Supplementary Material for: Effect of Surface Perturbation Treadmill Training Program on Strategies and Kinematics of Reactive Stepping during Standing in Older Adults: A Single-Blinded Randomized Controlled Trial

Introduction: perturbation-based balance training reduces fall rates dramatically by triggering and improving balance recovery skills. We aimed to investigate whether multidirectional surface perturbation treadmill training, which explicitly challenges age-related impairments in reactive responses, can improve balance recovery responses in standing and reduce annual falls. Methods: This was a two-arm parallel-group randomized controlled trial with concealed allocation, blinded assessors, data analyzers, and intention-to-treat analysis. Fifty-three older adults aged 80.1±5.2 years, living in retirement housing, were randomized into two groups: 1) surface perturbation-based hands-free treadmill training (SPTT, n=27) and control group, hands-free treadmill walking training without perturbations (TT, n=26). Both received a 12-week, 24-session training program. For primary outcomes, we evaluated balance recovery, pre- and post-intervention, by stepping thresholds, percent of stepping responses, total probability of stepping, and kinematics of reactive stepping to lateral-surface perturbations in standing. Fall incidents were monitored prospectively one year after training for a secondary outcome. Results: Both groups showed a significant decrease in the percentage of multiple-step responses (p=0.013) and a shorter total recovery time to recover balance (p=0.006). Compared with the TT, the SPTT led to a more significant reduction in single-step and multiple-step thresholds (p=0.003 and p=0.002, respectively), total probability of stepping (p=0.008), shorter first-step length (p=0.003), total steps path length (p=0.007) and decreased total center of mass (CoM) displacement (p=0.040) during recovery stepping. One-year prospective fall monitoring revealed nine fall events in the SPTT group compared to 17 in the TT group. Although these numbers are insignificant, they imply a potential generalization that SPTT can reduce annual falls. Conclusion: A 12-week SPTT reduces the risk of falls by improving reactive balance responses in retirement-housing older adults. Findings suggest that the primary benefit of SPTT was better control in the CoM following perturbations. This study addressed the generalizability of PBT benefits from walking to standing and the personalization of perturbation training to enhance effectiveness and real-life applicability.

引言：基于扰动的平衡训练（perturbation-based balance training, PBT）通过触发并优化平衡恢复能力，可显著降低跌倒发生率。本研究旨在探究多方向表面扰动跑步机训练——该训练可针对性挑战与年龄相关的反应性反应损伤——能否改善站立状态下的平衡恢复反应，并降低年度跌倒风险。

方法：本研究为双臂平行组随机对照试验，采用分配隐藏、评估者盲法、数据分析者盲法及意向性治疗分析方案。共招募53名年龄为80.1±5.2岁的退休养老社区老年居民，按随机原则分为两组：1）表面扰动式无扶手跑步机训练组（surface perturbation-based hands-free treadmill training, SPTT，n=27），以及对照组，即无扰动的无扶手跑步机步行训练组（hands-free treadmill walking training, TT，n=26）。两组均接受为期12周、共24次的训练计划。针对主要结局指标，我们通过步阈值、步反应占比、总步发生产生概率，以及站立时侧向表面扰动下反应性步行的运动学特征，评估了干预前后的平衡恢复情况。次要结局指标为训练结束后为期1年的前瞻性跌倒事件监测。

结果：两组均观察到多步反应占比显著降低（p=0.013），且平衡恢复总时长缩短（p=0.006）。与TT组相比，SPTT组在恢复步行过程中，单步与多步阈值（分别为p=0.003与p=0.002）、总步发生产生概率（p=0.008）、首次步长（p=0.003）、总步路径长度（p=0.007）以及总重心（center of mass, CoM）位移（p=0.040）均出现更显著的改善（即数值降低或时长缩短）。为期1年的前瞻性跌倒监测显示，SPTT组共发生9起跌倒事件，TT组则为17起。尽管该差异未达到统计学显著性，但该结果提示SPTT或可降低年度跌倒率的潜在普遍性结论具备合理性。

结论：为期12周的SPTT可通过改善退休养老社区老年居民的反应性平衡反应，降低跌倒风险。研究结果表明，SPTT的核心益处在于扰动后对重心（CoM）的更佳控制。本研究填补了基于扰动的平衡训练（PBT）益处从步行场景拓展至站立场景的研究空白，并实现了扰动训练的个性化优化，以提升训练效果与现实生活适用性。