The purposes of this study were to characterize the influence of seat back angle variations on the neck comfort of sleeping passengers without a pillow and provide suggestions for the design of economy-class seats. In this study, 17 subjects were subjected to a sleep experiment to test the effect of the backrest angle on head and neck rotation and the fatigue level of the neck muscles. The results showed that a reclined backrest (positioned at 110°) caused greater rotation of the head and neck and greater fatigue of the neck muscles than a vertical backrest. Additionally, the higher was the subject's head extended above the top of the backrest, the more complicated the head and neck rotation was and the more intense the stretching of muscles was. We conclude that, when sleeping in a sitting position without head support, passengers were more likely to experience neck muscle fatigue with the reclined backrest than with the vertical backrest. Passenger height was also found to be an important factor contributing to head and neck fatigue. On the basis of the experimental results, we offer suggestions for the design of backrests to improve passengers' sleeping experience. Our research and suggestions provide a new path for innovation in the design of economy-class seats and could help to improve the travel experience.

本研究的目的是表征座椅靠背角度变化对没有枕头的睡眠乘客颈部舒适度的影响，并为经济舱座椅的设计提供建议。在这项研究中，17 名受试者进行了睡眠实验，以测试靠背角度对头部和颈部旋转的影响以及颈部肌肉的疲劳程度。结果表明，与垂直靠背相比，倾斜靠背（定位在 110°）会导致头部和颈部更大的旋转和颈部肌肉的更大疲劳。此外，受试者的头部延伸到靠背顶部上方越高，头部和颈部的旋转就越复杂，肌肉的拉伸就越强烈。我们得出的结论是，在没有头部支撑的情况下以坐姿睡觉时，与垂直靠背相比，倾斜靠背的乘客更容易出现颈部肌肉疲劳。还发现乘客身高是导致头部和颈部疲劳的重要因素。在实验结果的基础上，我们对靠背的设计提出建议，以改善乘客的睡眠体验。我们的研究和建议为经济舱座椅的设计创新提供了一条新途径，有助于改善旅行体验。