Ground-shoe-foot interactions to biomechanics of the muscular-skeletal system in locomotion

In human locomotion like running the ground shoe foot interaction is frequently used to distinguish between running styles. Runner’s striking behavior has been shown to affect the mechanical loading conditions of the lower extremity during the braking phase of stance Barefoot running leads to a more plantar flexed striking behavior of the, which could be a strategy to reduce local pressures underneath the heel during the initial contact phase or to decrease the tibia and knee joint acceleration during initial stance. Changing the hardness of the surface or the midsole of a shoe affects the contact area as well as the time during which the impact energy is absorbed. Consequently, running on soft surfaces like natural grass has been shown to reduce peak plantar pressures underneath the foot, the peak impact force or at least the rate of impact force. A soft running surface might therefore allow for the maintenance of a more dorsi-flexed foot strike pattern in the absence of soft cushioning materials underneath the heel. Most published studies on barefoot and shod running or on running biomechanics in general did not alter the material properties of the running surface and therefore fail to clarify possible interactions between footwear and surface conditions. Competitive as well as recreational running is regularly performed on surfaces with different mechanical properties. A recent study investigated the effects of running shoes and surface conditions on the striking behavior and lower leg biomechanics in the sagittal and frontal planes of movement of male and female runners. Gender effects occurred mainly in shank and thigh frontal plane orientation and knee flexion angle. On harder surfaces and when running barefoot, subjects tended to land with a more plantar flexed foot position and ankle angle as well as a more vertical shank alignment. Different adaptation strategies to running surfaces were observed between barefoot and shod conditions. It seems that touchdown behavior is adapted to compensate for the force distributing and energy absorption potentials of distinct surface by shoe combinations. If the combined compliance of the shoe plus surface combination exceeds a certain level, touchdown kinematics seem to be adapted to improve joint stability during early stance. The surface shoe foot strongly interacts with the biomechanics of the muscular skeletal system at least with that of the lower extremity in human locomotion. Running habits (barefoot or shod) might play a role in this interaction but it is not finally understood