The Effect of Vibrotactile Feedback on Healthy People and People with Vestibular Disorders during Dual-task Conditions

Vibrotactile feedback (VTF) has been shown to improve balance performance in healthy people and people with vestibular disorders in a single-task experimental condition. However, typical balance activities occur in a multi-task environment. Dual-task performance can degrade with age and in people with vestibular disorders. It is unclear if the ability to use VTF might be affected by dual-task conditions in different age groups and people with vestibular disorders. The purposes of this dissertation are to investigate in healthy young and older adults, and people with vestibular disorders: 1) balance performance in a dual-task paradigm under various sensory conditions while using VTF, 2) reaction time during dual-task performance under different sensory conditions while using VTF, and 3) the effect of testing duration and visit on VTF use. Three study visits were included in this dissertation study: one screening visit and two experimental visits. Twenty younger and twenty older subjects were recruited in the first study to determine if VTF was affected by age. Seven people with unilateral vestibular hypofunction (UVH) and seven age-matched controls were recruited in the second study to investigate the effect of vestibular dysfunction. The results showed that young and older adults use VTF differently, depending on the underlying sensory integration balance task. Older adults increased postural sway during fixed platform conditions, but both young and older adults decreased postural sway during sway-referenced platform conditions. Reaction times on the secondary cognitive tasks increased more while using the VTF in older adults compared with young adults. This finding suggested that using VTF requires greater attention in older adults. The trial duration and visit also affected postural sway performance while VTF was applied. Similar postural sway results were found when comparing people with UVH and age-matched controls. However, no group difference was found between people with UVH and age-matched controls in the magnitude of postural sway, which suggested that people with UVH were able to use VTF under dual-task conditions similar to normal adults. Our data also indicated that people with UVH require more attentional resources to perform secondary cognitive tasks while using VTF

Benefits of short-term training with vibrotactile biofeedback of trunk sway on balance control in multiple sclerosis

Background and Aims: Patients with multiple sclerosis (MS) suffer from diminished balance control. We examined whether 4 sessions of training with vibrotactile biofeedback (VTfb) of trunk sway could improve their balance control and provide a carry-over effect. Methods: Baseline trunk sway was first measured for 15 MS patients. Then they received head mounted VTfb of trunk sway which was directionally active when trunk sway exceeded limits set using the baseline assessments. Stance and gait tasks were trained 2 times weekly for 2 weeks with VTfb. Assessments with VTfb were performed at the end of each week. Two weeks later balance was assessed without VTfb to determine if a carry-over effect was present. Results: Assessments with VTfb showed a significant decrease in trunk sway after 1 and 2 weeks of VTfb training (p<0.02). Carry-over improvements were also present (p<0.02). The greatest effects were found for tests of standing eyes closed stance on foam which resulted in a 59% decreased pitch sway angle (p=0.002) with VTfb and a 51% reduction (p=0.03) carry-over effect. Conclusions: This study indicates that balance control in MS patients improves rapidly after one week of training with VTfb and more slowly subsequently. The carry-over effect lasted at least 2 weeks. Future studies should determine, with more weeks of VTfb training, the time course of the slower balance and carry-over improvements following the first rapid improvement in balance control. We conclude that training with VTfb of trunk sway significantly improves balance control in MS patients, and could possibly reduce falls

Design and Assessment of Vibrotactile Biofeedback and Instructional Systems for Balance Rehabilitation Applications.

