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Abstract

Introduction:

Motion sickness (MS) has traditionally been attributed to visual-sensory mismatch. Research on the cause-and-effect relationship between postural instability and MS has emerged, although evidence remains scarce.

Methods:

A literature review from inception to December 31, 2024, was conducted to understand the relationship between MS and postural instability by searching several databases over a 1-month period in January 2025. The search was conducted according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The included studies investigated various forms of MS, including car sickness, virtual reality (VR), simulator sickness, cybersickness, travel-related sickness, and space MS.

Results:

A total of 16 articles were identified, encompassing 1518 participants with ages ranging from 9 to 63 years. Most studies used force platforms and balance boards to assess postural instability, and 13 studies reported a relationship between postural instability and MS. These findings were consistent across VR, simulator, and transport-based motion paradigms. In contrast, 3 studies reported no consistent relationship between sway magnitude and symptom development.

Conclusions:

Although postural instability precedes MS, the quality of evidence is inadequate to determine the cause-and-effect relationship between MS and postural instability until extensive, multicentre, randomised controlled studies are conducted.

Keywords

motion sickness visual vestibular mismatch vestibular otolith semicircular canal balance postural stability

Introduction

Motion sickness (MS) is a complex physiological response triggered by real or perceived motion, commonly presenting with symptoms such as nausea, dizziness, pallor, headache, and gastrointestinal discomfort. It can significantly impair daily functioning and quality of life, especially in children and adolescents who may be more susceptible due to their ongoing neurodevelopmental maturation.^1
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The widely accepted Sensory Conflict Theory (SCT) explains MS as arising from a mismatch between signals received from the visual, vestibular, and proprioceptive systems. However, this theory has limitations in explaining individual susceptibility. An alternative framework, the postural instability theory (PIT), suggests that MS results when individuals are unable to maintain postural stability in response to a challenging environment.^1,2 According to this model, prolonged instability is not merely a symptom but a causal precursor of MS. Several studies have been conducted to test this newer theory. However, we have noted that there are literature gaps which show inconsistent empirical support for PIT across modalities, the lack of pediatric-focused research, and the limited use of standardised diagnostic criteria (Bárány Society). This review aims to better understand and synthesize evidence on the association between MS and postural instability, evaluate methodological heterogeneity, and identify directions for future research.

Material and Methods

A systematic review of the literature was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline to identify studies that investigate the relationship between MS and postural stability.

Eligibility Criteria

We included studies investigating the relationship between MS and postural stability across all age groups. Conference abstracts, letters to editors, commentaries, review articles, publications without peer review, and grey literature were excluded. As the present evidence is limited, no restrictions on sample size are placed.

Exclusion Criteria

Non-relevant designs such as case reports and editorials, unretrievable reports, non-English publications, studies with a high risk of bias or insufficient methodological details, studies not reporting the primary or secondary outcomes defined in the reviews, and studies published outside the review period.

Data Sources and Searches

PubMed, Embase, and Scopus databases were searched to identify studies published from inception to December 31, 2024 using combinations of relevant terms relating to MS “motion sickness” OR “motion-sickness” OR “cybersickness” OR “cyber-sickness” OR “simulator sickness” OR “simulator-sickness” OR “visually induced motion sickness” OR “VIMS” OR “travel sickness” OR “sea sickness” OR “car sickness”) AND postural instability (“postural instability” OR “postural sway” OR “postural control” OR “postural stability” OR “balance” OR “center of pressure” OR “CoP” OR “sensory re-weighting”).

Only articles published in the English language were included. Complete details of the search strategy are in Figure 1. To ensure a robust search strategy, references of the included studies were included. We excluded duplicate studies using EndNote X8 software (Clarivate Analytics, Philadelphia, PA, USA). The search was conducted over a period of 1 month (January 2025) in accordance with PRISMA guidelines.

Figure 1.

Search strategy.

Sixteen original clinical research articles were selected after being scrutinised by the panel members (L.R. and J.S). Any disagreements regarding the inclusion of articles were discussed and resolved by consensus.

Data extraction was done independently by 2 authors (L.R. and J.S.). We extracted the following information from each eligible study and entered it into a predefined Excel spreadsheet.

Ethical Consideration

The study was performed in accordance with ethical standards. The authors declare no conflict of interest.

Results

A total of 16 studies published from inception to December 31, 2024, were identified after an initial literature search, removal of duplicates, abstract screening, and full-text review, which met the inclusion criteria, as summarised in Table 1. All included studies were experimental or cross-sectional in design, except for 2 review articles.

Table 1.

Summary of Main Findings (Types of MS, Comorbids, Objective).

