Head and Body Movements in the Coronal Plane during Straight Walking

Abstract

The purpose of this study was to obtain quantitative information about head movements during linear walking in humans. Subjects (26-33 years old) walked on a motor-driven linear treadmill (Q55, Quinton) at walking velocities of 0.6 to 2.2 m/sec. The head and trunk were modeled as rigid bodies, and their rotation and translation were determined in space coordinates using a video-based motion analysis system (OPTOTRAK 3020, Northern Digital Inc). During walking the trunk rotated in the coronal plane to the supporting limb side. This was compensated by the head roll rotation relative to the trunk over the range of walking speed tested, indicating that the angular VCR (vestibulocollic reflex) functions to produce a compensatory head roll on trunk to maintain head stability in the coronal plane during walking. Head, however, still rotated in space within a range of a few degrees during moderate-to-fast walking. This was almost in phase with change in the GIA (gravito-inertial acceleration vector), suggesting that in the coronal plane the head rotation is orientation response to change in the GIA. A series of our recent studies has revealed that there are considerable well-coordinated head and upper trunk movements in all three planes during locomotion, and have suggested that these compensatory and orienting responses of the head must be considered when modeling human bipedal walking.