## 3 Results
### sEMG
#### 3.2.1 Integrated Electromyography (IEMG)  
Integrated electromyography (IEMG) serves as a measure of muscle activity intensity over time. Studies indicate that higher IEMG values correlate with increased fatigue and, consequently, heightened discomfort. The comparative curves of the Integrated Electromyography data for different muscles in this experiment are illustrated in Figure 9 (The formula is shown in Appendix A).  
Figure 9: _Cont._Figure 9: Comparison of IEMG of different muscles: (**a**) IEMG of muscles under computer tasks; (**b**) IEMG of muscles under the writing task; (**c**) IEMG of muscles under ironing tasks.  
From Figure 9a, it is evident that during computer tasks, the Integrated Electromyography (IEMG) of the left erector spinae muscle remains relatively small and stable at a seat incline angle of 20\({}^{\circ}\), while it reaches its maximum value with larger fluctuations at 40\({}^{\circ}\). Similarly, the IEMG of the right erector spinae muscle is smaller at a seat incline angle of 20\({}^{\circ}\) and peaks at 40\({}^{\circ}\), displaying considerable fluctuations in both scenarios. At a seat incline angle of 40\({}^{\circ}\), the IEMG of both bilateral vastus lateralis muscles remains relatively small and stable. The IEMG of the left gastrocnemius muscle shows relatively small and stable fluctuations at a seat incline angle of 20\({}^{\circ}\), with a possible peak at the initial stage, possibly associated with changes in the participant's body center of gravity. Conversely, the IEMG of the right gastrocnemius muscle remains relatively small and stable at a seat incline angle of 40\({}^{\circ}\), confirming the possibility of a leftward shift in the participant's center of gravity.  
In Figure 9b, during writing tasks, the IEMG of the left erector spinae muscle exhibits relatively small and stable fluctuations at a seat incline angle of 20\({}^{\circ}\). Similarly, the IEMG of the right erector spinae muscle remains relatively small and stable at a seat incline angle of 20\({}^{\circ}\) but peaks at 40\({}^{\circ}\) with larger fluctuations initially. At a seat incline angle of 40\({}^{\circ}\), the IEMG of both bilateral vastus lateralis muscles remains relatively small and stable. The IEMG of the left gastrocnemius muscle is generally smaller at a seat incline angle of 20\({}^{\circ}\) compared with the other two conditions. However, it exhibits an initial peak, followed by stable fluctuations, possibly due to changes in the participant's center of gravity at the beginning. Conversely, the IEMG of the right gastrocnemius muscle remains relatively small and stable at a seat incline angle of 40\({}^{\circ}\).  
Finally, in Figure 9c, during ironing tasks, the IEMG of the bilateral erector spinae muscles is minimal and exhibits the most stable fluctuations at a seat incline angle of 20\({}^{\circ}\). The IEMG of both bilateral vastus lateralis muscles remains relatively small at a seat incline angle of 40\({}^{\circ}\), with stable fluctuations on the left side but excessive fluctuations on the right side. The IEMG of the left gastrocnemius muscle remains relatively small and stable at a seat incline angle of 0\({}^{\circ}\). Conversely, the IEMG of the right gastrocnemius muscle shows maximal activity with considerable fluctuations at a seat incline angle of 0\({}^{\circ}\), while it remains minimal and highly stable at 40\({}^{\circ}\).