New Insights on Emotional Contributions to Human Postural Control

Conscious Movement Processing, Fall-Related Anxiety, and the Visuomotor Control of Locomotion in Older Adults

Objectives

Older adults anxious about falling will often consciously process walking movements in an attempt to avoid falling. They also fixate their gaze on the present step rather than looking ahead to plan future actions. The present work examined whether conscious movement strategies result in such restricted visual planning.

Methods

A total of 18 community-dwelling older adults (age^mean = 71.22; SD = 5.75) walked along a path and stepped into two raised targets. Repeated-measures analyses of variance were used to compare gaze behavior and movement kinematics when participants walked: (a) at baseline (ground level); (b) under conditions designed to induce fall-related anxiety (walkway elevated 0.6 m); and (c) in the absence of anxiety (ground level), but with explicit instructions to consciously process movements.

Results

Participants reported increased conscious movement processing when walking both on the elevated walkway (fall-related anxiety condition) and at ground level when instructed to consciously process gait. During both conditions, participants altered their gaze behavior, visually prioritizing the immediate walkway 1–2 steps ahead (areas needed for the on-line visual control of individual steps) at the expense of previewing distal areas of the walking path required to plan future steps. These alterations were accompanied by significantly slower gait and increased stance durations prior to target steps.

Conclusions

Consciously processing movement (in the relative absence of anxiety) resulted in gaze behavior comparable to that observed during conditions of fall-related anxiety. As anxious participants also self-reported directing greater attention toward movement, this suggests that fall-related anxiety may disrupt the visual control of gait through increased conscious movement processing.

Postural effects of interoceptive imagery as a function of hypnotizability

The aim of the study was to investigate the effects of pleasant and unpleasant interoceptive imagery on postural control in participants with different hypnotizability, interoceptive sensibility and ability of imagery. Forty-one healthy individuals classified as high (highs), medium (mediums) and low hypnotizables (lows) according to the Stanford Hypnotic Susceptibility Scale, form A (SHSS, A) were characterized for Interoceptive Sensitivity (IS) through the Multisensory Assessment of Interoceptive Awareness (MAIA) and for organic mental imagery (ORG) through Betts' questionnaire. The experimental session included baseline closed eyes conditions preceding tasks of pleasant (P) and unpleasant imagery (U) and a neutral cognitive task (NT) while standing on a stabilometric platform. Subjective reports of vividness and pleasantness/unpleasantness of mental images were collected. Postural variables, ECG and pneumogram were acquired. Highs exhibited greater vividness of imagery than mediums/lows and larger Area of the Centre of Pressure (CoP), while mediums and lows decreased it during all tasks with respect to baseline conditions. Significant differences moderated by IS and ORG were found between highs and lows in the CoP Area. In all groups significant task related differences in the CoP Area were moderated only by IS. Cardiovascular variables were similar in the three groups, but differed among tasks and were influenced by IS and ORG. Our findings extend earlier observations on the role of hypnotisability in the postural correlates of sensorimotor imagery to interoceptive imagery, support the hypothesis that interoceptive sensibility moderates postural control and cardiorespiratory variables during interoceptive imagery, and confirm earlier reports of the absence of hypnotisability-related modulation of cardiorespiratory variables during emotional tasks.

'Excess anxiety' and 'less anxiety': both depend on vestibular function

PURPOSE OF REVIEW

To present evidence of a functional interrelation between the vestibular and the anxiety systems based on a complex reciprocally organized network. The review focuses on the differential effects of various vestibular disorders, on psychiatric comorbidity, and on anxiety related to vertigo.

RECENT FINDINGS

Episodic vertigo syndromes such as vestibular migraine, vestibular paroxysmia, and Menière's disease are associated with a significant increase of psychiatric comorbidity, in particular anxiety/phobic disorders and depression. Chronic unilateral and bilateral vestibulopathy (BVP) do not exhibit a higher than normal psychiatric comorbidity. Anxiety related to the vertigo symptoms is also increased in episodic structural vestibular disorders but not in patients with chronic unilateral or bilateral loss of vestibular function. The lack of vertigo-related anxiety in BVP is a novel finding. Several studies have revealed special features related to anxiety in patients suffering from BVP: despite objectively impaired postural balance with frequent falls, they usually do not complain about fear of falling; they do not report an increased susceptibility to fear of heights; they do not have an increased psychiatric comorbidity; and they do not report increased anxiety related to the perceived vertigo. Subtle or moderate vestibular stimulation (by galvanic currents or use of a swing) may have beneficial effects on stress or mood state in healthy adults, and promote sleep in humans and rodents. The intimate structural and functional linkage of the vestibular and anxiety systems includes numerous nuclei, provincial and connector hubs, the thalamocortical network, and the cerebellum with many neural transmitter systems.

