Methodological Choices in Muscle Synergy Analysis Impact Differentiation of Physiological Characteristics Following Stroke
Methodological Choices in Muscle Synergy Analysis Impact Differentiation of Physiological Characteristics Following Stroke
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DOI：
10.3389/fncom.2017.00078
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发表时间：
2017-08-31
影响因子：
3.2
通讯作者：
Patten, Carolynn
中科院分区：
文献类型：
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作者：
Banks, Caitlin L.;Pai, Mihir M.;Patten, Carolynn
肌肉协同分析 (MSA) 是一种降低肌电图 (EMG) 数据维度的数学技术。 MSA 越来越多地用于生物力学研究，需要在分析的每个阶段选择方法。方法步骤的差异会影响总体结果，因此很难比较不同研究的结果。我们将 MSA 应用于从中风后个人中收集的肌电图数据，根据治疗后步行速度的关键增加，确定为有反应者 (RES) 或无反应者 (nRES)。重要的是，没有临床或功能指标表明 RES 和 nRES 队列在基线时存在差异。在这项探索性研究中，我们从更大的样本中选择了 5 个最高 RES 和 5 个最低 nRES。我们的目标是评估 MSA 之前、期间和之后做出的方法选择如何影响根据 MSA 结果区分具有内在生理差异的两组的能力。我们研究了 MSA 方法的 30 种变体，以确定哪些选择可以在基线时区分 RES 和 nRES。与时间无关的协同向量（SV）和随时间变化的神经命令（NC）的试验间变异性被测量为以下函数：（1）计算出的协同效应数量； (2) MSA前肌电归一化方法； (3) SV 是否在试验中保持恒定，或者在 MSA 期间允许变化； (4)MSA后协同分析输出归一化方法。 MSA 方法对我们在基线上区分 RES 和 nRES 的能力有很大影响。在所有 10 个个体和 MSA 变异中，需要两种协同作用才能达到平均 90% 的方差解释 (VAF)。根据效应大小，使用每次试验中不同的 SV 的两种协同作用时，组间 SV 和 NC 变异性的差异最大。使用每次试验 EMG 标准化的单位幅度，SV 变异性的差异最为明显，而 NC 变异性对 EMG 标准化方法不太敏感。输出归一化方法没有对结果产生很大影响。一些（但不是全部）方法的 MSA 变异性成功地区分了传统临床或生物力学评估无法获得的内在生理差异。我们的结果对方法学选择很敏感，强调在未来的研究中需要披露 MSA 方法学的所有方面。
Muscle synergy analysis (MSA) is a mathematical technique that reduces the dimensionality of electromyographic (EMG) data. Used increasingly in biomechanics research, MSA requires methodological choices at each stage of the analysis. Differences in methodological steps affect the overall outcome, making it difficult to compare results across studies. We applied MSA to EMG data collected from individuals post-stroke identified as either responders (RES) or non-responders (nRES) on the basis of a critical post-treatment increase in walking speed. Importantly, no clinical or functional indicators identified differences between the cohort of RES and nRES at baseline. For this exploratory study, we selected the five highest RES and five lowest nRES available from a larger sample. Our goal was to assess how the methodological choices made before, during, and after MSA affect the ability to differentiate two groups with intrinsic physiologic differences based on MSA results. We investigated 30 variations in MSA methodology to determine which choices allowed differentiation of RES from nRES at baseline. Trial-to-trial variability in time-independent synergy vectors (SVs) and time-varying neural commands (NCs) were measured as a function of: (1) number of synergies computed; (2) EMG normalization method before MSA; (3) whether SVs were held constant across trials or allowed to vary during MSA; and (4) synergy analysis output normalization method after MSA. MSA methodology had a strong effect on our ability to differentiate RES from nRES at baseline. Across all 10 individuals and MSA variations, two synergies were needed to reach an average of 90% variance accounted for (VAF). Based on effect sizes, differences in SV and NC variability between groups were greatest using two synergies with SVs that varied from trial-to-trial. Differences in SV variability were clearest using unit magnitude per trial EMG normalization, while NC variability was less sensitive to EMG normalization method. No outcomes were greatly impacted by output normalization method. MSA variability for some, but not all, methods successfully differentiated intrinsic physiological differences inaccessible to traditional clinical or biomechanical assessments. Our results were sensitive to methodological choices, highlighting the need for disclosure of all aspects of MSA methodology in future studies.