CURRENT TOPICS IN SPORTS PODIATRY

The Biodynamics of Soccer and Soccer Cleat Design

Different field conditions require different patterns and types of cleats.

By Howard Liebeskind, DPM lions of fans and participants around the world, manufacturers of around the world, and more recent - soccer / are now more This article is provided exclusively ly its popularity has unquestion - committed than ever to meeting the to Podiatry Management by the Ameri - ably taken a foothold in the United needs of youth, adolescent, and ad - can Academy of Podiatric Sports States. It now vanced players. By Medicine. The AAPSM serves to ad - finds itself em - integrating con - vance the understanding, prevention bedded within cepts previously and management of lower extremity our culture (Fig - A quality and reserved for the sports and fitness injuries. The Acade - ure 1), be it on biodynamically sound elite and profes - my believes that providing such knowl - the street, beach, sional player, in edge to the profession and the public playground, or soccer must conjunction with will optimize enjoyment and safe par - the uncountable evidence-based ticipation in sports and fitness activi - soccer fields that allow for complete design and bio - ties. The Academy accomplishes this dot our country, freedom of function compatible com - mission through professional educa - and one is now ponents, soccer tion, scientific research, public aware - hard pressed to and movement. boots are reaching ness and membership support. For ad - find a moment consumers with a ditional information on becoming a where the game is quality and func - member of the AAPSM please visit our not being played. tional capacity website at www.aapsm.org or circle As a result of the exponential that has never been seen before. #151 on the reader service card. growth of soccer in the United As a profession and as individual States and continued growth and so - practitioners, we now more than occer is constantly immersed phistication of soccer/ ever have the responsibility to em - in a dynamic brace soccer as part of our culture Sof strategic and professional landscape (Figure change and physi - 2). The millions of beginning, inter - cal demand as mediate, and advanced players who players become live near our clinics require the high - stronger, faster, est level of care from sports podia - more agile, and fit trists and members of the multidisci - at younger ages. plinary sports team to meet their All this is evident growing clinical needs. Having a to the observer of basic introduction into the biody - professional soc - namics of soccer and a sophisticated cer, but especially understanding of the functional so for those who components of soccer boots can put follow and partici - the clinician in good stead with the pate in youth soc - challenges that he or she will face cer globally. Soc - when the next soccer injury or podi - cer’s public face is Figure 1: Global soccer icon David Beckham of the Los Ange - atric-related soccer malady presents. the focus of bil - les Galaxy in a “friendly match” versus FC Barcelona). Continued on page 190 www.podiatrym.com MARCH 2011 • PODIATRY MANAGEMENT 189 Soccer... movements, there is a change of speed Movement Dynamics every five to six sec - Soccer is characterized by sprinting, stopping, cut - onds. Such activity ting, and pivoting situations where shoe relations are es - requires a most sup - sential and frictional resistance must be within an opti - portive and com - mal range. 1 During the progressions of a typical 90- fortable cleat con - minute professional or international match a player will struction (Figure 3). frequently cover 8,000 to 11,000 meters. Two-thirds of Although youth the total distance covered is generally associated with soccer players might walking and jogging and one-third is associated cruising, not come within a sprinting, and backing. Approximately 800 meters of fraction of running each game requires bursts of 10-40 meters. Within these as much as or as forcefully as those in the professional game, soccer shoe development teams now incorporate the most important characteristics of pro - fessional cleats for Figure 3: U.S. Soccer Star Landon proportionate play. Donovan in action.

Functional Requirements of Soccer Boots A quality and biodynamically sound soccer shoe must allow for complete freedom of function and movement. Jiri Dvorak, MD, FIFA Chief Medical Officer; Howard F Liebe - 2 skind, DPM, Team Podiatrist US National Team; Bob Bradley, It must also provide total comfort and support. Unfortu - Head Coach, US Men's National Team; Bert Mandelbaum, nately, the principles governing control and comfort will MD, Team Physician, US National Team often be at odds with each other. The more control a cleat exhibits, the less flexible and more sturdy and con - trolling its structure will be. The opposite is true of the comfort scenario. One will find the more comfortable cleat to have a more flexible and somewhat less stable en - vironment. Both present with advantages and disadvan - tages. Developing a hybrid cleat that provides ergonomic performance and the best combination of comfort and control should be a guiding principle for manufacturers.