SUMMARY

The different involvement of emotional processes and anxiety - to the extent of 'excess anxiety' or 'less anxiety' - in structural vestibular disorders may be due to the specific dysfunction and whether the system activity is excited or diminished. Both psychiatric comorbidity and vertigo-related anxiety are maximal with excitation and minimal with loss of peripheral vestibular function.

Selective preservation of changes to standing balance control despite psychological and autonomic habituation to a postural threat

Humans exhibit changes in postural control when confronted with threats to stability. This study used a prolonged threat exposure protocol to manipulate emotional state within a threatening context to determine if any threat-induced standing behaviours are employed independent of emotional state. Retention of balance adaptations was also explored. Thirty-seven adults completed a series of 90-s standing trials at two surface heights (LOW: 0.8 m above ground, away from edge; HIGH: 3.2 m above ground, at edge) on two visits 2-4 weeks apart. Psychological and autonomic state was assessed using self-report and electrodermal measures. Balance control was assessed using centre of pressure (COP) and lower limb electromyographic recordings. Upon initial threat exposure, individuals leaned backward, reduced low-frequency centre of pressure (COP) power, and increased high-frequency COP power and plantar/dorsiflexor coactivation. Following repeated exposure, the psychological and autonomic response to threat was substantially reduced, yet only high-frequency COP power and plantar/dorsiflexor coactivation habituated. Upon re-exposure after 2-4 weeks, there was partial recovery of the emotional response to threat and few standing balance adaptations were retained. This study suggests that some threat-induced standing behaviours are coupled with the psychological and autonomic state changes induced by threat, while others may reflect context-appropriate adaptations resistant to habituation.

Consciously processing balance leads to distorted perceptions of instability in older adults

Background

Persistent dizziness without a clear cause is common in older adults. We explored whether an anxiety-driven preoccupation with consciously processing balance may underpin the distorted perceptions of unsteadiness that characterises ‘unexplained’ dizziness in older adults.

Methods

We experimentally induced anxiety about losing one’s balance (through a postural threat manipulation) in a cohort of asymptomatic older adults and evaluated associated changes in perceived stability, conscious movement processing and postural control. These outcomes were also assessed when performing a distracting cognitive task designed to prevent anxiety-related conscious movement processing, in addition to during baseline conditions (ground level).

Results

Despite a lack of increase in postural sway amplitude (p = 0.316), participants reported reductions in perceived stability during postural threat compared to baseline (p < 0.001). A multiple linear regression revealed that anxiety-related conscious movement processing independently predicted perceptions of instability during this condition (p = 0.006). These changes were accompanied by alterations in postural control previously associated with functional dizziness, namely high-frequency postural sway and disrupted interaction between open- and closed-loop postural control (ps < 0.014). While the distraction task successfully reduced conscious processing (p = 0.012), leading to greater perceived stability (p = 0.010), further increases in both postural sway frequency (p = 0.002) and dominance of closed-loop control (p = 0.029) were observed.

Conclusion

These findings implicate the role of conscious movement processing in the formation of distorted perceptions of unsteadiness, suggesting that such perceptions may be modifiable by reducing an over-reliance on conscious processes to regulate balance.

The direction of postural threat alters balance control when standing at virtual elevation

Anxiogenic settings lead to reduced postural sway while standing, but anxiety-related balance may be influenced by the location of postural threat in the environment. We predicted that the direction of threat would elicit a parallel controlled manifold relative to the standing surface, and an orthogonal uncontrolled manifold during standing. Altogether, 14 healthy participants (8 women, mean age = 27.5 years, SD = 8.2) wore a virtual reality (VR) headset and stood on a matched real-world walkway (2 m × 40 cm × 2 cm) for 30 s at ground level and simulated heights (elevated 15 m) in two positions: (1) parallel to walkway, lateral threat; and (2) perpendicular to walkway, anteroposterior threat. Inertial sensors measured postural sway acceleration (e.g., 95% ellipse, root mean square (RMS) of acceleration), and a wrist-worn monitor measured heart rate coefficient of variation (HR CV). Fully factorial linear-mixed effect regressions (LMER) determined the effects of height and position. HR CV moderately increased from low to high height (p = 0.050, g = 0.397). The Height × Position interaction approached significance for sway area (95% ellipse; β = - 0.018, p = 0.062) and was significant for RMS (β = - 0.022, p = 0.007). Post-hoc analyses revealed that sagittal plane sway accelerations and RMS increased from low to high elevation in parallel standing, but were limited when facing the threat during perpendicular standing. Postural response to threat varies depending on the direction of threat, suggesting that the control strategies used during standing are sensitive to the direction of threat.

