The periodic motion of the lower trunk region during human locomotion is analyzed from a kinematic perspective for different gaits using inertial measurement units (IMUs). Experiments are performed on subjects who walked or ran on a treadmill, each equipped with an IMU attached to their lower trunk. The treadmill speed was externally controlled according to a fixed protocol consisting of speed-up and speed-down phases. Time-series data of acceleration and angular velocity were collected and analyzed. We propose a method to estimate the initial elevation angle and velocity associated with the periodic motion, and we focus on the three dynamical aspects of the subject’s movements: the trajectory of the lower trunk in the sagittal plane, the excess kinetic energy ratio, and the position of the least acceleration fluctuation point. The results revealed that the rotation direction of the trajectory in the sagittal plane in the moving frame differed between walking and running for almost all subjects. This difference is interpreted kinematically in terms of the direction and timing of the ground reaction force. The excess kinetic energy ratio as a function of Froude number also well characterizes the gait differences. Furthermore, it is found that the point of least acceleration fluctuation is located consistently behind the body during running.
IKEMOTO et al. (Thu,) studied this question.