Can a thin mechanical stimulation on the plantar arch affect the head mobility? A preliminary report

Background Successfully controlling head posture demands the integration of sensory information arising from different receptors. Of particular interest is the influence of feet mechanoreceptors on the control of head position in space. Aim We ask whether a thin plantar insert can modify the range of motion (RoM) of the head and whether changes in RoM depend on the foot site where the insoles are positioned. Methods Twenty-four healthy subjects were randomly assigned to either experimental or control group. A plantar insole with a half-moon shape (1.5 mm thick) was used to stimulate the feet mechanoreceptors. For both groups, the head RoM in each of the three anatomical planes was assessed before and after participants walked for 15 min at 4 km/h on the treadmill. This procedure was applied four times for subjects in the experimental group: For each trial subjects walked with a plantar insole placed at a specific, foot location. Changes in head RoM were assessed through a symmetry index, accounting for differences in movement direction. Results In the control group, no pre-post differences in the symmetry index were observed for the sagittal, frontal and horizontal planes. Similarly, for the intervention group, ANOVA did not reveal both main and interaction effects of time and insole position on the symmetry index for the three planes of movement. Conclusion Our results do not evidence any effect of a 1.5-mm-thick mechanical stimulus on the head mobility, regardless of where the insole was placed for the latter group.