Fig. 16.1
Reebok women’s running shoe
The shoe upper which cradles the foot can be subdivided into a toe box, vamp, throat, collar, and heel cup. The closure (lacing) system serves to secure the shoe to the foot in a manner not to adversely impede function and comfort. The midsole acts to dissipate the forces of impact during the stance phase of gait and it acts to augment the transfer of stance phase forces through the lower extremity during the act of running. It is composed of a cushioning component which may include specialized stabilizing support units, thermal plastic units, and various specialized impact absorbing and force dissipating components. The outsole of the shoe is composed of a durable material with a sheet-like or modular pattern which promotes additional cushioning, support, and traction without sacrificing the transfer of stance phase forces through the lower extremity. The sock liner/foot-bed is the removable surface which serves to support the foot. It is typically composed of a fabric-covered and cushioned material molded to the shape of the foot which serves to promote a comfortable fit while wicking moisture and dissipating friction. It may also act to augment midsole cushioning and the transfer of stance phase forces through the lower extremity.
The modern running shoe can trace its roots back over four decades to the innovations and design concepts first explored by Coach Bill Bowerman of Oregon; however, the modern running shoe now more adequately blends anatomical form with biomechanic function. The modern running shoe is built around a model of the foot or last. While each shoe manufacturer maintains their own unique lasts, all lasts can be organized into one of three general categories based upon the shape of the last. A curve last has a distinct “C-shape,” and when bisected by an imaginary line extending from center of heel through the forefoot more of the shoe will appear medial to the bisection. This is easily viewed when the shoe is examined from the bottom of the outsole. Curve-lasted shoes are best suited to runners with a normal to cavus foot type with adduction of the forefoot. A straight last is characteristically straight, and when bisected from center of heel to forefoot the shoe is divided into two nearly equal halves. These shoes are best suited to runners with a normal to pes planus foot type with a more abducted forefoot. A combination last represents a hybrid of a curve last and straight last; the rearfoot portion of the shoe is straight while the forefoot portion of the shoe is more curved. When bisected this shoe appears straight through the rearfoot and midfoot with a slight tendency to be adducted through the forefoot. This last best suits the widest range of foot types.
Running shoes can also be categorized by the method of construction. Slip lasts are constructed in a manner that secures the upper of the shoe at the midsole with a serpentine stitched line. These shoes afford the maximum degree of flexibility and the lowest level of overall stability. A board last shoe applies a fiber board from heel to toe which is glued to the upper where the upper joins the midsole. This construction is inexpensive and affords the greatest degree of heel to toe stiffing and overall resistance to longitudinal torque. A combination last blends the advantages of slip and board last construction by securing the rearfoot portion of the shoes upper to the midsole via a fiber board or stiffener leaving the forefoot serpentine stitching exposed. This construction is very popular and has undergone refinements which have integrated the rearfoot stiffener directly to the upper not by direct gluing but rather by stitching the stiffener perimeter directly to the upper at the union with the midsole. This shoe construction provides a reliable and stable rearfoot while maintaining forefoot flexibility without sacrificing longitudinal stability. These refinements to the classical combination last have permitted shoe designers to integrate the shoe upper with the lasting permitting a more effective coupling of upper to midsole.
The most visible component of the modern distance running shoe is the upper. The upper is composed of a breathable tough and lightweight material which is reinforced with various swatches of synthetic leather to promote structural integrity, medial–lateral sway stability, and to enhance forefoot flexibility at heel off through toe-off. A handful have improved lining designs to the point that all interior seams have been eliminated. This is a significant advantage for the athlete who is susceptible to blistering. Likewise shoe tongue designs have improved balancing padding without excessive bulk. Traditionally a U-shaped throat has been utilized; this design is highly tolerant to a wide variety of midfoot anatomies ranging from the cavovarus foot to the low pes planus foot type. Various lacing systems have been employed but the variable lacing system is the most popular and functional. This system easily adapts to the introduction of a speed lacing system using elastic laces or a lace lock system.
