Energy aspects associated with sport shoes.

Sport shoes can have an influence on the energetics of human movement. The two main aspects where sport shoes can play a role are in maximizing the energy which is returned to the athlete and minimizing the energy which is lost by the athlete. Maximum values of energy storage in a shoe sole are on the order of 10 J. However, not all of this energy is returned to the athlete as shoe midsoles lose approximately 30% of the energy input. Depending on the movement, energy return sometimes occurs at the wrong time, frequency, location and in the wrong direction which compromises the ultimate influence on improving performance. As a result, the actual influence that energy return has on performance is probably minimal. Examples of the strategy to minimize energy loss include (1) reducing the mass of the shoe, (2) using appropriate midsole materials which dissipate unwanted vibrations, (3) implementing constructions which improve the stability of the ankle joint and (4) increasing the bending stiffness of shoe midsoles which reduces the energy lost at the metatarso-phalangeal joint. Energy that has not been lost for tasks not directly related to the actual performance may be applied to the movement and may result in an increase of athletic performance. We propose that athletic footwear can have a much larger influence on performance by minimizing the energy which is lost as opposed to maximizing the energy which is returned.