Kang, Nyeonju, Neuromechanical Rehabilitation Research Laboratory, Division of Sport Science, Incheon National University, 119 Academy-ro, Yeonsu-gu, Incheon, South Korea. Phone: +82 32 835 8573, Fax: +82 32 835 0788, E-mail: nyunju@inu.ac.kr, Korea, Republic of