The physical properties of the foam pad are central to the destabilising effect in foam posturography. Key parameters include foam density, thickness, compliance and material composition, all of which influence the degree of somatosensory perturbation during stance. Kapteyn and colleagues (50) originally showed that compliant surfaces disproportionately affect proprioceptive reliability thereby increasing reliance on vestibular inputs. Furthermore, studies by Patel and colleagues (13, 33) and subsequent layer variation experiments (52) have demonstrated that a foam with a higher elasticity modulus or foam thickness in the range of 4–5 cm (typically equivalent to 3–4 standard layers) optimally perturbs postural control while still permitting meaningful comparisons across individuals (13). Thinner pads (<2 cm) may be insufficient to induce measurable instability, while excessively thick foams (>6 cm) can result in intolerable imbalance, particularly in elderly or vestibular-impaired patients, increasing fall risk and confounding results due to premature trial termination.

Additionally, the foam density must balance rigidity and compliance. High-density foams may be so rigid as to effectively mimic firm ground, whereas ultra-low-density foams can behave unpredictably, producing non-linear CoP responses. Gosselin and Fagan emphasise that the foam–person interface constitutes a dynamic system subject to non-linear deformation (43), a concept aligned with the mass-dependent deformation effects observed by Kapteyn and colleagues (50). A high-mass individual may compress a foam pad beyond its linear elastic range, effectively “bottoming out” the material. This results in proprioceptive feedback from the rigid force plate beneath, fundamentally altering, and ultimately invalidating, the intended test condition, see Figure 1. These considerations point to the need for a load-matching paradigm in which the mechanical properties of the foam are appropriately scaled to the participant’s mass. Furthermore, Cohen and Sangi-Haghpeykar demonstrated that even minor variations in the density of foam can significantly affect performance. In their study, the denser foam was harder to stand on, underscoring the non-linear nature of postural challenge in foam-based assessments (53). Collectively, these findings suggest the existence of an optimal stiffness range that maximally taxes the postural control system. Despite these insights, no universal standard exists for foam material specifications, and variability between brands complicates reproducibility and inter-laboratory comparisons. This lack of standardisation remains a significant barrier to clinical adoption and normative data synthesis.

Stance configuration, whether the feet are placed together, shoulder-width apart, or in a semi-tandem position affects the challenge imposed on postural control systems, see Figure 2. Narrower bases of support (e.g., feet together or tandem) reduce mechanical stability and thus amplifies the postural instability associated with standing with eyes closed or when the quality of somatosensory information is reduced (54). Consequently, the same foam surface may produce markedly different CoP profiles depending on stance width. Although feet-apart stance is generally better tolerated and safer in clinical populations, it may diminish the sensitivity to vestibular and somatosensory deficits, particularly in patients with chronic or compensated vestibular pathology. As a result, studies using differing stances cannot be directly compared without adjustment.

Trial duration and stance posture exert a profound influence on sway measurements and diagnostic sensitivity. The most frequently adopted durations in the literature range from 30 to 120 s per condition, with longer durations increasing sensitivity to subtle instability but also elevating the likelihood of participant fatigue or falls (12). Longer durations of test enhance the accuracy of sway frequency analysis and identifying subtle variations between control individuals and vestibular patients.

The choice of instrumentation significantly determines the clinical utility of posturography data. High-resolution force platforms such as those integrated into laboratory-grade posturographic systems offer detailed recordings of CoP trajectories, velocity, area, path length and spectral components of sway. These metrics provide quantitative data for assessing sensorimotor integration and disease-specific signatures (55). In contrast, portable stabilometry systems, including smartphone-based or inertial sensor-based devices, often rely on more limited parameters, such as maximum sway distance, standing time or binary fall/no-fall outcomes (56). While these tools are more accessible and suitable for fieldwork or low-resource settings, their sensitivity and specificity may be reduced, especially in detecting subclinical deficits or distinguishing between vestibular and non-vestibular sources of instability (57).

Some clinicians may rely on qualitative observations or stopwatch-timed balance tests, whereas others use software-driven frequency domain analyses or stabilogram diffusion functions, providing greater diagnostic nuance. Thus, instrumentation and analysis heterogeneity are major limitations in standardising foam posturography across centres and studies, a challenge also pointed out by Duarte and Freitas (58).

Physiological and clinical characteristics of the tested population have a substantial impact on posturography outcomes and their interpretation. For example, individuals with acute vestibulopathies (e.g., vestibular neuritis within days of onset) often display profound postural instability, particularly when standing on a foam pad with EC. However, some patients in the chronic phase of vestibular neuritis, especially those >3 months post-injury, may exhibit partial or near-complete compensation, with more nuanced techniques needed to detect underlying deficits.

