Abstract: An energy return system to be positioned in the midsole region of an athletic shoe comprises a top member made of resilient material and including a base having a plurality of integrally formed, closely spaced, downwardly depending and downwardly tapering elements, a bottom member made of resilient material and including a base having a plurality of corresponding integrally formed, closely spaced, upwardly extending and upwardly tapering elements, and sandwiched between the tips of the two set of elements a thin stiff intermediate sheet, the tips of the two pluralities of elements being aligned face to face with the stiff sheet positioned between them.

Abstract: A polyisoprene elastomer has a polyisoprene content with an average molecular weight in the range of 15,000 to 70,000 and preferably 25,000 to 50,000. This has been cross-linked with an unsaturated aromatic compound and cured with a sulfur or peroxide curing system. The elastomer has an extremely low compression set (0 to 5%) and an extremely low durometer (Shore A, 0 to 20). The elastomer is lightweight, soft, flexible and durable and its properties make its shock-absorbing and shock-attenuating characteristics unique. It is therefore highly suitable for insole and/or midsole components in footwear.