Running shoe soles can be constructed in three layers: the outsole, midsole, and insole. The outsole, as the bottom layer, directly contacts the ground and its primary function is to provide slip resistance and durability. This layered design allows the sole to fulfill basic functions while also being technically optimized for different sports demands.
The midsole, as the name suggests, is the crucial part located between the insole and the outsole, typically composed of various foam materials. Its core function is cushioning, shock absorption, and rebound, aiming to reduce the impact force on the foot upon landing. It can be said that the design and material choice of the midsole largely determine the comfort and performance of a running shoe.
The insole, or insole, has the core function of absorbing sweat and inhibiting bacterial growth. In high-end running shoes, the insole often incorporates advanced technologies, such as shock absorption design, to ensure comfort while enhancing shock absorption. PU (polyurethane) is a commonly used material choice.
