## 1 Introduction  
In daily work environments, employees usually maintain a standing or sitting position [1]. However, sitting or standing for a long period may cause significant health risks. Prolonged sitting is linked to various musculoskeletal disorders [2], and \"Life\" magazine listed prolonged sedentary behavior as the third most unhealthy lifestyle in 2011. Similarly, prolonged standing can lead to lower back pain [3], while extended sitting can cause discomfort in the lower limbs [4] and chronic venous disease [5]. To mitigate these issues, individuals may take voluntary breaks [6] or use treadmill desks [7], although these breaks are typically brief. Various sit-stand desk converters are available to alleviate the discomfort of prolonged sitting and standing. Sit-stand chairs have been widely adopted [8], but most studies have focused on sit-stand converters without examining the influence of work environment and seat incline angle on comfort levels. [PERSON] et al. [9] found that saddle chairs with backtests received higher subjective ratings and exhibited lower peak trapezius muscle activity compared with standing and sitting. [PERSON] et al. [10] examined sex differences in neutral zone lumbar stiffness and lumbar and trunk-thigh angle boundaries to determine whether the standing lumbar angle falls within the neutral zone. They found that males exhibited significantly greater extensor stiffness. The neutral zone lumbar angle ranged from 22.2\({}^{\circ}\) to 0.2\({}^{\circ}\) for males and 17.8\({}^{\circ}\) to 1.3\({}^{\circ}\) for females, while the trunk-thigh angle ranged from 124.2\({}^{\circ}\) to 159.6\({}^{\circ}\) for males and 143.2\({}^{\circ}\) to 159.5\({}^{\circ}\) for females. Additionally, 44% of participants had standing lumbar angles outside the neutral zone. These findings are crucial for the design of hybrid posture chairs and provide essential kinematic parameters for comfort studies on standing chairs based on pressure sensors and sEMG. [PERSON] et al. [11] analyzed muscle parameters of the trunk, neck, shoulders, and buttocks in standing chair mode and investigated their overall comfort. [PERSON] and colleagues [12] performed a comparative analysis to investigate the impact of seated versus sit-stand workstations on muscle activity patterns and spinal shrinkage among office workers. It was found that the sit-to-stand workstation promoted less inactivity and more light muscle activity time, without negatively affecting spinal contraction. [PERSON] and colleagues [13] assert unequivocally that mitigating prolonged sitting during work hours can yield substantial increases in adjusted life years and life expectancy. This finding underscores the cost-effectiveness and profound significance of interventions aimed at reducing sedentary behavior in promoting public health. [PERSON] and colleagues [14] employed activPAL3c to assess sitting, standing, and other physical activity durations, alongside cardiac metabolic biomarkers and work efficiency. Their investigation revealed that embracing a standing posture effectively diminishes both workplace and overall daily sitting durations, while concurrently elevating standing periods in real-world settings. These findings underscore the role of standing interventions in alleviating the deleterious effects of prolonged sitting on human health. In light of the existing literature, it is evident that a variety of standing desk converters are readily accessible in the market, catering to the need for mitigating prolonged sitting and standing. Sit-stand desks have garnered widespread acceptance [8]. Consequently, there is a strong rationale for delving deeper into how the angle of standing chairs influences comfort. The purpose of this study is to utilize standing chairs with varying seat angles to measure participants' pressure distribution and muscle activity. By comparing these parameters across different seat angles and task environments, this study aims to conduct a comprehensive analysis of the advantages and disadvantages of different postures.