Components of running shoes:
• Upper – wraps around foot to provide support, protection and ventilation – made of leather, nylon, nylon mesh/weave or synthetic. Nylon mesh and leather provide ventilation.
• Heel counter – reinforcement in upper at rear of shoe – a sturdy heel counter is assumed important to provide rearfoot support and stability, but this is not supported by evidence – usually made of plastic. Heel tab above counter is to help with putting shoe on or taking off – if too high --> can irritate achilles tendon during foot plantarflexion.
• Innersole – generally for comfort – also give options for use of orthoses if more depth is needed in shoe. Moulded supports are found in a number of shoes, but are very compressible --> not really capable of providing support
• Lining – usually made of nylon (may be backed with foam) – aim is for strength and comfort
• Midsole – between upper and sole – aim is to provide sock absorption and stability. Mostly made of ethylene vinyl acetate (EVA) or polyurethane (PU). Firmer midsoles are suggested by manufacturers as being able to control excessive pronation and softer midsoles as being more able to absorb shock --> compromise has to be reached depending on the needs of individual runners. Midsoles are sometimes flared on the lateral and/or medial sides --> lateral flare can increase lever arm resulting in greater heel strike pronation. The medial arch area of midsole may be ‘cut out’ to decrease weight of shoe --> may compromise stability. Many have different densities under different parts of the foot to enhance motion control and shock absorption.
• Outersole – designed to provide traction, durability, abrasion resistance and flexibility. Usually made of a rubber compound – sometimes with carbon. May have different densities under areas of high wear. Sometimes have transverse groves in them in metatarsophalangeal region to facilitate flexibility, during propulsion.
Last:
the foot shaped form that the shoe is made on
3 types of construction used in sports shoes:
1. Board lasted – upper is pulled over last and cemented to flexile innersole board, then sole unit is attached. Shoes made this way are more rigid and stable. Have less flexibility around metatarsophalangeal joints
2. Slip lasted – upper is pulled over last and stitched on underside (no innersole board is used) and then glued to sole unit. Shoes made this way are more flexible and are lighter
3. Combination lasting – uses innersole board in rearfoot for stability and slip lasted in forefoot for flexibility
• last may have different shapes – they may be straight, semi-curved or curved --> these may be often important factors in individual comfort and fit. The straight last places more of the sole material in the arch area and is claimed to give more medial support to the foot. Curve last indicated for running at higher speeds.
Running shoe technology:
All manufacturers have different technologies for increasing motion control, anti-pronation and sock absorption – different claims are made by each manufacturer for their products.
many different opinions and claims made for each of the different technologies
Nike ‘Free’ Running shoe (‘minimal footwear’) – designed to mimic barefoot running; difficult to fit foot orthoses into if needed; have been shown to increase strength of some lower limb muscles ;
Prescribing running shoes:
• proper fit is key feature and is no different to the selection of any footwear
• difficult for health professionals to keep a database of available running shoes --> need to find a good local retailer and get to know them. The market is always rapidly changing in an unpredictable fashion.
• trade off/compromise between cushioning/shock absorption and stability/motion control
• decision regarding which shoe is based on the activity (eg running mileage, cross training, aerobics); structure and function of foot (eg high arch/low arch; pronated/supinated foot type); running style (eg heel, midfoot or forefoot striker)
• consensus is that:
• Pronator foot type --> high density midsole with higher density under medial heel area; firmer heel counter (maybe extended along medial arch area); combination lasted; straight last; no lateral heel flare; medial heel flare; wider toe box
• Supinator or rigid foot type --> more cushioning in rearfoot and forefoot; soft midsole; slip lasted; deeper toe box
• feet tend to increase in size during day --> shop for shoes at end of day
• most running shoes should last up to 800km, but will vary with material, density and runners body weight
Softer footwear are believed to inhibit sensory perception of hard surfaces and therefore moderates the lower limbs normal impact moderating behaviour --> assumed to alter the natural body shock absorbing functions --> may lead to long term structural and functional changes in the lower limb.
Lacing techniques:
Lacing techniques can be used to refine fit and many manufacturers incorporate changeable lacing patterns.
Variations in the lacing technique can be used to help manage some pathologies (eg if dorsal exostosis is painful, the eyelets for the laces in that area can not be used, so laces do not apply pressure to the painful area)
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