The midsole of the distance running shoe has undergone the greatest evolution. The modern midsole is constructed from a variety of cushioning materials, stabilizers and support components, or thermal plastic units (TPU). The role of the midsole is to absorb and dissipate impact, stabilize the foot, and enhance the forward progression of the runner. Ethyl vinyl acetate (EVA), polyurethane (PU), sealed oil and gel chambers, and sealed air chambers represent the most common materials used. Each of these materials comes in a range of firmnesses, and unique placement into the midsole will impart specific cushioning, flexibility, and movement transfer abilities to the shoe. Typically softer cushioning materials are placed under the heel and forefoot for cushioning while firmer materials are positions under the medial heel extending into the midfoot and forefoot to promote enhanced stability. These materials are also frequently wrapped up onto the shoe upper at the transition zone between shoe upper and midsole to promote medial–lateral stability and to increase longitudinal stability. TPUs of various sizes and shapes are typical to most midsoles; these inserts serve to promote stability, act as a rearfoot to forefoot bridge, and guide the foot through the gait cycle.
Outsole technology is dominated by modular designs. Durability, traction, and grip are primary goals for shoe outsoles, especially given the variety of surfaces over which the distance runner will pass. However, the unique placement of outsole modules of different firmness, materials, and density can also enhance heel contact cushioning, guide the foot through midstance, and maintain forefoot flexibility at heel and toe-off.
The Cycling Shoe
The cycling shoe is unique among athletic shoes and serves to integrate the foot and lower extremity with the crank arm and drivetrain of the bike by way of the pedal. The typical cleated cycling shoe is designed around an adducted last which is comparable to a 2–4 in. dress heel. The typical European designed cycling shoe also tends to be narrower than their domestic counter parts. However, the anatomy of a typical triathlon cycling shoe is standard and can be subdivided into four primary areas of importance:
Upper
Closure system
Sole/cleat anchor
Sock liner/foot-bed
Similar to running shoes, comfort and performance can be enhanced when triathletes carefully select training and racing shoes.
The upper of a cycling shoe is typically composed of leather, man-made synthetic leather substitutes (such as Lorica), synthetic fabric (nylons or polyesters), or a combination of materials. Backing materials may decrease irritation at pressure points but can also serve to increase internal heat and retention of moisture. The upper of the shoe should conform securely to the foot without excessive pressure points across critical anatomical structures (such as first and fifth metatarsal phalangeal joints) and promote adequate ventilation to avoid the buildup of excessive heat and moisture (perspiration) around the foot. The toe box and vamp shape should be adequate to fit the forefoot without crowding the toes unnecessarily, yet be adequately streamlined for efficient aerodynamics at higher speeds. Unlike running shoes most training and racing shoes suitable for triathlons will anchor the upper of the shoe directly to the sole. Additional stability may be achieved through the addition of TPU at critical stress points such as the forefoot and heel. The heel counter of the shoe will incorporate a firm heel cup composed of a thermoplastic material with light interior padding and a padded collar for comfort and to maintain a secure rearfoot fit.
Securing the shoe to the foot requires a closure system which is easy to use, adaptable to a variety of foot types, easy to use, and easily adjustable in transition and/or during training and racing. Multiple closure systems have evolved, one to three hook and loop straps and/or ratchet buckles are durable, secure, and easy to use. Strap systems which utilize hook and loop (Velcro) to secure the strap to the shoe have the advantages of reliability, ease of use, more adjustment possibilities, and speed of use. Unique to triathlon shoes are straps which are anchored laterally to the shoe and adjustable medially. This helps to keep loose “flapping” straps free of crank arms, bottom bracket, spinning wheels, and spokes.
The sole of the cycling shoe serves as the rigid link between the foot and pedal/crank arm and drivetrain. Typical outsoles are composed of a molded thermoplastic (nylon) material, carbon graphite, and molded thermoplastic reinforced with fiberglass. Rigidity, cleat mounting pattern, heel post, toe break angle, and stack height are all important characteristics to consider when selecting a cycling training or racing shoe. Carbon graphite soles offer the greatest rigidity while molded thermoplastic soles offer greater flexibility. While a rigid sole is important for efficient transfer of power from the lower extremity to rotational torque in the crank arms it may also prompt a more awkward running/jogging gait during triathlon/duathlon transition. Cleat mounting hardware is incorporated into the sole of the shoe and serves as the anchoring site for the pedal cleat. Anchor patterns may vary, some are unique to specific cleat–pedal systems while others may be more universal suitable for a wide variety of cleat–pedal systems. All anchoring systems approximate cleat placement at the metatarsal phalangeal joints and should permit cleat placement adjustment to suit the specific needs of individual cyclists. A heel post/pillar is typical to most shoes and serves to ease walking in cycling shoes, relieve strain on the Achilles tendon during walking, and provide limited protection to the sole. Running out of and into transition areas is awkward for the triathlete; to ease this brief run the triathlete may wish to consider a cycling shoe of a thermoplastic nylon or nylon reinforced with fiberglass sole to permit slight sole flex to ease an awkward run and to avoid running out the back of a more rigid sole shoe.
