Sanchis-Sales Enrique, Sancho-Bru Joaquín Luis, Roda-Sales Alba, Pascual-Huerta Javier
J Am Podiatr Med Assoc. 2019 Jul;109(4):291-298. doi: 10.7547/17-035. Epub 2017 Nov 13.
Comparison of dynamic stiffness of foot joints was previously proposed to investigate pathologic situations with changes in the properties of muscle and passive structures. Samples must be controlled to reduce the variability within groups being compared, which may arise from different sources, such as gait speed or Foot Posture Index (FPI).
Variability in the measurement of the dynamic stiffness of ankle, midtarsal, and metatarsophalangeal joints was studied in a controlled sample of healthy men with normal FPI, and the effect of gait speed was analyzed. In experiment 1, dynamic stiffnesses were obtained in three sessions, five trials per session, for each participant, taking the mean value across trials as representative of each session. In experiment 2, five trials were considered at slow, comfortable, and fast velocities.
Similar intersession and intrasession errors and intraparticipant errors within sessions were found, indicating the goodness of using five trials per session for averaging. The intraparticipant and interparticipant variability data provided can be used to select the sample size in future comparative analyses. Significant differences with gait speed were observed in most dynamic stiffnesses considered, with a general rise when gait speed increased, especially at the midtarsal joint, this being attributed to an active modulation produced by the central nervous system.
Differences with gait speed were higher than intrasession and intersession repeatability errors for the propulsion phases at the ankle and midtarsal joints; comparative analyses at these phases need more exhaustive control of gait speed to reduce the required sample size.
先前有人提出比较足部关节的动态刚度，以研究肌肉和被动结构特性发生变化的病理情况。必须对样本进行控制，以减少被比较组内的变异性，这种变异性可能源于不同的来源，如步态速度或足姿势指数（FPI）。
在FPI正常的健康男性受控样本中，研究了踝关节、中跗关节和跖趾关节动态刚度测量的变异性，并分析了步态速度的影响。在实验1中，每个参与者在三个时间段内获取动态刚度，每个时间段进行五次试验，将各次试验的平均值作为每个时间段的代表值。在实验2中，在慢、舒适和快三种速度下进行了五次试验。
发现各时间段之间、各时间段内以及各参与者在各时间段内的误差相似，这表明每个时间段使用五次试验进行平均是可行的。所提供的各参与者内和各参与者间的变异性数据可用于在未来的比较分析中选择样本量。在所考虑的大多数动态刚度中，观察到与步态速度存在显著差异，随着步态速度增加，刚度普遍升高，尤其是在中跗关节，这归因于中枢神经系统产生的主动调节。
在踝关节和中跗关节的推进阶段，与步态速度的差异高于各时间段之间和各时间段内的重复性误差；在这些阶段进行比较分析需要更详尽地控制步态速度，以减少所需的样本量。
