Current sports shoes for athletes have a plastic sole and textile upper. Such shoes are manufactured to be as light as possible in order to improve the performance of the athletes, particularly over short distances, e.g. 100 m or 200 m.
One example of a sports shoe is known from European Patent Application No. EP-A-0 799 583 (Technica S.p.A). The shoes described in this patent have a sole made from a resilient material such as rubber with a strengthening insert. This shoe is not suitable for short distance track events because of its weight.
A variety of athletics shoes are produced by several manufacturers. The Saucony middle distance race shoe has a very light-weight fabric to keep the total weight of the shoe as low as possible. An Asics sprinting spike shoe uses a rubber grip on the sole of the shoe from the footplate backwards.
Sandals are also known in the art which can be used for trail running and hiking. These sandals, such as those manufactured by the Teva Company, Flagstaff, Ariz., United States, have an open structure with straps to hold the sandals on the foot. The sandals have a substantially flat sole with an open toe, arch and heel areas. Whilst such sandals, such as the Wraptor 2 model, may be suitable for long-distance trail running their heavy weight makes them unsuitable for use by track athletes.
Cycling shoes are known in the art which are designed to be as light as possible and also to allow as much transmission of the athlete's muscular power to the cycle. For example, U.S. Pat. No. 5,836,094 (Figel) teaches a cycling shoe in which a composite made of fibre and resin replaces the sole and part of the upper of a traditional shoe. In this patent, the complete sole of the shoe is made from the composite. Manufacture of the composite is from carbon fibre, Kevlar fibres and epoxy resin which are built up using layers of carbon fibre sheets and Kevlar layers.
Another cycling shoe is described in U.S. Pat. No. 5,406,723 (Okajima, assigned to Shimano, Inc., Osaka, Japan). This patent describes a sole of a shoe with a fibrous layer surrounding a core made of polyurethane foam. A glass cloth is applied to the upper and lower surfaces of the core to form a layer. A carbon fibre sheet impregnated with phenol resin is then placed over the glass cloth followed by an impregnated glass cloth. This process is completed until a stiff sole is manufactured.
Cycling shoes are, however, not suitable for use by track athletes because they have a stiff sole which is substantially inflexible. Track athletes require a shoe which is flexible in order to maximise their performance, particularly at the starting blocks.