Effects of Noisy Galvanic Vestibular Stimulation on the Muscle Activity and Joint Movements in Different Standing Postures Conditions

Abstract

ObjectiveNoisy galvanic vestibular stimulation (nGVS) is an effective method for stabilizing posture; however, little is known regarding the detailed muscle activity and joint movement in the standing posture. This study aimed to clarify the changes in the lower limb muscle activity and joint angular velocity by nGVS intervention using the simultaneous assessment method of inertial measurement units and surface electromyography (EMG).MethodsSeventeen healthy participants were assessed for their physical responses under four conditions (standing on a firm surface with eyes-open/eyes-closed, and a foam surface with eyes-open/eyes-closed) without stimulation (baseline) and with stimulation (sham or nGVS). Noise stimuli were applied for 30 s at a level below the perceptual threshold. The body control response was evaluated using EMG activity and angular velocity of the lower limbs.ResultRegarding the change from baseline for each parameter, there was a significant interactive effect of EMG activity in the muscle type × intervention and EMG activity and angular velocity in the condition × intervention. Post hoc analysis revealed that the angular velocity was significantly decreased in the abduction-adduction direction in the standing on a foam surface with eyes-closed condition compared to that with eyes-open in the nGVS intervention.ConclusionOur results suggest that nGVS altered physical responses in different standing postural conditions. The present study is exploratory and therefore the evidence should be investigated in future studies specifically target those muscle activities and joint motion parameters.

Scoping out noisy galvanic vestibular stimulation: a review of the parameters used to improve postural control

“…Higher impedance will either reduce the current that a machine is able to deliver to the vestibular system or, will draw a higher voltage to maintain the current amplitude (it is assumed that below the specified impedance threshold the relationship between frequency and impedance should not affect the current amplitude). Only seven studies mention the level and whether impedance is controlled: keeping impedance below 600 Ohms ( Mulavara et al, 2011 ) or 1,000 Ohms ( Goel et al, 2015 ; Mulavara et al, 2015 ; Samoudi et al, 2015 ; Temple et al, 2018 ) in five studies and below 10,000 Ohms in two ( Nooristani et al, 2021 ; Mitsutake et al, 2022 ). Mulavara et al (2011) provided a frequency analysis of their signal at the machine but to our knowledge no one has investigated the waveform frequency at the skin level to determine how the conductive interface at the skin influences the final stimulation output.…”

“…In keeping with the theory of stochastic resonance, other studies have used various methods to individualize the amplitude to participants. This has been done by testing an array of amplitudes and choosing the amplitude that improves standing sway measures the most ( Mulavara et al, 2011 ; Iwasaki et al, 2014 , 2018 ; Mulavara et al, 2015 ; Fujimoto et al, 2016 , 2018 ; Asslander et al, 2021 ; Chen et al, 2021 ), or by calculating amplitude at a percentage of the cutaneous sensory threshold ( Wuehr et al, 2016a , b ; Piccolo et al, 2020 ; Lotfi et al, 2021 ; Mitsutake et al, 2022 ) or a percentage of the vestibular (motion) threshold of 1 Hz sinusoidal GVS stimulation, to determine the optimum signal ( Goel et al, 2015 ; Mulavara et al, 2015 ; Samoudi et al, 2015 ; Temple et al, 2018 ; Piccolo et al, 2020 ; Sprenger et al, 2020 ).…”

“…The cutaneous threshold, or the point at which nGVS starts to cause cutaneous sensation under the electrodes, has also been used as a method of optimization ( Wuehr et al, 2016a , b ; Lotfi et al, 2021 ; Mitsutake et al, 2022 ). The advantage of using cutaneous sensory threshold to determine the optimum amplitude is that it can be easily done outside a laboratory setting, it only requires one waveform and there is a low risk of delivering stimulation at a level that may cause unexpected imbalance.…”

Effects of transcranial electrical stimulation of the right posterior parietal cortex on physical control responses

“…Each experiment was conducted on a different day. The sample size for Experiment 1 was selected based on a previous study of tES during static standing with the IMU [11] (effect size = 1.32, α = 0.05, 1-β error probability = 0.8). Based on the effect size of Experiment 1, a sample size of N ≥ 20 was determined to be necessary to achieve a statistical power of 0.8 for Experiment 2.…”

“…The standing postural control system involves both sensory and motor strategies with the ankle and hip joints that result in appropriate postural control responses. In fact, standing on a soft-foam surface with closed eyes causes compensatory postural responses led by part of ankle-joint strategy [11]. Determining the changes in the body control response under this condition by modulation of the right PPC will enhance understanding of the functional coordination of sensory-motor associations.…”