Ethylene-vinyl acetate (EVA), simple referred to as EVA, is a material that is widely used in Adidas footwear. EVA is a combination of the following formula's CH3CO2CHCH2 (Vinyl acetate) and C2H4 or H2C=CH2 (Ethylene). EVA is a elastomeric polymer that is likened to a foam rubber: known for it's soft and versatile properties. EVA is placed in the midsole of Adidas shoes - inbetween the upper (the fabric that holds the foot) and the outersole (the part of the shoe that touches the ground) - although outside grade EVA is sometimes used in the outersole of Adidas shoes. The purpose of EVA is to provide cushioning; before EVA was invented, most sports shoes did not feature a midsole, and this meant that the foot was the recipient of the full force of every impact. For 'even' and smooth surfaces, like a running track, this was not a problem - most spikes designed for running tracks still don't feature a midsole - but for road running and cross country running, it had a huge detrimental effect on running performance. The EVA midsole is a buffer placed between the foot and uneven / rough running surfaces; ensuring that a runner can comfortable run for longer and will not sustain as many injuries.