Anatomy of an athletic footwear

Discussion in 'Physical and Sports Medicine' started by neo_star, Dec 28, 2012.

  1. neo_star

    neo_star Moderator

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    Over recent decades, the athletic footwear industry has expanded so much that a plethora of sports shoes now line the shelves of most sports stores. Health professionals working within sports medicine find the decision as to which shoe to select confusing. The reality is that the majority of athletic shoes are sold for aesthetic and fashion reasons rather than for their advertised biomechanical capabilities. A scientific paper appeared in the British Journal of Sports Medicine. entitled 'Hazards of deceptive advertising of athletic footwear'. ( Robbins and Waked, 1997 (topictext) ) The conclusions reached provide a plausible mechanism explaining higher injury frequency in the users of expensive athletic shoes.

    The report suggested that:



    1. Deceptive advertising of athletic footwear may represent a public health hazard and may have to be eliminated through regulation.
    2. There is a human tendency to be less cautious when using new devices of unknown benefit due to overly positive attitudes associated with new technology and novel devices. The message to the athlete should be: 'buyer beware!' Many shoes are built with inherent gimmicks so an expensive shoe is, by definition, not necessarily a better shoe than its less expensive counterpart.



    However, the athletic footwear industry has improved sports footwear over the past few decades and practitioners are advised to identify a local reliable sports store whose staff offer sensible advice about shoe selection. Some stores allow customers to walk or run on outside on hard surfaces to test a selection of new shoes, others provide a treadmill in the store. It is worth warning athletes of commercial bias they may meet when reading the 'athletic shoe reviews' in running magazines.



    Locating a shoemaker who can adjust athletic shoes to prescription is a benefit to health professionals who regularly treat athletes. A basic understanding of the construction of athletic shoes (topictext) is important. ( Costain, 1993 (topictext) )

    [​IMG]

    The anatomy of an athletic shoe includes the following:



    The upper

    Various functions of the upper include:

    1. Securing the foot in the correct position in the shoe. The upper must not be too unforgiving and restrict movement thereby increasing pressure on and friction against the foot. A unidirectional sport such as running requires less lateral foot control and therefore a softer upper than a shoe designed for multidirectional sports such as tennis/raquet ball/aerobics/fencing/badminton etc.
    2. The upper has to allow perspiration to evaporate, but not be too porous or be affected detrimentally by repeated soaking or washing, followed by drying. Stitching must be minimized to reduce areas of likely friction between the foot and the shoe.
    3. A padded 'collar' has been an innovation in recent years, improving comfort, fit, and reducing friction against the foot.
    4. The combined vamps and quarters are constructed from nylon mesh or weave in place of leather (leather is not used today as it stretches with use, especially when wet, and does not respond well to accelerated drying).
    5. For multidirectional sports where ankle stability may be compromised, and lateral ankle sprains are a risk (such as basketball and tennis) the upper is often brought up higher, in an attempt to offer stability to the ankle. Lacing/fastening
    A system of securing the foot firmly within the sports shoe is essential for sporting activities. There has been much research and experimentation with different securing techniques. Recent designs have incorporated 'neoprene socks' with and without lacing in an attempt to increase comfort and overcome the problem of the tongue slipping away from the dorsum of the foot. Others have incorporated a 'disc' with a securing system not dissimilar to a ski boot disc securing system. As with most revolutions in design, new concepts are advocated by some and rejected as gimmicks by others. There has, however, been a trend to increase the number of eyelets and length of lacing in an attempt to distribute the load more evenly across the dorsum of the foot, thereby reducing pressure effects on the foot and minimizing friction.