Sensory augmentation, a type of biofeedback, is a technique for supplementing or reinforcing native sensory inputs. In the context of balance-related applications, it provides users with additional information about body motion, usually with respect to the gravito-inertial environment. Multiple studies have demonstrated that biofeedback, regardless of the feedback modality (i.e., vibrotactile, electrotactile, auditory), decreases body sway during real-time use within a laboratory setting. However, in their current laboratory-based form, existing vibrotactile biofeedback devices are not appropriate for use in clinical and/or home-based rehabilitation settings due to the expense, size, and operating complexity of the instrumentation required. This dissertation describes the design, development, and preliminary assessment of two technologies that support clinical and home-based balance rehabilitation training. The first system provides vibrotactile-based instructional motion cues to a trainee based on the measured difference between the expert’s and trainee’s motions. The design of the vibrotactile display is supported by a study that characterizes the non-volitional postural responses to vibrotactile stimulation applied to the torso. This study shows that vibration applied individually by tactors over the internal oblique and erector spinae muscles induces a postural shift of the order of one degree oriented in the direction of the stimulation. Furthermore, human performance is characterized both experimentally and theoretically when the expert–trainee error thresholds and nature of the control signal are varied. The results suggest that expert–subject cross-correlation values were maximized and position errors and time delays were minimized when the controller uses a 0.5 error threshold and proportional plus derivative feedback control signal, and that subject performance decreases as motion speed and complexity increase. The second system provides vibrotactile biofeedback about body motion using a cell phone. The system is capable of providing real-time vibrotactile cues that inform corrective trunk tilt responses. When feedback is available, both healthy subjects and those with vestibular involvement significantly reduce their anterior-posterior or medial-lateral root-mean-square body sway, have significantly smaller elliptical area fits to their sway trajectory, spend a significantly greater mean percentage time within the no feedback zone, and show a significantly greater A/P or M/L mean power frequency.Ph.D.Mechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/91546/1/channy_1.pd

Perturbation-based detection and prosthetic correction of vestibulopathic gait

Thesis (Ph. D.)--Harvard-MIT Division of Health Sciences and Technology, February 2007.Includes bibliographical references.While being able to balance is something most of us take for granted, each year approximately 400,000 Americans are diagnosed with a balance disorder. In order to prevent fall-related injuries due to postural instability, it is important to create both diagnosis techniques so that therapy can be applied before a fall occurs and devices which can aid the balance-impaired population. The aims of this research are twofold: 1) to develop metrics that quantify the locomotor stability of individuals with reduced vestibular function and 2) to assess the capability of a noninvasive vibrotactile balance prosthesis for improving postural and gait stability. The clinical standards of practice for assessing vestibular deficiency include testing postural stability while standing but not during locomotion. This research examines one prospective locomotor-based technique involving the analysis of postural recovery from controlled surface perturbations. The research also investigates the use of a novel wearable vibrotactile sensory substitution device for enhanced postural and locomotor stability. The balance prosthesis is composed of an inertial motion-sensing system mounted on the lower back, a vibrotactile display worn around the torso, and a computer controller.(cont.) It can serve as a permanent or temporary replacement of motion cues, a tool for vestibular rehabilitation, or an additional sensory channel for military troops, pilots, and astronauts. This research demonstrates that well-compensated vestibulopathic patients can be differentiated from young and age-matched controls during over ground locomotion based on step width variability. Prior to this research, unilateral and bilateral vestibulopathic patients donning the vibrotactile balance prosthesis have demonstrated increased postural stability during single-axis support surface perturbations using single-axis sway information. This work shows that multi-directional vibrotactile tilt feedback reduces postural sway during multi-directional support surface perturbations, and has both short- and long-term effects on increasing postural stability. Finally, this research demonstrates for the first time that medial-lateral (M/L) tilt feedback can be used by balance-deficient subjects to reduce factors associated with fall risk (M/L tilt and M/L step width variability) during various locomotor tasks.by Kathleen H. Sienko.Ph.D

The use of biofeedback for gait retraining: A mapping review

Background: Biofeedback seems to be a promising tool to improve gait outcomes for both healthy individuals and patient groups. However, due to differences in study designs and outcome measurements, it remains uncertain how different forms of feedback affect gait outcomes. Therefore, the aim of this study is to review primary biomechanical literature which has used biofeedback to alter gait-related outcomes in human participants. Methods: Medline, Cinahl, Cochrane, SPORTDiscus and Pubmed were searched from inception to December 2017 using various keywords and the following MeSHterms: biofeedback, feedback, gait, walking and running. From the included studies, sixteen different study characteristics were extracted. Findings: In this mapping review 173 studies were included. The most common feedback mode used was visual feedback (42%, n=73) and the majority fed-back kinematic parameters (36%, n=62). The design of the studies were poor: only 8% (n=13) of the studies had both a control group and a retention test; 69% (n=120) of the studies had neither. A retention test after 6 months was performed in 3% (n=5) of the studies, feedback was faded in 9% (n=15) and feedback was given in the field rather than the laboratory in 4% (n=8) of the studies. Interpretation: Further work on biofeedback and gait should focus on the direct comparison between different modes of feedback or feedback parameters, along with better designed and field based studies

