Perturbation-based balance training for individuals with freezing of gait

In the current study, we conducted a randomized controlled clinical trial to assess the effect of a multisession training program based on sudden AP or ML perturbations of body balance on immediate and persistent postural response gains in individuals with PD+FoG. In addition, individuals with PD+FoG receiving muscular resistance training (RT) were employed as controls for possible gains not associated specifically with PBT, like physical activity leading to gains in muscular function and social interaction. We hypothesized that a multisession program of PBT through varied and unpredictable perturbations leads to persistent stability gains of reactive postural responses as reflected by decreased values of center of pressure (CoP) amplitude/velocity and decreased numbers of experimental near-falls. In an exploratory approach, we also tested the generalization of reactive postural responses to a context of reacting to perturbations while involved cognitively with mental operations or responding to a perturbation of higher magnitude than those experienced during training.
As the main findings, PBT led to balance stability gains in reactive responses, as indicated by decreased CoP (a) ML displacement amplitude, (b) AP/ML peak velocity, and (c) AP/ML time to peak displacement in response to perturbations. Performance gains in ML perturbations persisted over the rest interval of 30 days. PBT also led to reduced numbers of near-falls in responses to platform perturbations. Results showed no transfer either to a cognitive-motor dual-task or to faster-than-trained support base displacements.
Conclusions. A training program based on sudden balance perturbations led to persistent stability gains in reactive postural responses to different unpredictable perturbations applied when standing on a moveable platform. PBT also led to lower numbers of falls, better scores in qualitative global evaluation of body balance and reduction of fear of falling. No evidence of generalizability of performance gains to dual tasking or increased perturbation magnitude was found.

Therapeutic applicability. From a therapeutic perspective, we showed that a PBT program can lead to gains in the ability to recover body balance following an unpredictable perturbation. This increased resilience to perturbations threatening upright stance could potentially reduce the risk of falls in individuals with PD+FoG. Lack of drop-outs during the program and no cases of adverse effects are positive aspects favoring the adoption of this therapeutic strategy in clinical practice.

在本研究中，我们开展了一项随机对照临床试验（randomized controlled clinical trial），以评估基于突发前后向（Anteroposterior, AP）与内外向（Medial-Lateral, ML）平衡扰动的多疗程训练方案（multisession training program）对帕金森病伴冻结步态（Parkinson's disease with freezing of gait, PD+FoG）患者即刻及持续性姿势反应获益的影响。此外，我们将接受肌肉阻力训练（Resistance Training, RT）的PD+FoG患者设为对照组，以排除与基于扰动的平衡训练（Perturbation-based Balance Training, PBT）无关的获益因素，例如通过体育活动带来的肌肉功能提升与社交互动获益。我们提出如下假说：基于多变且不可预测的扰动实施的多疗程PBT方案，可使反应性姿势反应获得持续性稳定性提升，具体表现为压力中心（Center of Pressure, CoP）的幅度/速度降低，以及实验性近跌倒事件数量减少。作为探索性分析，我们还测试了反应性姿势反应的泛化性，即受试者在同时进行认知任务时应对扰动的表现，或是应对幅度高于训练期间所经历的扰动时的表现。

主要研究结果显示，PBT可使反应性姿势应答的平衡稳定性获得提升，具体表现为：(a) ML方向位移幅度降低，(b) AP/ML方向峰值速度降低，以及(c) 应对扰动时AP/ML方向位移达峰值的时间缩短。ML方向扰动下的表现获益在30天的休息间隔后仍持续存在。PBT还可减少平台扰动诱发的近跌倒事件数量。结果显示，无论是双任务（dual-task）场景或比训练中更快的支撑基底位移场景均未出现性能迁移。

结论。基于突发平衡扰动的训练方案，可使受试者在站立于可移动平台时应对不同不可预测扰动的反应性姿势反应获得持续性稳定性提升。PBT还可降低跌倒事件数量，提升身体平衡的定性整体评估评分，并减少跌倒恐惧心理。未发现性能获益可泛化至双任务场景或扰动幅度提升场景的证据。

治疗应用价值。从治疗视角来看，本研究证实PBT方案可提升受试者应对不可预测扰动后恢复身体平衡的能力。这种对威胁直立姿势的扰动的抵抗力提升，或可降低PD+FoG患者的跌倒风险。训练期间无受试者脱落，且未出现不良反应病例，这些积极因素支持该治疗策略在临床实践中的推广应用。