Abstract: A sole of a footwear is provided herein which may be designed to provide multifunctions suitable for particular sports. The sole may include a bladder which extends an entire length of a wearer's foot. The bladder may be pressurized with fluid for absorbing impact forces (e.g., landing impact forces, running impact forces, etc.). To prevent the bladder from having a balloon configuration, support columns may be attached to an upper layer and a lower layer of the bladder to maintain the spacing between the upper and lower layers. The lower layer of the bladder may be flat for optimizing the sole for skateboarding and other activity.

Abstract: This invention discloses an interchangeable midsole for use in the manufacture of shoes. The embodiments of the invention allow for greater rigidity, durability, and comfort for shoes to be used in every day life and in extreme sports as well as impact and abrasion protection for the wearer's feet, no matter what the wearer is doing. One or more embodiments of the invention are adapted to provide skateboard riders with increased durability and comfort in their riding shoes. Furthermore, because the novel midsole design is interchangeable among various shoe soles and uppers, the manufacturer is able to adapt various shoe designs and configurations around the common midsole.

Abstract: A replaceable shoe heel spring assembly allows the wearer of a shoe to selectively change the energy absorption and return characteristics of the heel portion of the shoe by changing shoe heel spring cartridges. The wearer activates a release mechanism located on an exterior surface of the shoe and a cartridge containing a shoe heel spring is ejected from a location in the mid-sole of the shoe. Another shoe heel spring cartridge having different energy absorption and return characteristics can then be inserted into the mid-sole. The cartridge is securely held in the mid-sole by a locking mechanism connected to the release mechanism. The shoe heel spring is provided with a cover which matches the material of the mid-sole. The cover assists in preventing debris from entering the mid-sole. The selectable range of energy absorption and return characteristics is limited only by the number of cartridges available.