Abstract: A rigid midsole structure for footwear extends from the metatarsal area to a rear-most portion proximate the heel of a wearer. The rigid midsole accepts any form of replaceable undercarriage structure, and includes means for attaching the undercarriage structure to the bottom side of the rigid midsole. The rigid midsole is preferably formed with an upper surface configured to conform with the bottom of a wearer's foot to provide sufficient rigidity and comfort.

Abstract: A shoe includes a rear sole support for receiving a replaceable rear sole to provide longer wear. The shoe may also include a flexible plate supported by the rear sole support between the heel and the rear sole to reduce midsole compression and provide additional spring. A mounting member secures the rear sole to the rear sole support, and a locking member prevents rotation of the rear sole relative to the rear sole support during use. The replaceable rear sole and the flexible plate allow the shoe to be adapted to different desired performance characteristics depending upon the intended activity and terrain or playing surface.

Abstract: Combination athletic shoes and plyometric training devices are disclosed. The said shoes having removable heels that include a snap-lock track slide retainer fixedly disposed in the sole at the instep of the athletic shoe, a heel track slide retainer fixedly disposed in the sole at the heel of the athletic shoe and having a lower surface with a female portion of a dovetail joint therein, and a heel track slide with integral forward snap-lock insert fixedly attached to the heel of the athletic shoe and having a male portion of a dovetail joint on the top thereof that slidably engages the female portion of the dovetail joint in the lower surface of the heel track slide retainer and which is releasibly retained thereto by a release disposed on the bottom of the athletic shoe. This arrangement allows for the athletic shoe to function in a combination use in that without the heel in place the shoe can be used as plyometric type strength training device for the lower leg muscles.

Abstract: A replaceable shoe sole is comprised of a mid-sole, which is securely attached to the upper portion of the shoe, and an out-sole removeably attached to the mid-sole. The upper surface of the out-sole is provided with a continuous ridge which is snapped into a matching, deformably resilient groove recessed into the bottom surface of the mid-sole. The configuration of the ridge and the resiliency of the out-sole and the mid-sole material, which is preferably a polyurethane resin or foam, permits the out-sole to be easily and selectively removed and replaced by an out-sole having a new or distinctive tread pattern, the replaced out-sole being reusable if desired. The ridge on the out-sole is provided with an undercut portion to provide secure retention of the out-sole in the mid-sole, although the specific cross sectional shape of the ridge may vary depending upon the retentiveness required by a particular activity.