Time course analysis of angular control of the body and head while rising from a chair

To use time course information to improve understanding of the vestibular contribution to postural control as one rises from a chair.

A total of 24 healthy controls and 42 patients with varying degrees of vestibular dysfunction were studied. The time course of the angular motion of the body and head when rising from a chair with eyes open and closed was evaluated. The delay between the onset of the motions of the body and head was compared between subject groups. We also investigated transition points from forward lean of the body to backward reversion and from backward tilt of the head to forward reversion.

With regard to the onset of chair rise, we found a significant difference in the delay between head and body motion between healthy controls and subjects with bilaterally impaired vestibular deficiency only when the eyes were closed. The time between the transition points of the head and body was stable between these groups.

The mechanisms controlling the onset of head and body movements differ between normal subjects and those with bilateral vestibular deficits. In the latter, the loss of a reference of gravity causes a decrease in feed-forward postural control, which is compensated for by a somato-sensory feedback mechanism. Visual input seems to provide an alternative reference of gravity.