Author (year),^Ref. country	Type of study	Total patient/gender	Age (mean)	Type of MS	Comorbid	Investigation
Dida et al (2024),¹⁶ France	RS	64 (36 Women, 28 men)	20.93 Years	Car sickness	No comorbids	To investigate car-sickness susceptibility and the spectral changes due to the onset of the sway reference.
Henriques et al (2014),⁴ Brazil	CS	831 (54.7% Female, 45.3% male)	9.3 Years	Travel sickness (car, bus, playground rides, etc)	Not explicitly mentioned, but children were screened for vestibular disorders and quality of life impairments	Assessed MS prevalence using the MSSQ-Short. Examined postural balance through the Romberg test and other balance assessments under different sensory conditions. Quality of life was measured using the DHI.
Dennison and D’Zmura (2017),⁶ United States	Experimental study	15 (4 Females, 11 males)	N/A	Cybersickness	Participants were screened for vestibular and neurological dysfunction	Tested whether postural instability is necessary for cybersickness. Used a virtual rotating tunnel viewed through a HMD to induce vection (illusory self-motion). Compared seated vs standing postural conditions while measuring perceived vertical orientation and postural sway.
Litleskare (2021),⁹ Norway	Experimental study	50 (22 Males, 28 females)	Males: 30.2 years, Females: 29.5 years	Cybersickness	Participants were screened for balance impairments, limited VR experience, and required to have normal or corrected-to-normal vision	Examined whether postural stability predicts or measures cybersickness using a force platform.
Pettijohn et al (2018),¹⁰ United States	Experimental	14 (4 Females, 13 males)	37.4 Years (range: 21-63 years)	Simulator-induced MS (seasickness)	None	Participants were exposed to simulated boat motion in VR using a motion platform.
Liu et al (2024),¹⁷ Japan	Experimental	17 (10 Female, 7 male)	22 to 29 Years (mean age: 23.5 years)	APMVs	None reported; participants were screened for prior experience with autonomous cars/APMVs	The study examined the impact of different visual conditions on MS using a newly proposed SVC model.
Widdowson et al (2019),⁷ United States	Experimental	48 Participants (24 in each of 2 experiments); gender not provided	Age not provided	Cybersickness (VR-induced)	Participants were screened for color blindness and had normal or corrected-to-normal vision	Two separate experiments were conducted: Experiment 1: linear motion (forward movement in a VR hallway). Experiment 2: circular motion (rotation inside a virtual cylindrical environment). Motion conditions: Constant Speed, Ramp Speed (gradual acceleration and deceleration). Polynomial Speed (sharp acceleration and deceleration changes). (1) Tested whether constant-speed motion profiles in VR reduce cybersickness compared to variable-speed motion profiles. (2) Assessed postural instability using CoP path length and DFA.
da Silva Marinho et al (2022),⁸ Australia	Experimental study	80 (49 Males, 31 females)	22.5	Cybersickness (VR-induced MS)	Not mentioned	Investigates symptoms of cybersickness and postural instability experienced by new users of HMD-VR, playing VR videogames over long and repeated sessions, and how these symptoms may be moderated by previous videogame experience and the intensity of stimuli in the videogames played.
Qi et al (2021),¹⁸ China	Experimental study with 2 experiments	Exp 1: 140 volunteers; Exp 2: 60 volunteers (selected from Experiment 1); all male	21-22 Years old	Cybersickness induced by VSM; two conditions tested: Degree 3 and Degree 5 sea conditions; with or without GVS	None (exclusion criteria included vestibular disorders, visual difficulties, history of drug addiction or long-term medication)	Investigate the combined effects of sinusoidal GVS and VSM immersion on cybersickness and postural control.
Hald et al (2022),⁵ Denmark	Experimental study	21 (15 Males, 6 females)	13.7 Age	General MS (travel-related)	Two students diagnosed with migraine; 8 students had a history of concussion; 5 students reported daily medication (paracetamol/allergy medication)	To investigate the correlation between posturography and clinical test. Evaluated postural control using clinical balance tests and static posturography. Examined associations between MS and postural stability.
Owen et al (1998),³ United Kingdom	Experimental	34 (20 Males, 14 females)	28.9	General	Not mentioned	To investigate susceptibility to MS and anxiety in different situation (altered perception).
Teixeira et al (2024),¹¹ Australia	Experimental study	40 (19 Males and 21 females)	23.9 ± 3.3 Years	HMD-VR	Not mentioned	Comparing the novel unexpected vection hypothesis and postural instability-based explanations of cyber-sickness in VR using HMD (Exposure to the virtual environment by using HMD, HMD-VR game software used in this study was “Aircar”).
Smart et al (2002),¹⁵ United States	Cross sectional	13 (9 Male and 4 female)	19.85	General	General health	To confirm postural instability can predict MS and study the relations among instability, MS, and vection.
Bos et al (2013),¹⁹ Netherlands	Observational study	19 (9 Females and 10 males)	42	Cinerama sickness	Not mentioned	MS symptoms and increased postural instability induced by motion pictures in cinema.
Chang et al (2021),¹³ Taiwan	Experimental study (yoked-control design)	52 (26 Males, 26 females)	Drivers: 9.50 ±± 0.52 years; Passengers: 9.35 ± 0.81 years	Simulator sickness (induced by a virtual driving game)	General health	To investigate MS in persons in control of a vehicle (ie, drivers) compared to persons in the same vehicle who do not control it. Measured postural activity, MS incidence, and severity using head and torso movement tracking.
Stoffregen et al (2000),¹⁴ United States	Cross sectional	Experiment 1: 12 participants (7 men, 5 women); Experiment 2: 8 participants (5 men, 3 women)	(1) Aged 18-25 (mean: 21.1 years); (2) aged 18-21 (mean: 19.3 years).	General	Good health, with no history of vestibular dysfunction, and normal or corrected vision	Test the hypothesis that postural instability precedes the onset of MS.

