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.
RELATED APPLICATIONS
This application is a continuation application of U.S. Ser. No. 10/780,257 filed on Feb. 18, 2004, now U.S. Pat. No. 7,082,699, which is a continuation application of U.S. Ser. No. 10/132,013 filed on Apr. 25, 2002, now U.S. Pat. No. 6,789,333, which claims the foreign priority of Japanese application Serial Number 2001-141157 filed on May 11, 2001. The entire disclosures of these patents and applications are incorporated herein by reference.
Priority Data
May 11, 2001 [JP] 2001-141157 Jun 29, 2001 [JP] 2001-198609 Apr 08, 2002 [JP] 2002-63522
