Influence of a portable audio-biofeedback device on structural properties of postural sway

Assessing Cognitive Effort in Ménière's Disease: Pupillometry as a Novel Tool for Postural Control

BACKGROUND

This study aimed to investigate the utility of pupillometry as a measure of cognitive effort in individuals with Ménière's disease experiencing chronic postural destabilization. By integrating pupillometry with static posturography, we sought to gain deeper insights into the cognitive demands and arousal levels associated with postural control in this specific patient population.

METHODS

The study included 36 patients who met the diagnostic criteria for Ménière's disease and a control group comprising 36 healthy volunteers. We performed static posturography using a computerized static posturography platform to objectively assess postural imbalance. Additionally, pupillometry was recorded using infrared video-oculoscopy. Pupil dilation was measured before and after participants walked for 7 steps on-site with their vision obscured.

RESULTS

Baseline tonic pupil size showed no significant difference between healthy controls and Ménière's patients. However, after walking stimulation, Ménière's patients exhibited highly significant abnormal walking-induced pupil dilation. This suggests increased arousal in response to the challenging task of walking with closed eyes, linked to static upright stance imbalance as correlated with posturography parameters.

CONCLUSION

Pupillometry holds promise as an objective tool to assess cognitive effort and arousal during postural control in Ménière's disease. Implementing pupillometry in clinical practice could enhance the management of postural instability in these patients. Our findings contribute to the understanding of cognitive aspects in balance control and open new avenues for further investigations in vestibular dysfunction.

Adaptive Control Method for Gait Detection and Classification Devices with Inertial Measurement Unit

Cueing and feedback training can be effective in maintaining or improving gait in individuals with Parkinson's disease. We previously designed a rehabilitation assist device that can detect and classify a user's gait at only the swing phase of the gait cycle, for the ease of data processing. In this study, we analyzed the impact of various factors in a gait detection algorithm on the gait detection and classification rate (GDCR). We collected acceleration and angular velocity data from 25 participants (1 male and 24 females with an average age of 62 ± 6 years) using our device and analyzed the data using statistical methods. Based on these results, we developed an adaptive GDCR control algorithm using several equations and functions. We tested the algorithm under various virtual exercise scenarios using two control methods, based on acceleration and angular velocity, and found that the acceleration threshold was more effective in controlling the GDCR (average Spearman correlation -0.9996, p < 0.001) than the gyroscopic threshold. Our adaptive control algorithm was more effective in maintaining the target GDCR than the other algorithms (p < 0.001) with an average error of 0.10, while other tested methods showed average errors of 0.16 and 0.28. This algorithm has good scalability and can be adapted for future gait detection and classification applications.

Differences between physical therapist ratings, self-ratings, and posturographic measures when assessing static balance exercise intensity

Introduction

In order for balance therapy to be successful, the training must occur at the appropriate dosage. However, physical therapist (PT) visual evaluation, the current standard of care for intensity assessment, is not always effective during telerehabilitation. Alternative balance exercise intensity assessment methods have not previously been compared to expert PT evaluations. The aim of this study was therefore to assess the relationship between PT participant ratings of standing balance exercise intensity and balance participant self-ratings or quantitative posturographic measures.

Methods

Ten balance participants with age or vestibular disorder-related balance concerns completed a total of 450 standing balance exercises (three trials each of 150 exercises) while wearing an inertial measurement unit on their lower back. They provided per-trial and per-exercise self-ratings of balance intensity on a scale from 1 (steady) to 5 (loss of balance). Eight PT participants reviewed video recordings and provided a total of 1,935 per-trial and 645 per-exercise balance intensity expert ratings.

Results

PT ratings were of good inter-rater reliability and significantly correlated with exercise difficulty, supporting the use of this intensity scale. Per-trial and per-exercise PT ratings were significantly correlated with both self-ratings (r = 0.77-0.79) and kinematic data (r = 0.35-0.74). However, the self-ratings were significantly lower than the PT ratings (difference of 0.314-0.385). Resulting predictions from self-ratings or kinematic data agreed with PT ratings approximately 43.0-52.4% of the time, and agreement was highest for ratings of a 5.

Discussion

These preliminary findings suggested that self-ratings best indicated two intensity levels (i.e., higher/lower) and sway kinematics were most reliable at intensity extremes.

Are static posturography-assisted biofeedback exercises effective in Parkinson's disease?

BACKGROUND

Parkinson disease (PD) is a progressive condition that causes disorders in movement and balance.

OBJECTIVE

To evaluate the effectiveness of static posturography-assisted biofeedback exercises in PD-related balance disorder.

METHODS

We screened 83 patients, 48 of whom were enrolled, and 41 completed the study. The sample was randomized into two groups, one submitted to static posturography-assisted biofeedback exercises and the other, to a conventional exercise program. The patients in the biofeedback group (n = 20) performed biofeedback exercises in addition to conventional balance exercises. Those in the conventional exercise group (n = 21) performed classic balance exercises. Both groups were treated for 20 minutes per session 3 times a week for 6 weeks. The patients were evaluated using the Hoehn and Yahr Scale, the Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS), the Berg Balance Scale (BBS), the Tinetti Gait and Balance Assessment (TGBA), the Timed Up and Go Test (TUG), the Tandem Stance Test (TST), a Turkish version of the Stanford Health Assessment Questionnaire (HAQ), and the Beck Depression Inventory (BDI) before and at the end of the treatment.

RESULTS

No statistically significant differences were observed between the two groups in terms of the MDS-UPDRS, BBS, TGBA, TST, TUG, HAQ, or BDI measurements before and after the treatment (p > 0.05).

CONCLUSIONS

Improved balance parameters were observed following balance training in the patients with PD, although static posturography-assisted biofeedback exercises appeared to provide no additional benefit. However, larger, randomized controlled trials are needed to investigate their effectiveness.

Less Vibrotactile Feedback Is Effective to Improve Human Balance Control during Sensory Cues Alteration

For individuals with altered sensory cues, vibrotactile feedback improves their balance control. However, should vibrotactile feedback be provided every time balance control is compromised, or only one-third of the time their balance is compromised? We hypothesized that vibrotactile feedback would improve balance control more when provided every time their balance is compromised. Healthy young adults were randomly assigned to two groups: group 33% feedback (6 males and 6 females) and group 100% feedback (6 males and 6 females). Vibrotactile feedbacks related to the body's sway angle amplitude and direction were provided, while participants stood upright on a foam surface with their eyes closed. Then, we assessed if balance control improvement lasted when the vibrotactile feedback was removed (i.e., post-vibration condition). Finally, we verified whether or not vibrotactile feedback unrelated to the body's sway angle and direction (sham condition) altered balance control. The results revealed no significant group difference in balance control improvement during vibrotactile feedback. Immediately following vibrotactile feedback, both groups reduced their balance control commands; body sway velocity and the ground reaction forces variability decreased. For both groups, unrelated vibrotactile feedback worsened balance control. These results confirmed that participants processed and implemented vibrotactile feedback to control their body sways. Less vibrotactile feedback was effective in improving balance control.

