Postural responses of galvanic vestibular stimulation: comparison between groups of older adults and young people

Abstract Objective: To evaluate the effect of vestibular manipulation on the postural sway and muscle activation of younger and older adults. Methods: The study analyzed the effects of three intensity levels of galvanic vestibular stimulation (GVS) (0.3; 0.6 and 1m) on the pattern of muscle activity and center of pressure (CP) displacements of 12 older adults (EG) and 12 young adults (CG) while maintaining their balance on a stable surface, with no vision. Results: The EG showed a positive correlation between CP displacement and muscle activity and GVS intensity. On the other hand, the magnitude of postural response in the EG was not modulated in accordance with GVS intensities. Additionally, during the highest GVS intensity level (1 mA) greater muscle activity was used to increase stiffness, decrease the amplitude of oscillation and ensure stability. This unusual response characterizes a pattern of co-activation and is perhaps a safety mechanism to ensure stability. Conclusion: The EG individuals were not able to select the appropriate motor strategy to efficiently compensate the effects of GVS. This unusual strategy reflects deficits in the vestibular system of older adults, a fact which negatively interferes with their ability to reevaluate sensory information.