Toe break angle and stack height are two variables unique to cycling shoes. Toe break angle is the degree of rise of the forefoot of the shoe. Shoes with greater toe break angles may permit the cyclist to generate greater power during the power and recovery phases of cycling and ease muscular fatigue. A moderate toe break angle will permit the downward force applied by the extending lower extremity to the crank arm to remain closer to perpendicular to the crank arm, thereby achieving a more efficient transfer of force to rotational torque as the ankle plantarflexes through late power phase. However, high toe break angles will preload the plantar fascia and potentially increasing its intrinsic tension through excessive tightening of windlast mechanism increasing the potential for plantar (fascia) forefoot pain. Stack height of a cycling shoe may vary by brand, model, and design. It is the thickness of the sole of the shoe at the cleat attachment point measured in millimeters. By maintaining the foot close to the pedal axle power transfer during both the power and the recovery phases of cycling will be enhanced. Higher stack heights are more typical of molded thermoplastic nylon soles which require greater thickness to achieve sole rigidity. Carbon and carbon composite soles achieve equal to greater sole rigidity while maintaining low stack heights and can improve the overall shoe pedal–drivetrain efficiency. High stack heights may adversely impact the triathlete during run transitions in cycling shoes. During the brief run through transition, a high stack height can potentially dorsiflex the foot at the ankle increasing the concentric tension imparted upon the Achilles tendon and calf muscles. High stack heights can also increase the potential for lateral instability of the foot and ankle during run transitions.
A shoe foot-bed or sock liner is typically a thin and protective liner which separates the plantar surface of the foot from the interior of the shoe. This liner should be removable to permit replacement of the liner with a more efficient custom or prefabricated foot orthoses. However, when for those triathletes not requiring foot orthoses these liners should help to dissipate heat buildup, improve ventilation through sole, provide minimal cushioning, and carry moisture and perspiration away from the skin of the foot.
Classifying Running Shoes
Numerous guidelines for the categorization of running shoes have been circulated in the popular press. The following list of general categories is the most widely accepted and used for running shoes:
Cushioning
Neutral
Stability
Motion control
Racing
Considerable overlap may exist; shoe authorities and manufactures may disagree on the assignment of a shoe to a category. However, based upon long-standing use and acceptance by the public this system provides a good starting point for the selection of an optimal training and racing shoe for the triathlete.
Shoes for cushioning represent designs which emphasize cushioning and flexibility. These shoes typically possess a uniform density midsole, limited shoe stabilizing add-in features, and an outsole which promotes flexibility while maintaining good traction with the support surface. These shoes promote an efficient running gait and rely on normal lower extremity and foot biomechanics. These shoes are best suited for the efficient lightweight runner with a normal to high-arched foot who demonstrates normal lower extremity biomechanics. The neutral shoe represents a design which promotes adequate cushioning, flexibility with the addition of limited stabilizing features. These shoes are best worn by a lightweight runner who exhibits normal lower extremity biomechanics. Stability running shoes are designed with the intent to augment the natural stability of the foot through all phases of gait. These shoes emphasize adequate cushioning and forefoot flexibility and enhanced motion controlling properties. These shoes are best worn by lightweight through normal weight runners with normal through moderately abnormal lower extremity biomechanics. Runners with normal foot biomechanics may elect to use this shoe to promote greater stability, especially during runs when fatigue influences normal running gait. Motion control shoes are intended to promote a maximum level of support and influence under the most extreme levels of excessive pronation of the foot during all phases of the running gait cycle. These shoes are better suited for runners with low-arched or a pes planus foot type and work well for individuals competing in the heavy weight class. These shoes are generally poorly suited for the lightweight runner due to the presence of very firm midsole materials which can promote excessive resistance to the normal foot function. Racing shoes represent a very special classification of running shoe; these shoes are intended to be lightweight and generally are poorly suited for the average triathlete.