A Pilot Study Comparing the Effects of Concurrent and Terminal Visual Feedback on Standing Balance in Older Adults

While balance training with concurrent feedback has been shown to improve real-time balance in older adults, terminal feedback may simplify implementation outside of clinical settings. Similarly, visual feedback is particularly well-suited for use outside the clinic as it is relatively easily understood and accessible via ubiquitous mobile devices (e.g., smartphones) with little additional peripheral equipment. However, differences in the effects of concurrent and terminal visual feedback are not yet well understood. We therefore performed a pilot study that directly compared the immediate effects of concurrent and terminal visual feedback as a first and necessary step in the future design of visual feedback technologies for balance training outside of clinical settings. Nineteen healthy older adults participated in a single balance training session during which they performed 38 trials of a single balance exercise including trials with concurrent, terminal or no visual feedback. Analysis of trunk angular position and velocity features recorded via an inertial measurement unit indicated that sway angles decreased with training regardless of feedback type, but sway velocity increased with concurrent feedback and decreased with terminal feedback. After removing feedback, training with either feedback type yielded decreased mean velocity, but only terminal feedback yielded decreased sway angles. Consequently, this study suggests that, for older adults, terminal visual feedback may be a viable alternative to concurrent visual feedback for short duration single-task balance training. Terminal feedback provided using ubiquitous devices should be further explored for balance training outside of clinical settings.

Gait Disorder Detection and Classification Method Using Inertia Measurement Unit for Augmented Feedback Training in Wearable Devices

Parkinson's disease (PD) is a common neurodegenerative disease, one of the symptoms of which is a gait disorder, which decreases gait speed and cadence. Recently, augmented feedback training has been considered to achieve effective physical rehabilitation. Therefore, we have devised a numerical modeling process and algorithm for gait detection and classification (GDC) that actively utilizes augmented feedback training. The numerical model converted each joint angle into a magnitude of acceleration (MoA) and a Z-axis angular velocity (ZAV) parameter. Subsequently, we confirmed the validity of both the GDC numerical modeling and algorithm. As a result, a higher gait detection and classification rate (GDCR) could be observed at a higher gait speed and lower acceleration threshold (AT) and gyroscopic threshold (GT). However, the pattern of the GDCR was ambiguous if the patient was affected by a gait disorder compared to a normal user. To utilize the relationships between the GDCR, AT, GT, and gait speed, we controlled the GDCR by using AT and GT as inputs, which we found to be a reasonable methodology. Moreover, the GDC algorithm could distinguish between normal people and people who suffered from gait disorders. Consequently, the GDC method could be used for rehabilitation and gait evaluation.

Vestibular Evaluation and Management of Children with Sensorineural Hearing Loss

Vestibular dysfunction is the most common comorbidity associated with childhood sensorineural hearing loss. Early identification of vestibular dysfunction enables early intervention to mitigate its impact of motor, behavioral, and neurocognitive deficits of developing children. Screening for vestibular impairment can be achieved in the busy clinical setting.

Differential effects of visual versus auditory biofeedback training for voluntary postural sway

Augmented sensory biofeedback training is often used to improve postural control. Our previous study showed that continuous auditory biofeedback was more effective than continuous visual biofeedback to improve postural sway while standing. However, it has also been reported that both discrete visual and auditory biofeedback training, presented intermittently, improves bimanual task performance more than continuous visual biofeedback training. Therefore, this study aimed to investigate the relative effectiveness of discrete visual biofeedback versus discrete auditory biofeedback to improve postural control. Twenty-two healthy young adults were randomly assigned to either a visual or auditory biofeedback group. Participants were asked to shift their center of pressure (COP) by voluntary postural sway forward and backward in line with a hidden target, which moved in a sinusoidal manner and was displayed intermittently. Participants were asked to decrease the diameter of a visual circle (visual biofeedback) or the volume of a sound (auditory biofeedback) based on the distance between the COP and the target in the training session. The feedback and the target were given only when the target reached the inflection points of the sine curves. In addition, the perceptual magnitudes of visual and auditory biofeedback were equalized using Stevens’ power law. Results showed that the mean and standard deviation of the distance between COP and the target were reduced int the test session, removing the augmented sensory biofeedback, in both biofeedback training groups. However, the temporal domain of the performance improved in the test session in the auditory biofeedback training group, but not in the visual biofeedback training group. In conclusion, discrete auditory biofeedback training was more effective for the motor learning of voluntarily postural swaying compared to discrete visual biofeedback training, especially in the temporal domain.

Effects of Combined Balance and Strength Training on Measures of Balance and Muscle Strength in Older Women With a History of Falls

OBJECTIVE

We investigated the effects of combined balance and strength training on measures of balance and muscle strength in older women with a history of falls.

METHODS

Twenty-seven older women aged 70.4 ± 4.1 years (age range: 65 to 75 years) were randomly allocated to either an intervention (IG, n = 12) or an active control (CG, n = 15) group. The IG completed 8 weeks combined balance and strength training program with three sessions per week including visual biofeedback using force plates. The CG received physical therapy and gait training at a rehabilitation center. Training volumes were similar between the groups. Pre and post training, tests were applied for the assessment of muscle strength (weight-bearing squat [WBS] by measuring the percentage of body mass borne by each leg at different knee flexions [0°, 30°, 60°, and 90°], sit-to-stand test [STS]), and balance. Balance tests used the modified clinical test of sensory interaction (mCTSIB) with eyes closed (EC) and opened (EO), on stable (firm) and unstable (foam) surfaces as well as spatial parameters of gait such as step width and length (cm) and walking speed (cm/s).

RESULTS

Significant group × time interactions were found for different degrees of knee flexion during WBS (0.0001 < p < 0.013, 0.441 < d < 0.762). Post hoc tests revealed significant pre-to-post improvements for both legs and for all degrees of flexion (0.0001 < p < 0.002, 0.697 < d < 1.875) for IG compared to CG. Significant group × time interactions were found for firm EO, foam EO, firm EC, and foam EC (0.006 < p < 0.029; 0.302 < d < 0.518). Post hoc tests showed significant pre-to-post improvements for both legs and for all degrees of oscillations (0.0001 < p < 0.004, 0.753 < d < 2.097) for IG compared to CG. This study indicates that combined balance and strength training improved percentage distribution of body weight between legs at different conditions of knee flexion (0°, 30°, 60°, and 90°) and also decreased the sway oscillation on a firm surface with eyes closed, and on foam surface (with eyes opened or closed) in the IG.

CONCLUSION

The higher positive effects of training seen in standing balance tests, compared with dynamic tests, suggests that balance training exercises including lateral, forward, and backward exercises improved static balance to a greater extent in older women.

