Background: Effective training of the backward step response could be beneficial to improve postural stability and prevent falls. Unpredicted perturbation-based balance training (PBT), widely known as compensatory-step training, may enhance the fear of falling and the patterns of postural muscle co-contraction. Contrastingly, PBT with predictable direction or both direction and timing would suppress the fear and the co-contraction patterns during training, but the efficacy of predictable PBT for unpredictable perturbations is still unknown. Objective: To compare the adaptation effects of compensatory-step training with and without predictable perturbations on backward stepping against unpredictable perturbations. Methods: Thirty-three healthy young adults were randomly assigned to one of the following step training groups: Unpredicted, Predicted, and Self-initiated. In training sessions, participants were perturbed to induce a compensatory step with (Predicted group) or without (Unpredicted group) knowledge of the perturbation’s direction or while knowing both the direction and timing of the perturbation (Self-initiated group). In test sessions (pre- and post-training), participants were instructed to recover their postural stability in response to an unpredicted perturbation. The margin of stability (MOS), center of mass (COM), and step characteristics were measured during a backward step in both test and training sessions. Results: All three groups showed a significant increase in the step length and velocity in the post-training sessions compared to those in the pre-training sessions. Moreover, in the Unpredicted and Predicted groups, but not in the Self-initiated group, the MOS at step contact was significantly increased following the training session. In addition, the Self-initiated group showed a significant increase in COM shift at 50 ms after slip onset during training compared to the Unpredicted and Predicted groups. Conclusions: Unpredicted and predicted PBT improve step characteristics during backward stepping against unpredictable perturbations. Moreover, the unpredictable PBT and PBT with direction-predictable perturbations enhance the feedback postural control reflected as the postural stability at step contact. Contrastingly, PBT with direction- and timing-predictable perturbations may enhance feedforward postural control.

中文翻译：

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可预测和不可预测的扰动训练后补偿性步进响应的适应

背景：有效的后退步反应训练有助于提高姿势稳定性和防止跌倒。不可预测的基于扰动的平衡训练 (PBT)，被广泛称为补偿步训练，可能会增强对跌倒的恐惧和姿势肌肉共同收缩的模式。相比之下，具有可预测方向或方向和时间的 PBT 会抑制训练期间的恐惧和共同收缩模式，但可预测 PBT 对不可预测扰动的功效仍然未知。目的：比较有和没有可预测扰动的补偿步骤训练对后退步骤对不可预测扰动的适应效果。方法：33 名健康的年轻人被随机分配到以下步骤训练组之一：未预测、预测、和自发的。在培训课程中，参与者被扰动以诱导补偿步骤，无论是（预测组）还是不知道（未预测组）扰动方向的知识，或者同时知道扰动的方向和时间（自发组）。在测试阶段（训练前和训练后），参与者被要求恢复他们的姿势稳定性以应对不可预测的扰动。稳定性边际 (MOS)、质心 (COM) 和步进特性是在测试和训练课程的后退步骤中测量的。结果：与训练前相比，所有三组在训练后的步长和速度均显着增加。此外，在未预测和预测组中，而不是在自发组中，培训课程后，阶梯接触时的 MOS 显着增加。此外，与未预测组和预测组相比，自发组在训练期间滑倒后 50 毫秒的 COM 偏移显着增加。结论：不可预测和可预测的 PBT 在反向步进过程中改善了步进特性，以应对不可预测的扰动。此外，不可预测的 PBT 和具有方向可预测扰动的 PBT 增强了反馈姿势控制，反映为台阶接触时的姿势稳定性。相比之下，具有方向和时间可预测扰动的 PBT 可以增强前馈姿势控制。与未预测组和预测组相比，自发组在训练期间滑倒发生后 50 毫秒的 COM 移位显着增加。结论：不可预测和可预测的 PBT 在反向步进过程中改善了步进特性，以应对不可预测的扰动。此外，不可预测的 PBT 和具有方向可预测扰动的 PBT 增强了反馈姿势控制，反映为台阶接触时的姿势稳定性。相比之下，具有方向和时间可预测扰动的 PBT 可以增强前馈姿势控制。与未预测组和预测组相比，自发组在训练期间滑倒发生后 50 毫秒的 COM 移位显着增加。结论：不可预测和可预测的 PBT 在反向步进过程中改善了步进特性，以应对不可预测的扰动。此外，不可预测的 PBT 和具有方向可预测扰动的 PBT 增强了反馈姿势控制，反映为台阶接触时的姿势稳定性。相比之下，具有方向和时间可预测扰动的 PBT 可以增强前馈姿势控制。不可预测的 PBT 和具有方向可预测扰动的 PBT 增强了反馈姿势控制，反映为台阶接触时的姿势稳定性。相比之下，具有方向和时间可预测扰动的 PBT 可以增强前馈姿势控制。不可预测的 PBT 和具有方向可预测扰动的 PBT 增强了反馈姿势控制，反映为台阶接触时的姿势稳定性。相比之下，具有方向和时间可预测扰动的 PBT 可以增强前馈姿势控制。