Abbreviations: APMV, autonomous personal mobility vehicle; CoP, center of pressure; DFA, detrended fluctuation analysis; DHI, Dizziness Handicap Inventory; GVS, galvanic vestibular stimulation; HMD, head-mounted display; MS, motion sickness; MSSQ-Short, Motion Sickness Susceptibility Questionnaire-Short; SVC, Subjective Vertical Conflict; VR, virtual reality; VSM, virtual ship motion.

Table 2.

Summary of Main Findings (Tests, Finding, Supporting Findings and Outcomes).

Author (year),^Ref. country	Postural test	Findings	Other test/findings	Outcome
Dida et al (2024),¹⁶ France	Force platform with sway-referenced and static phases.	(1) Individuals less susceptible to car sickness showed increased energy ratios upon regaining reliable proprioception, indicating better sensory re-weighting. (2) Car-sick individuals lacked this transient response.	Car sickness susceptibility questionnaire MISC	(1) Postural control differences correlate with car sickness susceptibility. Non-car-sick individuals adapt their balance control more dynamically when sensory conditions change. (2) Car-sick individuals exhibit weaker sensory re-weighting, potentially making them more prone to MS. (3) Sensory integration plays a key role in MS. MS might stem from an inability to rapidly adjust to sensory input changes, rather than postural instability alone.
Henriques et al (2014),⁴ Brazil	(1) Romberg test with different conditions (eyes open/closed, standing on the floor/mat, sharpened stance). (2) Spinning test (five 360° turns) to evaluate vestibular response.	(1) Prevalence of MS: 43.4% in cars, 43.2% on buses, 11.7% on park swings, 11.6% on Ferris wheels. (2) Higher MSSQ scores in girls than boys (6.6 vs 4.2, P < .001). (3) MS was significantly correlated with postural instability. (4) Peak MS susceptibility occurred at age 9, with symptoms declining afterward.	DHI	(1) MS prevalence is highest in cars and buses among schoolchildren. (2) Postural instability correlates with MS severity, suggesting a link between balance dysfunction and susceptibility. (3) Quality of life is significantly affected by MS, as measured by the DHI.
Dennison and D’Zmura (2017),⁶ United States	(1) Postural sway was measured using a Nintendo Wii Balance Board. (2) Forward-Backward and Right-Left sway were analyzed. (3) Head movement was tracked using an Oculus Rift HMD.	(1) Cybersickness increased with rotation speed but was not linked to postural instability. (2) Most participants exhibited little or no postural sway in response to VR motion. (3) Seated and standing participants experienced similar levels of cybersickness, contradicting PIT. (4) Greater cybersickness was associated with less postural sway, possibly due to participants reducing movement to minimize symptoms.	(1) MSSQ; (2) SSQ	(1) Postural instability is not a prerequisite for cybersickness, challenging PIT. (2) Findings support SCT, which suggests that conflicting sensory signals (visual vs vestibular) cause cybersickness rather than postural instability. (3) Future research should explore neural mechanisms of cybersickness rather than focusing solely on postural stability.
Litleskare (2021),⁹ Norway	(1) Force platform (FP4, Hur labs Oy, Finland) was used to measure postural sway. (2) Measurements were taken in different conditions: Eyes open (EO1, baseline); EC (visual dependency test); First minute of VR exposure (VR1, initial impact); Last minute of VR exposure (VR2, long-term effect); Post-exposure eyes open (EO2, recovery test).	(1) Participants who experienced cybersickness had greater postural instability in the first minute of VR exposure (VR1) compared to those who did not. (2) No significant difference in visual dependency between sick and well participants. (3) A significant correlation between postural sway and cybersickness severity was found in the last minute of VR exposure (VR2). Postural stability returned to baseline within 10 minutes after VR exposure.	SSQ	(1) Postural instability was both a predictor and an objective measure of cybersickness at the group level. (2) However, large individual variability limited its predictive value for identifying susceptible individuals. (3) Findings suggest cybersickness and postural instability are linked, but the relationship is complex and inconsistent across individuals.
Pettijohn et al (2018),¹⁰ United States	Active condition: Participants freely adjusted posture to maintain balance. Passive condition: Participants’ feet were strapped in place, preventing postural adjustments. Measurements: Postural stability was assessed using sample entropy (head movement analysis). Postural sway was measured using ellipses (spatial complexity of movements).	(1) Participants in the passive condition exhibited greater postural instability (lower sample entropy). (2) MS symptoms increased over time, but no significant difference was found between active and passive conditions. (3) No direct correlation was found between postural instability and MS symptoms, contradicting PIT.	(1) SSQ; (2) Balance tests (heel-to-toe walking & one-leg standing) were conducted before exposure	(1) Postural instability was not found to be a causal factor in MS. (2) The study contradicts prior research suggesting postural instability is a key predictor of MS.
