NHMRC Centre of Clinical Research Excellence in Spinal Pain, Injury and Health, School of Health and Rehabilitation Sciences, University of Queensland, Brisbane, Australia.
Physiotherapy Department, Faculty of Applied Medical Sciences, Umm Al-Qura University, Mecca, Saudi Arabia.
J Neurophysiol. 2021 May 1;125(5):1814-1824. doi: 10.1152/jn.00555.2020. Epub 2021 Apr 7.
Unstable sitting paradigms have been used to assess the trunk's contribution to postural control. The coordination of spine or hip with an unstable seat that underpin postural control during this task remain unclear. This study aimed to address this issue using analysis in the frequency domain. Seventy-two healthy pain-free participants maintained balance while sitting on a seat fixed to a hemisphere. Angular motion of seat, spinal regions (lower lumber, lumbar, upper lumbar, and thoracic), and hip was recorded with a three-dimensional (3-D) motion capture system. Coordination between spinal regions and hip with the seat was quantified using cross-spectral analyses. In the sagittal plane, amplitude spectrum of hip and lumbar segments were higher than other segments, coherence between these segments and the seat was high, and their motion was generally opposite in direction to the seat. In the frontal plane, amplitude spectrum of lower lumbar and lumbar segments, but not the hip, were higher than other segments, and coherently moved in the opposite direction to the seat. Segments closest to the seat made a direction-specific and greater contribution to maintenance of equilibrium than upper body segments, which were more limited during unstable sitting. Although eye closure and higher body mass index involved larger amplitude of center of pressure movement, rather than inferring poor control, this was associated with enhanced coordination between segments and seat. Understanding how hip/spine segments are coordinated with the seat is important to interpret postural strategies used to maintain equilibrium and to interpret observations for other populations (e.g., back pain). This is the first multidirectional spectral analysis of how the hip and spine coordinate during unstable sitting and how different factors impact this coordination. Seat movement was coherently counteracted (out-of-phase) by angular motion of the hip and lower lumbar spine in the sagittal plane and by the lumbar spine in the frontal plane. Although higher BMI and balancing with eyes closed increased movement amplitude, this did not compromise coordination between segments to control balance, instead, coherence increased.
不稳定的坐姿范式被用于评估躯干对姿势控制的贡献。在这个任务中，支撑脊柱或臀部与不稳定座椅之间的协调关系仍然不清楚。本研究旨在使用频域分析来解决这个问题。72 名健康无痛的参与者在一个固定在半球上的座椅上保持平衡。使用三维（3-D）运动捕捉系统记录座椅、脊柱区域（下腰椎、腰椎、上腰椎和胸椎）和臀部的角运动。使用交叉谱分析来量化脊柱区域和臀部与座椅之间的协调关系。在矢状面中，髋关节和腰椎节段的幅频谱高于其他节段，这些节段与座椅之间的相干性很高，它们的运动方向通常与座椅相反。在额状面中，下腰椎和腰椎节段的幅频谱高于其他节段，但髋关节没有，它们与座椅相反地运动。与上半身节段相比，靠近座椅的节段对维持平衡做出了特定的、更大的贡献，而在上身节段在不稳定坐姿时受到更多限制。尽管闭眼和更高的身体质量指数（BMI）涉及更大的中心压力运动幅度，但这并不意味着控制能力差，而是与节段和座椅之间的协调性增强有关。了解髋关节/脊柱节段如何与座椅协调，对于解释用于维持平衡的姿势策略以及解释其他人群（例如腰痛）的观察结果非常重要。这是首次对髋关节和脊柱在不稳定坐姿下如何协调以及不同因素如何影响这种协调的多向频谱分析。在矢状面中，髋关节和下腰椎的角运动与座椅的运动方向相反（相位相反），在额状面中，腰椎的角运动与座椅的运动方向相反。虽然较高的 BMI 和闭眼平衡增加了运动幅度，但这并没有影响节段之间的协调来控制平衡，反而增加了相干性。
