Abstract: Attachable and detachable footwear components are disclosed which contribute to the development of certain muscles and tendons in the lower body, including the gluteus maximus, gluteus medius, sartorius, plantaris, and the like. The disclosed footwear components are inflatable in some embodiments and made in the preferred embodiment of flexible elastomeric polymers. The disclosed components detach to and from the soles of common footwear commonly available in the market, and comprise a distal ball, a proximal ball, and some embodiments, one or more mid-balls. When affixed to standard footwear, the disclosed components destabilize the foot longitudinally and laterally, and plyometrically stress tendons and muscles in the legs of a wearer, toning and strengthening the wearer's legs with time.