Title: Preventing Falls from Unpredictable Balance Disturbances Abstract approved:

Falls, particularly those due to slips, constitute a major health risk for older adults. Past research has found that individuals can learn not to fall through repeated exposure to a slipping perturbation. Slips can be unpredictable, however. The goal of this study was to determine whether similar adaptations would occur for repeated slips in unpredictable directions. A sliding platform was used to cause 30 apparently healthy young adults to lose their balance while rising from a semi-squatted position during a lifting task. A series of 27 perturbations were administered in unpredictable directions, forcing participants to either fall or step to recover. Participants were grouped based on whether they fell or successfully recovered in response to the first perturbation. Twenty-two variables quantifying proactive and reactive behavior were derived from motion capture data and compared between groups and across the first, second, and fifth perturbations that caused a backward balance loss, as well as a final “predictable ” perturbation. Eight participants fell upon first exposure to the perturbation. Fallers had