INTRODUCTION

How is a mother's gait velocity affected by carrying a baby on her hip versus her front trunk? If a difference in walking speed exists, what are the primary causes? We investigated whether one of the positions, hip or front trunk, will cause a greater shift in the body's center of mass. A shift in the center of mass may require the body to utilize more energy while walking in order to compensate for the disturbance in the normal posture. We investigated if it is possible that this increase in energy decreased the normal gait velocity. We also investigated whether the direction of the shift of the center of mass required the body to use more energy while walking. In our experiment, there were two directions in which the center of mass was shifted. According to a recent study, carrying the baby on the hip causes a lateral shift of mass due to its asymmetric position on the body (DeVita et al., 1991). This lateral shift is different form carrying the baby on the front trunk, which causes an anterior shift of mass. According to another experiment, carrying a contralateral load increases the hip joint force on the side which the load is being carried. This augmentation require d an increase in hip muscle force on the side with the load. We investigated whether a greater muscle force required the exertion of more energy , and whether or not this slowed the mother's gait (Bergmann et al., 1997).

This topic is of interest to us because we are all females who have either experienced or plan to experience the phenomenon of carrying a baby on both the hip and front trunk. By investigating which position allows for the greater walking speed, it may be possible to determine the maximum time it takes to carry a child from one place to another. In general, our main goal was to analyze the kinematics involved in carrying a load on the hip versus front trunk. Our purpose in doing this experiment was to determine whether gait velocity is affected by positioning the baby on the hip as opposed to the front trunk.