Liu et al (2024),¹⁷ Japan	(1) Participants’ head movements and visual perception were tracked using a Helmet-Mounted Measurement Instrument equipped with IMU to record head acceleration and angular velocity. (2) Camera to capture visual vertical perception.	(1) Participants experienced higher MS symptoms when using a tablet during autonomous driving (WAD condition) compared to looking ahead (LAD condition). (2) The proposed SVC model incorporating visual vertical predictions improved the accuracy of MS prediction.	MISC	Suggest an indirect link between postural stability and MS: (1) The study supports SVC theory, which suggests that MS arises from a mismatch between sensed vertical direction (vestibular input) and expected vertical orientation (visual input). When participants used a tablet (WAD condition), their visual reference was blocked, leading to an impaired sense of spatial orientation, which could affect postural control. (2) The study measured head movements using an IMU-Restricted head movement (due to focusing on a tablet) was associated with increased MS symptoms, possibly due to reduced sensory integration for maintaining postural stability. (3) The study notes that in autonomous vehicles, passengers lack control over their movement, making adaptive postural adjustments more difficult. This lack of control, combined with frequent obstacle avoidance maneuvers, leads to unexpected body movements, potentially destabilizing posture and increasing MS susceptibility.
Widdowson et al (2019),⁷ United States	(1) CoP path length analysis measured via a Nintendo Wii Balance Board as a low-cost alternative to a force platform. (2) Postural stability measures were analyzed along AP and ML axes.	(1) No significant difference in cybersickness between constant-speed and variable-speed motion profiles. (2) No baseline postural measures predicted cybersickness severity. (3) Greater CoP movement was observed along the AP axis compared to the ML axis, but this was not linked to cybersickness.	SSQ	(1) The study did not support the hypothesis that constant-speed motion is more comfortable than variable-speed motion. (2) Postural instability was not found to be a reliable predictor of cybersickness in VR. (3) Findings suggest VR motion design guidelines may need to be reconsidered.
da Silva Marinho et al (2022),⁸ Australia	Participants stood on the Wii balance board on both legs with EC and head tilted up for 30 s.a AP path velocity in cm/second) from the 4 force sensors at the corners of the balance board . 2 group: Gamers (40 participants) – Played at least 4 hours/week of video games. Non-gamers (40 participants) – Played less than 4 hours/week.	(1) All participants experienced cybersickness after 30 minutes of VR. (2) No adaptation over 2 sessions. (3) Gamers recovered faster than non-gamers. (4) Postural stability improved post-VR instead of worsening. (5) Action games induced more nausea symptoms than adventure games.	SSQ	(1) Cybersickness remains a significant issue even with modern VR headsets (HTC Vive Pro). (2) Gaming experience helps in recovery but does not prevent cybersickness. (3) VR exposure did not cause postural instability; rather, balance improved post-VR. (4) Game type influences nausea levels, with action games inducing stronger cybersickness symptoms.
Qi et al (2021),¹⁸ China	Balance testing using a 360° wobbly board (Step360 Pro). Subjects required to maintain balance for 15 minutes. Number of times subjects dropped from the balance board was counted. Assessment of coordination between balance perception and balance control activity.	VSM induced cybersickness with symptom profile: Nausea syndrome > central (headache and dizziness) > peripheral (cold sweating) > increased salivation. GVS effects: Aggravated balance disturbance, Did not affect most cybersickness symptoms except cold sweating, Delayed cybersickness habituation in repeated exposures. Balance disturbance: Increased with higher VSM intensity, not correlated with cybersickness severity. Habituation-Occurred after repeated exposure, was delayed by GVS treatment.	N/A	GVS was found not to be a suitable countermeasure against VSM-induced cybersickness. The study demonstrated different roles of vestibular inputs in cybersickness and balance disturbance during VR exposure. GVS delayed habituation to cybersickness and worsened balance disturbance.
Hald et al (2022),⁵ Denmark	Clinical tests: Romberg test (eyes open/closed), standing on one leg, standing on a pillow. Static posturography: Tetrax Interactive Balance System (4-force plate system measuring postural sway).	For NO, NC, PO and PC, the sway scores were higher for subjects suffering from current MS compared to subjects not suffering from MS, however this was not significant. Clinical tests had a ceiling effect, meaning most participants achieved maximum balance scores. Static posturography was more reliable for assessing postural control. 43% of participants reported MS, but sway scores were not significantly different between those with and without MS. Higher sway scores were observed in MS sufferers, but the difference was not statistically significant.	MS questionnaire	Static posturography is superior to clinical tests for assessing postural control. Higher sway scores were observed in MS sufferers, but the difference was not statistically significant.
Owen et al (1998),³ United Kingdom	Sway was measured by a force platform. Standing with eyes open, EC and viewing a disorienting VR display. These measures were repeated with vibration of the calf muscles to distort the somatosensory feedback from the legs (total 6 conditions).	Greater postural instability was correlated with susceptibility to MS.	Susceptibility to MS and anxious personality were evaluated by questionnaire.	(1) Greater postural instability was correlated with susceptibility to MS. (2) MS susceptibility correlated most strongly with increased sway when the visual and somatosensory feedback was absent or distorted. (3) Anxiety was correlated with reported susceptibility to MS but not with postural stability. These findings suggest that deficient perceptual-motor responses to disorienting conditions may contribute to MS susceptibility.
