) VEL ACC Technique Full Instep Full Instep Task Max KV Max KA CoV6 kicks 0,034 0,044 CoV6 kicks 0,633 0,550 Inner Instep Inner Instep Max KV Max KA 0,032 0,052 0,477 0,613 Side Foot Side Foot Max KV Max KA 0,029 0,047 , 0,573 0,572 , Reduction of velocity did not lead to more constant accuracy. Movement Measurement Technology Performance Footwear Perspective Findings • VEL differences between techniques confirmed • ACC differences between techniques fundamentally quantified • VEL and ACC relation appeared stable for the two performance tasks • Variability of VEL extremely low within subjects Motor Input • Variability of ACC considerably high especially within subjects Motor Output Movement Measurement Technology Performance Footwear Perspective 14 Discussion of Speed – Accuracy Trade-off Tennis Serve Slice Kick Straight p = n. s. Ball Velocitty [km/h] Ball Accura acy [cm] p < 0.01 Sterzing & Rodewald 2010 Movement Measurement Technology Performance Footwear Perspective Does footwear influence kicking velocity? commercial shoe models 2004 Copa Mundial PR Mania Tiempo Premier [km/h] p < 0.05 100 97.5 95 92.5 90 87.5 85 82.5 80 < Copa Mundial Movement Mercurial Vapor AZT 90 II PR Mania Tiempo Premier AZT 90 II Mercurial Vapor Measurement Technology Performance Footwear Perspective 15 Requirements of Soccer Footwear Questionnaire n = 249 less 5 important 4,5 4 3,5 3 2,5 2 1,5 more important 1 Flexibility Kicking Accuracy Kicking Velocity Comfort Spin Weight Traction Ball Sensing Stability Protection Durability Sterzing et al. 2007 Movement Measurement Technology Performance Footwear Perspective Kicking Velocity & Soccer Footwear Movement Measurement Technology Performance Footwear Perspective 16 Systematic Evaluation of Isolated Shoe Features 9 Movement Measurement Technology Performance Footwear Perspective General Testing Procedures Biomechanics Laboratory University of Duisburg-Essen Movement Measurement Technology Radar Gun Stalker Pro Performance Footwear Perspective 17 General Testing Procedures ctd. Force Plate – Kistler Photo Cell Arrangement Swing Phase Time: foot strike (GRFs) to initial ball movement (photo cell) Movement Measurement Technology Performance Footwear Perspective General Testing Procedures ctd. Movement Measurement Technology Performance Footwear Perspective 18 Neutral Shoe Method at Contra Lateral Foot Support Foot Kicking Foot Movement Measurement Technology Performance Footwear Perspective General Testing Procedures ctd. • About 20 experienced soccer players • Familiarization with laboratory testing environment Warm-up Practice trials • 6 maximum full instep kicks per shoe condition – stationary ball 3-step approach Standardized resting intervals Randomization of shoe conditions between subjects • Ranking of ball velocity Rating of study specific items Movement Measurement Technology Performance Footwear Perspective 19 Support Foot Traction Diego Forlan (Uruguay) – World Cup 2010: Uruguay vs. Netherlands (2-3) Movement Measurement Technology Performance Footwear Perspective Support Foot Traction Yasuhito Endo (Japan) – World Cup 2010: Denmark vs. Japan (1-3) Movement Measurement Technology Performance Footwear Perspective 20 Plantar Pressures – Support Foot Sterzing & Hennig 2005 Peak Pressure Time to Peak Pressure Movement Measurement Technology Performance Footwear Perspective Plant Foot Forces Barfield 1995 Movement Measurement Technology Performance Footwear Perspective 21 ZFG FSG FFG HFG Swing Phase Time Resultant Shear Force max. p < 0.01 p < 0.01 [N] 1400 [ms] 135 1200 1000 800 600 400 200 0 130 125 120 115 110 105 100 ZFG Movement HFG FFG FSG Measurement Technology ZFG ZFG p < 0.01 slow 105 100 95 90 85 fast 80 FFG FSG Perception Ball Velocity p < 0.01 HFG FSG Perspective FFG G HFG ZFG FFG Footwear Performance Ball Velocity [km/h] HFG 4,5 4 3,5 3 2,5 2 1,5 1 FSG ZFG HFG FFG FSG Functional traction necessary for fast kicking Movement Measurement Technology Performance Footwear Perspective 22 Shod vs. Barefoot Kicking Beach Soccer Regular Soccer Movement Measurement Technology Performance Footwear Perspective Ball Condition outdoor – regular • circumference: • weight: indoor – regular 68.6 cm 436.6 436 6g • circumference: • weight: 71.9 cm 422.9 422 9g Reduction of Skin Pain Movement Measurement Technology Performance Footwear Perspective 23 Kicking Velocity own shoe OSH BAR SOC AAA NNN [km/h] p = 0.05 100 97,5 95 92,5 90 87,5 85 82,5 Mean (SEM) 80 OSH Movement NNN Measurement Technology AAA SOC BAR Footwear Performance Perspective Perception Variables own shoe OSH Perception Pain Perception Ball Velocity worse better p < 0.01 5 high 8 7 3 6 5 2 4 3 low OSH NNN AAA SOC