Basic Structural and Functional Characteristics of Soccer Boots The goal of today’s product development teams is to adequately address flexibil - ity and stability within the confines of a lightweight . Incorporating these elements in conjunction with a clean functional kicking surface will yield longer periods of grip, in - creased friction between the boot and , greater ball control, increased power and swerve, along with biomechanical sta - bilities (Figure 4). Excessive motion of the foot during play has long plagued boot manu - Figure 4: Boots facturers and develop - ment teams. This has been addressed vigorously over the past several years. Numerous improvements are now part of the boot’s environment; these include bet - Continued on page 192

190 PODIATRY MANAGEMENT • MARCH 2011 www.podiatrym.com Soccer...

ter lining materials, softer/more conforming construc - tions, and more effective lacing systems. Excessive motion can lead to a multitude of issues ranging from simple blistering to severely debilitating tendinopathies and stress injuries. Many soccer-specif - ic functional and stabilizing components are now combined to provide the control and comfort needed for youth, adolescent and advanced play.

Lasting Characteristics of Soccer Boots

External Last Dynamics Lasts are forms on which boots are constructed. The global three-dimensional shape of a boot mimics the design form of the last and gives the upper its shape and volume. Anatomical lasts are more con - toured to match the shape of the foot, while generic lasts are based on morphological averages. Individuals with rectus or moderately pronated foot types will likely find themselves most comfortable in boots fabricated from a somewhat straight or slightly curved last. Those with an adducted forefoot or a clini - cally supinated foot type will find a slightly curved lasted or a more significantly curve lasted boot to their liking.

Internal Last Dynamics A boot’s footbed can have a profound impact on play - er performance. Foot-bed construction delivers the opti - mal blend of stability and flexibility and lends personality to the shoe. It is the functional interface between the play - er’s foot and the studs found on the exterior of the outsole plate. The internal last refers to the structure of the foot- bed found under the sockliner of the boot. A quality inter - nal last construction, along with a well-designed sockliner, can help provide proper midfoot support, torsional con - trol, and forefoot flexibility for the user. Despite best attempts, supportive adjuncts found in many boots may not always provide the needed con - trol for the foot and might need to be replaced by a prescriptive insert or functional orthotic appliance. Or - thotic control in soccer boots is a constantly evolving science due to the myriad of seasonal manufacturing changes in boot design. Boots should be submitted to a soccer-specific orthotics laboratory, along with the pa - tient’s casts and/or digital data to properly accommo - date the player’s foot, chosen footplate design, and in - ternal/external lasting dynamic. Elite and professional soccer players are known to occa - sionally wear their cleated shoes one to one and a half sizes (U.S.) smaller than their known Brannock measurements. For this reason, it is essential to follow the boot submission guidelines for proper orthotic fabrication and fit. A properly advised internal and external supportive boot structure can minimize common soccer maladies such as calcaneal apophysitis, plantar fasciitis, shin splints/anterior tibial tendinitis, posterior tibial ten - dinitis, and turf toe, just to name a few.

The Upper The upper is that portion of the cleat visualized from Circle #29 Continued on page 193

192 PODIATRY MANAGEMENT • MARCH 2011 www.podiatrym.com Soccer... ferences in stability between the vari - ioning to the foot, disperses stud ous versions of lightweight shoes. pressure, and reduces foot-to-boot dorsal, medial and lateral views. It slip (that can lead to blisters and covers all but the contacting plantar The External Heel Counter frictional conditions). surface of the boot. More than just a The heel counter is a structure that place for advertising, it acts as a pro - anatomically cradles the back of the Field Conditions and Cleat tective functional foot covering. It is heel. It must be bonded strongly to the Assortment firmly bonded to the outsole plate. outsole plate as well as the remainder Field conditions frequently dic - The upper contributes significantly of the upper (the soft portion of the tate the need for variation and toward medial to lateral stability cleat that surrounds the foot). Higher change in one’s cleat pattern and within the boot and is also of impor - heel counters tend to yield greater rear - cleat type. We generally break tance in controlling the ball during foot control to the vigorously training down pitch conditions and cleat play. It has unique and distinct fea - player. A well-constructed counter will types into various categories for tures as determined by the fabrica - not bend out of alignment with varus outdoor play: tor; the upper may be synthetic or or valgus game force and will maintain Turf Fields (TF) leather. Synthetics don’t over- a parallel, vertical position when Hard Ground (HG) stretch and don’t absorb water. In viewed from the posterior of the cleat, Firm Ground (FG) addition, they are gaining populari - even after long-term use. If the counter Soft Ground (SG) ty because of their ability to influ - “gives” to either side or a parallelo - Regardless of environmental con - ence swerve on the ball. gram appears, then the cleat is at a ditions, the outsole and cleat pattern Some synthetically manufactured functional deficit. A quality external must communicate with the pitch and boots now weigh less than six heel counter should be rigid. It must yield maximum grab and traction. ounces. Despite the perceived bene - also be accompanied by comfortable fits of lightweight boot technology, padding on the internal surface to pre - Cleat, Blade, and Stud studies are now beginning to indicate vent friction, irritation, and blistering. Patterns for Outdoor Play that weight reduced versions should Cleat, blade, and stud patterns, not take precedence at the expense of Sockliner as well as their placement and de - pedal stability. There also appears to The sockliner is a dynamically sign, are an art and a science. Re - be evolving evidence validating dif - fabricated insole that offers cush - Continued on page 194

