DESCRIPTION (provided by applicant): Falls are the most significant cause of accidental death among older adults in the United States. Previous research from our lab as well as others has shown that stance balance control is significantly affected in balance-impaired older adults when simultaneously performing a secondary cognitive task. Most of the previous dual task research in balance impaired subjects has been limited to the study of balance control during stance; thus the effect of performing a secondary task on stability during challenges to gait is not known for this population. In light of results from research on stance balance control in balance impaired elders, one would predict that in this population, the ability to maintain stability during obstacle avoidance tasks in gait would be greatly decreased under dual task conditions. Specific Aim 1 examines the role of attention in postural recovery in the activity in which most falls occur, locomotion. Experiments are designed to determine the relative contributions of age (comparing young vs healthy older adults) and balance impairment (healthy vs balance impaired older adults) on balance during obstacle avoidance in dual task conditions. In addition experiments are designed to test three alternative hypotheses regarding the mechanisms contributing to age-related reductions in balance abilities in dual task situations: 1) reduced ability to allocate attention, 2) reduced general attentional capacity, or 3) postural deficits requiring increased attentional resources. Specific Aim 2 applies research on attentional demands of postural control to clinical methods for assessing and training stability in older adults. The first experiment is a longitudinal study to investigate the predictive capability of single versus dual task clinical measures of balance in identifying older adults who will develop balance problems within the next three years. The second experiment will compare the effects of single versus dual task training on stability in balance impaired older adults.