使用HHT探討在長時間乘坐輪椅時姿勢改變與椅背傾斜度的關聯性

Abstract

本研究的主要目的是找出正常人長時間乘坐輪椅時，姿勢變動情形與椅背傾斜度的關聯性。受測者部分，徵求10位自願受測者參與，在連續80分鐘的實驗過程中，請受試者坐在可調整背靠傾斜角度為100度、110度、120度與130度的電動輪椅上，並使用感壓墊量測受試者在被要求靠在特定角度的椅背上，維持坐姿時，臀部及背部的壓力分佈數據。之後計算壓力中心位置，並運用希爾伯特-黃轉換時頻分析法與其他非時變分析法，分析不同角度下變換姿勢的方式與頻率。初步實驗結果顯示，在實驗設置的四個角度中，110度為最穩定的坐姿角度，且椅背傾斜角度會影響坐姿變動的策略；另外，若將男女分成兩組比較，則男性在矢狀面(Sagittal plane)與冠狀面(Coronal plane)的平均移動範圍分別為11.7±0.7公分與6.5±1.8公分，而女性則為10.2±1.9公分與3.9±1.6公分。結果顯示男性坐姿變動範圍差值平均值大於女性(p < 0.05)。在姿勢衡定模式方面，於100度時受試者傾向左右擺動的方式，而在130度時則傾向前後擺動。綜合本研究之實驗結果，希爾伯特-黃轉換可用來分析壓力中心時間序列，判斷坐姿衡定情形，且姿勢變動與角度和性別有關聯性。

This study investigates the effect of seat inclination on posture during prolonged sitting. Ten healthy subjects sat on a powered wheelchair whose inclination was adjusted to 100°, 110°, 120° and 130°. A pressure mat was used to measure the pressure under the hip and back during prolonged sitting in the wheelchair, and the center of pressure (COP) was calculated to analyze the nature and range of change in posture at various seat inclinations using a time-frequency analytical method - Hilbert-Huang transform (HHT) - and another time-invariant analytical method. Analytical results reveal that 110° is a relatively stable or/and hard to move seat inclination. The inclination affects the change in posture. The extent of motion in the sagittal and coronal planes was 11.7 ± 0.7 and 6.5 ± 1.8 cm for males, and 10.2 ± 1.9 and 3.9 ± 1.6 cm for males. The difference between the extents of motion of males and females was significant. Males moved to a larger extent than did females (p < 0.05). According to the pattern of posture homeostasis, subjects tended to move in the ML direction when sitting at 100°, and in the AP direction when sitting at 130°. The results of this investigation demonstrate that HHT can be utilized to analyze the COP time series to examine the characteristics of posture homeostasis. Change in posture is related to seat inclination and gender.