## 3 Results  
Stiffness: For the masseter muscle, there was a significant interaction between time and intervention on stiffness (\(\beta=-88.60\), t(745) = \(-9.03\), \(p<0.001\)). In practical terms, the stiffness of the masseter increased by 14.46% (\(p<0.001\)) following the Exercise intervention, whereas it decreased by 8.82% (\(p<0.001\)) following the Chewing intervention. By contrast, no significant interaction or main effects were detected for trapezius stiffness (all \(p>0.05\)) (Figure 2). Tone: For the masseter muscle, there was a significant interaction between time and intervention on tone (\(\beta=-2.15\), t(745) = \(-11.08\), \(p<0.001\)). Post hoc comparisons indicated that tone increased by 7.03% (\(p<0.001\)) for the Exercise group, whereas it declined by 5.53% (\(p>0.001\)) following the Chewing intervention. In the trapezius muscle, a statistically significant interaction also emerged between time and intervention (\(\beta=1.38\), t(683) = 6.40, \(p<0.001\)). Post hoc tests showed that tone decreased by 7.65% (\(p<0.001\)) in the Exercise group and by 1.06% (\(p=0.003\)) in the Chewing group (Figure 3). Decrement: For the masseter muscle, there was no significant interaction between time and intervention on decrement (\(\beta=-0.0014\), t(745) = \(-0.07\), \(p=0.943\)). The main effect of the intervention was significant (\(\beta=-0.03\), t(745) = \(-2.08\), \(p=0.038\)), while the main effect of time did not reach any statistical significance (\(p=0.965\)). In practical terms, both the Exercise and Chewing interventions showed a negligible change in decrement. By contrast, the trapezius muscle exhibited a significant interaction between time and intervention (\(\beta=0.15\), t(683) = 7.45, \(p<0.001\)). In practical terms, the Exercise group demonstrated an 11.57% decrease (\(p<0.001\)), whereas the Chewing group showed no statistically significant changes (\(p=0.861\)) (Figure 4). Figure 2: Tissue stiffness is defined as the peak acceleration of the Myoton probe. The mean, standard error, and individual changes in stiffness of the masseter and upper trapezius muscles. \(p\): statistical significance; Std. Beta: effect size of the interaction between time and intervention; d: [PERSON] d.  
Crep: For the masseeter muscle, there was a significant interaction between time and intervention on creep (\(\beta\) = 0.19, t(745) = 11.52, \(p\) < 0.001). In practical terms, the Exercise group experienced a 9.71% decrease in creep (\(p\) < 0.001), whereas the Chewing group exhibited a 9.68% increase (\(p\) < 0.001). By contrast, no significant main or interaction effects were found for creep in the trapezius muscle (all \(p\) > 0.05) (Figure 5). Figure 4: Decrement represents the relaxation of the muscle after the mechanical stimulus induced by the Myoton device. The mean, standard error, and individual changes in the decrement of the masseeter and upper trapezius muscles. \(p\): statistical significance; Std. Beta: effect size of the interaction between time and intervention; d: [PERSON] d.  
Figure 3: Tone is defined as the oscillation frequency of the Myoton probe. The mean, standard error, and individual changes in tone of the masseeter and upper trapezius muscles. \(p\): statistical significance; Std. Beta: effect size of the interaction between time and intervention; d: [PERSON] d.  
Relaxation: For the masseter muscle, there was a significant interaction between time and intervention on relaxation (\(\beta\) = 3.27, t(745) = 11.38, \(p\) < 0.001). Post hoc tests revealed that the Exercise intervention led to an 11.36% decrease in relaxation time (\(p\) < 0.001), whereas the Chewing intervention produced a 9.98% increase (\(p\) < 0.001). Turning to the trapezius muscle, there was a significant main effect of intervention (\(\beta\) = 0.57, t(683) = 3.59, \(p\) < 0.001), but neither the main effect of time (\(p\) = 0.090) nor the interaction (\(p\) = 0.441) reached statistical significance (Figure 6). Figure 5: Creep parameter is defined as the ratio between deformation and relaxation time.