## 4 Discussion
For ironing tasks, the Mean Power Frequency (MPF) for all muscles indicated greater comfort at 0\({}^{\circ}\), with seven parameters suggesting greater comfort at 0\({}^{\circ}\), three at 20\({}^{\circ}\), and two at 40\({}^{\circ}\). However, during ironing tasks, the Integrated Electromyography (IEMG) of the bilateral erect spinae is significantly smaller at a 20\({}^{\circ}\) incline angle compared with the other conditions. Yet, at 0\({}^{\circ}\), the Mean Power Frequency (MPF) of the bilateral erect spinae is slightly higher than at 20\({}^{\circ}\). Therefore, a 20\({}^{\circ}\) incline angle provides greater comfort for the erector spinae muscles during ironing tasks, while 0\({}^{\circ}\) is more conducive to the comfort of the vastus lateralis and gastrocnemius muscles. The reason for this difference in various task environments is that computer and writing tasks usually require prolonged sitting with relatively fixed postures. This demands a slightly inclined angle to reduce lumbar pressure and promote blood circulation. On the other hand, ironing tasks involve frequent forward and backward movements and standing. Therefore, during computer and writing tasks, a 20\({}^{\circ}\) tilt angle helps maintain the natural spinal curve, reduces pressure on the hips and lower back, and provides better support and distribution of hip pressure, thereby enhancing comfort. In contrast, during ironing tasks, a 0\({}^{\circ}\) tilt angle allows users to stand up and sit down more easily, reducing the accumulation of static pressure, which helps relax the hip muscles and improve comfort. This result aligns with the findings on body pressure distribution. Additionally, as shown in Figure 9, some EMG signal data exhibit periodic peaks, indicating the repetitiveness of the measured activities. For example, during computer typing and writing tasks, the periodic peaks correspond to the repetitive movements of the hands and fingers, resulting in continuous bursts of muscle activity. Similarly, during the ironing process, the repetitive back-and-forth movements of the iron produce periodic peaks in the EMG signals of the shoulder and arm muscles. These patterns are crucial for understanding muscle activation and fatigue. Considering both body pressure distribution and surface electromyographic (sEMG) signals, our analysis indicates that a seat incline angle of 20\({}^{\circ}\) generally provides higher levels of comfort during computer and writing tasks. However, during ironing tasks, the comfort of the erector spinae muscles is notably enhanced at a 20\({}^{\circ}\) incline angle, while the comfort of the vastus lateralis and gastrocnemius muscles is maximized at 0\({}^{\circ}\). These findings underscore the individualized nature of comfort preferences across different task scenarios, suggesting that users may tailor their choice of seat incline angle to suit the demands of their specific work tasks or accommodate their unique physical health considerations. These experimental results, obtained through various experimental methods, are generally consistent with the findings of [PERSON] et al. [8]. Unlike previous studies that only focused on muscle parameters [11; 12], our method combines body pressure distribution and sEMG, overcoming the limitations of past approaches and making this objective measure of comfort more convincing. Certainly, there are several limitations in this study. Although a sample size of 12 participants is sufficient to detect significant differences (medium effect size, effect size = 0.8) according to [PERSON]'s guidelines, it remains relatively small for this experiment, limiting the generalizability of the results. Within the graduate student population, factors such as different majors, genders, and health statuses might lead to varying outcomes. The experiment's participants were primarily graduate students, whose age, health status, and lifestyle habits are relatively uniform, potentially not representing a broader population or individuals from other age groups.