Effects Of Children’s Footwear Rearsole Material Hardness On Running And Walking Biomechanics

Purposes:The purpose of this study is to explore the influence of the hardness of children’s shoes on the biomechanical parameters of children’s walking and running lower limbs by changing the hardness of children’s shoes,so as to provide reference for the development and design of children’s shoes,and at the same time provide basis for choosing shoes suitable for children,preventing foot injury,deformity and abnormal gait,and provide reference for subsequent research.Methods:10 children aged about 3-5 years were recruited and randomly wore three pairs of children’s shoes with the same thickness(10mm)and different midsole hardness,of which two pairs were added with gaskets(hardness:no support piece,55～60A support piece,75～80A support piece)to complete walking and running.Kinematics and dynamics data were collected synchronously by Qualisys lens infrared motion capture system and Kistler three-dimensional force measuring platform system Impact test was carried out on sole with impact tester.Kinematics and dynamics data were processed by Qualisys,Visual 3D.4.0,Matlab R2009a and other software,and analyzed by SPSS20.0.Kinematics and dynamics indexes of three pairs of shoes were analyzed by single factor repeated measurement,and LSD method was used for comparison in back testing.Results:The kinematic parameters of children wearing shoes with different hardness during walking,swing time(p=0.041),minimum knee flexion angle(p=0.044),peak knee flexion angular velocity(p=0.048),peak ankle plantar flexion angle(p=0.048),ankle valgus angle(p=0.045)and landing Dynamic parameters:the time when the vertical ground reaction force reaches the second peak value(p=0.045)and the first loading rate of the vertical ground reaction force(p=0.045)are significantly different.During running,children’s shoes with different hardness soles have kinematic parameters,such as extension angle(p=0.001),peak angle(p=0.002),range of motion(p=0.033),peak knee flexion angle(p=0.022)and minimum knee external rotation angle(p=0.029)the peak ankle dorsiflexion angle(p=0.005),the plantar flexion angle of ankle joint(p=0.003)and the peak flexion angle of metatarsophalangeal joint(p=0.044)have significant differences.There is a significant difference between the first peak of vertical ground reaction force(p=0.019)and the minimum force in left and right directions(p=0.017).Conclusion:(1)Children’s shoes with different midsole hardness cause different compensatory changes in lower limb kinematics when children walk,and shoes with softer midsole increase foot valgus and decrease walking stability;Wearing shoes with hard midsole will increase the loading rate when landing,and the cushioning performance of shoes is poor.The knee joint can cushion the impact of the ground by increasing the flexion angle during the supporting period.(2)The difference between children’s shoes with different midsole hardness and children’s lower limb joints during running is mainly reflected in the knee joint.Wearing shoes with softer midsole results in an increase in the frontal movement of the knee joint and a decrease in the stability of the knee joint.Wearing shoes with hard midsole will reduce the angle of hip joint and knee joint in support period,which is not conducive to the absorption of impact force of lower limbs.May cause increased joint load of lower limbs.(3)The hardness of the midsole of children’s shoes has no effect on the loading rate of ground reaction force during running.