The Effects of Cognitive Task and Change of Height on Postural Stability and Cardiovascular Stress in Workers Working at Height

The purpose of the study was to analyze the effects of cognitive task and change of height on the postural stability and cardiovascular stress of at-height workers. The study included 32 healthy men aged 25-47. Due to the type of work performed, two groups were identified: at‒height workers, HW (n = 16), and office workers (mainly work at desk with a computer) OW (n = 16). The objective measures of postural stability (posturography) and cardiovascular stress (heart rate monitor) were evaluated for both groups at two different platform heights (ground level and 1 m above the ground) with or without cognitive task (backward counting). The increased height and the cognitive task were found to significantly affect measures of postural stability and cardiovascular stress. It was observed that in inexperienced OW employees, higher platform height and performing a cognitive task meant that posture stability significantly decreased, while cardiovascular stress and difficulties in maintaining balance increased. In HW group postural stability is less affected by distress conditions than in OW group.

Re-evaluating the measurement and influence of conscious movement processing on gait performance in older adults: Development of the Gait-Specific Attentional Profile

BACKGROUND

Recent decades have seen increased interest in how anxiety-and associated changes in conscious movement processing (CMP)-can influence the control of balance and gait, particularly in older adults. However, the most prevalent scale used to measure CMP during gait (the Movement-Specific Reinvestment Scale (MSRS)) is generic (i.e., non-gait-specific) and potentially lacks sensitivity in this context.

METHODS

In a preliminary study, we first sought to evaluate if MSRS scores associated with the number of CMP-related thoughts self-reported by older adults while walking. The next aim was to develop and validate a new questionnaire (the Gait-Specific Attentional Profile, G-SAP) capable of measuring gait-specific CMP, in addition to other attentional processes purported to influence gait. This scale was validated using responses from 117 (exploratory) and 107 (confirmatory factor analysis) older adults, resulting in an 11-item scale with four sub-scales: CMP, anxiety, fall-related ruminations, and processing inefficiencies. Finally, in a separate cohort of 53 older adults, we evaluated associations between scores from both the G-SAP CMP subscale and the MSRS, and gait outcomes measured using a GAITRite walkway in addition to participants' fall-history.

RESULTS

MSRS scores were not associated with self-reported thoughts categorised as representing CMP. In regression analyses that controlled for functional balance, unlike the MSRS, the G-SAP subscale of CMP significantly predicted several gait characteristics including velocity (p = .033), step length (p = .032), and double-limb support (p = .015).

SIGNIFICANCE

The G-SAP provides gait-specific measures of four psychological factors implicated in mediating the control of balance and gait. In particular, unlike the MSRS, the G-SAP subscale of CMP appears sensitive to relevant attentional processes known to influence gait performance. We suggest that the G-SAP offers an opportunity for the research community to further develop understanding of psychological factors impacting gait performance across a range of applied clinical contexts.

The effects of perturbation type and direction on threat-related changes in anticipatory postural control

The purpose of this study was to determine whether the type and direction of postural perturbation threat differentially affect anticipatory postural control. Healthy young adults stood on a force plate fixed to a translating platform and completed a series of rise-to-toes movements without (No Threat) and with (Threat) the potential of receiving a postural perturbation to either their feet (15 participants) or torso (16 participants). Each type of perturbation threat was presented along the anteroposterior (A-P) or mediolateral (M-L) axis. For each condition, the A-P center of pressure (COP) signal and tibialis anterior (TA) and soleus (SOL) electromyographical (EMG) recordings were used to quantify the anticipatory postural adjustment (APA). Results indicated that across both threat types and directions, postural threat induced a 40.2% greater TA activation (p < 0.001), a 18.5% greater backward COP displacement (p < 0.001) and a 23.9% greater backward COP velocity (p < 0.001), leading to larger and faster APAs than the No Threat condition. Subsequently, a 7.7% larger forward COP displacement (p = 0.001), a 20.4% greater forward COP velocity (p < 0.001) and 43.2% greater SOL activation (p = 0.009) were observed during the execution phase of the rise-to-toes for the Threat compared to the No Threat condition. Despite these threat effects, there were no differences in the magnitude or velocity of APAs between the threat directsion conditions. Since the type and direction of perturbation-induced postural threat had minimal differential effects on anticipatory postural control, these factors are unlikely to explain the discrepancy of previous findings.

