Indução de oscilações posturais periódicas em seres humanos por vibração tendinosa e avaliação de sua atenuação por toque leve (\"light touch\").

Abstract

Humans exhibit natural oscillations while maintaining a quiet standing posture (QsP), influenced by intrinsic and extrinsic factors. The control of these oscillations is carried out by the postural control system, which integrates signals from the proprioceptive, vestibular, and visual systems. In this study, we focused on disturbing the proprioceptive system, specifically the muscle spindles of the triceps surae, using bilateral vibration on the Achilles tendon.The input signal consists of amplitude-modulated vibrations (AM vibrations), with a high-frequency carrier signal (sine wave at 100 Hz) and a low-frequency modulator signal f m (sine wave from 0.1 to 0.5 Hz). Body movement is represented by the projection of the center of mass on the ground in the sagittal plane (COMap) and is evaluated through spectral analysis.The objective is to determine if it is possible to generate a deterministic slow oscillation, at frequency f m , in addition to the natural stochastic oscillations of the human body. Once the induction of postural oscillations at frequency f m is confirmed, we evaluate the effect of incorporating a haptic sensory cue through light touch.The results revealed an increase in power and high coherence values for the evaluated modulation frequencies. Additionally, light touch was able to decrease the amplitude of these induced postural oscillations.This study presents an innovative methodology for applying vibration to the Achilles tendon, providing a valuable tool for understanding the impact of proprioceptive sensory input on postural control. Deepening the understanding of these mechanisms is essential to contribute to the prevention and diagnosis of postural and balance dysfunctions.