Teixeira et al (2024),¹¹ Australia	Using Bertec balance plate: (1) quiet stance: spontaneous fluctuations in their A/P and M/L centre of pressure (CoP) for two 60 seconds periods (sampled at 500 Hz). (2) Their standing postural sway while they were playing the HMD-VR game.	Unexpected vection was a significant predictor of cybersickness. Sickness severity increased with the strength of unexpected vection but not expected vection. Increased postural instability preceded sickness onset, supporting PIT. When combined, unexpected vection remained the strongest predictor of sickness.	Questionnaire of subjective feeling of sick/well and severity and nature of their experiences of vection during HMD-VR.	(1) “Sick” participants were significantly more likely to report unexpected vection. (2) Sickness severity increased (exponentially) with the strength of any unexpected (but not expected) vection.
Smart et al (2002),¹⁵ United States	Stimuli: Optical flow was generated using a moving room. Data on postural motion were collected using an electromagnetic tracking system.	Postural instability precedes visually induced MS.	SSQ, vector questionnaire	(1) Postural instability precedes visually induced MS. (2) It is possible to use postural measures to predict future occurrences of MS.
Bos et al (2013),¹⁹ Netherlands	Subjects stood in a quasi-tandem (slightly apart) stance for 60 seconds. Data were sampled at 40 Hz and analyzed using low-pass filtering at 1 Hz (for overall sway) and 0.1 Hz (to assess low-frequency sway components in lateral and for-aft directions), immediately and 45 minutes after watching a 1 hour 3D aviation documentary in a cinema.	(1) Sickness ratings (using a 0-10 misery scale) were significantly higher immediately after the movie compared to before, with partial recovery after 45 minutes. (2) The standard deviation of lateral CoP excursions was significantly larger immediately after the movie. (3) When analyzing low-frequency sway (filtered at 0.1 Hz), both lateral and for-aft excursions increased immediately post-exposure, with for-aft instability remaining elevated 45 minutes later. (3) No significant correlations were observed between individual MS ratings and postural instability ratios.	MISC	Low-frequency (0.1 Hz) for-aft postural instability component remained significantly elevated for at least 45 minutes. Watching a 3D movie in a cinema can induce significant MS and measurable postural instability. While the visual stimulus produced a clear increase in sickness and instability immediately after the movie, certain low-frequency postural effects (especially in the for-aft direction) persisted for at least 45 minutes. The findings suggest potential safety concerns for activities requiring stable postural control (eg, vehicle operation) after exposure to pronounced 3D visual motion.
Chang et al (2021),¹³ Taiwan	Stimuli: Xbox system (which included the game unit, the game pad, and a handheld device that participants used to play the game. The video and audio portions of the game were presented using an LCD monitor. Postural stability measurement: magnetic tracking system (Flock of Birds, Ascension Technologies, Inc., Burlington, VT).	(1) Passengers (73.08%) experienced more MS than drivers (42.31%). (2) Drivers exhibited greater movement magnitude and multifractality than passengers. (3) MS incidence was higher in male passengers (92.31%) than female passengers (53.85%). (4) MS was associated with greater movement magnitude, supporting the PIT. (5) Motion coupling differed between well and sick participants, with stronger coupling in sick individuals.	At end of 40 minutes (or at the time of discontinuation, whichever came first): (1) participants were asked to state, yes or no, whether they were motion sick, (2) exposure SSQ.	(1) Participants who viewed pre-recorded performances (Passengers) were more likely to state that they were motion sick than participants who controlled the virtual vehicle (Drivers), confirms the existence of the driver-passenger effect among pre-adolescent children and, therefore, among a population in which no members had ever driven a physical automobile. (2) Control of a virtual vehicle reduced MS risk in pre-adolescent children, consistent with findings in adults. MS was preceded by changes in postural control.
Stoffregen et al (2000),¹⁴ United States	Participants stood in a “moving room” (a cubical frame with oscillating walls creating large-field optical flow). Optical motion was controlled by a computer, producing oscillations at 0.2 Hz or a sum-of-sines waveform between 0.1 and 0.3 Hz, mimicking spontaneous postural sway frequencies. Postural motion was tracked using an electromagnetic system.	MS Incidence: Experiment 1: 42% of participants (5/12) developed MS. Experiment 2: 50% of participants (4/8) developed MS. Postural Instability Preceded MS: Significant increases in postural sway variability, range, and velocity were observed before the onset of symptoms. Differences in sway were most pronounced in the AP axis but also affected lateral sway.	Coupling with Optical Flow: Sick participants exhibited stronger coupling between their postural motion and the room’s oscillation compared to non-sick participants. Predictive Indicators: Even before optical flow exposure, participants who later developed MS showed greater baseline postural instability during unperturbed stance.	Support for PIT: Findings confirmed that MS is preceded by measurable increases in postural instability. Results challenged sensory conflict theories, emphasizing the role of postural control dynamics. Practical Applications: Potential for real-time monitoring of postural motion to predict susceptibility to MS. Insights into MS prevention, such as stabilizing posture or reducing visual disturbances. Future Research: Investigate other metrics of postural instability and expand studies to seated participants (eg, head and neck instability).

