Subsensory electrical noise stimulation applied to the lower trunk improves postural control during visual perturbations

Zahra Bassiri; Caroline Austin; Christian Cousin; Dario Martelli

doi:10.1016/j.gaitpost.2022.05.010

Subsensory electrical noise stimulation applied to the lower trunk improves postural control during visual perturbations

Gait Posture. 2022 Jul:96:22-28. doi: 10.1016/j.gaitpost.2022.05.010. Epub 2022 May 7.

Authors

Zahra Bassiri¹, Caroline Austin², Christian Cousin³, Dario Martelli⁴

Affiliations

¹ Department of Mechanical Engineering, University of Alabama, Box 870276, Tuscaloosa, AL 35487, USA. Electronic address: zbassiri@crimson.ua.edu.
² Department of Aerospace Engineering, University of Alabama, Box 870280, Tuscaloosa, AL 35487, USA. Electronic address: craustin1@crimson.ua.edu.
³ Department of Mechanical Engineering, University of Alabama, Box 870276, Tuscaloosa, AL 35487, USA. Electronic address: cacousin@eng.ua.edu.
⁴ Department of Mechanical Engineering, University of Alabama, Box 870276, Tuscaloosa, AL 35487, USA. Electronic address: dmartelli@ua.edu.

PMID: 35561569
DOI: 10.1016/j.gaitpost.2022.05.010

Abstract

Background: Low levels of sensory noise applied to the skin through electrical stimulation (ES) can improve balance control through a mechanism called stochastic resonance (SR). Little is known regarding the extent subsensory ES can improve reactive control of balance after unanticipated balance perturbations and the best location where to apply the stimulation.

Research questions: How efficient is subsensory ES in improving reactive control of balance following visual perturbations delivered in a virtual reality (VR) environment? 2) Does lower trunk stimulation have greater effects than lower legs stimulation?

Methods: Eighteen healthy young adults stood on a force plate while wearing a Valve Index VR headset in eyes closed (EC), eyes open (EO), eyes open with anteroposterior visual perturbations (AP) and eyes open with mediolateral visual perturbations (ML) conditions. No-stimulation (NS), leg stimulation (LS), or trunk stimulation (TS) equal to 90% of the sensory threshold (ST) was applied. The 95% confidence ellipse area (95%EA), the lengths of AP and ML sway path (APPath, MLPath), and the AP and ML 50% and 95% power frequencies (APPF50, MLPF50, APPF95, and MLPF95) were calculated. Repeated-measures ANOVA and Tukey post-hoc tests were used to analyze the main and interaction effects of stimulation and visual conditions.

Results: During AP perturbations, participants showed higher frequencies, longer paths, and larger ellipse areas. TS caused lower APPF50, MLPF50, MLPF95, APPath and EA while LS caused lower MLPF50 and EA. During ML perturbations, TS reduced APPF50 and both LS and TS caused reduction of MLPF95. Higher instability following AP perturbations was associated with greater effects of TS and LS.

Significance: The application of subsensory ES improved postural control during AP perturbations and TS reduced postural sway more effectively than LS. TS may be an effective strategy to enhance balance control during reactive postural tasks, thus potentially reducing fall risk.

Keywords: Balance; Electrical stimulation; Stochastic resonance; Virtual reality; Visual perturbations.

MeSH terms

Electric Stimulation
Humans
Noise
Postural Balance* / physiology
Sensory Thresholds / physiology
Vibration*
Young Adult