This invention relates generally to footwear such as a shoe, including an athletic shoe, with a shoe sole, including at least one removable midsole section formed by a midsole portion, wherein the removable midsole section is non-orthotic. The removable midsole section is inserted within the shoe upper, the sides of which hold it in position. The shoe sole includes a concavely rounded side or underneath portion, which may be formed in part by the removable midsole section. The removable midsole section may extend the length of the shoe sole or may form only a part of the shoe sole and can incorporate cushioning or structural compartments or components. The removable midsole section provides the capability to permit replacement of midsole material which has degraded or has worn out in order to maintain optimal characteristics of the shoe sole. The shoe sole can, in another embodiment, include at least one compartment containing a fluid, a flow regulator, a pressure sensor to monitor the compartment pressure, and a control system such as a computer processor capable of automatically adjusting the pressure in the compartment(s) in response to the impact of the shoe sole with the ground surface.