Roelofs Jolanda M B, de Kam Digna, van der Zijden Astrid M, Robinovitch Stephen N, Weerdesteyn Vivian
Radboud University Medical Center, Donders Centre for Neuroscience, Department of Rehabilitation, Nijmegen, The Netherlands.
Radboud University Medical Center, Donders Centre for Neuroscience, Department of Rehabilitation, Nijmegen, The Netherlands.
Hum Mov Sci. 2019 Aug;66:383-389. doi: 10.1016/j.humov.2019.05.017. Epub 2019 May 29.
Compensatory stepping is an important protective mechanism to prevent falling. To recover from sideways perturbations side steps are generally more advantageous than cross-over steps. However, there is lack of understanding of the characteristics of compensatory side steps following sideways perturbations that separate successful recoveries (i.e., no falls) from falls, the most clinically relevant outcome following a balance perturbation. We aimed to identify the critical determinants for successful side stepping after large sideways balance perturbations. Twelve healthy young adults were subjected to large leftward perturbations at varying intensities on a translating sheet. For recovery attempts started with a side step, we determined body configuration variables (frontal-plane leg and trunk angle) at first step contact, as well as spatiotemporal step variables (onset, length, duration, velocity). A logistic regression analysis was conducted to determine the predictive ability of body configuration and spatiotemporal variables on the probability of success (no fall vs. fall); perturbation intensity (peak jerk of translating sheet) and a random effect for individual were also included in the model. In the final model, leg angle and peak jerk were retained as predictors of successful balance recovery and these variables correctly classified the recovery outcome in 86% of the trials. This final 'body configuration' model yielded a -2 log likelihood of -36.3, whereas the best fitting model with only spatiotemporal variables yielded a -2 log likelihood of -45.8 (indicating a poorer fit). The leg angle at a given perturbation intensity appears to be a valid measure of reactive side step quality. The relative ease of measuring this leg angle at step contact makes it a candidate outcome for reactive stepping assessments in clinical practice.
代偿性踏步是预防跌倒的重要保护机制。为了从侧向扰动中恢复，侧步通常比交叉步更具优势。然而，对于侧向扰动后代偿性侧步的特征，即区分成功恢复（即未跌倒）与跌倒（平衡扰动后最具临床相关性的结果），人们还缺乏了解。我们旨在确定在大的侧向平衡扰动后成功侧步的关键决定因素。12名健康的年轻成年人在可移动平板上接受不同强度的大的向左扰动。对于以侧步开始的恢复尝试，我们确定了第一步接触时的身体构型变量（额面腿和躯干角度）以及时空步变量（起始、长度、持续时间、速度）。进行了逻辑回归分析，以确定身体构型和时空变量对成功概率（未跌倒与跌倒）的预测能力；模型中还包括扰动强度（可移动平板的峰值加速度）和个体的随机效应。在最终模型中，腿角度和峰值加速度被保留为成功平衡恢复的预测因子，这些变量在86%的试验中正确分类了恢复结果。这个最终的“身体构型”模型的-2对数似然值为-36.3，而仅有时空变量的最佳拟合模型的-2对数似然值为-45.8（表明拟合较差）。在给定扰动强度下的腿角度似乎是反应性侧步质量的有效指标。在步接触时测量这个腿角度相对容易，这使其成为临床实践中反应性踏步评估的一个候选结果指标。