Age is a particularly important modifier. Older adults exhibit naturally increased postural sway due to age-related declines in visual, somatosensory, and vestibular inputs, as well as reduced musculoskeletal responses (59). Normative data must therefore be stratified by age, with age-adjusted cutoffs used in clinical interpretation. However, such data remains limited, particularly for individuals over 80 years or children under 10 years, restricting widespread implementation of age-normed diagnostic thresholds (60).

Additionally, comorbidities and central neurological disorders can introduce confounding effects. For example, PPPD patients may show exaggerated sway due to maladaptive sensory weighting (e.g., visual dependence), while those with Ménière’s disease may demonstrate intermittent instability depending on disease phase or otolithic involvement (61).

Finally, studies have reported varying results in relation to sex, height, body mass index and foot size, although these are less frequently controlled for (43). Until comprehensive, population-specific normative datasets are developed, accounting for clinical diagnoses, disease chronicity and demographic factors, interpretation of foam posturography should be performed cautiously and contextually.

Fujimoto et al. (46) have investigated the clinical sensitivity of foam posturography in peripheral vestibular deficits (46). In their cohort study involving 68 patients with unilateral vestibulopathy (UVH) and 16 with bilateral vestibulopathy (BVH), postural sway metrics were evaluated against a control group of 66 healthy subjects under four standardised conditions: standing on firm and foam surfaces, with EO and EC. The study assessed eight CoP-based metrics, including mean sway velocity, sway area, and derived ratios such as the Romberg ratio (EC/EO on firm surface) and the foam ratio (foam/firm EO). Six metrics including CoP velocity and sway area were significantly elevated (p < 0.001) in both UVH and BVH patients relative to controls. The Romberg velocity ratio during the foam EC condition demonstrated the highest receiver operating characteristic (ROC) area under the curve (AUC), indicating excellent discriminative ability between affected and healthy individuals. In a subsequent analysis, Fujimoto’s group extended their findings to patients with chronic-stage UVH (>3 months post-onset). Even in the compensated phase, most sway parameters remained significantly elevated (greater postural instability) compared to controls (p < 0.01), providing strong evidence that impaired vestibulospinal postural responses may persist long after resolution of acute symptoms. This challenges the assumption that vestibular compensation fully restores balance and emphasises the role of continued rehabilitation for postural control.

The role of the otolithic organs, particularly the utricle, in Ménière’s disease has garnered increasing attention, particularly due to the limitations of traditional caloric testing, which fails to adequately assess otolithic function. In this context, Lin et al. (62) conducted a novel study examining the relationship between foam posturography metrics and ocular vestibular-evoked myogenic potentials (oVEMP), a validated measure of utricular function (62). Results demonstrated that patients with abnormal oVEMPs had significantly higher Romberg area quotients compared to those with normal oVEMPs. This finding suggests that patients with utricular deficits are more reliant on vision to maintain balance, a compensatory mechanism consistent with central sensory reweighting. Although the AUC was not as high as in studies of UVH using sway velocity, the result is nonetheless clinically meaningful. The moderate correlation between oVEMP results and Romberg quotient implies that foam posturography is sensitive to subtle deficits in otolithic input, even in the absence of overt canal dysfunction. Importantly, sway area is influenced not only by dynamic instability but also by the magnitude of corrective strategies employed by patients, which may be greater in patients with reduced otolithic function. This study therefore supports the inclusion of foam posturography in the assessment of Ménière’s disease, particularly when oVEMP testing is unavailable or inconclusive. Furthermore, the elevated Romberg quotients suggest that Ménière’s disease patients with utricular involvement may benefit from vestibular rehabilitation that targets visual dependence and utricular adaptation.

Foam posturography has also been explored in the context of functional vestibular disorders, most notably Persistent Postural-Perceptual Dizziness (PPPD). This chronic condition, characterised by non-spinning dizziness, unsteadiness, and hypersensitivity to motion or visual complexity, is hypothesised to involve maladaptive central sensory processing rather than peripheral vestibular loss. In a recent study, Ichijo et al. (63) assessed 53 PPPD patients and age- and sex-matched healthy controls using foam posturography (63). They observed a consistent elevation in Romberg ratios, indicating an overreliance on visual input for balance. Simultaneously, foam ratios were decreased, suggesting underutilisation of somatosensory inputs even when available. Strikingly, these sensory imbalance patterns were evident even among PPPD patients with normal caloric tests, VEMPs, and vHIT, reinforcing the notion that central maladaptation, rather than peripheral dysfunction, is the principal driver of postural control abnormalities in PPPD. These findings underscore the value of foam posturography in capturing functional postural strategies and sensory weighting anomalies that elude traditional vestibular tests. Such insight is critical for designing personalised rehabilitation programs for PPPD, such as graded visual motion habituation, and retraining exercises that recalibrate sensory over-reliance.