A new postural stability-indicator to predict the level of fear of falling in Parkinson's disease patients

BACKGROUND

Fear of falling (FoF) is defined as a lasting concern about falling that causes a person to limit or even stop the daily activities that he/she is capable of. Seventy percent of Parkinson's disease (PD) patients report activity limitations due to FoF. Timely identification of FoF is critical to prevent its additional adverse effects on the quality of life. Self-report questionnaires are commonly used to evaluate the FoF, which may be prone to human error.

OBJECTIVES

In this study, we attempted to identify a new postural stability-indicator to objectively predict the intensity of FoF and its related behavior(s) in PD patients.

METHODS

Thirty-eight PD patients participated in the study (mean age, 61.2 years), among whom 10 (26.32%) were identified with low FoF and the rest (73.68%) with high FoF, based on Falls Efficacy Scale-International (FES-I). We used a limit of stability task calibrated to each individual and investigated the postural strategies to predict the intensity of FoF. New parameters (FTRis; functional time ratio) were extracted based on the center of pressure presence pattern in different rectangular areas (i = 1, 2, and 3). The task was performed on two heights to investigate FoF-related behavior(s).

RESULTS

FTR1/2 (the ratio between FTR1 and FTR2) was strongly correlated with the FES-I (r = - 0.63, p < 0.001), Pull test (r = - 0.65, p < 0.001), Timed Up and Go test (r = - 0.57, p < 0.001), and Berg Balance Scale (r = 0.62, p < 0.001). The model of FTR1/2 was identified as a best-fitting model to predicting the intensity of FoF in PD participants (sensitivity = 96.43%, specificity = 80%), using a threshold level of ≤ 2.83.

CONCLUSIONS

Using the proposed assessment technique, we can accurately predict the intensity of FoF in PD patients. Also, the FTR1/2 index can be potentially considered as a mechanical biomarker to sense the FoF-related postural instability in PD patients.

The Influence of Proprioceptive Training with the Use of Virtual Reality on Postural Stability of Workers Working at Height

The aim of the study was to assess the impact of proprioceptive training with the use of virtual reality (VR) on the level of postural stability of high-altitude workers. Twenty-one men working at height were randomly assigned to the experimental group (EG) with training (n = 10) and control group (CG) without training (n = 11). Path length of the displacement of the center of pressure (COP) signal and its components in the anteroposterior and medial-lateral directions were measured with use of an AccuGaitTM force plate before and after intervention (6 weeks, 2 sessions × 30 min a week). Tests were performed at two different platform heights, with or without eyes open and with or without a dual task. Two-way ANOVA revealed statistically significant interaction effects for low-high threat, eyes open-eyes closed, and single task-dual task. Post-training values of average COP length were significantly lower in the EG than before training for all analyzed parameters. Based on these results, it can be concluded that the use of proprioceptive training with use of VR can support, or even replace, traditional methods of balance training.

The influence of postural threat on strategy selection in a stepping-down paradigm

To walk safely in their environment, people need to select adequate movement strategies during gait. In situations that are perceived as more threatening, older adults adopt more cautious strategies. For individuals with excessive fear, selecting adequate strategies might be troubling. We investigated how a postural threat affects the selection of strategies within and between older adults by using a stepping-down paradigm. In twenty-four older adults we determined the height at which they switched in stepping-down strategies from a less demanding but more balance threatening heel landing to a more demanding yet safer toe landing. We expected that this switching height would be lower in the high (0.78 m elevation) compared to low threat (floor level) condition. Furthermore, we investigated if older adults, for which the postural threat evoked an increase in the perceived fear, presented a different stepping down strategy due to the postural threat. Our results indicated that the postural threat changed older adults' strategies selection towards a more conservative toe landing. Hence, despite the additional effort, older adults prefer more cautious strategies during a postural threat. No effects of perceived fear on strategy selection between individuals were observed, potentially due to relatively small differences in fear among participants.