Design innovations are frequently introduced to existing shoe models or shoe line-ups; however, rarely are entirely new design concepts introduced. However, Nike with introduction of the Nike Free brought to the running community an entirely new shoe classification. These shoes are designed as training or racing flats which intend to simulate the act of running barefoot while still proving adequate protection from foreign objects. These shoes do offer the triathlete with a training shoe to augment the strengthening of intrinsic musculature, otherwise not strengthened in a traditional shoe. However, these shoes provide little in the way of support for a foot which exhibits excessive pronation or for the runner which exhibits pronation of the foot through the midstance and propulsive phases of gait.
Finding the Perfect Triathlon Shoe
Finding the best training or racing shoe can be a formidable task. Numerous options exist; each shoe type and category is rich with near equal choices and each manufacture provides proprietary technology designed to enhance each run or ride; considerable overlap exists between manufacturers promoting shoes within any given category. The process of selecting a suitable running shoe can be enhanced by following a few simple rules:
Examine shoe for appropriate last shape
Examine shoe for neutral position
Examine shoe forefoot flexibility
Examine shoe midfoot torsional stability
Examine shoe heel counter rigidity
Examine shoe upper side-to-side stability
Examine shoe lacing system
Examine shoe outsole traction
Examine shoe last for orthoses fit
A few moments spent examining a new shoe can prevent the selection of a poorly constructed, designed, or possibly mismatched training or racing shoe.
To achieve an optimal fit, match the shape of the foot to the shoe last shape; fit an adducted foot and or cavus foot type to a curve-lasted shoe, a low/flat-arched pes planus foot type to a straight-lasted shoe, and fit the normal foot type to a combination-lasted shoe. The modern running shoe is built around a neutral position which places the heel counter of the shoe perpendicular to the support surface. Evaluate a shoe for neutral position on a flat and level surface; heel counters which are inverted or everted will impose an abnormal influence upon the foot through heel contact and can adversely effect the intended influence of foot orthoses throughout the gait cycle. Unnecessarily stiff or too proximal forefoot flexibility will increase the resistance to heel off leading to excessive momentary loads to the metatarsophalangeal joints and to the distal expansion of the plantar fascia. Midfoot torsional stability permits the rearfoot and forefoot to function independently in the frontal plain, yet provide resistance to sagittal and transverse plain movement. Excessive midfoot flexibility may increase the risks of overuse injuries linked to excessive and prolonged midstance and propulsive phase pronation of the foot. Heel counter stiffness relates to the rigidity or compressibility of the shoes rearfoot. Shoes with greater heel counter stiffness promote enhanced rearfoot stability at heel contact through midstance phases of gait. Heel counters with greater stiffness also provide a stabilizing influence to foot orthoses; enhancing orthoses heel cup influences directly to the foot and by providing a firm barrier against which the foot orthoses rearfoot posting may establish a predictable seating and a surface from which to establish leverage. Shoe upper (vamp and quarter) side-to-side stability is critical to maintaining the foot directly over the outsole and midsole of the shoe during all phases of running gait and under all circumstances of running surface and terrain. Excess shoe upper side-to-side movement will increase the risk of both chronic overuse injuries and even acute inversion (foot and ankle) injuries. Stable shoe uppers are well reinforced and exhibit minimal transverse plain (side-to-side) shift when stressed. Securing the shoe to the foot is the role of the shoe lacing system; important features for the triathlete to consider include adequate variability to the lacing system to suit the specific needs of the athlete, suitability of the lacing system to the introduction of elastic or speed laces, and a design which avoids pressure points across the dorsum of the foot. Triathletes train year round and under a wide variety of conditions. In many regions of the world training may occur on slippery, wet, or icy conditions providing far less than optimal footing and traction. Careful inspection of outsole traction design patterns and outsole composition should be considered when selecting a training/racing shoe. Bill Bowerman, Coach Oregon State University, was the first to introduce the waffle sole pattern which has given rise to a myriad of outsole designs. While waffle-type soles provided superb combination of flexibility and traction; its lack of surface area compromises its stability and traction on firm and slippery or icy surfaces. Mixed high–low horizontal and diagonal patterns with crisp edges and traction and flex channels will provide better traction on firm surfaces with poor traction but will become unsuitable when traction is required such as when running on trails. The firmness of the outsole will also influence flexibility, traction, and wear potential. Hard firm materials promote the greatest durability but may sacrifice traction, cushion, and flexibility while softer materials sacrifice durability. Most modern training shoes will accept foot orthoses; however, special considerations should be made for the suitability of the shoe to accommodate a foot orthoses. Shoes which will eventually be used with a foot orthoses should provide a versatile lacing system, alternatives to secure the rearfoot snuggly, adequately deep heel cup and rear quarter, removable sock liner, flat stable insole, torsional stability, minimal instep cut out, and adequate width and length. Many times the introduction of a foot orthoses will increase the shoe size need (length) by one half size.
