出版社：Japan Society of Physical Education, Health and Sport Sciences
摘要：This study was performed to clarify the kinetic and kinematic properties of trunk motion while performing the bar twist exercise. The increasing length and increasing mass of the exercise bars were taken as the independent variables. A total of 21 male athletes who regularly performed strength and power training were included in the study. The bar twist exercise was performed using 5 bars, comprising 1 bar 2.00 m in length and 10.00 kg in weight (NB), 2 long bars with an increased length without changing the mass (2LB, 3LB), and 2 heavy bars with a mass that was increased by adding weight to the bar without changing the length (2HB, 3HB). The three-dimensional kinetic and kinematic variables were then calculated. The principal findings were as follows: 1) The torque of the trunk twist increased as the length or mass of the bar was increased. 2) The torques of trunk flexion and lateral flexion to the left against translational motion were greater for HB than for LB (flexion (Nm⁄kg): 3LB [0.23 ± 0.22] < 3HB [0.34 ± 0.25]; lateral flexion to the left (Nm⁄kg): 2LB [0.35 ± 0.23] < 2HB [0.39 ± 0.28], 3LB [0.33 ± 0.21] < 3HB [0.35 ± 0.28], Nm⁄kg). 3) The rate of torque development (RTD) of trunk twist torque was greater for LB than for HB (2HB: 6.90 ± 3.22 < 2LB: 7.84 ± 2.58, 3HB: 6.09 ± 1.63 < 3LB: 6.88 ± 2.13, Nm⁄s⁄kg). However, the RTD of trunk twist torque for LB and HB was smaller than for NB (9.13 ± 2.53 Nm⁄s⁄kg). These results indicate that the trunk twist torque increases with the moment of inertia of the bar due to the increase in length or mass, which is a standard feature. In contrast, it was suggested that the increase in mass contributed to the increase in trunk flexion–extension and lateral bending torque. The RTD of trunk twist torque was decreased due to the increase in length or mass. However, the amount of decrease in RTD of trunk twist torque was smaller for LB than for HB.
