Differences in the First Reactive Step Response to Unannounced Lateral Perturbation During Walking in Older Adults...

Unexpected loss of balance during walking and ineffective reactive response are major causes of falls in older adults. We aimed to compare the kinematics of the first reactive step to unannounced balance perturbation while walking in older adults with and without a fall history. In an exploratory cross-sectional study, 14 older adults (84% female) who reported a fall in the past year and 21 older adults (72% female) without a fall history were instructed to walk on a treadmill that provided unannounced lateral surface perturbations. The perturbation magnitudes were systematically increased from low to high. The average values of first reactive step parameters across all perturbation magnitudes were compared between the groups. The step initiation time and the step duration of the first reactive step in older adults with a fall history were slower than older adults without a fall history (342 ± 124 ms vs. 306 ± 122 ms, p = .001 and 670 ± 195 ms vs. 602 ± 191 ms, p < .001, respectively), and step length was larger (21 ± 10 cm vs. 17 ± 9 cm, p < .001). The displacement of the center of mass after the perturbation tended to be larger in older adults with a fall history (p = .047). In addition, the highest perturbation achieved by older adults with a fall history was lower (p = .016). The results indicate that the ability of older adults with a fall history to initiate a recovery step during gait is delayed; the first reactive step was slower and larger as they were less able to control the moving center of mass over the base of support provided by the feet.