NATURAL MOTION – AIM OR ORIGIN FOR FUTURE FOOTWEAR DESIGN
AbstractInfluenced by the fitness and running boom in the last three decades, athletic footwear established from simple shoes to a high tech product. New designs, manufacturing techniques and materials were introduced into the construction of technical athletic shoes. This development was further influenced by biomechanical and orthopedic research which supported the establishment of functional concepts and designs. Functional factors (comfort, performance and injury prevention) and also less-functional factors (e.g. price, fashion, and durability) are relevant for the design of athletic footwear. Millions of people are involved in court activities, running and jogging activities. From the runners, it is reported that between 37-56% are injured during the period of one year. Pre injuries, excessive training volume, training mistakes, excessive impact forces, excessive pronation or excessive knee joint moments (adduction-abduction moments, external rotation moments) have been proposed as major reasons for the development of overuse injuries. Footwear and sport surface were assumed to influence impact forces, foot pronation and knee joint moments. Ankle sprains are one the most frequent acute injuries in sports related activities. It was speculated that appropriate footwear is capable to reduce the risk of over-supination and injuries of the ankle joint complex. Concepts of "impact cushioning" and "motion control" were developed, and strategies were studied to reduce potentially the impact forces and foot pronation through appropriate athletic footwear, shoe inserts, and sport surface designs. However, results of recent studies challenged the proposed association between impact forces, foot pronation, and running injuries. A critically review of injury frequency, injury location and severeness of injuries does not support that the developed technical strategies have been adequate to decrease the risk of injuries in sports through footwear. Probably the concepts did not fit at all or the basic consideration to decrease the amplitude of forces applied to the biological structures or to align the skeleton are principally wrong and thus failed. One can speculate that the purpose of footwear to control foot motion, to align the skeleton and to modify the forces acting of the biological structures should be the improper strategy to decrease the frequency of sport related injuries and/or to enhance performance. One can also speculate that a deviation from a preferred or natural joint motion, muscle activation and thus force application through footwear may not be benefit able for the joint health and lower extremity performance potential.