The utility of foam posturography is perhaps most effective when the results quantify sensory weighting strategies through derived ratios. For example, patients with PPPD often display an elevated Romberg ratio with minimal change in foam ratio, reflecting an overdependence on vision and underutilisation of somatosensory feedback (63). In contrast, patients with peripheral neuropathy may exhibit heightened sway across all foam conditions due to impaired proprioceptive input from the lower limbs with EO and EC (68–70), but standing with EC increases the contribution from the vestibular system (71).

The differential pattern of these ratios enables clinicians to distinguish between visual dependence, somatosensory loss and vestibular hypofunction, thereby tailoring rehabilitation approaches. Patients with high visual dependency may benefit from exercises reducing reliance on vision (e.g., EC balance training), whereas somatosensory impairment may require tactile enhancement or surface-specific retraining. Quantitative sensory weighting analysis thus offers a framework for rehabilitation planning and represents a significant advantage over qualitative balance assessments.

Foam posturography also serves as a longitudinal monitoring tool, enabling clinicians to track recovery and assess the effectiveness of vestibular rehabilitation interventions. Several studies have reported high test–retest reliability in sway parameters particularly in CoP velocity and sway area, across time points, making foam posturography suitable for serial assessments (48, 49). Moreover, tracking improvements in postural sway over multiple sessions allows clinicians to quantify patient progress, identify plateaus and adjust therapeutic intensity or modality accordingly. The ability to objectively document functional gains is particularly valuable in multidisciplinary care models. The low cost of foam posturography, portability and minimal setup requirements make it well-suited for use in outpatient vestibular clinics, tele-rehabilitation and even home-based rehabilitation programs.

While many balance disorders share overlapping symptoms such as unsteadiness and fall risk, the underlying mechanisms differ substantially. Foam posturography provides a means to dissect these mechanisms based on performance under controlled sensory conditions. Patients with vestibular dysfunction typically perform well on a firm surface with EO and EC but experience marked instability on foam with EC (63, 72). In contrast, individuals with peripheral neuropathy, characterised by impaired proprioceptive feedback, exhibit poor balance on foam regardless of visual input (68–70). Similarly, patients with cerebellar ataxia often demonstrate increased sway even on firm surfaces, reflecting a central integrative deficit independent to sensory challenges (73, 74). Such patterns help clinicians determine which primary sensory deficit is causing the imbalance. Foam posturography provides clinically relevant information that is not given by conventional Romberg or tandem stance testing. It can also guide additional examinations (such as nerve conduction studies or neuroimaging) when results point to non-vestibular causes.

Foam posturography fills a clinical need as it addresses limitations inherent in standard balance assessments. Bedside “push-pull” tests and the SOT primarily determine whether balance is maintained under altered sensory conditions but does not provide insight into how postural stability is achieved or which postural control strategies are used. As such, early or subtle deficits, such as maladaptive shifts from ankle-, knee- to hip- control, excessive high-frequency corrective activity or impaired adaptability may remain undetected despite preserved stance. Foam posturography enables quantification of frequency-specific sway and torque dynamics, allowing identification of pathological direction-specific behaviours and compensatory strategies that are analytically missed in commercial postural control analytics. Furthermore, whereas reflex-based vestibular tests assess peripheral pathway integrity in isolation, foam posturography with EC probes the vestibular contribution within a functional, whole-body task that simultaneously alters postural mechanics. By explicitly treating foam as a sensory manipulation, and also as a mechanical perturbation, foam posturography captures the CNS’s capacity for postural adaptation. When combined with appropriate sampling frequencies and analysis methods, foam posturography offers a pragmatic compromise between validity and quantitative rigour, enabling objective assessment of postural control when high-cost instrumentation is unavailable.