When carefully selected, a well-designed cycling shoe can shave seconds off an athlete’s finishing time and help the athlete to avoid injury. While overlap exists between running shoes and cycling shoes, such as last shape, neutral position, heel counter rigidity, and orthoses suitability, features unique to cycling shoes should be considered separately when selecting a cycling shoe:
Examine shoe upper for comfort
Examine shoe closure system
Examine shoe sole for stability
Examine shoe for cleat anchoring
Examine shoe toe break and stack height
The heart of every cycling shoe is a comfortable upper that snugly fits to the foot without contributing to pressure points, promotes good air flow through the shoe, and minimizes irritating internal seams. The triathlete should carefully examine the closure system for durability, ease of use, adjustability, and security. A stable sole is critical for the transfer of power from the lower extremity to the bike drivetrain; examine the cycling shoe for longitudinal and torsional stability. The sole should resist torsional flexion when a twisting force is applied especially during climbing and sprinting out of the saddle. While longitudinal flexion will ease running and walking through transitions zones too much flexion will sacrifice power transfer to the bicycle. Avoid cycling shoes that permit longitudinal flexion. Examine the shoe sole for proper cleat anchoring; a secure and adjustable anchoring site/system that fits to the intended pedal system is important to optimize power transfer, comfort, and minimize the potential for overuse injuries of the foot, knee, and hip. Examine the shoe sole for toe break angle and stack height; avoid excessive toe break angles which may enhance power transfer when pushing big gears but are not well suited for spinning in lower gears as is more typical to triathlon training and racing. Avoid excessive stack height, by keeping the pedal/cleat close to the shoe sole power transfer from the lower extremity to the bicycle drivetrain will be improved through all phases of riding.
Pedal and Cleat Systems
No discussion of cycling shoes should go without a brief discussion of pedal systems. Pedals serve as the link between the cycling shoe and the crank arms of the bicycle. Careful selection of a proper pedal system has been shown to reduce overuse injuries of the knee. Float is a terminology used to describe the ability of the cyclists foot to rotate in the transverse plain or for the shoe to be adjusted upon the pedal (in-toed or out-toed) to suite the structural/anatomical needs of the cyclists. Clip-type pedals into which the forefoot slips allow the foot to move side-to-side and to rotate in the transverse plane with limited resistance. However, this method of securing the foot to the pedal is inefficient and permits a significant loss of power during both the power and the recovery phases of the pedal cycle. Clipless pedals secure the foot directly to the pedal minimizing the loss of power during both phases of the pedaling cycle. Some clipless pedal systems permit the rider to adjust the angle of float necessary to achieve a neutral position of the lower leg (patella) to the pedal axle. Three basic systems are available and include unrestricted float, limited float, and fixed float angle; each permit transverse plane (in-toe or out-toe) adjustments of the shoe/cleat position in relationship to the pedal axle and when properly adjusted can reduce lower extremity overuse injuries resulting from transverse plane malalignment of the lower extremity. These pedal systems are especially effective when applied to reduce chronic overuse and torque strain exerted upon the knee and hip during the power phase of cycling. Common overuse injuries such as patellofemoral pain syndrome and iliotibial band syndrome will often respond favorably to a properly fit pedal system.
