The Impact of Visual Perturbations on Balance Control during Walking

Visual perturbations may lead to a perception of self-motion and affect balance control. We studied effects of different visual perturbations in 16 healthy young participants walking on a treadmill, by assessing foot placement and center of mass (CoM) movement. Three different visual perturbations were applied: fixating a stationary target at eye level while the background moved to the right (MB), tracking a target moving rightward over a stationary background with head rotation (MT-HR), and tracking the moving target with eye movement only (MT-EM). Linear models were fit to the kinematics data to predict foot placement from CoM state at mid-swing. Over the whole trial, MT-HR and MT-EM caused an increase in step width variability, CoM position variability and foot placement residual error. During visual perturbation epochs specifically, in MB, a left deviation of foot and CoM trajectories was observed from the start of background movement. In MT-HR and MT-EM, a right deviation of foot and CoM trajectories was observed only after the target had stopped moving. Contrary to our expectations, foot placement errors did not coincide with subsequent CoM deviations in the opposite direction. An obvious change in frontal plane trunk orientation was found only in MT-HR. While all visual perturbations affected control of the CoM trajectory in the frontal plane, these effects appeared caused by effects on heading as well as balance control. Head rotation appears to additionally disturb balance through a coupling with trunk orientation.