## 1 Introduction  
**Masticatory muscle pain is the most common source of pain related to temporomandibularibular disorders (TMDs), affecting up to 10% of the population [1]. This medical condition, which is 1.5-2 times more frequent in women than in men, can be classified into certain forms such as myofascal pain (MFP), local muscle soreness, protective co-contraction, centrally mediated mylalgia, and myospasm [2]. MFP can be caused by myofascal trigger points (MTrPs) which are classified as active or latent [3]. Active MTrPs are associated with spontaneous pain in the surrounding tissue or to distant sites, in comparison to latent MTrPs, which are not associated with a spontaneous pain complaint [4]. Even though elastography, Doppler imaging, diagnostic ultrasound, or biomarkers can be used in the diagnosis of MTrPs, the current gold standard for the MTrPs diagnosis is the manual palpation according to criteria set by [PERSON], such as taut band, tender nodule on the taut band with increased pain on pressure, referred recognition pain, and local twitch response [4; 5; 6].  
Active MTrPs can be associated with a reduced range of motion through muscle dysfunction and muscle weakness. Within the stomatognathic system, MTrPs in the masticatory muscles may restrict active maximum mouth opening (MMO) [7]. Moreover, masticatory muscle pain may contribute to the reduction of maximum bite force [8]. Changes in the masticatory muscles associated with the presence of MTrPs can be observed in the electromyographic examination. MFP among masticatory muscles may be associated with increased surface electromyography (sEMG) values during resting mandibular position [9]. Furthermore, a decrease in bioelectrical masticatory muscle activity during teeth clenching has been demonstrated in patients with MFP within the stomatognathic system [10]. Moreover, the relationship between the presence of MTrPs in masticatory muscles and temporomandibular joint hypomobility is frequently recognized by dentists and physiotherapists.  
There are multiple ways to deactivate active MTrPs, including manual therapy, dry needling, local heat/cold, kinesiotaping, ultrasound therapy, and laser therapy [11; 12; 13]. Among the manual treatments for MTrPs and MFP, the compression technique (CT), myofascal release, acupressure, muscle energy technique, and specific soft tissue mobilization techniques are most often used. A systematic review and meta-analysis of randomized controlled trials reported that manual MTrPs treatment of head and neck muscles may reduce the frequency, intensity, and duration of tension-type headache, but the quality of evidence was very low [14]. Moreover, it is currently impossible to identify the most effective treatment technique for MTrPs among those proposed. Hence, studies on the effectiveness of manual techniques in the treatment of active MTrPs are necessary.  
Although the etiology and pathomechanism of MTrPs among masticatory muscles is complex and not yet fully understood, both diagnosis and treatment of MTrPs is an extremely important clinical aspect in preventing the development of MFP within the stomatognathic system. Thus, the presented study aims to analyze the acute effect of the CT on active maximal mouth opening and the electromyographic activity of the masseter (MM) and temporalis anterior (TA) muscles in subjects with active MTrPs in the MM muscles. The null hypothesis is that CT influences both MMO and bioelectrical masticatory muscle activity in patients with MTrPs. Through the deactivation of active MTrPs, the parameters of resting bioelectrical activity will decrease with an increase in functional activity during teeth clenching.