Abbreviations: AP, anterior-posterior; CoP, center of pressure; CS, Comforatbel stance; DHI, Dizziness Handicap Inventory; EC, eyes closed; GVS, galvanic vestibular stimulation; HMD, head-mounted display; IMU, Inertial Measurement Unit; LAD, LAteral Angular Deviation; MISC, Misery scale; ML, medial-lateral; MS, motion sickness; MSSQ, Motion Sickness Susceptibility Questionnaire; N/A, Not applicable; NO, Normal outcome; PC, Postural control; PIT, postural instability theory; Po, Postural orientation; SCT, Sensory Conflict Theory; SSQ, simulator sickness questionnaire; SVC, Subjective Vertical Conflict; s.a, static assessment; VR, virtual reality; VSM, virtual ship motion, WAD, Wide-Based Stance.

A total of 1518 participants were included across all studies, with age ranges spanning from 9 to 63 years. There was a general male predominance in the experimental studies. The studies investigated various forms of MS, including car sickness, simulator sickness, cybersickness, travel-related sickness, and space MS.

Types of Studies

The studies varied in design and methodology, including experimental studies (n = 12), which simulated MS through various methods, including VR, cybersickness, vehicle motion, simulations, and optical flow environments and cross-sectional studies (n = 4), which included population-level investigations or single-time-point analyses of balance and MS.

Comorbidities

Most experimental studies excluded participants with known vestibular, neurological, or visual impairments to reduce confounding. Owen et al³ noted anxiety levels were correlated with MS susceptibility, although not with postural instability. Comorbid conditions and participant screening varied among these studies. Henriques et al⁴ screened children for vestibular disorders and found MS affected quality of life, while Hald et al⁵ reported that participants included individuals with migraines, concussions, and regular medication use

Postural Tests and Findings

Postural assessments included a range of clinical and experimental tools (Table 2). The most commonly used tools will be the force platforms and balance boards. The Nintendo Wii Balance Board was used as a low-cost force platform by Dennison and D’Zmura⁶ and Widdowson et al⁷ and da Silva et al.⁸ Tetrax Interactive Balance System and Bertec balance plate were also used for measuring center of pressure displacement and sway dynamics, such as in Hald et al,⁵ Litleskare,⁹ Pettijohn et al¹⁰ and Teixeira et al¹¹ Other instruments, such as Step360 Pro, a wobbly board used to simulate visual ship motion in investigating cybersickness by Qi et al¹² in 2020, while Chang et al¹³ used an Xbox to simulate a driving game. Romberg test and static posturography were utilised in clinical settings and pediatric populations, Henriques et al⁴ and Hald et al⁵ Stoffregen et al¹⁴ and Smart et al¹⁵ used virtual perturbation environments, such as moving room paradigms, and simulated large-field optical flow to test sway adaptation. Dida et al used a force platform with sway referenced to demonstrate that non-susceptible individuals displayed effective sensory reweighting upon reintroduction of reliable proprioceptive cues.¹⁶

A total of 14 studies revealed a relationship between postural instability and MS, in support of and challenging the PIT.^{3
-5,8-11,13
-18} These studies supported the PIT, which posits that postural instability precedes the onset of MS symptoms. Postural instability preceded MS onset in several studies, such as Stoffregen et al,¹⁴ Smart et al,¹⁵ and Teixeira et al,¹¹ supporting PIT. These studies demonstrated that increased postural sway or instability, especially in anterior-posterior directions, significantly predicted subsequent development of MS. These findings were consistent across VR, simulator, and traditional transport settings.

Three studies reveal contradicting results for the PIT. While Dennison and D’Zmura,⁶ Petitjohn et al¹⁰ and Widdowson et al⁷ found no consistent link between postural instability and MS, favouring SCT.