Fear of Falling Alters Anticipatory Postural Control during Cued Gait Initiation

Fear of falling can have a profound influence on anticipatory postural control during dynamic balance tasks (e.g., rise-to-toes and leg-raise tasks), with fearful individuals typically exhibiting postural adjustments of smaller magnitudes prior to movement onset. However, very little is known about how fear of falling influences the generation of anticipatory postural adjustments (APAs) during gait initiation; a task in which producing smaller APAs may compromise stability. Sixteen young adults initiated gait as fast as possible following an auditory cue during two conditions: Baseline (ground level), and Threat (fear of falling induced via a platform raised 1.1 m). While the magnitude and duration of APAs did not change between conditions, participants executed steps of shorter lengths during Threat. As APAs during gait initiation are typically proportionate to the length of the first step, the APAs during Threat are therefore disproportionately large (given the shorter step length). We suggest that such failure to scale the APA to the magnitude of the motor output represents a fear-related 'overcompensation', whereby fearful participants sought to ensure that the APA was sufficient for ensuring that their centre of mass was positioned above the support leg prior to gait initiation. During conditions of threat, participants also exhibited greater postural sway prior to initiating gait (i.e., following the auditory cue) and took longer to generate the APA (i.e., impaired reaction). As greater reaction times during voluntary stepping is consistently associated with increased fall-risk, we suggest this as one mechanism through which fear of falling may reduce balance safety.

Challenging balance during sensorimotor adaptation increases generalization

From reaching to walking, real-life experience suggests that people can generalize between motor behaviors. One possible explanation for this generalization is that real-life behaviors often challenge our balance. We propose that the exacerbated body motions associated with balance-challenged whole body movements increase the value to the nervous system of using a comprehensive internal model to control the task. Because it is less customized to a specific task, a more comprehensive model is also a more generalizable model. Here we tested the hypothesis that challenging balance during adaptation would increase generalization of a newly learned internal model. We encouraged participants to learn a new internal model using prism lenses that created a new visuomotor mapping. Four groups of participants adapted to prisms while performing either a standing-based reaching or precision walking task, with or without a manipulation that challenged balance. To assess generalization after the adaptation phase, participants performed a single trial of each of the other groups' tasks without prisms. We found that both the reaching and walking balance-challenged groups showed significantly greater generalization to the equivalent, nonadapted task than the balance-unchallenged groups. Additionally, we found some evidence that all groups generalized across tasks, for example, from walking to reaching and vice versa, regardless of balance manipulation. Overall, our results demonstrate that challenging balance increases the degree to which a newly learned internal model generalizes to untrained movements.NEW & NOTEWORTHY Real-life experience indicates that people can generalize between motor behaviors. Here we show that challenging balance during the learning of a new internal model increases the degree of generalization to untrained movements for both reaching and walking tasks. These results suggest that the effects of challenging balance are not specific to the task but instead apply to motor learning more broadly.

The feasibility of using virtual reality to induce mobility-related anxiety during turning

The fear of falling, or mobility-related anxiety, profoundly affects gait, but is challenging to study without risk to participants.

PURPOSE

To determine the efficacy of using virtual reality (VR) to manipulate illusions of height and consequently, elevated mobility-related anxiety when turning. Moreover, we examined if mobility-related anxiety effects decline across time in VR environments as participants habituate.

METHODS

Altogether, 10 healthy participants (five women, mean (standard deviation) age = 28.5 (8.5) years) turned at self-selected and fast speeds on a 2.2 m walkway under two simulated environments: (1) ground elevation; and (2) high elevation (15 m above ground). Peak turning velocity was recorded using inertial sensors and participants rated their cognitive (i.e., worry) and somatic (i.e., tension) anxiety, confidence, and mental effort.

RESULTS

A significant Height × Speed × Trial interaction (p =  0.013) was detected for peak turning velocity. On average, the virtual height illusion decreased peak turning velocity, especially at fast speeds. At low elevation, participants decreased speed across trials, but not significantly (p =  0.381), but at high elevation, they significantly increased speed across trials (p =  0.001). At self-selected speeds, no effects were revealed (all p >  0.188) and only effects for Height were observed for fast speeds (p <  0.001). After turning at high elevation, participants reported greater cognitive (p =  0.008) and somatic anxiety (p =  0.007), reduced confidence (p = 0.021), and greater mental effort (p <  0.001) compared to the low elevation.

CONCLUSION

VR can safely induce mobility-related anxiety during dynamic motor tasks, and habituation effects from repeated exposure should be carefully considered in experimental designs and analysis.

