The main structure of better quality running shoes is similar regardless of the brand. Among them, the outsole is the layer that touches the ground. There are also a few very light running shoes that do not have an outsole. These shoes are only suitable for running on a treadmill. The middle bottom is the most important shock-absorbing layer. It is softer than the outsole. The support at the arch of the foot can control the twisting force of the shoe and transmit the impact force from the heel to the sole of the foot. The shock absorber in the heel is the most important, and each brand has its own technology and characteristics. The insole can usually be taken out, and it is the last line of defense for shock absorption and correction of foot defects. There are mainly three types of shoe uppers: pure leather, GTX fabric and nylon weaving. The main purpose is to make the foot and the shoe tightly integrated, and has the function of ventilation and heat dissipation. The hard upper of the heel can improve the stability of the foot when landing