Friday, June 13, 2008

Olympics: What's new in sport shoes?

Many new shoe innovations on show at the XXVIV Olympiad, Beijing 2008 have been in development for sometime and most are incorporated into all the leading brands. Sports shoes were initially lasted with the upper stitched to thin fibreboard to give the shoe a stable platform. Since fibreboard degrades with excessive use, more manufacturers now prefer to use ethyl vinyl acetate (EVA). In trainers this technique has more or less replaced 'slip lasting' where for flexibility the upper was stitched to itself. By varying the density of EVA the manufacturers provide different properties more specific to the sport in different sections of the shoe. EVA is light in weight and hardwearing in higher densities with the polymers offering cushioning by absorption or resistance to compression. When combined with dual density midsoles, combination of high and low density EVA on the medial side of the rear foot present tilts the calcaneum, presenting ground resistance to subtalar joint pronation during propulsion. A significant advance for female athletes has been acknowledgement women's feet are different from men. The female foot is generally narrower with a broad forefoot and a narrow heel fitting is required. Until recently, women's footwear were just downsized male models but now more manufacturers including Nike, Adidas, Reebok and Asics are catering specifically for females with special lasted shoes. These lasts are made wider and accommodate the foot within the platform of midsole and outsole. Having shoes specific to female athletes also has meant upswing in designer fashion which has made a positive impact in sales. More shoe designers are placing greater emphasis on the sagittal plane model of the foot i.e. the leverage of ankle and first metatarsal phalangeal joints, but the frontal plane model traditionally directed to inversion and eversion is still heavily featured. Less emphasis is now Less emphasis is now placed on the rather oversimplified, rule of toe, mobile flat feet into straight lasted shoes and supinators or high arched feet into a curved lasted shoe and straight lasted shoes are still popular. Shoes meant for everyday training are called training flats and shoes for road races or cross country are referred to as racing flats. Shoes with spikes or spike plates on their soles are called racing spikes. Training and competition shoes are different. Many athletes train in shoes that protect their feet, and then wear different footwear for competition which is light in weight, tight fitting and allows the foot complete range of natural movement, torsion and distortion during the athletic process. Racing flats are intended to go forward and feature sagittal plane emphasis, whereas contact sports require lateral stability and padding. Technological development in the construction of midsoles, which are now thinner and stiffer, has led to lighter shoes more capable to combat excessive stress so closely associated with athletic footwear. Inclusion of biotechnologies is very evident with inlays capable of antifungal properties and wicking. Ankle cuffs and TA protectors now incorporate padded neoprene sleeves to prevent blistering. Construction of outsole continues to gain the attention of designers with new combination materials, patterns and traction designs. Adoption of lacing mechanism more associated with hiking boots mean acceptance of round laces rather than flat laces. The 'laceronis' laces slit more smoothly into the loops and help distribute pressure across the dorsum of the foot. One disadvantage is knots tend to untie more easily and the laces need to be double knotted or lace locked. Some shoes now have lace guards which are sold as wind resistance features.

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