## 4 Discussion
For these investigations, all systems of postural stability maintenance, such as visual, somatosensory and vestibular systems,should be included as either one or a combination of these systems may be inherently different between the sexes or contribute to the observed differences in postural stability. The reduction of the sway area and the resulting improvement of stance stability by wearing the splint, which places the occlusion in centric-like jaw relation, were also confirmed by [PERSON] et al. [38]. [PERSON] et al. [41] have also proved the influence of a splint by demonstrating a significant increase in the anterior-posterior speed of the CoP in TMD patients. The improved ROM of the cervical spine in the present study contrasts with that of adolescent dancers analyzed by [PERSON] [42]. Here, [PERSON] [42] could not detect any changes in cervical mobility by means of a temporarily generated occlusion block. Furthermore, [PERSON] et al. [43] could not prove any influence of wearing a splint for a period of six months on the cervical spine position in women with TMD. However, a divergent subject collective (women, TMD and no athletes) as well as other measurement systems have to be considered here. Consequently, it would be interesting to analyze in a follow-up study whether changes in balance and movement of the cervical spine are due to changes in the mechanical properties of the upper airway and, thus, still a lowered respiratory rate and ventilation. Thus, it becomes clear that the analysis of the use of splints is not only the subject of scientific research in the field of sports, but also in rehabilitation, such as in the therapy of CMD or Pediatric Obstructive Sleep Apnea Syndrome. The possible treatment goals of a centric relation occlusal splint in case of rehabilitation are stabilization of the orofacial system; improvement and relief of temporomandibular dysfunctions, such as temporomandibular joint clicking and muscular pain, abnormal loading of the condyle and bilaminar zone. A good functional pre-treatment with a splint is also crucial for forensic reasons before large extensive restorations and tooth replacements. The study also has limitations which are indicated in the following. Likewise, only ad-hoc effects have been presented in the current cross-sectional study where the subjects wore the splint, for the first time, 20 min before the measurement. Whether these can still be preserved within a longitudinal study cannot be answered in the present study and, so, this would be desirable to investigate in future studies. Another limitation of this study is the fact that the measurements were taken while standing and not while moving. Whether the improvements of wearing a splint found here can also be positively demonstrated during the performance of daily or sport-related activities remains unclear, however, it could potentially be a very important factor, especially in competitive sports. Furthermore, the effect of wearing a splint on unathletic people or patients with TMD using the same study design has not been investigated. In addition, correlation calculations between the cervical spine movements and balance stability do not appear to be appropriate because the cervical spine movements were measured while sitting and the balance stability was measured while standing. Furthermore, the effect of past (sports) injuries were not considered. Past unilateral injuries, for example, to the lower extremity, could potentially result in compensatory mechanisms that may affect balance stability. Therefore, recovered past injuries should also be considered in future studies. Here, it should be examined whether these possibly affect either the postural control or movement motor control, or both sequentially, and if they can extend their effects beyond one body area [44].