The numbering system indicates the cushioning of the shoe and follows a scale ranging from 0 (barefoot) to 10 (normal running shoe), i. e. Free 3. 0 being the least and Free 7. 0(discontinued) being the most cushioned model so far. Runners are advised to gradually break in the shoe rather than immediately running long distances as to prevent muscle cramps and other discomforts, such as the notorious shin splints.
Here are the best fashion photos: Nike free run 4.0 black and white.
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