1. Department of Rehabilitation Medicine, Institute of Medicine, University of Tsukuba, Tsukuba 305-8575, Japan
2. Ibaraki Prefectural University of Health Sciences Hospital, Ami 300-0331, Japan
3. Department of Electrical and Electronic Engineering, Shonan Institute of Technology, Fujisawa 251-8511, Japan
4. Saitama Prosthetics and Orthotics Manufacturing Service Co., Ltd., Saitama 337-0051, Japan
5. Department of Neurophysiology, National Center of Neurology and Psychiatry, Kodaira 187-8551, Japan
6. Department of Precision Engineering, University of Tokyo, Bunkyo 113-8656, Japan
7. Department of Orthopaedic Surgery, Institute of Medicine, University of Tsukuba, Tsukuba 305-8575, Japan
8. Center for Medical Science, Ibaraki Prefectural University of Health Sciences, Ami 300-0331, Japan