A significant limitation across studies is the absence of standardised specifications for the foam surfaces employed. The destabilising effect of foam in posturography is governed by several characteristics, each of which influences postural responses through distinct mechanisms. The most relevant foam properties include thickness, density, compliance and material composition. Investigations have utilised foam pads of varying thicknesses (ranging from 2 cm to 10 cm), densities, and material compositions, ranging from open-cell polyurethane to viscoelastic memory foams, without reporting mechanical properties such as compliance, damping coefficients or the elastic modulus. The thickness of foam is a crucial property that determines the extent of somatosensory distortion and mechanical impedance at the foot–surface interface. Increasing foam thickness generally increases instability. Density and compliance (often measured as the elastic modulus) jointly determine how the foam deforms under body weight. Importantly, foam deformation is non-linear and load-dependent where heavier individuals may compress compliant foam beyond its linear elastic range. Material composition (e.g., polyurethane vs. viscoelastic memory foam) further modulates these effects. Viscoelastic materials exhibit time-dependent deformation and recovery, meaning that postural responses may change over the course of a trial as the foam progressively deforms and adapts to the load. This introduces additional variability and may obscure deficits in postural control, particularly in longer trials. Collectively, these characteristics directly influence the extent to which vestibular contributions to balance are evidenced and how impairment is presented. Establishing consensus recommendations for foam mechanical properties, linked to participant mass or load-response characteristics, would represent a critical step toward standardising foam-based posturography protocols.

Given that the biomechanical challenge posed by the foam is the central variable in these assessments, such heterogeneity prevents the replication of studies and precludes meta-analysis (53). Without a standardised foam type and configuration, it is not possible to develop consistent diagnostic thresholds or normative benchmarks for sway metrics. As a result, clinicians and researchers lack a firm basis upon which to interpret patient results or compare findings across populations. This problem is exacerbated by the absence of regulatory guidance or consensus protocols from professional bodies.

A methodological challenge of many foam posturography studies is the issue of fall censoring. To ensure test safety and protect participants from injury, most studies either terminate trials once instability leads to stepping or falling, or they exclude patients deemed too unstable to perform foam-based trials safely. While this is ethically necessary, such exclusion introduces a censoring bias that potentially underestimates the true extent of postural instability in vestibular populations, especially those at highest risk for real-world falls. By systematically removing data from fall-prone individuals, researchers risk mischaracterising the distribution of sway metrics and overestimating average postural performance. This has important implications for both the sensitivity and ecological validity of the test. Future research should aim to develop adapted protocols that can capture instability without excluding fall-prone patients, such as using harnessed balance platforms or data extractions, to mitigate this bias and improve the generalisability of findings to clinical assessment of fall risk.

Many studies with foam posturography rely on relatively small sample sizes, often with fewer than 30 patients per diagnostic group, and utilise heterogeneous inclusion criteria that encompass a broad range of vestibular disorders, disease durations and comorbidities. This methodological heterogeneity impairs the statistical power to detect subtle differences in sway parameters, particularly in subgroups such as early-stage unilateral vestibulopathy. Moreover, pooling data across diagnostically diverse patient populations complicates the interpretation of findings, as distinct vestibular syndromes may exhibit unique patterns of sensory compensation and postural adaptation. Without adequately powered and stratified analyses, foam posturography may not be fully utilised to inform differential diagnosis or individualised rehabilitation.

The interpretability of foam posturography remains severely limited by the absence of large-scale normative data across key demographic and clinical populations. Current reference values are derived from small, age-restricted samples, typically composed of healthy young adults. There is a critical need for normative data that encompass a wider age range including paediatric, middle-aged, and older adult populations and account for age-related changes in proprioception, vestibular function and postural control strategies. Moreover, normative values should be stratified by foot stance (e.g., Romberg vs. tandem), as well as by test condition (e.g., EO vs. EC, firm vs. foam surface). This is necessary to derive age-appropriate cutoffs for abnormal sway, develop percentile-based reporting systems and calibrate risk thresholds for clinical populations. Importantly, the development of normative values must also account for different posturographic parameters. As discussed by Paillard and Noé (75), posturographic measures such as sway area, path length, and velocity exhibit variability and inconsistent responsiveness across populations when task demands and conditions vary. Without consensus on which postural parameters offer the greatest sensitivity to disease and robustness, normative thresholds risk being misleading. To summarise, disease-specific normative comparisons are needed to refine diagnostic sensitivity in conditions. Until such data are available, clinicians must interpret foam posturography results with caution, relying on relative comparisons or within-subject longitudinal trends rather than absolute thresholds.