Dual-Task Gait Stability after Concussion and Subsequent Injury: An Exploratory Investigation

Persistent gait alterations can occur after concussion and may underlie future musculoskeletal injury risk. We compared dual-task gait stability measures among adolescents who did/did not sustain a subsequent injury post-concussion, and uninjured controls. Forty-seven athletes completed a dual-task gait evaluation. One year later, they reported sport-related injuries and sport participation volumes. There were three groups: concussion participants who sustained a sport-related injury (n = 8; age =15.4 ± 3.5 years; 63% female), concussion participants who did not sustain a sport-related injury (n = 24; 14.0 ± 2.6 years; 46% female), and controls (n = 15; 14.2 ± 1.9 years; 53% female). Using cross-recurrence quantification, we quantified dual-task gait stability using diagonal line length, trapping time, percent determinism, and laminarity. The three groups reported similar levels of sports participation (11.8 ± 5.8 vs. 8.6 ± 4.4 vs. 10.9 ± 4.3 hours/week; p = 0.37). The concussion/subsequent injury group walked slower (0.76 ± 0.14 vs. 0.65 ± 0.13 m/s; p = 0.008) and demonstrated higher diagonal line length (0.67 ± 0.08 vs. 0.58 ± 0.05; p = 0.02) and trapping time (5.3 ± 1.5 vs. 3.8 ± 0.6; p = 0.006) than uninjured controls. Dual-task diagonal line length (hazard ratio =1.95, 95% CI = 1.05–3.60), trapping time (hazard ratio = 1.66, 95% CI = 1.09–2.52), and walking speed (hazard ratio = 0.01, 95% CI = 0.00–0.51) were associated with subsequent injury. Dual-task gait stability measures can identify altered movement that persists despite clinical concussion recovery and is associated with future injury risk.

Vibrotactile -Feedback Device for Postural Balance Among Malocclusion Patients

Multiple studies have suggested that some associations exist between occlusal factors and postural alterations. Objectives: This study aimed to evaluate the effectiveness of a vibrotactile posture trainer device, comprised a wearable device containing an accelerometer sensor to measure the angle of the neck flexion (input) and provided real-time vibrotactile biofeedback (output) for postural balance among patients with malocclusion. Methods: Twenty-four subjects were divided in 3 groups based on occlusion and using Angle’s classification. Each group consisted of 8 patients for class I, II and III malocclusion. The Posture Trainer System was used for feedback concerning neck flexion angles when higher than 15 degrees. A 4-week training program to adjust posture balance in 2 axes (flexion-extension, lateral-flexion) was applied in activities for daily living. The assessments in this study were comprised of neck flexion angles from the Posture Trainer System and the center of pressure (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}$\text{N}\cdot \text{m}$ \end{document}) using a force plate. The effects of a vibrotactile posture trainer (baseline vs. post-training test) were evaluated using the paired t-test and were assumed to be significant at p < 0.05 (two-side). All analyses were conducted using the Statistical Package for Social Sciences, Version 21.0 (SPSS, Chicago, IL, USA). Results: Neck flexion angles and center of pressure significantly decreased post-training by the Posture Trainer System among patients with class II malocclusion. No changes in the above parameters post-training were found in class I and class III. Conclusion: The results demonstrated that patients with class II malocclusion training by the Posture Trainer System lowered neck flexion angles and COP compared with pre-training. Clinical Impact: Feedback by the Posture Trainer System can help improve the postural balance in class II malocclusion.

Vibrotactile Feedback for Improving Standing Balance

Maintaining balance standing upright is an active process that complements the stabilizing properties of muscle stiffness with feedback control driven by independent sensory channels: proprioceptive, visual, and vestibular. Considering that the contribution of these channels is additive, we investigated to what extent providing an additional channel, based on vibrotactile stimulation, may improve balance control. This study focused only on healthy young participants for evaluating the effects of different encoding methods and the importance of the informational content. We built a device that provides a vibrotactile feedback using two vibration motors placed on the anterior and posterior part of the body, at the L5 level. The vibration was synchronized with an accelerometric measurement encoding a combination of the position and acceleration of the body center of mass in the anterior-posterior direction. The goal was to investigate the efficacy of the information encoded by this feedback in modifying postural patterns, comparing, in particular, two different encoding methods: vibration always on and vibration with a dead zone, i.e., silent in a region around the natural stance posture. We also studied if after the exposure, the participants modified their normal oscillation patterns, i.e., if there were after effects. Finally, we investigated if these effects depended on the informational content of the feedback, introducing trials with vibration unrelated to the actual postural oscillations (sham feedback). Twenty-four participants were asked to stand still with their eyes closed, alternating trials with and without vibrotactile feedback: nine were tested with vibration always on and sham feedback, fifteen with dead zone feedback. The results show that synchronized vibrotactile feedback reduces significantly the sway amplitude while increasing the frequency in anterior-posterior and medial-lateral directions. The two encoding methods had no different effects of reducing the amount of postural sway during exposure to vibration, however only the dead-zone feedback led to short-term after effects. The presence of sham vibration, instead, increased the sway amplitude, highlighting the importance of the encoded information.

Neuromodulation to improve gait and balance function using a sensory neuroprosthesis in people who report insensate feet - A randomized control cross-over study

Peripheral neuropathy may cause loss of sensory information from plantar cutaneous mechanoreceptors that is important for balance control and falls management. The current study investigated short-term effects of using Walkasins, an external lower-limb sensory neuroprosthesis, on clinical outcomes of balance and gait in persons who reported peripheral neuropathy and balance problems. The device replaces lost plantar sensation with tactile balance information that modulates cutaneous mechanoreceptors above the ankle where sensation is intact. Thirty-one male community-dwelling Veterans, 56–84 years old with insensate feet and balance problems participated. Initial Functional Gait Assessment, gait speed, and 4-Stage Balance Test outcomes were assessed. After initial assessment, subjects were randomly assigned to either wearing Walkasins turned ON, or OFF, and outcomes were re-assessed following a set of standardized balance exercises. Following a one-hour rest and washout period, treatments were crossed-over between groups and a third outcomes assessment was performed. Before cross-over, 10 of 15 subjects in the ON-then-OFF group improved their Functional Gait Assessment score by at least four points, the Minimal Clinically Important Difference, compared to 5 of 16 in the OFF-then-ON group. After cross-over, 7 of 16 subjects in the OFF-then-ON group improved by at least four points versus 2 of 15 in the ON-then-OFF group. ON treatment was associated with a Functional Gait Assessment improvement of 4.4 ± 3.7 points versus 1.5 ± 1.2 for the OFF treatment (p<0.01). Overall, Functional Gait Assessment scores changed from 15.2 ± 4.8 at initial assessment to 21.1 ± 5.2 after final assessment (p<0.001). At the end of the two treatment sessions, 16 of the 31 individuals had improved their Functional Gait Assessment score beyond 23, indicating normal fall-risk status. Future studies should investigate long-term benefits of the device to reduce fall risk and actual falls in patients with peripheral neuropathy and balance problems.