Socks for the Triathlete
Socks are often one of the most frequently overlooked pieces of sporting equipment/apparel; in our zeal to run and ride triathletes too often discount the potential benefit derived from the garment enveloping the foot. Over 30 years ago DuPont developed synthetic fibers which ushered in an era of technical knitwear. Today, this specialize off shoot of the sock and fiber producing industry has created wide variety of very specialized socks and sock fiber blends. When carefully selected the athlete is assured of a sock that will perform under the stresses of both running and riding.
The primary role of athletic socks is to protect the exercising foot from excess moisture accumulations, such as perspiration or extrinsic moisture (rain and spray/mist stations), promote padding, accommodate anatomical irregularities, reduce pressure, and reduce friction and torque forces. The military has long held to the recommendation of a two-sock system to minimize the occurrence of friction blisters. The military has exerted a considerable effort to evaluate socks and boots in an effort to identify the best boot–sock system. Herring and Richie observed that sock fiber-type and sock construction properties could be linked to the frequency, size, and severity of friction blisters among runners, and with careful sock fiber and construction selection the frequency of potentially disabling friction blisters could be reduced. More recent evidence from the Office of Navel Research has associated the development of more serious lower extremity injuries including overuse injuries with military recruits suffering from frequent friction blister events. Based upon these data alone the triathlete should carefully examine the intrinsic and extrinsic circumstances associated with running and cycling in an effort to select an optimal sock to reduce the risk of skin and thereby other musculoskeletal injuries.
Sock fibers can be grouped into two primary categories: natural fibers such as wool, cotton, and silk and man-made fibers such as acrylic, nylon, polyester, and polypropylene. Natural fibers have long been touted for their overall ease of handling, wearability, durability, and ease of cleaning. Man-made fibers (synthetic fibers) on the other hand offer a wider range of thermal and moisture management properties as well as providing fibers of excellent wearability, comfort, and durability. Each fiber possesses unique properties; the primary properties include fiber length, tenacity (strength), flexibility, extensibility, elasticity, and cohesion while the secondary properties include fiber resiliency, cross section, surface geometry, specific gravity, and moisture regain. When woven into yarns and knit into technical knitwear the resulting sock will exhibit characteristics consistent with the fiber content and fiber proportionality. For triathletes the properties of moisture and thermal management, cushioning, and the dissipation of friction and shearing forces are important attributes to seek in a technical sock.
The human foot exhibits a significant potential to produce perspiration. The human foot possesses approximately 3300 eccrine sweat glands per square inch or approximately 200,000 eccrine sweat glands per foot. At rest the human foot is capable of producing approximately 1/4 cup of sweat in a 12-h period. With vigorous activities, such as running and cycling, the triathletes’ foot may produce vastly more perspiration in the same 12 h dramatically increasing the potential risk for friction blisters. This risk can be reduced by selecting socks which contain a high percent of CoolMax fibers; these synthetic polyester fibers are specially designed to minimize moisture regain (absorption) and possess a four-channel cross section which enhances the wicking potential of the sock. Polypropylene is another frequently encountered synthetic sock fiber used to manage moisture; however, due to these fibers’ extreme hydrophobic tendencies it can trap excess moisture on the skin and limit the wicking of moisture away from the skin and increase the risk of friction blisters. Synthetic acrylic fibers are also excellent fibers from which to make athletic socks. These fibers offer the distinct advantage of a soft feel, comfort, durability, and excellent wearability, but due to the fibers’ low moisture regain (absorption) and limited moisture wicking abilities they may leave the foot feeling slightly damp. Merino wool is an excellent natural fiber from which athletic socks are knit. Unfortunately, these wool fibers exhibit moderately high extensibility (stretch), poor overall elasticity (return to original shape during vigorous use), and moderately high moisture regain (absorption). The best sock would benefit from the properties of CoolMax, Merino wool, and acrylic blended together into one sock. This sock would exhibit the thermal benefit and moisture absorption properties of wool, the moisture wicking and low moisture regain properties of CoolMax, and the wearability and durability of acrylic.