Jun Iwamoto1, Tsuyoshi Takeda2, Yoshihiro Sato3, Mitsuyoshi Uzawa4. 1. Department of Sports Medicine, Keio University, School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan. jiwamoto@sc.itc.keio.ac.jp. 2. Department of Sports Medicine, Keio University, School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan. 3. Department of Neurology, Mitate Hospital, Fukuoka, Japan. 4. Department of Orthopaedic Surgery, Keiyu Orthopaedic Hospital, Gunma, Japan.