A Review on the Relationship Between Sound and Movement in Sports and Rehabilitation

The role of auditory information on perceptual-motor processes has gained increased interest in sports and psychology research in recent years. Numerous neurobiological and behavioral studies have demonstrated the close interaction between auditory and motor areas of the brain, and the importance of auditory information for movement execution, control, and learning. In applied research, artificially produced acoustic information and real-time auditory information have been implemented in sports and rehabilitation to improve motor performance in athletes, healthy individuals, and patients affected by neurological or movement disorders. However, this research is scattered both across time and scientific disciplines. The aim of this paper is to provide an overview about the interaction between movement and sound and review the current literature regarding the effect of natural movement sounds, movement sonification, and rhythmic auditory information in sports and motor rehabilitation. The focus here is threefold: firstly, we provide an overview of empirical studies using natural movement sounds and movement sonification in sports. Secondly, we review recent clinical and applied studies using rhythmic auditory information and sonification in rehabilitation, addressing in particular studies on Parkinson's disease and stroke. Thirdly, we summarize current evidence regarding the cognitive mechanisms and neural correlates underlying the processing of auditory information during movement execution and its mental representation. The current state of knowledge here reviewed provides evidence of the feasibility and effectiveness of the application of auditory information to improve movement execution, control, and (re)learning in sports and motor rehabilitation. Findings also corroborate the critical role of auditory information in auditory-motor coupling during motor (re)learning and performance, suggesting that this area of clinical and applied research has a large potential that is yet to be fully explored.

Young, Healthy Subjects Can Reduce the Activity of Calf Muscles When Provided with EMG Biofeedback in Upright Stance

Recent evidence suggests the minimization of muscular effort rather than of the size of bodily sway may be the primary, nervous system goal when regulating the human, standing posture. Different programs have been proposed for balance training; none however has been focused on the activation of postural muscles during standing. In this study we investigated the possibility of minimizing the activation of the calf muscles during standing through biofeedback. By providing subjects with an audio signal that varied in amplitude and frequency with the amplitude of surface electromyograms (EMG) recorded from different regions of the gastrocnemius and soleus muscles, we expected them to be able to minimize the level of muscle activation during standing without increasing the excursion of the center of pressure (CoP). CoP data and surface EMG from gastrocnemii, soleus and tibialis anterior muscles were obtained from 10 healthy participants while standing at ease and while standing with EMG biofeedback. Four sensitivities were used to test subjects' responsiveness to the EMG biofeedback. Compared with standing at ease, the two most sensitive feedback conditions induced a decrease in plantar flexor activity (~15%; P < 0.05) and an increase in tibialis anterior EMG (~10%; P < 0.05). Furthermore, CoP mean position significantly shifted backward (~30 mm). In contrast, the use of less sensitive EMG biofeedback resulted in a significant decrease in EMG activity of ankle plantar flexors with a marginal increase in TA activity compared with standing at ease. These changes were not accompanied by greater CoP displacements or significant changes in mean CoP position. Key results revealed subjects were able to keep standing stability while reducing the activity of gastrocnemius and soleus without loading their tibialis anterior muscle when standing with EMG biofeedback. These results may therefore posit the basis for the development of training protocols aimed at assisting subjects in more efficiently controlling leg muscle activity during standing.

Use of smartphones and portable media devices for quantifying human movement characteristics of gait, tendon reflex response, and Parkinson's disease hand tremor

Smartphones and portable media devices are both equipped with sensor components, such as accelerometers. A software application enables these devices to function as a robust wireless accelerometer platform. The recorded accelerometer waveform can be transmitted wireless as an e-mail attachment through connectivity to the Internet. The implication of such devices as a wireless accelerometer platform is the experimental and post-processing locations can be placed anywhere in the world. Gait was quantified by mounting a smartphone or portable media device proximal to the lateral malleolus of the ankle joint. Attributes of the gait cycle were quantified with a considerable accuracy and reliability. The patellar tendon reflex response was quantified by using the device in tandem with a potential energy impact pendulum to evoke the patellar tendon reflex. The acceleration waveform maximum acceleration feature of the reflex response displayed considerable accuracy and reliability. By mounting the smartphone or portable media device to the dorsum of the hand through a glove, Parkinson's disease hand tremor was quantified and contrasted with significance to a non-Parkinson's disease steady hand control. With the methods advocated in this chapter, any aspect of human movement may be quantified through smartphones or portable media devices and post-processed anywhere in the world. These wearable devices are anticipated to substantially impact the biomedical and healthcare industry.

Immediate effects of rhythmic auditory stimulation with tempo changes on gait in stroke patients

[Purpose] The aim of this study was to investigate the effects of tempo changes in rhythmic auditory stimulation (RAS) on gait in stroke patients. [Subjects] Forty-one chronic stroke patients who had had a stroke with more than 6 months previously were recruited for this study. [Methods] All participants were asked to walk under 5 different conditions in random order: (1) no RAS (baseline); (2) baseline-matched RAS (0%); and (3) −10%, (4) +10%, and (5) +20% of the baseline. A GAITRite system was used to evaluate the spatial and temporal parameters of gait. [Results] Compared with under the RAS 0% conditions, the gait velocity, cadence, and stride length on the affected side were significantly decreased under the RAS −10% conditions. Gait velocity and cadence were significantly improved, but gait symmetry was significantly decreased under the RAS +10% and +20% conditions compared with under the RAS 0% conditions. [Conclusion] A faster RAS tempo significantly improved gait velocity and cadence, and applying RAS significantly improved the gait symmetry of stroke patients.

A systematic review of mapping strategies for the sonification of physical quantities

The field of sonification has progressed greatly over the past twenty years and currently constitutes an established area of research. This article aims at exploiting and organizing the knowledge accumulated in previous experimental studies to build a foundation for future sonification works. A systematic review of these studies may reveal trends in sonification design, and therefore support the development of design guidelines. To this end, we have reviewed and analyzed 179 scientific publications related to sonification of physical quantities. Using a bottom-up approach, we set up a list of conceptual dimensions belonging to both physical and auditory domains. Mappings used in the reviewed works were identified, forming a database of 495 entries. Frequency of use was analyzed among these conceptual dimensions as well as higher-level categories. Results confirm two hypotheses formulated in a preliminary study: pitch is by far the most used auditory dimension in sonification applications, and spatial auditory dimensions are almost exclusively used to sonify kinematic quantities. To detect successful as well as unsuccessful sonification strategies, assessment of mapping efficiency conducted in the reviewed works was considered. Results show that a proper evaluation of sonification mappings is performed only in a marginal proportion of publications. Additional aspects of the publication database were investigated: historical distribution of sonification works is presented, projects are classified according to their primary function, and the sonic material used in the auditory display is discussed. Finally, a mapping-based approach for characterizing sonification is proposed.

The Impact of Vibrotactile Biofeedback on the Excessive Walking Sway and the Postural Control in Elderly

Gait and postural control are important aspects of human movement and balance. Normal movement control in human is subject to change with aging. With aging, the nervous system comprising, somatosensory, visual senses, spatial orientation senses, and neuromuscular control degrade. As a result, the body movement control such as the lateral sway while walking is affected which has been shown to be a significant cause of falling among the elderly. Biofeedback has been investigated to assist elderly improve their body movement and postural ability, by supplementing the feedback to the nervous system. In this paper, we propose a wearable low-power sensor system capable of characterizing lateral sway and gait parameters. Then, it can provide corrective feedback to reduce excessive sway in real-time via vibratory feedback modules. Real-time and low-power characteristics along with wearability of our proposed system allow long-term continuous subjects' sway monitoring while giving direct feedback to enhance walking sway and prevent falling. It can also be used in the clinics as a tool for evaluating the risks of falls, and training users to better maintain their balance. The effectiveness of the biofeedback system was evaluated on 12 older adults as they performed gait and stance tasks with and without biofeedback. Significant improvement (p-value < 0.1) in sway angle in variance of the sway angle, variance of gait phases, and in postural control while on perturbed surface was detected when the proposed Sway Error Feedback System was used.

