Effect of wearing a mouthguard on the vestibulocollic reflex

It has been speculated that the use of a mouthguard improves athletic ability such as muscular strength and equilibrium. The postural system is equipped with response patterns that correct for unexpected perturbations. These responses are driven by immediate feedback from visual, vestibular, and somatosensory information. These are integrated by the central nervous system. We analysed the possibility that wearing a mouthguard influences vestibular information via the vestibulocollic reflex (VCR) in the sagittal plane. The input of the VCR is vestibular afferent activity and its output is neck muscle activation. With the subject in the supine position, the apparatus used in this study induces the VCR by subjecting the head to abrupt vertical acceleration by sudden free fall under the head's own weight. Surface electromyographic (EMG) recordings in the sternocleidomastoid muscles (SCM) of 14 participants were analysed. There were no significant differences in the amplitude of the VCR within the left and right SCM whether subjects were or were not wearing a mouthguard (P=0.3227 within left SCM; P=0.9686 within right SCM). These results suggest that wearing a mouthguard has no effect on the VCR in the sagittal plane when supine, and so that vestibular sensory information is unaffected by wearing a mouthguard, in this context. Further research is required to examine whether this also holds true in more functional, upright and dynamic body positions. (c) 2006 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.