Postural and Perceptual Measurements during Performance of Static Standing Balance Exercises

Purpose: Balance training has shown benefits in improving balance in older adults and people with vestibular disorders. However, the evidence for determining the appropriate intensity and progression of balance exercises is very limited. The purpose of this study was to develop a method for quantifying intensity of balance exercises, and to determine guidelines for progressing exercises. Participants: Sixty-two healthy subjects who were between the ages of 18 and 85 years old (50% female, mean age 55 ± 20 years), and eight participants with vestibular disorders (50% female. mean age 56 ± 16 years) enrolled in the study. Methods: Healthy subjects were tested during two visits and performed two sets of 24 randomized static standing exercises in each visit. Participants with vestibular disorders were tested in one visit and performed two sets of 16 randomized static standing exercises. The exercises consisted of combinations of the following factors: surface (firm and foam), vision (eyes open and eyes closed), stance (feet apart and semi-tandem), and head movement (still, yaw, and pitch). Postural sway and ratings of perceived difficulty were measured for each exercise. The test-retest reliability of subjects’ performance and their rating of perceived difficulty of different standing balance exercises was examined. Two scales of rating of perceived difficulty of balance exercises were validated by comparing them with quantitative sway measures. The effect of age and vestibular disorders on postural and perceptual measures were tested using linear mixed models. Results: Position and acceleration sway measures demonstrated acceptable test-retest reliability, while sway velocity measures were the most reliable. The rating of perceived difficulty scales demonstrated fair to substantial agreement with few exceptions. Moderate to strong, positive correlations were observed between the rating of perceived difficulty scales and all sway measures establishing their validity. Sway and ratings of perceived difficulty increased in the older subject groups. Individuals with vestibular disorders did not produce more sway compared with controls, but they did have higher ratings of perceived difficulty. Conclusion: Quantitative sway measures and ratings of perceived difficulty can be used to prescribe intensity of balance exercises and guide progression during rehabilitation

