Age-related difference in postural control during recovery from posterior and anterior perturbations.

Decreased reactive postural responses in elderly adults may place them at increased risk for falls and related injuries. The first step in addressing the high rate of falls in the elderly population is to determine a baseline for postural response in healthy young and healthy elderly individuals. To determine these age-related differences in reactive postural responses during recovery from posterior and anterior perturbations, we used the tether-release method in conjunction with a motion analysis system to evaluate overall movement latencies, overall movement amplitude and velocity, and joint-specific amplitude and velocity in healthy young (n = 10, mean age=25 ± 5) and healthy elderly participants (n = 10, mean age = 67 ± 6). During posterior perturbations, healthy elderly participants had increased recovery time (P = 0.01) and ratio of center of mass to step length (P = 0.013) when compared with young participants. Elderly participants also had decreased step length (P = 0.006), peak COM velocity (P = 0.01), peak knee flexion angle (P = 0.002), and decreased hip (P = 0.005) and knee (P = 0.0005) average angular velocity when compared with young participants. We conclude that these movement deficiencies at the hip and knee limited the length of the recovery step. With this restricted step, elderly participants could not achieve adequate mechanical advantage to counteract the displacement of their COM using a single step. During anterior perturbations, elderly participants did not exhibit any significant differences compared to young participants in overall movement variables. This understanding of postural responses in healthy individuals is clinically relevant to the development of rehabilitation programs for individuals at high fall risk.