Neurorehabilitation Research Center, Kio University, 4-2-2 Umaminaka, Koryo-cho, Kitakatsuragi-gun, Nara 635-0832, Japan; Department of Physical Therapy, Faculty of Rehabilitation Sciences, Nagoya Gakuin University, 3-1-17 Taihou, Atsuta, Nagoya, Aichi 456-0062, Japan.
Graduate School of Health Sciences, Kio University, 4-2-2 Umaminaka, Koryo-cho, Kitakatsuragi-gun, Nara 635-0832, Japan.
Hum Mov Sci. 2022 Feb;81:102909. doi: 10.1016/j.humov.2021.102909. Epub 2021 Nov 27.
Haptic feedback by light touch with a fingertip influences the postural control of the human body by postural orientation. Postural control might therefore differ depending on the characteristics of the contacting object. The main experimental targets of contact have been a fixed object (fixed light touch: FLT) and an individual (interpersonal light touch: ILT), but the postural control characteristics of FLT and ILT have not been directly compared within the same study. Nor has there been a study comparing frequency characteristics in these conditions. We hypothesized that (1) the frequency of postural sway would be higher in FLT and that no such change would be observed in ILT, and (2) the interpersonal postural coordination that is specific to ILT, i.e., sway that resembles the other person's sway, would be observed in the low-frequency component (≤0.4 Hz) rather than the high-frequency component (>0.4 Hz). We applied a closed-eyes tandem stance by adult subjects as the standard condition, and the center of pressure was measured when they performed four standing conditions: no-touch, FLT, stable ILT with a bipedal partner, and unstable ILT with a tandem partner. The results demonstrated that the FLT condition and both the stable and unstable ILT conditions also stabilized the posture, but the stability was superior in the FLT condition. Further, the difference in postural stability depending on the axis is not clear in any conditions for velocity, whereas for amplitude, stabilization by contact is more easily captured in the medio-lateral (ML) axis than in the anterior-posterior (AP) axis. The mean power frequency (MPF) in the FLT condition was higher than the no-touch condition, and the stable ILT condition in the ML axis and was higher than any other conditions in the AP axis. Moreover, the stable ILT condition in both axes was not significantly different from the no-touch condition. The unstable ILT condition in the AP axis was also not significantly different, though the ML axis was higher than the no-touch condition. The interpersonal postural coordination in both the stable and unstable ILT conditions was observed in the low-frequency component (except for the ML axis of the unstable ILT condition) and not in the high-frequency component. These results support our hypotheses and suggest that although FLT and ILT exert effects on reducing postural sway to some certain extent, in actuality, these conditions result in different postural controls in the frequency domain due to postural coordination based on the low-frequency component.
轻触指尖的触觉反馈通过姿势定向影响人体的姿势控制。因此，姿势控制可能会因接触物体的特征而有所不同。接触的主要实验目标一直是固定物体（固定轻触：FLT）和个体（人际轻触：ILT），但在同一研究中尚未直接比较 FLT 和 ILT 的姿势控制特征，也没有研究比较这些条件下的频率特征。我们假设：(1) FLT 时姿势摆动的频率会更高，而在 ILT 中则不会观察到这种变化；(2) ILT 特有的人际姿势协调，即类似于他人摆动的摆动，将在低频分量（≤0.4 Hz）而不是高频分量（>0.4 Hz）中观察到。我们应用成人受试者的闭眼串联姿势作为标准条件，并在他们执行四种站立条件时测量中心压力：无接触、FLT、与双足伙伴的稳定 ILT 和与串联伙伴的不稳定 ILT。结果表明，FLT 条件以及稳定和不稳定的 ILT 条件也稳定了姿势，但在 FLT 条件下稳定性更好。此外，在任何条件下，速度的轴间稳定性差异都不明显，而对于幅度，接触的稳定性更容易在中侧（ML）轴上捕捉到，而不是在前后（AP）轴上。FLT 条件下的平均功率频率（MPF）高于无接触条件，ML 轴上的稳定 ILT 条件高于 AP 轴上的任何其他条件。此外，AP 轴上的稳定 ILT 条件与无接触条件没有显著差异。AP 轴上的不稳定 ILT 条件也没有显著差异，尽管 ML 轴高于无接触条件。在稳定和不稳定的 ILT 条件下都观察到人际姿势协调在低频分量（不稳定的 ILT 条件的 ML 轴除外），而不在高频分量。这些结果支持我们的假设，并表明尽管 FLT 和 ILT 在一定程度上对减少姿势摆动有影响，但实际上，由于基于低频分量的姿势协调，这些条件在频域中导致不同的姿势控制。
