Analysis, Assessment, and Evaluation of Postural Instability for Bipedal Locomotion

Abstract

Postural instability or poor balance is primarily attributed to the shifting of the center of mass (COM) during static postural instability motions such as sitting up, bending down, or leaning from an upright position. Recent studies have been conducted on the associated roles of hip and ankle torque movements during these static postural instability motions. However, many of these studies have not addressed a direct correlation between the hip and ankle torque movements, especially during dynamic postural instability motions such as running or walking. Thus, it is the intent of this paper to discuss hip and ankle torque movements for a specific dynamic experimental motion and its role in postural stability. The dynamic motion used for this study is a steady paced treadmill walk with a twenty percent increase and decrease in treadmill speed to assess the subject’s control response to dynamic postural instability. In this study, five male and five female able-bodied subjects with similar body mass indices were used from a gait-knowledge data-base to determine if there is a direct relationship between the hip and ankle joint torque movements during the dynamic postural instability motion. The resulting relationship is then correlated and compared with a prerecorded non-postural stability trial for each subject to analyze any dynamic postural instability. This work is also relevant to the development of a lower body three-dimensional model for analyzing the contributions of somatosensory, vestibular, and visual systems for postural stabilization for aerospace applications.