Balance control is more affected in older than younger adults by repeated visual perturbations during walking

Sensory degradation with aging can impair balance control, partly by disrupting visual contributions to self-motion estimation. We investigated age-related differences in center of mass (CoM) trajectories controlling in the frontal plane during exposure to repeated visual perturbations in walking. We hypothesized that the older adults would show larger responses to visual perturbations and less adaptation to repeated visual perturbation exposure. We applied three visual perturbations to 14 healthy older (age = 75.0 ± 2.4) and 16 younger adults (age = 23.4 ± 3.9) walking on a treadmill: fixating a stationary target with the background moving to the right (MB), tracking a target moving rightward over a stationary background with head rotation (MT-HR), and tracking a moving target with eye movement only (MT-EM). CoM position deviations due to the visual perturbations were assessed. Over the whole trial, the older adults did not show larger CoM position variability than the younger during visual perturbation walking, which was contrary to our hypothesis. During visual perturbation epochs, both age groups deviated in the same direction except MB. In MB, the older adults deviated to an opposite direction after a few perturbation repetitions. Moreover, in MT-HR and MT-EM, the older adults deviated earlier than the younger adults and they deviated more in the MT-HR condition. This indicates that older adults exhibit reduced ability to accurately estimate self-motion through correction by other sensory modalities when exposed to visual perturbations. Over repeated perturbations, the older adults showed decreased CoM deviations in MT-EM, which suggests that they still maintain the capacity to downweight visual information after repeated exposure.