A further obstacle to the clinical adoption of foam posturography is the lack of protocol standardisation across research studies. Variations in trial duration, foot stance, visual conditions and instrumentation (force plates vs. inertial measurement units) lead to substantial variability in measured outcomes. Even small changes in stance width or trial duration can significantly affect CoP velocity and sway area, making it difficult to interpret findings or apply them to clinical practice. Standardised testing protocols are urgently needed to facilitate cross-study comparisons, enable normative benchmarking and enhance reliability. Protocol elements such as foam type, foot positioning, trial length, instructions to participants (e.g., “stand naturally” vs. “stand as still as possible”), and exclusion criteria must be consistent if foam posturography is to transition from research to routine vestibular diagnostics.

In a controlled investigation, Liu and colleagues explored how changing the thickness of the foam pad affected the sensitivity and specificity of posturography testing in UVH (52). The study was driven by the understanding that foam pads degrade somatosensory input by introducing compliance and instability to the base of support. However, there exists an important trade-off, while increased thickness may enhance the challenge to proprioception, it can also lead to an increased rate of falls or compensatory stepping, as distance between the feet and firm surface beneath the foam pad increases, thereby limiting clinical utility.

Participants stood on foam composed of 1 to 5 stacked layers, each approximately 1 cm thick. The test was conducted with both EO and EC for each foam thickness. CoP velocity and standing time were recorded as primary outcome measures. Healthy controls and UVH patients were included for comparative analysis. The results showed a linear relationship between foam thickness and postural instability, as sway velocity increased progressively with each added layer of foam, with both EO and EC. Critically, while both investigational groups exhibited increased sway with thicker foam, UVH patients showed a disproportionately greater deterioration in postural control with EC, particularly with 4- and 5-layers of foam. Additionally, the average standing time prior to loss of balance (defined as stepping, stumbling or falling) decreased markedly in UVH patients as foam thickness increased. These effects were most pronounced at the 4-layer level, where the difference between UVH patients and controls for sway velocity was highest.

To quantify the diagnostic efficacy of these conditions, ROC curve analysis was performed. The ROC for sway velocity in the 4-layer foam EC condition yielded an AUC of 0.90, demonstrating excellent diagnostic discrimination. Sensitivity and specificity at this thickness were approximately 85 and 87% respectively, suggesting that this configuration strikes the optimal balance between challenge and clinical feasibility. The study’s findings have direct implications for standardising foam posturography protocols. Specifically, the 4-layer foam pad with EC appears to be the most sensitive and specific configuration for distinguishing UVH from healthy balance. Using thinner foam may not adequately destabilise posture, while thicker configurations risk inducing early termination due to falls.

Longitudinal cohort studies are required to evaluate how foam-based metrics change over time in patients undergoing vestibular rehabilitation or pharmacologic treatment. These studies should aim to establish

Ideally, such investigations should be multicentre in nature to ensure sufficient sample sizes and external validity.

For a clinical balance assessment tool to be considered robust, high test–retest reliability is essential. To explore this, Liu and Kong (49) conducted important studies evaluating the reproducibility of foam posturography metrics in both patients with vertigo and healthy controls. Across repeated sessions under multiple test conditions, Liu and Kong reported intraclass correlation coefficients (ICCs) ranging from 0.887 to 0.973 for sway velocity. These values fall within the range considered “excellent reliability” by established psychometric standards, suggesting that foam posturography yields consistent and reproducible results when performed under standardised protocols. Importantly, trials in which participants lost balance or stepped were excluded to avoid statistical artifacts introduced by fall-related variance. This exclusion, while methodologically sound for evaluating reliability, also highlights the need for protocols that can safely include fall-prone individuals in future research to ensure broader applicability.

Although CDP remains the gold standard for comprehensive balance testing, it is costly and often inaccessible in resource-limited settings. Several studies have evaluated foam posturography as a cost-effective alternative. Enache et al. (76) directly compared traditional foam-based posturography with the SOT component of CDP in a population of patients with diagnosed peripheral vestibular dysfunction. They found that patients exhibited significantly increased CoP sway in foam conditions (p < 0.05), particularly during the foam EC task. The results correlated strongly with SOT scores, supporting the view that foam posturography captures similar postural deficits while circumventing the need for expensive, mechanised platforms. Celebisoy and colleagues echoed these findings in a policy-oriented publication, advocating for the widespread use of foam posturography in countries where healthcare budgets and equipment access may limit routine CDP availability (77). Celebisoy and colleagues argued that foam-based testing offers a scalable, low-barrier tool for screening and rehabilitation, particularly in primary care or community-based vestibular clinics. Collectively, these studies position foam posturography as a feasible, economical alternative to CDP, enabling broader access to balance diagnostics across wide healthcare environments.