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Open Access Research article

Simultaneous transcutaneous electrical nerve stimulation mitigates simulator sickness symptoms in healthy adults: a crossover study

Hsin Chu12*, Min-Hui Li1, Yu-Cheng Huang1 and Shih-Yu Lee1

Author Affiliations

1 Institute of Aerospace and Undersea Medicine, School of Medicine, National Defense Medical Center, Taipei, Taiwan

2 Department of Neurology, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan

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BMC Complementary and Alternative Medicine 2013, 13:84  doi:10.1186/1472-6882-13-84

Published: 15 April 2013

Abstract

Background

Flight simulators have been used to train pilots to experience and recognize spatial disorientation, a condition in which pilots incorrectly perceive the position, location, and movement of their aircrafts. However, during or after simulator training, simulator sickness (SS) may develop. Spatial disorientation and SS share common symptoms and signs and may involve a similar mechanism of dys-synchronization of neural inputs from the vestibular, visual, and proprioceptive systems. Transcutaneous electrical nerve stimulation (TENS), a maneuver used for pain control, was found to influence autonomic cardiovascular responses and enhance visuospatial abilities, postural control, and cognitive function. The purpose of present study was to investigate the protective effects of TENS on SS.

Methods

Fifteen healthy young men (age: 28.6 ± 0.9 years, height: 172.5 ± 1.4 cm, body weight: 69.3 ± 1.3 kg, body mass index: 23.4 ± 1.8 kg/m2) participated in this within-subject crossover study. SS was induced by a flight simulator. TENS treatment involved 30 minutes simultaneous electrical stimulation of the posterior neck and the right Zusanli acupoint. Each subject completed 4 sessions (control, SS, TENS, and TENS + SS) in a randomized order. Outcome indicators included SS symptom severity and cognitive function, evaluated with the Simulator Sickness Questionnaire (SSQ) and d2 test of attention, respectively. Sleepiness was rated using the Visual Analogue Scales for Sleepiness Symptoms (VAS-SS). Autonomic and stress responses were evaluated by heart rate, heart rate variability (HRV) and salivary stress biomarkers (salivary alpha-amylase activity and salivary cortisol concentration).

Results

Simulator exposure increased SS symptoms (SSQ and VAS-SS scores) and decreased the task response speed and concentration. The heart rate, salivary stress biomarker levels, and the sympathetic parameter of HRV increased with simulator exposure, but parasympathetic parameters decreased (p < 0.05). After TENS treatment, SS symptom severity significantly decreased and the subjects were more able to concentrate and made fewer cognitive test errors (p < 0.05).

Conclusions

Sympathetic activity increased and parasympathetic activity decreased after simulator exposure. TENS was effective in reducing SS symptoms and alleviating cognitive impairment.

Trial registration number

Australia and New Zealand Clinical Trials Register: http://ACTRN12612001172897 webcite

Keywords:
Transcutaneous electrical nerve stimulation; Motion sickness; Simulator sickness; Crossover; Autonomic nervous system; Heart rate variability; Salivary biomarker; Alpha amylase; Cortisol