Postural response to slow perturbations: a preliminary study of young vs. elderly subjects

The sensitivity to detect a perturbation at low speed and small magnitude was evaluated to determine the physiological response differences that arise with age. Seven slow speeds ranging from 1.25-4.3 cm/s were chosen to evaluate the postural responses (electromyograms) and postural behavior (center of pressure) while subjects stood on a platform that was perturbed anteriorly. This preliminary study indicated that the muscle activation latency is longer in the older population, though both groups show an effect of speed. A significant difference does exist between groups at the intermediate speeds, but center of pressure data showed little differences between groups in regard to the behavior of the body´s movements. Future tests will include larger subject groups, neurological deficit groups, and the addition of kinematic data to evaluate joint rotations.