1. Department of Rehabilitation Medicine and Institute of Wonkwang Medical Science, Wonkwang University School of Medicine, Iksan 570-749, Korea.
2. Department of Rehabilitation Medicine, Hallym University College of Medicine, Kangdong Sacred Heart Hospital, Seoul 134-701, Korea.
3. Department of Physiology, Wonkwang University School of Medicine, Iksan 570-749, Korea.