6.5.2 Running Injuries as a Result of Impact Forces There is no conclusive evidence that impact forces in heel-toe running are associated with an increase in injury frequency or with a specific running-related injury. In this context, the concept that the arch of the foot should act as a shock absorber (Robbins and Hanna, 1987) needs further consideration. The impact force peak occurs at about 30 to 50 ms after contact. For a medium running speed with a ground contact of about 400 ms, the deformation of the arch of the foot is at its maximum at about 200 ms. Thus, the effects of this arch deformation are much too late to act as a shock absorber. 6.6 BAREFOOT PRODUCTS Compared to shod movement, the barefoot movement has many different aspects, includingthe shape of the barefoot compared to the shape of the shoe, the specific kinematics of barefoot and shod movements, and the feeling of barefoot or shod movement Based on such considerations, several manufacturers have developed "barefoot shoes," suggesting that some of the perceived advantages of barefoot running can be transferred into a shod condition. Four now designs using different "barefoot concepts" are discussed in this section