The effects of augmented visual feedback during balance training in Parkinson's disease: study design of a randomized clinical trial

BACKGROUND

Patients with Parkinson's disease often suffer from reduced mobility due to impaired postural control. Balance exercises form an integral part of rehabilitative therapy but the effectiveness of existing interventions is limited. Recent technological advances allow for providing enhanced visual feedback in the context of computer games, which provide an attractive alternative to conventional therapy. The objective of this randomized clinical trial is to investigate whether a training program capitalizing on virtual-reality-based visual feedback is more effective than an equally-dosed conventional training in improving standing balance performance in patients with Parkinson's disease.

METHODS/DESIGN

Patients with idiopathic Parkinson's disease will participate in a five-week balance training program comprising ten treatment sessions of 60 minutes each. Participants will be randomly allocated to (1) an experimental group that will receive balance training using augmented visual feedback, or (2) a control group that will receive balance training in accordance with current physical therapy guidelines for Parkinson's disease patients. Training sessions consist of task-specific exercises that are organized as a series of workstations. Assessments will take place before training, at six weeks, and at twelve weeks follow-up. The functional reach test will serve as the primary outcome measure supplemented by comprehensive assessments of functional balance, posturography, and electroencephalography.

DISCUSSION

We hypothesize that balance training based on visual feedback will show greater improvements on standing balance performance than conventional balance training. In addition, we expect that learning new control strategies will be visible in the co-registered posturographic recordings but also through changes in functional connectivity.

Effectiveness of different visual biofeedback signals for human balance improvement

The aim of this study was to examine the effectiveness of visual biofeedback (VBF) signals from a force platform and accelerometer sensors placed on different body segments. The study was performed on 20 young subjects during standing on a firm and foam support surface with a VBF signal sensed from CoP, lower trunk (L5) and upper trunk (Th4). The VBF signal was controlled by 2D-movement of chosen body segment, which was presented as a red point on a monitor screen. Location of VBF signal had a significant effect on each postural parameter of CoP and trunk segments. RMS and amplitudes of postural sway in medial-lateral and anterior-posterior directions decreased during standing on both types of support surface due to VBF. L5-VBF and CoP-VBF significantly reduced CoP displacements and lower trunk tilts. Th4-VBF reduced upper trunk tilts. Frequency analysis of postural sway revealed a decrease of power spectral density (PSD) values in low frequency range (0.02-0.3Hz) and an increase of PSD values in higher frequency range (0.5-1.4 Hz) in the VBF conditions during the stance on the firm surface in anterior-posterior direction. Reduction of body sway was the most significant in the body segment from which the VBF signal was sensed. The CoP position and L5 position provided the best signals for VBF. Changes in frequency ranges of body sway suggest voluntary activation of balance control. The results open new opportunities to optimize VBF system for balance improvement using accelerometers.

The effect of vibrotactile feedback on postural sway during locomotor activities

Background

Although significant progress has been achieved in developing sensory augmentation methods to improve standing balance, attempts to extend this research to locomotion have been quite limited in scope. The goal of this study was to characterize the effects of two real-time feedback displays on locomotor performance during four gait-based tasks ranging in difficulty.

Methods

Seven subjects with vestibular deficits used a trunk-based vibrotactile feedback system that provided real-time feedback regarding their medial-lateral (M/L) trunk tilt when they exceeded a subject-specific predefined tilt threshold during slow and self-paced walking, walking along a narrow walkway, and walking on a foam surface. Two feedback display configurations were evaluated: the continuous display provided real-time continuous feedback of trunk tilt, and the gated display provided feedback for 200 ms during the period immediately following heel strike. The root-mean-square (RMS) trunk tilt and percentage of time below the tilt thresholds were calculated for all locomotor tasks.

Results

Use of continuous feedback resulted in significant decreases in M/L trunk tilt and increases in percentage times below the tilt thresholds during narrow and foam trials. The gated display produced generally smaller changes.

Conclusions

This preliminary study demonstrated that use of continuous vibrotactile feedback during challenging locomotor tasks allowed subjects with vestibular deficits to significantly decrease M/L RMS trunk tilt. Analysis of the results also showed that continuous feedback was superior.

Biofeedback in rehabilitation

This paper reviews the literature relating to the biofeedback used in physical rehabilitation. The biofeedback methods used in rehabilitation are based on biomechanical measurements and measurements of the physiological systems of the body. The physiological systems of the body which can be measured to provide biofeedback are the neuromuscular system, the respiratory system and the cardiovascular system. Neuromuscular biofeedback methods include electromyography (EMG) biofeedback and real-time ultrasound imaging (RTUS) biofeedback. EMG biofeedback is the most widely investigated method of biofeedback and appears to be effective in the treatment of many musculoskeletal conditions and in post cardiovascular accident (CVA) rehabilitation. RTUS biofeedback has been demonstrated effective in the treatment of low back pain (LBP) and pelvic floor muscle dysfunction. Cardiovascular biofeedback methods have been shown to be effective in the treatment of a number of health conditions such as hypertension, heart failure, asthma, fibromyalgia and even psychological disorders however a systematic review in this field has yet to be conducted. Similarly, the number of large scale studies examining the use of respiratory biofeedback in rehabilitation is limited. Measurements of movement, postural control and force output can be made using a number of different devices and used to deliver biomechanical biofeedback. Inertial based sensing biofeedback is the most widely researched biomechanical biofeedback method, with a number of studies showing it to be effective in improving measures of balance in a number of populations. Other types of biomechanical biofeedback include force plate systems, electrogoniometry, pressure biofeedback and camera based systems however the evidence for these is limited. Biofeedback is generally delivered using visual displays, acoustic or haptic signals, however more recently virtual reality (VR) or exergaming technology have been used as biofeedback signals. VR and exergaming technology have been primarily investigated in post-CVA rehabilitation, however, more recent work has shown this type of biofeedback to be effective in improving exercise technique in musculoskeletal populations. While a number of studies in this area have been conducted, further large scale studies and reviews investigating different biofeedback applications in different clinical populations are required.

