Typically softer midsoles will be less responsive then their firmer counterparts. This energy give-and-take measures the responsiveness of a shoe. The marker of a well made midsole isn’t how firm or soft the foam feels (that’s more of a matter of personal preference), but how the midsole absorbs energy as it strikes the ground and then is able to return that energy upward and forward. Every company’s midsole is unique and can vary greatly from super soft to downright firm.
The midsole, which makes up the majority of material between your foot and the ground is usually made of either a ethyl vinyl acetate (know as EVA) or a polyurethane foam compound. The two most predominate parts of a running shoe are the midsole and the upper. While it’s not necessary to know the entire anatomy of a running shoe, it is helpful to understand a few key parts of the shoe. Shoes weighing 10 ounces for men and 8 ounces for women and/or have stack heights (the total height of material between the ground and your heel and toes) of 20mm or more under the heel are placed in the cushioned category for testing. They tend to have thicker midsoles and are heavier which make them slower and less efficient then their lightweight counterparts, but are generally more comfortable and durable. Cushioned shoes are designed primarily for shock absorption and comfort.
To help simplify the shoe buying process Gear Institute divides road shoe tests between two categories: Cushioned and Lightweight Road Shoes.
Having a good pair of running shoes to protect you is the single most important piece of equipment a runner can own, yet with so many options on the market today, finding the perfect pair can be an exhaustive and often times an uninformative process. Mile after mile your feet pound the pavement with roughly three times your body weight and the only protection between the ground and your feet (hence your knees, etc.) are a pair of shoes. Nothing beats a great-fitting, comfortable pair of running shoes.