Running shoes for road use are designed primarily to provide cushioning and shock absorption to minimise jarring to the bone structure and joint.
A wedge of shock absorbing foam usually pre-compressed into a mould, with a thickness of about 25mm under the heel and tapering to 12-15mm under the ball of the foot, is used.
In certain models a strip of harder foam varying in thickness from about 1cm to 2cm is placed on the inside edge of the wedge running from the side of the heel to as far as the ball of the foot to minimise the natural rotation inwards of the ankle joint (pronation) often the cause of the most common running injuries such as “runners’ knee” and “shin splints”.
The size and shape of the wedge creates “stability” or “motion control” in varying degrees to meet the needs of various foot types.
The construction of the inner layers of the shoe also adds to the stability or cushioning of the shoe. The “upper” part of the shoe is made with synthetic fabrics and meshes. Leathers and suedes are not used any longer as they shrink when wet or stretch easily, losing shape rapidly. Synthetic meshes provide a degree of breatheability required for this activity.
The soling of a running shoe is normally constructed using rubber with a high carbon content for added durability, hardened at the heel and often using two different densities under the forefoot. (The high carbon content rubber also leaves black marks on wooden gym floors.)
Trail or off-road running
Trail or off-road running have become increasingly popular in cities with access to trails, forest and mountain paths. Incorporating cushioning features similar to road shoes, trail shoes have soles with better grip, additional robust support around the heel and are heavier due to the use of anti-scuffing rubberised materials. They are usually distinguished by their darker colours. Trail running shoes are also ideal for most types of off-road hiking.
The construction of running shoes provides support primarily for forward movement, hence are not suitable for any sports where lateral (sideways) movement takes place such as squash and tennis. Running shoes are also suitable for most walking activities and today comprise the largest category of shoes purchased internationally. The growth of gym activity and the move from high impact aerobics to stretching, circuit work, spinning, stepping cycling and treadmill activity has shifted from the use of high impact aerobic shoes to running shoes.
Purchase of “high impact” aerobic shoes to running shoes which are ideally suited to these activities. Internationally manufacturers now offer more products in the running shoes category than in other categories. Running shoes are generally lighter and have more “breathable” uppers, factors which have shifted the consumers’ choice to this category.