## 4 Discussion
\(\Delta\)% represents the relative changes from pre- to post-measurements. Sig. represents the statistical relevance of post hoc tests, where asterisks represent the following: *** 0.001.  
with previous studies conducted on leg muscles, where the authors reported that the maximal muscle contraction level and stiffness were positively correlated [57]. Similarly, a fatigue-induced decrease in muscle tone, assessed using tensiomyography, was recently reported after an intervention inducing peripheral fatigue but without inducing central fatigue [58], suggesting that the type, duration, and mode of muscle contraction might have an important role in the fatigue-induced modulation of muscle tone. The trapezius muscle, however, showed decreased tone following both interventions, potentially leading to a relaxation of neck and shoulder muscles. These results support previous findings that demonstrate the impact of various therapeutic and exercise interventions on the upper trapezius, for example, after thoracic mobilisation [59], after resistance training of the cervical and scapular region [60], and after trigger point therapy [61]. Creep represents the viscoelastic properties of skeletal muscles reflecting muscle extensibility over time [62]. In this study, we found a significant decrease in masseter muscle creep following the Exercise intervention, and an increase after the Chewing intervention, while the trapezius muscle showed no significant changes in creep. This pattern of response is in contrast with findings from a previous study on the rectus femoris muscle, where creep decreased after strengthening exercises and increased following massage [63]. Our results suggest that the creep response may be muscle-specific and influenced by each muscle's contraction history, indicating a multifaceted interplay of factors that determine a muscle's viscoelastic properties. The parameter decrement is inversely proportional to muscle elasticity, which represents the muscle ability to revert its initial shape after a contraction or a removal of an external deformation force [62]. In our study, we observed a significant decrease in decrement following the Exercise intervention in the trapezius muscle, but not in the masseter muscle. Namely, the trapezius muscle was able of regaining its original shape quicker after the deformation induced by the myometer probe [26]. On the contrary, there were no statistically significant changes in masseter and trapezius muscles following the Chewing intervention. The results of this study are consistent with previous research, highlighting the variable responses of upper trapezius decrement to different treatments. For instance, lumbar lordosis assistive support, aimed to optimise the muscular dynamics of office workers, decreased decrement [37], which is similar to the effects ultrasound therapy [43]. In contrast, an increase in upper trapezius muscle decrement was observed in sedentary workers with a rounded shoulder posture [26], patients with ecrvicogenic headache [25], and those with myogenous and mixed TMDs [27]. In our study, unlike the decrement parameter, which did not show statistically significant changes in the masseter muscle after exercise, the relaxation of the masseter muscle significantly decreased following the Exercise intervention and increased after the Chewing intervention. This decrease in relaxation may suggest a reduction in the dissipation of muscle mechanical energy [64], indicating that the masseter muscle required less effort to return to its original resting position after being mechanically stimulated by the myotonometric probe. Our results align with previous findings, where relaxation in the masseter and sternocleidomastoid muscles increased in patients with malocclusion [40]. Additionally, the relaxation of the trapezius muscle increased after both Exercise and Chewing interventions. This increase implies that the upper trapezius muscle needed more time to revert to its structural baseline [62]. These observations align with the findings of [PERSON] et al.