    Heel cup

    Whatever the foot shape, it is highly important that the heel is firmly secured with a robust, comfortable heel cup in order to minimize frontal plane movement of the calcaneus. However, some patients with heel bumps (syn. pump bumps/Haglund's deformities/posterior calcaneal exostoses) encounter frictional problems in this region with the firm heel cup. If problems persist with increased frontal plane movement of the calcanei, altering footwear and the selective use of orthoses often in combination with felt padding and anti-friction taping may solve the problem. Surgical excision of the exostosis remains a final option. Heel tabs or Achilles tendon supports have been found to irritate the Achilles tendons, and should therefore be avoided. ( Helal et al., 1986 (topictext) )



    The sock liner


    Sock liners are various inserts and accessories added to the interior of the weightbearing surface of the athletic shoe; the intention being to increase comfort. Various shapes have been used in an attempt to achieve this goal. The softness and comfort of the insole can persuade someone to buy shoes that are, in many other respects, unsuitable. The sock liner needs to absorb sweat and reduce the effects of friction between the foot and the shoe as well as respond well to washing and drying regularly. Underneath the sock liner is the insole board of which there are basically three types

    [​IMG]

    1. Slip lasted shoes
    2. Board lasted shoes
    3. Combination lasted shoes

    Slip lasted shoes have their uppers brought down around the foot and are sewn together under the forefoot. The advantages of slip lasted shoes include their lightweight and soft construction, but their disadvantage is that their light construction compromises their stability. Thus they are generally reserved for racing, i.e. racing flats and shoes.

    Board lasted shoes have a more robust construction and offer better motion control. To achieve this, they have a regenerated leather board material covering the midsole which helps to resist frontal plane movement often referred to as pronation and supination.

    Combination lasted shoes offer the athlete the benefits of slip lasted shoes with soft shock absorbing qualities in the forefoot and a board lasted more stable rearfoot. This seems to be the most efficient combination for most road running shoes.


    Mid soles

    Over the last half century, rearfoot wedging, which raises the rearfoot in relation to the forefoot, has being incorporated into most distance running shoes . This advancement relieves various parts of the foot and leg of much of the strain of running, and has reduced the incidence of overuse injury. For multidirectional sports however, too high a rearfoot wedge may compromise ankle stability, so a lower profile shoe is required.

    The effect of using soft and hard midsole materials together with different shoe hardness values in the midsole has enabled manufacturers to create a 'combination midsole'. Lower density EVA rubber can be used on the lateral border of the heel section to absorb the shock of heel strike, whilst harder higher densities are used on the medial border designed to resist frontal plane overpronation compression effects. Distance running shoes in the past have occasionally produced 'flanged midsoles and heels', both laterally and posteriorly in an attempt to distribute the pressure effects of running over a broader surface area. This has, however, created an increase in the velocity and degree of rearfoot pronation as the flange tends to cantilever the foot into overpronation at heel strike . Flanged running shoes are now seldom seen. Current trends are to offer greater rearfoot motion control and shock-absorption. However, the addition of excessive soft shock absorbing materials into the midsole may offer the runner comfort but they create instability, reducing frontal plane motion control. Pronation and supination movements increase, creating overuse syndromes in the lower limb. Runners are advised to avoid the see through or extremely soft, unstable midsole materials and studies indicate that running shoe design should be focused more on the control of the rearfoot movement during heel strike and less on pure shock attenuation. ( Stacoff, 1988 )

    Outer soling

    Outer soles have to be hard-wearing and above all, ensure good traction between the shoe and the running surface. Manufacturers achieve this by offering a varying pattern to the outsole, designed to cater for different athletic surfaces, e.g. track/cross country/road racing. Spikes or studs are often added to the under surface of track/sprinting shoes and for rugby, soccer, hockey, cricket, and golf footwear.


    Lasting

    The shape of the shoe may be determined by viewing it from underneath. A curve lasted shoe viewed from underneath is more banana shaped than its straight lasted counterpart and may well suit an adductus foot shape. This foot shape is often supinated in construction and as such, may not overpronate when running - in fact, it may exhibit cavoid tendencies. A robust anti-pronation shoe construction for this foot type may be superfluous to requirement. A foot which is flatter in shape and function, and displays overpronation whilst walking and running, requires a more robust shoe construction in an attempt to resist overpronation and as such, a straight lasted shoe may be more suitable. This type of shoe is often heavier in construction .

    A simple way to determine shoe requirements based on foot type for the sports person, is to examine the shape of the weightbearing surface of the foot by wetting the foot and treading on a surface e.g. a bathroom mat. A better method is to use an in-shoe computerized pressure transduction system , e.g. F-Scan (movie) , combining the results with video analysis of the subject running in the footwear.



    ref - Anatomy.tv ( sports injuries - foot injuries section )



     

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    Last edited: Dec 28, 2012

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