Rehabilitation Engineering in Parkinson's disease

Impairment of postural control is a common consequence of Parkinson's disease (PD) that becomes more and more critical with the progression of the disease, in spite of the available medications. Postural instability is one of the most disabling features of PD and induces difficulties with postural transitions, initiation of movements, gait disorders, inability to live independently at home, and is the major cause of falls. Falls are frequent (with over 38% falling each year) and may induce adverse consequences like soft tissue injuries, hip fractures, and immobility due to fear of falling. As the disease progresses, both postural instability and fear of falling worsen, which leads patients with PD to become increasingly immobilized. The main aims of this dissertation are to: 1) detect and assess, in a quantitative way, impairments of postural control in PD subjects, investigate the central mechanisms that control such motor performance, and how these mechanism are affected by levodopa; 2) develop and validate a protocol, using wearable inertial sensors, to measure postural sway and postural transitions prior to step initiation; 3) find quantitative measures sensitive to impairments of postural control in early stages of PD and quantitative biomarkers of disease progression; and 4) test the feasibility and effects of a recently-developed audio-biofeedback system in maintaining balance in subjects with PD. In the first set of studies, we showed how PD reduces functional limits of stability as well as the magnitude and velocity of postural preparation during voluntary, forward and backward leaning while standing. Levodopa improves the limits of stability but not the postural strategies used to achieve the leaning. Further, we found a strong relationship between backward voluntary limits of stability and size of automatic postural response to backward perturbations in control subjects and in PD subjects ON medication. Such relation might suggest that the central nervous system presets postural response parameters based on perceived maximum limits and this presetting is absent in PD patients OFF medication but restored with levodopa replacement. Furthermore, we investigated how the size of preparatory postural adjustments (APAs) prior to step initiation depend on initial stance width. We found that patients with PD did not scale up the size of their APA with stance width as much as control subjects so they had much more difficulty initiating a step from a wide stance than from a narrow stance. This results supports the hypothesis that subjects with PD maintain a narrow stance as a compensation for their inability to sufficiently increase the size of their lateral APA to allow speedy step initiation in wide stance. In the second set of studies, we demonstrated that it is possible to use wearable accelerometers to quantify postural performance during quiet stance and step initiation balance tasks in healthy subjects. We used a model to predict center of pressure displacements associated with accelerations at the upper and lower back and thigh. This approach allows the measurement of balance control without the use of a force platform outside the laboratory environment. We used wearable accelerometers on a population of early, untreated PD patients, and found that postural control in stance and postural preparation prior to a step are impaired early in the disease when the typical balance and gait intiation symptoms are not yet clearly manifested. These novel results suggest that technological measures of postural control can be more sensitive than clinical measures. Furthermore, we assessed spontaneous sway and step initiation longitudinally across 1 year in patients with early, untreated PD. We found that changes in trunk sway, and especially movement smoothness, measured as Jerk, could be used as an objective measure of PD and its progression. In the third set of studies, we studied the feasibility of adapting an existing audio-biofeedback device to improve balance control in patients with PD. Preliminary results showed that PD subjects found the system easy-to-use and helpful, and they were able to correctly follow the audio information when available. Audiobiofeedback improved the properties of trunk sway during quiet stance. Our results have many implications for i) the understanding the central mechanisms that control postural motor performance, and how these mechanisms are affected by levodopa; ii) the design of innovative protocols for measuring and remote monitoring of motor performance in the elderly or subjects with PD; and iii) the development of technologies for improving balance, mobility, and consequently quality of life in patients with balance disorders, such as PD patients with augmented biofeedback paradigms

Automatic Posture Correction Utilizing Electrical Muscle Stimulation

Habitually poor posture can lead to repetitive strain injuries that lower an individual\u27s quality of life and productivity. Slouching over computer screens and smart phones, asymmetric weight distribution due to uneven leg loading, and improper loading posture are some of the common examples that lead to postural problems and health ramifications. To help cultivate good postural habits, researchers have proposed slouching, balance, and improper loading posture detection systems that alert users through traditional visual, auditory or vibro-tactile feedbacks when posture requires attention. However, such notifications are disruptive and can be easily ignored. We address these issues with a new physiological feedback system that uses sensors to detect these poor postures, and electrical muscle stimulation to automatically correct the poor posture. We compare our automatic approach against other alternative feedback systems and through different unique contexts. We find that our approach outperformed alternative traditional feedback systems by being faster and more accurate while delivering an equally comfortable user experience

A Personalized Sensor Support Tool for the Training of Mindful Walking

The exploitation of sensor features offered by present smart mobile devices is a trend that becomes increasingly important in various domains. In healthcare, for example, these sensors are used to cheaply gather valuable data for chronic disease management or health care. Regarding the latter, health insurers crave for effective methods that can be offered to their customers. Moreover, smart mobile devices provide many advantages compared to approaches hitherto applied in the aforementioned contexts as they can be easily used in everyday life. Thereby, when taking these advantages properly into account, new mobile application types become possible. Body sensor networks are such an application type that aim at monitoring users in vivo. Furthermore, data gathered with body sensor networks may be a valuable basis to provide user interventions. This paper presents an application that shall support users to walk mindfully. The motivation was to create a mobile tool that can make mindful walking more effective to reduce stress and to target noncommunicable diseases such as diabetes or depression. It is a mobile personalized tool that senses the walking speed and provides haptic feedback thereof. The mindful walking procedure, the technical prototype as well as preliminary study results are presented and discussed in this work. The reported user feedback and the study results indicate promising perspectives for a tool that supports a mindful walking behavior. Altogether, the use of smart mobile device sensors constitutes a promising instrument for realizing mobile applications in the context of health care and disease management