1. Department of Neurosurgery, University of Occupational and Environmental Health, Kitakyushu, Fukuoka 807-8555, Japan
2. Department of Spinal Surgery, Brain Attack Center, Ota Memorial Hospital, Fukuyama, Hiroshima 720-0825, Japan
3. Department of Nursing, Human Health Sciences, Kyoto University, Kyoto, Kyoto 606-8507, Japan
4. Division of Sports Medicine/Laboratory Medicine, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki 305-8577, Japan