ASSISTIVE VIBROTACTILE BIOFEEDBACK SYSTEM FOR POSTURAL CONTROL ON PERTURBED SURFACE

Postural control is an important aspect of human locomotion and stance. When inputs to the Central Nervous System (CNS), consisting of the vestibular, somatosensory, and visual senses, degrade or become dysfunctional, the postural control is affected. Biofeedback has been established as a potential intervention method to assist individuals improve postural control, by augmenting or complementing signals to the CNS. This paper presents an approach to help achieve better postural control using vibrotactile biofeedback. Tests to monitor postural control, in eyes open and eyes closed states, on a wobble board were introduced to assess the viability of the designed system in providing accurate real-time biofeedback responses. Postural control was gauged by measuring the angular displacement of perturbations experienced. Perturbations along the anterior and posterior direction are used to determine the level of provided vibrotactile biofeedback. The feedback informs subjects the severity of perturbation and direction of imbalance. Significant improvement (p-value < 0.05) in postural control while on perturbed surface was detected when the designed biofeedback system was used. The wearable system was found to be effective in improving postural control of the subjects and can be expanded for rehabilitation, conditioning, and strengthening applications dealing with human postural control.

The effects of vibrotactile biofeedback training on trunk sway in Parkinson's disease patients

BACKGROUND

Postural instability in Parkinson's disease (PD) can lead to falls, injuries and reduced quality of life. We investigated whether balance in PD can improve by offering patients feedback about their own trunk sway as a supplement to natural sensory inputs. Specifically, we investigated the effect of artificial vibrotactile biofeedback on trunk sway in PD.

METHODS

Twenty PD patients were assigned to a control group (n = 10) or biofeedback group (n = 10). First, all patients performed two sets of six gait tasks and six stance tasks (pre-training assessment). Subsequently, all subjects trained six selected tasks five times (balance training). During this training, the feedback group received vibrotactile feedback of trunk sway, via vibrations delivered at the head. After training, both groups repeated all twelve tasks (post-training assessment). During all tasks, trunk pitch and roll movements were measured with angular velocity sensors attached to the lower trunk. Outcomes included sway angle and sway angular velocity in the roll and pitch plane, and task duration.

RESULTS

Overall, patients in the feedback group had a significantly greater reduction in roll (P = 0.005) and pitch (P < 0.001) sway angular velocity. Moreover, roll sway angle increased more in controls after training, suggesting better training effects in the feedback group (P < 0.001).

CONCLUSIONS

One session of balance training in PD using a biofeedback system showed beneficial effects on trunk stability. Additional research should examine if these effects increase further after more intensive training, how long these persist after training has stopped, and if the observed effects carry over to non-trained tasks.

What is the most effective type of audio-biofeedback for postural motor learning?

Biofeedback is known to improve postural control and reduce postural sway. However, the effects that different biofeedback modes (coding for more or less complex movement information) may have on postural control improvement are still poorly investigated. In addition, most studies do not take into account the effects of spontaneous motor learning from repetition of a task when investigating biofeedback-induced improvement in postural control. In this study, we compared the effects of four different modes of audio-biofeedback (ABF), including direction and/or magnitude of sway information or just a non-specific-direction alarm, on the postural sway of 13 young healthy adults standing on a continuously rotating surface. Compared to the non-specific-direction alarm, ABF of continuous postural sway direction and/or amplitude resulted in larger postural sway reduction in the beginning of the experiment. However, over time, spontaneous postural motor learning flattened the effects of the different modes of ABF so that the alarm was as effective as more complex information about body sway. Nevertheless, motor learning did not make ABF useless, since all modes of ABF further reduced postural sway, even after subjects learned the task. All modes of ABF resulted in improved multi-segmental control of posture and stabilized the trunk-in-space. Spontaneous motor learning also improved multi-segmental control of posture but not trunk-in-space stabilization as much as ABF. In conclusion, although practice standing on a perturbing surface improved postural stability, the more body sway information provided to subjects using ABF, the greater the additional improvement in postural stability.

Audio-biofeedback training for posture and balance in patients with Parkinson's disease

Background

Patients with Parkinson's disease (PD) suffer from dysrhythmic and disturbed gait, impaired balance, and decreased postural responses. These alterations lead to falls, especially as the disease progresses. Based on the observation that postural control improved in patients with vestibular dysfunction after audio-biofeedback training, we tested the feasibility and effects of this training modality in patients with PD.

Methods

Seven patients with PD were included in a pilot study comprised of a six weeks intervention program. The training was individualized to each patient's needs and was delivered using an audio-biofeedback (ABF) system with headphones. The training was focused on improving posture, sit-to-stand abilities, and dynamic balance in various positions. Non-parametric statistics were used to evaluate training effects.

Results

The ABF system was well accepted by all participants with no adverse events reported. Patients declared high satisfaction with the training. A significant improvement of balance, as assessed by the Berg Balance Scale, was observed (improvement of 3% p = 0.032), and a trend in the Timed up and go test (improvement of 11%; p = 0.07) was also seen. In addition, the training appeared to have a positive influence on psychosocial aspects of the disease as assessed by the Parkinson's disease quality of life questionnaire (PDQ-39) and the level of depression as assessed by the Geriatric Depression Scale.

Conclusions

This is, to our knowledge, the first report demonstrating that audio-biofeedback training for patients with PD is feasible and is associated with improvements of balance and several psychosocial aspects.

Wearable systems with minimal set-up for monitoring and training of balance and mobility

With the objective to release solutions which can be easily manageable by their final users, including older users, we worked to design methods and devices which rely on a minimal set-up for monitoring and rehabilitation of balance and mobility. A single inertial sensing unit, typically worn on the trunk, was hence engineered to accomplish for activity monitoring and event detection (including fall detection), tremor rejection, instrumented clinical tests (e.g. stabilometry, Timed-Up and Go), and sensory biofeedback (audio, visual or tactile). The sensing unit is wirelessly connected with a processing unit, which can in turn act as a gateway to remote applications or caregivers. Promising results were obtained, which may pave the way to novel intensive and pervasive neurorehabilitation strategies.

Application of vibrotactile feedback of body motion to improve rehabilitation in individuals with imbalance

BACKGROUND AND PURPOSE

Balance rehabilitation and vestibular or balance prostheses are both emerging fields that have a potential for synergistic interaction. This article reviews vibrotactile prosthetic devices that have been developed to date and ongoing work related to the application of vibrotactile feedback for enhanced postural control. A vibrotactile feedback device developed in the author's laboratory is described.

METHODS

Twelve subjects with vestibular hypofunction were tested on a platform that moved randomly in a plane, while receiving vibrotactile feedback in the anteroposterior direction. The feedback allowed subjects to significantly decrease their anteroposterior body tilt but did not change mediolateral tilt. A tandem walking task performed by subjects with vestibulopathies demonstrated a reduction in their mediolateral sway due to vibrotactile feedback of mediolateral body tilt, after controlling for the effects of task learning. Published findings from 2 additional experiments conducted in the laboratories of collaborating physical therapists are summarized.

RESULTS

The Dynamic Gait Index scores in community-dwelling elderly individuals who were prone to falls were significantly improved with the use of mediolateral body tilt feedback.

DISCUSSION AND CONCLUSIONS

Although more work is needed, these results suggest that vibrotactile tilt feedback of subjects' body motion can be used effectively by physical therapists for balance rehabilitation. A preliminary description of the third-generation device that has been reduced from a vest format to a belt format is described to demonstrate the progressive evolution from research to clinical application.