BAR p < 0.01 9 4 1 BAR SOC AAA NNN 2 1 OSH NNN AAA SOC BAR Mean (SEM) Movement Measurement Technology Performance Footwear Perspective 24 Impact Phase: High Speed Video (1 kHz) Reduction of „passive, forced plantarflexion“ for barefoot kicks initial full final „Passive, forced plantarflexion“ for shod kicks Lees 1993, Shinkai et al. 2009 Movement Measurement Technology Stance Leg Performance Footwear Stud Configuration Traction Properties Functional Traction/ Swing Phase Time Shoe Models Multiple Complex Features Interdependent Mechanisms Shoe Upper Material Interaction Ball – Shoe Dorsal Foot Protection Reduction Pain Rigidity Lower Limb/Foot Effective Mass Toe Box Height Angle Metatarsophalangeal Joint Comfort Improvement Comfort Shoe Weight Shoe Weight Effective Mass/ Foot Velocity Effective Mass/ Foot Velocity Outsole Stiffness Foot Rigidity/ Foot Deformation Capacity/ Rebound Effect Soccer Shoe Perspective Ball Velocity Swing Leg Shoe as such Player Shoe Influence Movement Shoe Property No Influence Potential Influence Measurement Technology Mechanism Performance Sterzing & Hennig 2008 Footwear Perspective 25 Summary – Kicking Velocity • Functional, rather than maximal, traction at the support foot is needed. • Soccer shoes at the kicking foot actually reduces ball velocity. • Some shoe features influence kicking velocity, velocity others do not. not • Both feet need to be considered for adequate footwear design. Kicking Foot Movement Measurement Technology Support Foot Performance Footwear Perspective Kicking Accuracy & Soccer Footwear Movement Measurement Technology Performance Footwear Perspective 26 Kicking Accuracy Chu-Young Park (South Korea) – World Cup 2010: Uruguay vs. South Korea (2-1) Movement Measurement Technology Performance Footwear Perspective Kicking Accuracy – Benefit Hypotheses • Shape: Homogenous pressure distribution between ball and shoe • Friction: High friction between ball and shoe • Spin: Spin production allows stable flight path • Ball Sensing: Better ball sensing • Shoe Weight: Larger moment of inertia results in more stable swing leg path • Support foot stability: Enhancement of kicking foot movement control Hennig & Sterzing 2010 Movement Measurement Technology Performance Footwear Perspective 27 Set-up • Circular electronic target (concentric wire frame) • Ball contact generates electrostatic charges • Software based determination of ball impact location Footwear Conditions Movement Measurement Technology Footwear Performance [cm] 36 35 34 ++ * 33 Perspective ++ ++ ** p < 0.01 p < 0.01 * + * p < 0.05 p < 0.05 + * + ** + * 32 31 30 ** 29 + 28 A-PRED Movement A-TUNE BAREF Measurement Technology N-ALG NT-SYN NT-LEA Performance Footwear Perspective 28 Discussion: Barefoot vs. Shod Kicks • Bony structures of the foot may create pressure peaks not allowing a homogenous pressure distribution between ball and foot. • Sh Shoe upper material t i l may provide id an iinterface t f providing idi more h homogenous pressure distribution between foot and ball. Polyurethane soft foam 10 Shore A, 6 mm Movement Measurement Technology Dr. Scholl Silicone Gel Pads Performance Footwear Perspective Follow-up Study: Foot Padding Side Foot Kicks Instep Kicks Movement Measurement Technology Performance Footwear Perspective 29 Implementation of Knowledge into Products provided by Nike Inc., USA Nike Laser Elite Series T90 Laser Soccer shoe specifically designed to enhance accuracy by even pressure • shape correcting foam inside the shoe • flat shot shield on top at ball contact area for a full instep kick Movement Measurement Technology Performance Footwear Perspective Research Perspective Siphiwe Tshabalala (South Africa) – World Cup 2010: South Africa vs. Mexico (1-1) Movement Measurement Technology Performance Footwear Perspective 30 Research Perspective Maicon (Brazil) – World Cup 2010 Brazil vs. North Korea (2-1) Movement Measurement Technology Performance Footwear Perspective Research Perspective Luis Fabiano (Brazil) – World Cup 2010: Brazil vs. Ivory Coast (3-1) Movement Measurement Technology Performance Footwear Perspective 31 Research Perspective Andrés Iniesta (Spain) – World Cup 2010: Netherlands vs. Spain (0-1) Movement Measurement Technology Performance Footwear Perspective Status Quo: Review Articles 2007 - 2010 Movement Measurement Technology Performance Footwear Perspective 32 Future Directions • Kicking analysis of non-stationary balls (rolling, bouncing balls) • Gender • Ball construction • Determination of performance influencing variables University of Nagoya, Japan Movement Measurement Technology Performance Footwear Perspective Thank you very much for your attention! 33