## 4 Discussion
### RSP and the Mechanical Characteristics  
RSP can be associated with repetitive overhead activities, backpack carriage, computer and laptop use, and prolonged study hours [23]. This study shows a substantial difference in the mechanical characteristics between the NSP and RSP groups. The tone and elasticity of the UT and MT muscles are statistically significant, whereas stiffness is not significant between the NSP and RSP groups. About a 21% decrement in tone, 7% drop in stiffness, and 33% increase in elasticity of the UT muscle was observed, while a 30% increase in tone, 19% increase in stiffness, and 41% decrease in elasticity of the MT muscles was observed between the NSP and RSP groups. According to a study conducted by [PERSON] et al. on the alteration of muscle contractions in two different sitting postures, there is a substantial difference between the slouched and erect postures [24]. [PERSON] et al. found that when the  
Figure 2: Mechanical parameters of muscles: (**a**) tone; (**b**) stiffness; (**c**) elasticity of muscles; ns—not significant; **\(\leq\)**0.05, ***\(\leq\)0.01, and ***\(\leq\)0.001—statistically significant.  
arm was elevated in a slouched posture and the UT muscle was active for a longer period of time, this could produce pain and continual strain in the cervical and shoulder regions [25].  
Interestingly, the results show that the NSP group has much higher muscle tone, stiffness, and elasticity of the UT than the RSP group. The characteristics of the MT muscle, on the other hand, are significantly lower in the NSP group than in the RSP group. In our opinion, this could be because of the variation in shoulder and scapular movements as well as the elbow positioning of each individual in their sitting posture. The primary function of the middle trapezius is to retract the scapula and to maintain the acromihumeral distance during shoulder elevation due to minimizing of the internal rotation and anterior tilting of the scapula [26]. [PERSON] et al.'s findings indicated an increase in the activation levels of middle deltoid and middle trapezius at 0\({}^{\circ}\) to 90\({}^{\circ}\) of shoulder abduction without scapular retraction [26]. [PERSON] et al. reported a significant decrease in the middle trapezius muscle activity at 30\({}^{\circ}\) extended position and the full range of motion positions as compared to the neutral position (\(p<0.05\)) [27].  
The tone and stiffness of the PM muscle is statistically significant, whereas elasticity is not significant between the NSP and RSP groups. In the PM muscle, mechanical characteristics such as tone, stiffness, and elasticity tend to drop by 38%, 14%, and 18% between NSP and RSP. The initial decrease in PM muscle tone that happens while shifting from NSP to RSP indicates that sustaining a seated position demands more tension. According to a study on posture and fitness by [PERSON], the anterior muscles (pectoralis major and minor) become stiff in the shoulder forward position because they are always shortened [28]. Furthermore, the stiffness of the PD muscle is statistically significant, but there is no difference in tone or elasticity between the NSP and RSP groups. The results show a 12% increase in tone, 12% increase in stiffness, and 6% decrease in elasticity of the PD muscle between the NSP and RSP groups. As mentioned earlier, this immediate increase in stiffness of the PD muscle occurred when shifted from NSP to RSP, indicating that a sitting position requires less stiffness during work. Our earlier study related to muscle activation in various sedentary postures exhibited similar differences in the PD muscle [29]. According to [PERSON] et al., the presence of trauma, and a substantially higher degree of stiffness, increases the preoperative joint range of motion limitations [30; 31]. Moreover, sedentary work can cause shoulder instability because the prime movers, such as the deltoids, pectoralis major/minor, latissimus dorsi, and teres major, are not used as often [32].