EEG correlates of postural audio-biofeedback

The control of postural sway depends on the dynamic integration of multi-sensory information in the central nervous system. Augmentation of sensory information, such as during auditory biofeedback (ABF) of the trunk acceleration, has been shown to improve postural control. By means of quantitative electroencephalography (EEG), we examined the basic processes in the brain that are involved in the perception and cognition of auditory signals used for ABF. ABF and Fake ABF (FAKE) auditory stimulations were delivered to 10 healthy naive participants during quiet standing postural tasks, with eyes-open and closed. Trunk acceleration and 19-channels EEG were recorded at the same time. Advanced, state-of-the-art EEG analysis and modeling methods were employed to assess the possibly differential, functional activation, and localization of EEG spectral features (power in α, β, and γ bands) between the FAKE and the ABF conditions, for both the eyes-open and the eyes-closed tasks. Participants gained advantage by ABF in reducing their postural sway, as measured by a reduction of the root mean square of trunk acceleration during the ABF compared to the FAKE condition. Population-wise localization analysis performed on the comparison FAKE - ABF revealed: (i) a significant decrease of α power in the right inferior parietal cortex for the eyes-open task; (ii) a significant increase of γ power in left temporo-parietal areas for the eyes-closed task; (iii) a significant increase of γ power in the left temporo-occipital areas in the eyes-open task. EEG outcomes supported the idea that ABF for postural control heavily modulates (increases) the cortical activation in healthy participants. The sites showing the higher ABF-related modulation are among the known cortical areas associated with multi-sensory, perceptual integration, and sensorimotor integration, showing a differential activation between the eyes-open and eyes-closed conditions.

Directional effects of biofeedback on trunk sway during stance tasks in healthy young adults

Biofeedback has been shown to improve balance in a number of different populations. As certain clinical populations have a tendency to fall in one direction, the provision of biofeedback in the impaired direction may improve balance in that direction but not in others. The purpose of this study was to determine the effects of uni-directional biofeedback on stance tasks in healthy young adults. Trunk sway was measured in 40 healthy young adults as they performed nine stance tasks with and without biofeedback. Participants received biofeedback about their trunk sway in either the anterior-posterior (AP) or medial-lateral (ML) direction using a multi-modal head-mounted biofeedback device. An overall effect of reduced sway angle and increased sway angular velocity was noted with biofeedback. Some of the effects of biofeedback were dependent on the direction in which biofeedback was given and whether vision was present during the stance task. These effects were strongest in the pitch direction for AP biofeedback with vision present. This study showed direction specific effects of biofeedback are greatest in the sagittal plane. These results are important clinically as the use of biofeedback during stance tasks, similar to gait tasks, appears to work best in the AP direction when vision is present.

Trunk sway reductions in young and older adults using multi-modal biofeedback

This study investigated whether real-time biofeedback of angular trunk displacement could alter balance performance among healthy older and young adults. Healthy community-dwelling older adults (n=32) and healthy young adults (n=32) were included in the randomized control trial study. The intervention group received combined vibrotactile, auditory and visual biofeedback of angular trunk displacement in real-time during training on a battery of static and dynamic balance tasks and during the subsequent post-training balance re-assessment. The control group received balance training and were re-assessed in the absence of real-time biofeedback of their trunk displacement. The 90% range of angular trunk displacement was calculated for each balance task pre- and post-training. Significant age-related differences were observed independent of the intervention. Biofeedback intervention significantly changed the angular displacement of the trunk for both young and older participants on a number of balance tasks compared to control treatment (40-60% reduction in angular displacement). In some cases, biofeedback influenced balance in older adults, but not younger adults.

Salient and placebo vibrotactile feedback are equally effective in reducing sway in bilateral vestibular loss patients

This study explores the effect of vibrotactile biofeedback on body sway in stance in patients with severe bilateral vestibular losses in a placebo-controlled study. A tilt sensor mounted on the head or trunk is used to detect head or body tilt and activates via a microprocessor 12 small vibrators that are placed around the waist with a mutual distance of 30 degrees. Two positions of the tilt sensor (head and trunk) and three types of biofeedback (normal, full and random) were evaluated, besides no biofeedback. Body sway during stance was assessed in 10 patients with bilateral vestibular areflexia and performance was scored in the seven different conditions. Inter-individual and test-retest variability without biofeedback was assessed in 10 additional patients with bilateral vestibular areflexia. In six patients no significant change in body swaypath was observed using biofeedback. In four patients body swaypath decreased significantly using biofeedback and sensor on the head in all three activation modes, whereas with sensor on the trunk only one patient showed a significant improvement in swaypath in all three activation modes. The patients rated the functionality of the AVBF system and its effect on balance on average 6.5 on a scale from 0 to 10. Thus, body sway improved in 4 out of 10 patients using biofeedback, but the improvement with true biofeedback was only observed in those subjects where an improvement was present in placebo mode as well. The improvement was, at least partially, caused by other effects than biofeedback, like training, increased self-confidence or alertness.

Effects of biofeedback on trunk sway during dual tasking in the healthy young and elderly

We examined the effect of biofeedback of trunk sway on balance control while walking and performing a simultaneous cognitive or motor task. Thirteen healthy elderly (mean age (+/-S.E.M.) 70.8+/-2.0 years) and 16 healthy young (mean age 21.5+/-0.7 years) subjects performed three gait tasks while wearing body-worn gyroscopes, mounted at L1-3, to measure trunk sway. The gait tasks were walking normally, walking and counting backwards in 7's, and walking while carrying a tray with cups of water. Differences in trunk sway were examined when subjects performed the gait tasks with or without a head mounted actuator system which provided subjects with vibro-tactile, auditory and visual biofeedback of trunk sway. In the young, trunk pitch (fore-aft) angles, and trunk roll (sideways) and pitch angular velocities were significantly reduced using biofeedback across all three gait tasks. In the elderly, the same angle and angular velocities were also significantly reduced while walking normally. During walking while carrying a tray, only trunk sway velocities were significantly reduced, whereas no improvements were seen for walking while counting backwards. Counting backwards ability significantly improved with feedback. Young participants were able to perform a dual task during gait and employ biofeedback to reduce trunk sway. Elderly participants were not able to reduce sway using biofeedback during the cognitive task but were able to reduce sway velocities with biofeedback during the motor task.

Directional effects of biofeedback on trunk sway during gait tasks in healthy young subjects

Biofeedback of trunk sway is a possible remedy for patients with balance disorders. Because these patients have a tendency to fall more in one direction, we investigated whether biofeedback has a directional effect on trunk sway during gait. Forty healthy young participants (mean age 23.1 years) performed 10 gait tasks with and without biofeedback. Combined vibrotactile, auditory and visual feedback on trunk sway in either the lateral or anterior-posterior (AP) direction was provided by a head-mounted actuator system. Trunk roll and pitch angles, calculated from trunk angular velocities measured with gyroscopes, were used to drive the feedback. A reduction in sway velocities occurred across all tasks regardless of feedback direction. Reductions in sway angles depended on the task. Generally, reductions were greater in pitch. For walking up and down stairs, or over barriers, pitch angle reductions were greater with AP than lateral feedback. For tandem and normal walking, reductions were similar in pitch and roll angles for both feedback directions. For walking while rotating or pitching the head or with eyes closed, only pitch angle was reduced for both feedback directions. These results indicate that the central nervous system is able to incorporate biofeedback of trunk sway from either the AP or lateral direction to achieve a reduction in both pitch and roll sway. Greater reductions in pitch suggest a greater ability to use this direction of trunk sway biofeedback during gait.

