Galvanic vestibular stimulation as a novel treatment for seasickness

Motion sickness is the cause of major physical discomfort and impaired performance in many susceptible individuals. Some habituate to sea conditions, whereas others remain chronically susceptible, requiring lifelong pharmaceutical treatment. The present study sets out to investigate whether galvanic vestibular stimulation (GVS) coupled with rotatory chair stimulation could mimic sea conditions and alleviate motion sickness symptoms in individuals deemed chronically susceptible. Thirty seasickness susceptible subjects, after at least six months of regular sailing, were enrolled in a prospective, single-blind, randomised controlled study. The treatment group underwent GVS coupled with inverse phase rotatory chair impulse in sinusoidal harmonic acceleration protocol. The control group underwent a sham procedure. All subjects performed repeated velocity step tests to determine the vestibular time constant (Tc) and completed a seasickness questionnaire. The GVS rotatory chair procedure decreased the prevalence of severe seasickness. The number of motion sickness clinic visits and anti-motion sickness drug consumption were reduced in the treatment group three-month post intervention as compared to control. In addition, there was significant reduction of Tc in the treatment group. GVS coupled with rotatory chair impulse could decrease motion sickness severity, induce neurophysiological learning processes and promote habituation to seasickness in chronic susceptible subjects. This is a novel and promising non-pharmacological method to treat motion sickness susceptible individuals. Furthermore, the investigation demonstrated that adaptation to sea conditions may take place even after years of susceptibility to seasickness. This study was retrospectively registered on August 10th 2021 and assigned the identifier number NCT05004818.

Postural sway in men and women during nauseogenic motion of the illuminated environment

We exposed standing men and women to motion relative to the illuminated environment in a moving room. During room motion, we measured the kinematics of standing body sway. Participants were instructed to discontinue immediately if they experienced any symptoms of motion sickness, however mild. For this reason, our analysis of body sway included only movement before the onset of motion sickness. We analyzed the spatial magnitude of postural sway in terms of the positional variability and mean velocity of the center of pressure. We analyzed the multifractality of postural sway in terms of the width of the multifractal spectrum and the degree of multiplicativity of center of pressure positions. Results revealed that postural sway differed between participants who later reported motion sickness and those who did not, replicating previous effects. In a novel effect, postural responses to motion of the illuminated environment differed between women and men. In addition, we identified statistically significant interactions that involved both Sex and motion sickness status. Effects were observed separately in the spatial magnitude and multifractality of sway. The results were consistent with the postural instability theory of motion sickness (Riccio and Stoffregen in Ecol Psychol 3:195-240, 1991) and suggest that Sex differences in motion sickness may be related to Sex differences in the control and stabilization of bodily activity.

Precursors of post-bout motion sickness in adolescent female boxers

Athletic head trauma (both concussive and sub-concussive) is common among adolescents. Head trauma often is followed by motion sickness-like symptoms, by changes in cognitive performance, and by changes in standing body sway. We evaluated adolescent female boxers who did and did not report motion sickness after a bout (i.e., a boxing match), together with a control group of non-boxers. We asked whether pre-bout body sway would differ between boxers who experienced post-bout motion sickness and those who did not. In addition, we asked whether pre-bout cognitive performance would differ between non-boxers and boxers with and without post-bout motion sickness. Seven of twenty boxers reported motion sickness after a bout. Pre-bout measures of cognitive performance and body sway were different in boxers who reported post-bout motion sickness than in boxers without post-bout sickness or controls. The results suggest that susceptibility to motion sickness-like symptoms in adolescent female boxers may be manifested in characteristic patterns of body sway and cognitive performance. It may be possible to use pre-bout data to predict susceptibility to post-bout symptoms.

Body load and the postural precursors of motion sickness

Physical properties of the body affect the control of standing body sway. One example occurs when loads are added to the body, such as occurs when wearing a backpack. Other research has shown that subjective symptoms of motion sickness are preceded by differences in body sway between individuals who later report motion sickness and those who do not. In the present study we asked whether loads worn on the body would affect relations between body sway and motion sickness. We measured standing body sway without load and then with loads worn at the shoulders or thighs. Then participants were exposed to potentially nauseogenic visual motion stimulation while wearing shoulder or thigh loads. We measured body sway continuously during exposure to visual motion. Thirteen of 36 participants (36%) reported motion sickness. Body sway was affected by loads and by load position, consistent with previous research. Also consistent with previous research, sway differed between well and sick participants both before and during exposure to visual motion stimuli. In addition, during room motion the well and sick participants responded differently to loads. The results are consistent with the hypothesis that physical properties of the body can affect relations between body sway and motion sickness.

Cognitive and postural precursors of motion sickness in adolescent boxers

Athletic head trauma (both concussive and sub-concussive) is common among adolescents. Concussion typically is followed by motion sickness-like symptoms, by changes in cognitive performance, and by changes in standing body sway. We asked whether pre-bout body sway would differ between adolescent boxers who experienced post-bout motion sickness and those who did not. In addition, we asked whether pre-bout cognitive performance would differ as a function of adolescent boxers' post-bout motion sickness. Nine of nineteen adolescent boxers reported motion sickness after a bout. Pre-bout measures of cognitive performance and body sway differed between boxers who reported post-bout motion sickness and those who did not. The results suggest that susceptibility to motion sickness-like symptoms in adolescent boxers may be manifested in characteristic patterns of body sway and cognitive performance. It may be possible to use pre-bout data to predict susceptibility to post-bout symptoms.

Getting Your Sea Legs

Sea travel mandates changes in the control of the body. The process by which we adapt bodily control to life at sea is known as getting one's sea legs. We conducted the first experimental study of bodily control as maritime novices adapted to motion of a ship at sea. We evaluated postural activity (stance width, stance angle, and the kinematics of body sway) before and during a sea voyage. In addition, we evaluated the role of the visible horizon in the control of body sway. Finally, we related data on postural activity to two subjective experiences that are associated with sea travel; seasickness, and mal de debarquement. Our results revealed rapid changes in postural activity among novices at sea. Before the beginning of the voyage, the temporal dynamics of body sway differed among participants as a function of their (subsequent) severity of seasickness. Body sway measured at sea differed among participants as a function of their (subsequent) experience of mal de debarquement. We discuss implications of these results for general theories of the perception and control of bodily orientation, for the etiology of motion sickness, and for general phenomena of perceptual-motor adaptation and learning.