www.podiatrym.com MARCH 2011 • PODIATRY MANAGEMENT 193 Soccer... • Firm Ground (FG) —for playing on the firm to moderately forgiving field search and development in conjunction with field-test - Firm ground cleats are perhaps the most commonly ing have provided the playing public with a myriad of used cleat type; they generally vary from 10-14 on the excellent choices. Studs are firmly bonded or optional - outsole plate. Firm ground blades and studs provide and ly screwed into the outsole plate depending on prefer - address pivot points, impact points, and stability in ence, functional need, and pitch conditions. order to maintain control and comfort for the average player. Blades and round studs are equally • Turf Field (TF) —for play on extreme - preferred in today’s market place. In addi - ly hard and/or original synthetic surfaces tion, firm ground cleats help each player These cleats have been designed for harsh keep a low center of gravity on a field that and/or extreme field conditions as well as has been fairly well manicured (Figure 5). older original synthetic surfaces. These finely studded shoes are most helpful where the • Soft Ground (SG) —for playing on soft field is balanced or when natural grass may field not be available or in its best form. They are Soccer shoes for rain-soaked or soft field grippy and can provide maneuverability. conditions occasionally require longer, de - tachable studs. Replaceable studs are found • Hard Ground (HG) —for play on in various shapes and forms, generally num - hard unforgiving field conditions bering six, and are used most frequently by These cleats generally have short studs the most advanced and competitive player. and appear in fairly uniform patterns across They are fabricated in different lengths the outsole plate. In this grouping of cleats, Figure 5: Typical FG cleat (12mm-19mm), so one can adjust his or her pattern the studs are prepared from thermal plastic or soccer shoes based on the condition of the rubber-like materials. They are very effective for grab in dif - field at the time of play. Soft ground studs should not be ficult-to-penetrate field surfaces and conditions. They can used on firm fields because they can lead to a higher in - provide adequate traction and simultaneous comfort with - jury rate. Detachable studs are declining in popularity out significant loss of mechanical control. Studs tend to be due to the fact that today’s fields have better drainage. shorter and softer than the Firm Ground (FG) variety. Many professional soccer players now use a mixed SG/FG system for standard field conditions.

Summary Biomechanical design concepts, once reserved for cleats worn only by professional , are now found in numerous models used by youth players. Choosing the proper soccer boot based on the ’s foot type will lead to improved performance and will reduce the frequency of injury. With a fundamental understanding of the biodynamics of soccer and soccer cleats, podia - trists can advise and protect those athletes who seek ad - vice and guidance. By embracing soccer as part of our new cultural sports landscape, the “beautiful game” or “jogo bonito” can bring you the same enjoyment expe - rienced by those who have sought your services. I

References 1 Ekstrand J., Nigg B.M.: Surface Related Injuries in Soccer. Am J Sports Med., 1998. 2 Lees, A and Nolan, L., The Biomechanics of Soccer: A Re - view. Journal of Sports Sciences, (1998) 16, 211-234.

Dr. Liebeskind has been team podia - trist to the U.S. Men’s and Women’s National soccer teams for the past 19 years, serving the United States Soccer Federation through a combined seven FIFA World Cups. He currently sits on the Medical Advisory Board of the USSF and is a member of the Ameri - can Academy of Podiatric Sports Medicine. Dr. Liebeskind also serves as team podiatrist to the Los Angeles Galaxy and Chivas USA of Major League Soccer in addition to the UCLA and Pepperdine University Athletic Departments.

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