Objective

This study examined a system-level perspective to investigate the changes in the whole trunk and head postures while sitting with various lower extremity postures.

Background

Sitting biomechanics has focused mainly on the lumbar region only, whereas the anatomy literature has suggested various links from the head and lower extremity.

Method

Seventeen male participants were seated in six lower extremity postures, and the trunk kinematics and muscle activity measures were captured for 5 s.

Results

Changes in the trunk-thigh angle and the knee angle affected the trunk and head postures and muscle recruitment patterns significantly, indicating significant interactions between the lower extremity and trunk while sitting. Specifically, the larger trunk-thigh angle (T135°) showed more neutral lumbar lordosis (4.0° on average), smaller pelvic flexion (1.8°), smaller head flexion (3.3°), and a less rounded shoulder (1.7°) than the smaller one (T90°). The smaller knee angle (K45°) revealed a more neutral lumbar lordosis (6.9°), smaller pelvic flexion (9.2°), smaller head flexion (2.6°), and less rounded shoulder (2.4°) than the larger condition (K180°). The more neutral posture suggested by the kinematic measures confirmed significantly less muscular recruitment in the trunk extensors, except for a significant antagonistic co-contraction.

Conclusion

The lower and upper back postures were more neutral, and back muscle recruitment was lower with a larger trunk-thigh angle and a smaller knee angle, but at the cost of antagonistic co-contraction.

Application

The costs and benefits of each lower extremity posture can be used to design an ergonomic chair and develop an improved sitting strategy.

中文翻译：

---

椅子设计中下半身姿势的重要性

客观的

本研究从系统层面的角度来研究以各种下肢姿势坐着时整个躯干和头部姿势的变化。

背景

坐姿生物力学主要只关注腰部区域，而解剖学文献则提出了头部和下肢的各种联系。

方法

17 名男性参与者以 6 种下肢姿势坐着，躯干运动学和肌肉活动测量被捕获 5 秒。

结果

躯干-大腿角度和膝盖角度的变化显着影响躯干和头部姿势以及肌肉募集模式，表明坐姿时下肢和躯干之间存在显着相互作用。具体而言，较大的躯干-大腿角度 (T135°) 表现出更多的中性腰椎前凸（平均 4.0°）、较小的骨盆屈曲度（1.8°）、较小的头部屈曲度（3.3°）和较不圆肩（1.7°）较小的 (T90°)。与较大的条件 (K180°) 相比，较小的膝关节角度 (K45°) 显示更中性的腰椎前凸 (6.9°)、更小的骨盆屈曲 (9.2°)、更小的头部屈曲 (2.6°) 和更少的圆肩 (2.4°) ). 运动学测量表明的更中立的姿势证实了躯干伸肌的肌肉募集明显减少，除了显着的拮抗性共同收缩。

结论

下背部和上背部姿势更中立，背部肌肉募集较低，躯干-大腿角度较大，膝盖角度较小，但以拮抗性共同收缩为代价。

应用

每种下肢姿势的成本和收益可用于设计符合人体工程学的椅子并开发改进的坐姿策略。