| 摘要 |
A midsole includes a thick plate-shaped or column-shaped cushioning portion. A plurality of grooves is formed on an outer peripheral surface of the cushioning portion. The respective grooves are helically formed around a substantially vertical line. The respective grooves are arranged substantially parallel with each other. A range alpha in which each of the grooves is formed is larger than a range of 15 degrees around the axial line and is smaller than a range of 180 degrees around the axial line.
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