Complementing Tests and Findings

Complementary assessments provided further insights, such as MS susceptibility questionnaires (MSSQ – Motion Sickness Susceptibility Questionnaires, SSQ – simulator sickness questionnaires, MISC – Misery scale), which were widely used to evaluate symptom severity and history. Visual vertical perception used by Liu et al¹⁷ using head-mounted display (HMD) to compare perceived against actual vertical orientation, aligning with the Subjective Vertical Conflict (SVC) model. Qi et al¹² used Galvanic vestibular stimulation (GVS), revealing that GVS exacerbated balance disturbances but had minimal effect on nausea. Postural control coupling by Chang et al found that drivers experienced less MS and showed stronger movement control than passive passengers.¹³ Teixeira et al showed that unexpected vection was a stronger predictor of cybersickness than instability, indicating that perceptual mismatch may result in MS symptoms.¹¹

Supporting Outcomes

Through this review, we have also noted other supporting outcomes from the studies. Notably, cybersickness is common in VR-based studies, such as those by da Silva Marinho et al⁸ noted postural stability improved after VR exposure in gamers while Teixeira et al¹¹ highlighted unexpected vection as a primary driver of symptoms. In a study by Henriques et al, high rates of MS were reported in children travelling in cars and buses.⁴ Liu et al showed that restricted head movement during tablet use increased symptoms of MS.¹⁷ Bos et al found persistent low-frequency postural instability after watching a 3D film, which resulted in visual MS.¹⁹ Some studies, such as in da Silva Marinho et al,⁸ revealed that gamers recovered more rapidly from VR-induced MS, likely due to prior sensory adaptation. In supporting the multifactorial cause of MS, Dida et al highlighted that better reweighting of proprioceptive and vestibular inputs correlated with reduced MS susceptibility.¹⁶

Overall, the findings highlight a complex interplay between sensory processing, postural control, and perceptual mismatch in the development of MS across various environments and populations.

Discussion

Postural Instability as a Predictor of MS

The PIT proposes that MS arises due to an inability to maintain stable posture in unfamiliar motion environments.^11,14,15 Several studies in this review support PIT by demonstrating increased postural sway and delayed postural adaptation in individuals susceptible to MS.

This theory was introduced in the early 1990s and described by Riccio and Stoffregen in a review article as a theory bridging the gap between perception, action, and environmental dynamics by emphasising the role of stability in maintaining effective behaviour. This theory explains that when individuals are unable to maintain stability in response to environmental or self-generated perturbations, MS symptoms arise. PIT is further discussed regarding the source of MS, which is described as a challenge to postural stability. This includes low-frequency vibration in the 0.1 to 1.0 Hz range (eg, on ships or vehicles), which disrupts feedback necessary for stable posture. The body’s natural postural control operates within this frequency range, leading to destabilisation. Other causes are also described, such as weightlessness in microgravity, coriolis forces, such as when the head is rotated during motion, changing gravitoinertial force relationships, causing rapidly changing direction of force, such as in roller coasters, and visual-vestibular mismatches where visual motion is not aligned with physical motion (eg, in simulators or moving rooms).¹

Following the introduction of the new theory of MS, multiple studies have been conducted to analyse the PIT. One of the earlier studies, by Stoffregen et al in 1998 and 2000, showed significant increases in postural sway variability, range, and velocity before the onset of MS symptoms.² These findings confirmed that measurable increases in postural instability precede MS.

Vehicular MS and PIT

A total of 6 studies describe the relationship between vehicular MS and PIT.

Henriques et al in 2014 assessed 831 children and found that MS prevalence peaked at age 9, aligning with periods of postural instability during development. This study, which utilises clinical tests (the Romberg test in various conditions and the Spinning test) to assess postural stability, reveals that postural instability is correlated with the severity of MS, and quality of life is also significantly impacted by MS.⁴

While Dida et al in 2024 analysed 64 adults and found that individuals who exhibit car sickness have weaker sensory re-weighting, potentially making them more susceptible to MS. This reinforces the idea that failure to adapt to postural control increases the risk of MS.¹⁶

Liu et al conducted a study in Japan on autonomous vehicles, where it was found that when passengers lack control over their movement, making adaptive postural adjustments is more difficult. This lack of control, combined with frequent obstacle avoidance manoeuvres, leads to unexpected body movements, potentially destabilising posture and increasing susceptibility to MS. This study also explores and supports the SVC theory, which suggests that MS arises from a mismatch between the sensed vestibular input and the expected visual input for vertical orientation.¹⁷

While studies such as Smart et al¹⁵ and Owen et al³ support PIT as a contributor to MS susceptibility, Hald et al⁵ in 2022 conducted a study among students with a mean age of 13.7, using clinical tests and static posturography, found no significant correlation between MS and postural control.

