Cervical Myofascial Pain Is Associated with an Imbalance of Masticatory Muscle Activity.

This study aimed to assess the relationship between the occurrence of cervical myofascial pain with active myofascial trigger points (MTrPs) within the upper trapezius muscle and the electromyographic asymmetry index (AsI) of masticatory muscles: temporalis anterior (TA), superficial part of the masseter muscle (MM), and anterior belly of the digastric muscle (DA). The study group comprised 100 subjects (80 women and 20 men) aged 18 to 30 years (mean 23 ± 2.6 years) reporting pain in the neck muscles, diagnosed with myofascial pain with active MTrPs only within the upper trapezius muscle. The control group comprised 60 healthy, pain-free subjects (42 women and 18 men) aged 20 to 30 years (mean 22.8 ± 2.6 years) without MTrPs in the upper trapezius muscle. The palpation measurement, based on the diagnostic criteria of Travell and Simons, was used to diagnose active MTrPs. The masticatory muscle activity was recorded using an 8-channel device for surface electromyography-BioEMG IIITM. Significant differences in electromyographic patterns between the group with MTrPs in the right side of upper trapezius muscle and the control group were observed within resting activity for the AsI TA (MTrPs: 8.64 vs. controls: -3.22; p = 0.001) and AsI MM (MTrPs: 7.05 vs. controls: -2.09; p = 0.018). Controls presented different electromyographic patterns during maximum voluntary clenching with cotton rolls between teeth within masseter muscle compared to the MTrPs group (MTrPs: 9.27 vs. controls: -0.43 vs. p = 0.041). Participants with MTrPs in the left side of upper trapezius muscle presented predomination of left-sided electromyographic patterns at rest within temporalis anterior in comparison to controls (MTrPs: -19.22 vs. controls: -3.22; p = 0.001). MTrPs within the trapezius muscle may be related to asymmetry within the masticatory muscle activity, suggesting that the presence of myofascial pain within the cervical muscles plays a role in the imbalance of the stomatognathic system. A unilateral active MTrPs within the trapezius muscle may increase the sEMG activity on the same side of the temporalis anterior and masseter muscles.

Differences in myoelectric manifestations of fatigue during isometric muscle actions.

INTRODUCTION: Muscle fatigue has been studied for a long time with the use of a wide variety of exercise models, protocols and assessment methods, among which surface electromyography (sEMG) is most commonly used. The main sEMG parameters (amplitude and frequency) are prevalently used to evaluate the level of muscle fatigue in static and dynamic contractions. OBJECTIVE: The purpose of this study is to determine and compare 2 separate indices: IF1 basis of the sEMG signal amplitude analysis and IF2 basis of the sEMG median frequency analysis, related to muscles fatigue during an isometric contraction. MATERIAL AND METHODS: The study was performed on 60 professional runners divided into 2 equal groups. The first group comprised sprinters, competing in short distance track and field events (100 and 200 meters). The second group consisted of middle-distance runners, competing in middle-distance track and field events (800 and 1,500 meters). The electrical activity of the VMO muscles of the right and left lower limbs was recorded simultaneously during isometric activity in a squatting position. The sEMG data was used to determine and compare IF1 and IF2 indices. RESULTS: During isometric measurement, sprinters presented a much more significant increase in the mean amplitude of sEMG signal in comparison to middle-distance runners (mean IF1 difference: 0.228; p=0.007). Analysis of the median frequency did not show significant differences between the 2 groups (mean IF2 difference: 0.037; p=0.12). CONCLUSIONS: Change in sEMG amplitude during isometric exercise may be related to muscles fatigue. The use of fatigue indices, based on sEMG amplitude, as an objective indicator of the efficacy of an endurance training programme for sportsmen requires further research.

Different association between specific manifestations of bruxism and temporomandibular disorder pain.

INTRODUCTION: A growing body of evidence suggests that bruxism exists in two separate manifestations. However, little is known about the association between specific manifestations of bruxism and temporomandibular disorder (TMD) pain. AIM: The aim of our study was to analyze the association between TMD pain and specific diagnoses of bruxism (sleep, awake, and mixed diagnosis of sleep and awake bruxism). MATERIAL AND METHODS: 508 adult patients (296 women and 212 men), aged between 18 and 64 years (mean age 34±12 years), attending to a clinic for general dental treatment. Patients were asked to fill an anonymous questionnaire, consisting of three questions, verifying the presence of TMD pain and two forms of bruxism. All questions were based on the Polish version of the Research Diagnostic Criteria for Temporomandibular Disorders patient history questionnaire. Cross tabulation was done, and χ2 was used as a test of significance to find the association between the variables. RESULTS: Awake bruxism was associated with TMD pain only in men (χ2=7.746, p<0.05) while mixed diagnosis of bruxism was associated with TMD pain in both women (χ2=10.486, p<0.05) and men (χ2=4.314, p<0.05). There was no statistically significant association between sleep bruxism and TMD pain. Gender-related differences in the presence of all bruxism diagnoses were also statistically insignificant. CONCLUSIONS: Interaction between sleep and awake bruxism may increase the risk for TMD pain. We suggest considering concomitance as a confounder, when studying sleep or awake bruxism.