Takahiro Ohkawa1, Tomoaki Atomi2, Katsuya Hasegawa3, Yoriko Atomi4. 1. Department of Physical Therapy, Faculty of Health Science Technology, Bunkyo Gakuin University, 1196 Kamekubo, Fujimino-shi, Saitama 356-8533, Japan; Department of Material Health Science, Faculty and Graduate School of Engineering, Tokyo University of Agriculture and Technology, 204 Research Center for Science and Technology, Koganei-shi, Tokyo 184-8588, Japan. Electronic address: tohkawa@bgu.ac.jp. 2. Department of Physical Therapy, Faculty of Medical Sciences, Teikyo University of Science, 2525 Yatsuzawa, Uenohara-shi, Yamanashi 409-0193, Japan. Electronic address: atomi@ntu.ac.jp. 3. Department of Material Health Science, Faculty and Graduate School of Engineering, Tokyo University of Agriculture and Technology, 204 Research Center for Science and Technology, Koganei-shi, Tokyo 184-8588, Japan; Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara-shi, Kanagawa 252-5210, Japan. Electronic address: hasegawa@keisoku.jaxa.jp. 4. Department of Material Health Science, Faculty and Graduate School of Engineering, Tokyo University of Agriculture and Technology, 204 Research Center for Science and Technology, Koganei-shi, Tokyo 184-8588, Japan. Electronic address: yatomi@cc.tuat.ac.jp.
Abstract
BACKGROUND: During walking, the friction between the foot and the ground surface causes a free moment (FM), which influences the torsional stress on the lower extremity. However, few studies have investigated the FM during natural walking. The main aim of this study was to examine the relationship between the FM and the absolute and relative rotation angles of the foot and pelvis. METHODS: The rotation angles of foot and pelvic were measured in 18 healthy men using a motion capture system. Rotation angles were measured in absolute and relative coordinates as well as in reference to the line connecting the center of pressure (CoP) line under the right and left feet to evaluate the effects of the opposite lower limb on the FM. The absolute and relative rotation angles of the foot and pelvis were entered into forced-entry linear regression models to evaluate the influence on the FM. FINDINGS: Only the relative angle of rotation between the foot and pelvis could explain the prediction equations significantly. In the Pearson's product-moment correlation coefficient, the rotation angles of the foot and pelvis defined using the bilateral CoP points had not significantly correlated with FM. No joint rotation movement was correlated with FM. INTERPRETATION: The torsion of the entire lower extremity should be performed principally through hip internal rotation. When evaluating the FM as a torsional stress, focusing on the rotation of the entire lower extremity, rather than on one segment, is beneficial.
BACKGROUND: During walking, the friction between the foot and the ground surface causes a free moment (FM), which influences the torsional stress on the lower extremity. However, few studies have investigated the FM during natural walking. The main aim of this study was to examine the relationship between the FM and the absolute and relative rotation angles of the foot and pelvis. METHODS: The rotation angles of foot and pelvic were measured in 18 healthy men using a motion capture system. Rotation angles were measured in absolute and relative coordinates as well as in reference to the line connecting the center of pressure (CoP) line under the right and left feet to evaluate the effects of the opposite lower limb on the FM. The absolute and relative rotation angles of the foot and pelvis were entered into forced-entry linear regression models to evaluate the influence on the FM. FINDINGS: Only the relative angle of rotation between the foot and pelvis could explain the prediction equations significantly. In the Pearson's product-moment correlation coefficient, the rotation angles of the foot and pelvis defined using the bilateral CoP points had not significantly correlated with FM. No joint rotation movement was correlated with FM. INTERPRETATION: The torsion of the entire lower extremity should be performed principally through hip internal rotation. When evaluating the FM as a torsional stress, focusing on the rotation of the entire lower extremity, rather than on one segment, is beneficial.