3D analysis of human locomotion before and after caloric stimulation

Human locomotion was analysed in the sagittal and coronal planes using a position detector system composed of 2 infrared video cameras and a data processor. Normal healthy volunteers with 8 marker points on the body were asked to walk in place (WIP) and on a treadmill (WOT). Vertical and medial/lateral (M/L) translational movements were measured. Head angular movements in the sagittal (pitch) and coronal (roll) planes were also analysed. Pitch movements counteracted the vertical head movements. Head movement was remarkably attenuated in the vertical axis compared with that of the trunk. However, head M/L movement showed no difference with that of the lower part of the body. Ice water caloric stimulation was introduced to cause acute unilateral vestibular deficit. The stride length and step cycle became small after caloric stimulation in WOT, but not in WIP. The characteristic change in locomotive pattern was a large lateral sway of the hip joint occurring to the side away from calorization (right) during one foot standing (right foot) (t-test, p = 0.057). Measurement of M/L sway amplitude showed an increase only at the hip joint. As the changes in head and neck movements were not significant after caloric stimulation, it appears that the vestibulo-spinal reflex contributes little to maintaining the dynamic balance of the upper body. The importance of the hip joint for locomotion (hip strategy) was confirmed from the present data.