Cybersickness and Simulator-Induced MS and PIT

In VR studies, though findings suggest individual variability in postural adaptation, PIT remains relevant. Litleskare in 2021 examined 50 participants in a VR setting and found that there was a significant correlation between the severity of cybersickness and the change of postural stability from the first to the last minute of VR exposure for trace length (rs = 0.32, P = .027), but not standard deviation velocity (rs = 0.20, P = .187). The deteriorations had returned to baseline levels 10 minutes after exposure. These findings suggest that deterioration of postural stability was both a predictor and an objective measure. However, due to significant individual variations and the limited strength of correlations, deterioration of postural stability has limited practical value as both a predictor and objective measure, suggesting a complicated association.⁹

Teixeira et al provided more substantial support for PIT. Participants who developed sickness during HMD-VR exposure exhibited increased postural instability prior to symptom onset. However, the study emphasised the role of unexpected vection, where a mismatch between expected and perceived self-motion is a more robust predictor of sickness.¹¹

In contrast, Qi et al examined cybersickness induced by virtual ship motion, with and without GVS. While GVS aggravated postural imbalance and delayed habituation, it did not significantly worsen cybersickness symptoms. This decoupling between balance disturbance and symptom severity further undermines a direct causal role for postural instability, offering limited support for PIT and supporting the idea that postural control still relies on peripheral vestibular input during VR immersion.¹²

Bos et al in 2013 measured postural sway before and after exposure to a 3D aviation documentary in a cinema simulator setting. The study shows a significant increase in low-frequency sway, especially in the fore-aft direction, up to 45 minutes. The persistence of low-frequency sway suggests a lingering vestibular or sensorimotor disruption; however, no correlation was found between sway magnitude and individual sickness ratings. This suggests that postural instability alone may not be a sufficient predictor for MS.¹⁹

Additional insights from Dennison and D’Zmura et al reinforce this complexity. Using a rotating tunnel simulation in 15 adult participants, the study found that cybersickness occurred despite minimal postural sway. In fact, in contradiction to PIT, those who experienced more severe symptoms often demonstrated less movement, suggesting an adaptive reduction in sway to mitigate discomfort.⁶

Likewise, da Silva Marinho et al found that simulator-induced sickness occurred across all VR participants irrespective of gaming experience after prolonged exposure, but postural stability actually improved post-VR exposure for 30 minutes. This improvement, along with the absence of predictive sway data, challenged PIT’s assumption that instability precedes and predicts simulator-induced sickness.⁸ Simulator studies, such as a study by Pettijohn et al, exposed participants to simulated boat motion (active patients where subjects could actively adapt their posture, while passive patients had their feet affixed) and observed that MS symptoms increased over time despite varying levels of postural control. However, there was no difference between the active and passive groups. In addition, there were no differences in symptoms and postural instability in both groups, contradicting PIT.¹⁰

In investigating cybersickness, Widdowson et al used 2 VR simulation experiments involving linear and circular motion. Although differences in postural movement patterns were observed, these did not correlate with cybersickness symptoms.²⁰ Baseline postural stability failed to predict which participants would become sick.⁷ In contrast, Chang et al, in a study of preadolescent subjects, provide support for the PIT. In a virtual driving simulation, passengers (who lacked control over the vehicle) experienced a significantly higher incidence of MS compared to drivers. These results support the idea that reduced postural flexibility and control might increase susceptibility to simulator-induced sickness.¹³

In this review, we acknowledge the heterogeneity of MS presentations (eg, car sickness, simulator sickness, cybersickness, seasickness, visually induced MS) and measurement tool and that these variations in symptom presentation, environments, and measurement tools across studies may limit direct comparability of findings and contribute to inconsistent conclusions regarding the role of postural instability.

The review highlights consistent signals that postural instability often precedes MS in several paradigms but also shows many null findings; this mixed pattern implies multiple interacting mechanisms (PIT and SCT), not a single universal cause. We recommend the adoption of standardized diagnostic criteria and standardized postural metrics in future studies.

We propose research priorities: (1) prospective pediatric cohort studies using standardized criteria, (2) randomized controlled trials testing balance-training interventions for MS rehabilitation, (3) multimodal studies integrating vestibular, visual-vertical, and postural measures; to get more comprehensive information and work toward intervention, prevention, and rehabilitation of MS.

Conclusion

Footnotes

ORCID iD

Jeyasakthy Saniasiaya

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Declaration of Conflicting Interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Data Availability Statement

Available upon request.

References

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Xiao

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Relationship Between Motion Sickness and Postural Stability: A Systematic Review

Abstract

Introduction:

Methods:

Results:

Conclusions:

Keywords

Introduction

Material and Methods

Eligibility Criteria

Exclusion Criteria

Data Sources and Searches

Ethical Consideration

Results

Types of Studies

Comorbidities

Postural Tests and Findings

Complementing Tests and Findings

Supporting Outcomes

Discussion

Postural Instability as a Predictor of MS

Vehicular MS and PIT

Cybersickness and Simulator-Induced MS and PIT

Conclusion

Footnotes

ORCID iD

Funding

Declaration of Conflicting Interests

Data Availability Statement

References