Three-dimensional motion of the pelvis during human walking

The knowledge of the pelvis kinematics plays an important role in the equilibrium control during walking. The previous research technique on the pelvis locomotion is impractical in some fields such as clinic practice. This paper illustrates a new method based on a treadmill and three precise displacement-sensors. 20 healthy young adults of both sexes are instructed to naturally walk on a treadmill at different speeds. A model is presented to calculate the medial-lateral and vertical displacements of the pelvis during any able-bodied walking. The presented data and curves indicate that the medial-lateral and vertical displacements of the pelvis are cyclical and roughly sinusoidal during normal walking. The frequency is equal to the gait frequency in medial-lateral direction, and twice as much as that in vertical direction. In addition, the research subject's height and walking velocity have an effect on the amplitude of displacement of the pelvis. The presented data define the normal movement behavior of the pelvis during walking. As a result, it produces a standard to compare normal gait with pathological gait. The presented model may be useful in the position control of a patient's trunk for rehabilitation robot and the clinical evaluation of rehabilitation effect. In the field of humanoid robot, it is a necessary parameter for the path planning.

I. Introduction

The general goal of any form of animal locomotion can be defined as the displacement of the body's center of mass (COM). In terrestrial locomotion this is achieved by limb movements generating propulsive forces which result in a displacement of the trunk^[1]. The locomotion displacements of the COM, centre of gravity (COG) and pelvis are three important parameters in the fields of human kinematics and biomechanics. The pelvis moves forward and backward with each step during human walking, and it subsequently moves upward when body weight is transferred from one leg to the other. The weight transferring from one supporting leg to the other also coincides with cyclic medial-lateral movements of the pelvis. Due to an active stabilization of the head, arms, and trunk (HAT), the movement pattern of the HAT largely follows that of the pelvis. Knowledge of the pelvis kinematics during walking thus is essential to understanding the regular locomotor pattern and the mechanisms that play a role in the equilibrium control during walking^[2].