Tuning of Standing Postural Responses to Instability and Cost Function

Whole-body movements are performed daily, and humans must constantly take into account the inherent instability of a standing posture. At times these movements may be performed in risky environments and when facing different costs of failure. The aim of the study was to test the hypothesis that in upright stance participants continuously estimate both probability of failure and cost of failure such that their postural responses will be based on these estimates. We designed a snowboard riding simulation experiment where participants were asked to control the position of a moving snowboard within a snow track in a risky environment. Cost functions were provided by modifying the penalty of riding in the area adjacent to the snow track. Uncertainty was modified by changing the gain of postural responses while participants were standing on a rocker board. We demonstrated that participants continually evaluated the environmental cost function and compensated for additional risk with feedback-based postural changes, even when probability of failure was negligible. Results showed also that the participants' estimates of the probability of failure accounted for their own inherent instability. Moreover, participants showed a tendency to overweight large probabilities of failure with more biomechanically constrained standing postures that results in suboptimal estimates of risky environments. Overall, our results suggest that participants tune their standing postural responses by empirically estimating the cost of failure and the uncertainty level in order to minimize the risk of falling when cost is high.

The effects of distraction on threat-related changes in standing balance control

Research indicates that threat-induced changes in standing balance are associated with shifts in attention focus. This study investigated whether distracting attention modifies threat-induced changes in standing balance. Twenty-five healthy young adults stood without (No Threat) and with (Threat) the possibility of receiving a temporally unpredictable anteroposterior support surface translation. In both conditions, participants completed a distractor task that consisted of counting how often a pre-selected letter occurred in an auditory sequence, or no distractor task. Emotional responses to threat were quantified using electrodermal activity and self-report measures, while attention focus was quantified using self-report. Centre of pressure (COP) was measured to assess changes in standing balance. Results indicate that postural threat induced an emotional response, as well as broad shifts in attention focus and changes in standing balance. Distracting attention with a cognitive task mitigated threat-induced increases in medium-frequency COP displacements (0.5-1.8 Hz). These results provide support for a relationship between threat-related changes in balance control and attention focus.

Adaptation of emotional state and standing balance parameters following repeated exposure to height-induced postural threat

Height-induced postural threat influences standing balance control. However, it is unknown if minimizing individuals’ emotional response to threat moderates this relationship. This study repeatedly exposed individuals to height-induced postural threat to determine if reducing the emotional response to threat influences standing balance control. Sixty-eight young adults completed a series of standing trials at LOW (0.8 m above ground, away from edge) and HIGH (3.2 m above ground, at edge) postural threat conditions. Emotional state was assessed using self-report and electrodermal measures. Standing balance was assessed through analysis of centre of pressure (COP) movement and lower leg electromyographic activity. Individuals’ emotional response to threat was attenuated following repeated threat exposure. However, threat-induced changes in standing balance were largely preserved. When initially threatened, individuals leaned backward and demonstrated smaller amplitude and higher frequency of COP adjustments; these balance outcomes did not change following repeated threat exposure. Only high frequency COP oscillations (>1.8 Hz) and ankle muscle co-contraction showed any adaptation; regression analyses showed that these behavioural adaptations were accounted for by a combination of emotional and cognitive state changes. This suggests that some threat-induced standing balance changes are more closely linked with the emotional response to threat than others, and are therefore amendable to intervention.

Fear of heights in virtual reality saturates 20 to 40 m above ground

Recent epidemiological studies indicate that about one-third of the general population suffers from a more or less disabling height intolerance, with a relevant impact on quality of life in many of them. Acrophobia, the most severe form of visual height intolerance, has a life-time prevalence of around 5%. Although it is commonly believed that fear of heights should continuously aggravate with increasing elevation, this issue has not been systematically investigated yet. Here, we examined this topic using immersive virtual reality, an established tool in therapy for fear of heights, that allows to flexibly manipulate height stimuli. In a comprehensive cohort (including insusceptible subjects as well as subjects with height intolerance up to acrophobia) height intolerance severity was graded by an established metric scale (vHISS). Participants were randomly exposed to different virtual elevations using a head-mounted display. Behavioral responses to virtual height exposure were analogous to exposure in vivo. Participants exhibited increased anxiety and musculoskeletal stiffening with enhanced high-frequency body sway, to an extend that corresponded to the individual subjective height intolerance rating. For all behavioral responses, we observed a saturation above a certain altitude. Body sway and musculoskeletal stiffening became maximal at 20 m above ground, whereas anxiety saturated above 40 m. These results suggest that fear of heights is characterized by a nonlinear stimulus-response relationship and a dissociation between visual-height-induced bodily and emotional reactions.