Could sound be used as a strategy for reducing symptoms of perceived motion sickness?

BACKGROUND

Working while exposed to motions, physically and psychologically affects a person. Traditionally, motion sickness symptom reduction has implied use of medication, which can lead to detrimental effects on performance. Non-pharmaceutical strategies, in turn, often require cognitive and perceptual attention. Hence, for people working in high demand environments where it is impossible to reallocate focus of attention, other strategies are called upon. The aim of the study was to investigate possible impact of a mitigation strategy on perceived motion sickness and psychophysiological responses, based on an artificial sound horizon compared with a non-positioned sound source.

METHODS

Twenty-three healthy subjects were seated on a motion platform in an artificial sound horizon or in non-positioned sound, in random order with one week interval between the trials. Perceived motion sickness (Mal), maximum duration of exposure (ST), skin conductance, blood volume pulse, temperature, respiration rate, eye movements and heart rate were measured continuously throughout the trials.

RESULTS

Mal scores increased over time in both sound conditions, but the artificial sound horizon, applied as a mitigation strategy for perceived motion sickness, showed no significant effect on Mal scores or ST. The number of fixations increased with time in the non-positioned sound condition. Moreover, fixation time was longer in the non-positioned sound condition compared with sound horizon, indicating that the subjects used more time to fixate and, hence, assumingly made fewer saccades.

CONCLUSION

A subliminally presented artificial sound horizon did not significantly affect perceived motion sickness, psychophysiological variables or the time the subjects endured the motion sickness triggering stimuli. The number of fixations and fixation times increased over time in the non-positioned sound condition.

Energetic assessment of trunk postural modifications induced by a wearable audio-biofeedback system

This paper investigates the trunk postural modifications induced by a wearable device which assesses the trunk sway and provides biofeedback information through sonification of trunk kinematics. The device is based on an inertial wearable sensing unit including three mono-axial accelerometers and three rate gyroscopes embedded and mounted orthogonally. The biofeedback device was tested on nine healthy subjects during quiet stance in different conditions of sensory limitation eyes closed on solid surface, eyes open on foam cushion surface, eyes closed on foam cushion surface. Five trials were performed for each condition; the order of the trials was randomized. The results reported in this paper show how subjects reduced their rotational kinetic energy by using the biofeedback information and how this reduction was related to the limitation of sensory information.

Balance (perceived and actual) and preferred stance width during pregnancy

BACKGROUND

Pregnant women often remark that their balance degrades during pregnancy; however, it appears that no studies have documented the gravida's perception of her balance nor measured direction-specific changes in balance throughout pregnancy or after delivery.

METHODS

Thirty women, fifteen pregnant and fifteen non-pregnant controls, were tested monthly and through 6-month postpartum. For each session, perceived degradation in sense of balance, laboratory-based balance measures, stance width, and the number of falls since the previous session were recorded. Laboratory-based balance measures, quantified by direction-specific measures of postural sway, were computed from ten 30s quiet-standing trials on a stationary force platform. Repeated-measures analysis of variance, paired t-tests, and Pearson correlations were use to examine group and time effects.

FINDINGS

For the pregnant group, perceived balance degradation and stance width were highly correlated (r = 0.94). Both increased during pregnancy (P < or = 0.016) and dropped to near-control levels after delivery (P < or = 0.004). Compared to the control group, pregnant subjects displayed increased sway, especially in the anterior-posterior and radial directions (P < or = 0.039). Anterior-posterior sway measures strongly correlated with perceived balance (0.82 > r > 0.72) and also decreased significantly between the third trimester and postpartum (P < or = 0.029). Interestingly, medial-lateral balance measures varied little during pregnancy, but increased after delivery. Contrary to recent work suggesting fall rates of 25%, only 13% of our subjects (n = 2) fell during pregnancy.

INTERPRETATION

Perceived degradation in balance during pregnancy was strongly related to increasing postural sway instability in the anterior-posterior direction. Lateral stability was maintained during pregnancy and likely accomplished by increasing stance width.

Game-based exercises for dynamic short-sitting balance rehabilitation of people with chronic spinal cord and traumatic brain injuries

BACKGROUND AND PURPOSE

Goal-oriented, task-specific training has been shown to improve function; however, it can be difficult to maintain patient interest. This report describes a rehabilitation protocol for the maintenance of balance in a short-sitting position following spinal cord and head injuries by use of a center-of-pressure-controlled video game-based tool. The scientific justification for the selected treatment is discussed.

CASE DESCRIPTION

Three adults were treated: 1 young adult with spina bifida (T10 and L1-L2), 1 middle-aged adult with complete paraplegia (complete lesion at T11-L1), and 1 middle-aged adult with traumatic brain injury. All patients used wheelchairs full-time.

OUTCOMES

The patients showed increased motivation to perform the game-based exercises and increased dynamic short-sitting balance.

DISCUSSION

The patients exhibited increases in practice volume and attention span during training with the game-based tool. In addition, they demonstrated substantial improvements in dynamic balance control. These observations indicate that a video game-based exercise approach can have a substantial positive effect by improving dynamic short-sitting balance.

Effects of Maintaining Touch Contact on Predictive and Reactive Balance

Light touch contact between the body and an environmental referent reduces fluctuations of center of pressure (CoP) in quiet standing although the contact forces are insufficient to provide significant forces to stabilize standing balance. Maintenance of upright standing posture (with light touch contact) may include both predictive and reactive components. Recently Dickstein et al. (2003) demonstrated that reaction to temporally unpredictable displacement of the support surface was affected by light touch raising the question whether light touch effects also occur with predictable disturbance to balance. We examined the effects of shoulder light touch on SD of CoP rate (dCoP) during balance perturbations associated with forward sway induced by pulling on (voluntary), or being pulled by (reactive), a hand-held horizontal load. Prior to perturbation, SD dCoP was lower with light touch, corresponding to previous findings. Immediately after perturbation, SD dCoPAP was greater with light touch in the case of voluntary pull, whereas no difference was found for reflex pull. However, in the following time course, light touch contact again resulted in a significantly lower SD dCoP and faster stabilization of SD dCoP. We conclude that shoulder light touch contact affects immediate postural responses to voluntary pull but also stabilization after voluntary and reflex perturbation. We suggest that in voluntary perturbation CoP fluctuations are differentially modulated in anterioposterior and mediolateral directions to maintain light touch, which not only provides augmented sensory feedback about body self-motion, but may act as a “constraint” to the postural control system when preparing postural adjustments.