Relationship between standing posture and stability.
BACKGROUND AND PURPOSE: This study determined whether persons with stability impairments have postural aberrations. We investigated whole-body posture and its relationship to center-of-gravity (COG) stability. SUBJECTS: Data from 27 subjects with vestibular hypofunction and 26 subjects without vestibular impairment were analyzed. METHOD: An optoelectronic full-body system measured kinematics. Force plates measured ground reaction forces while subjects stood with their feet 30 cm apart and eyes open and with their feet together and eyes closed. RESULTS: The subjects with vestibular hypofunction demonstrated less stability than the subjects without impairment, but there were no postural differences. Subjects with vestibular hypofunction had more weight on the left lower extremity during standing with feet apart. In all subjects in both groups, during standing with feet apart, the COG was anterior to the ankle, knee, back, and shoulder and posterior to the hip and neck. Subjects had an anterior pelvic tilt, extended trunk and head, right laterally flexed trunk and pelvis, and flexed knees. With their feet together, subjects increased their anterior pelvic tilt; trunk, head, and knee flexion; and anterior COG position. CONCLUSION AND DISCUSSION: Posture and stability had a low correlation. Subjects with bilateral vestibular hypofunction did not demonstrate a forward head or backward trunk lean, as has been reported anecdotally. Changing from standing with feet apart to feet together increased whole-body movement patterns to control standing stability.