Postural control in the older adult.

Age-related changes in the neural, sensory, and musculoskeletal systems can lead to balance impairments that have a tremendous impact on the ability to move about safely. The many complex substrates of the posture control system subserve a common functional goal: regulation of the relationship between the center of mass and the base of support. Traditional approaches, which have focused on the control of the center-of-mass displacement, have documented age-related changes in "feet-in-place" responses: during quiet standing, during volitional movement, or in response to applied perturbation. Recently, increasing attention has been directed toward the control of the base of support, that is, compensatory leg and arm movement, as an important element of the postural repertoire, and early results suggest profound age-related impairment in the control of compensatory stepping movements. For both feet-in-place and stepping responses, control of lateral stability appears to be a major problem associated with increased risk of falling. In view of age-related differences in ability to adapt postural responses under predictable task conditions, future work will likely benefit by mimicking, as much as possible, the varied and unpredictable nature of the events that often precipitate falls in daily life, in order to draw connections between the laboratory or clinic and "real-life" stability.