A Vibrotactile Feedback Device for Seated Balance Assessment and Training
January 20th, 2019
A sitting platform has been developed and assembled that passively destabilizes sitting posture in humans. During the user's stabilizing task, an inertial measurement unit records the device's motion, and vibrating elements deliver performance-based feedback to the seat. The portable, versatile device may be used in rehabilitation, assessment, and training paradigms.
Many people suffer from seated instability, which can compromise functional independence and lead to secondary health complications. Our protocol holds the potential to assess, challenge, and improve balance during sitting. Our technique combines elements of existing balance research tools into one novel device that is optimized for clinical use and accessibility.
Individuals who suffer under a newer muscular impairment may struggle to maintain seated balance. Our protocol provides access to assessment and training techniques that are known to benefit balance rehabilitation outcomes. This protocol can be applied to investigate balance control mechanisms and to optimize sensory feedback methods.
New users of this protocol should be sure to use our supplemental drawing and solid model files to produce a working replica of the device. At the beginning, weld a base nut to a steel plate to construct an attachment interface for interchangeable, hemispherical bases. Using a computer numerical controlled, or CNC milling machine, construct a cylindrical chassis, lid, and base from polyethylene, then bolt the base plate to the base, and place the chassis on the base.
Use the milling machine to construct a 37mm-long, 32mm outer diameter cylindrical polyvinyl chloride sleeve that fits onto a threaded rod. After welding steel flanges to each side of a steel hitch, bolt the hitch to the front of the base. Use a CNC turning machine to construct five identical 63mm-high, 152mm diameter polyethylene cylinders.
In the center of the top surface of each cylinder, cut a 32mm hole to a depth of 38mm so that it fits the cylindrical sleeve with some interference. On the bottom surface of each cylinder, use the CNC turning machine to cut a uniformly curved base with the unique radius of curvature for each of the five cylinders, maintaining the overall height of 63mm. To construct the leg support attachment, first weld a 70mm steel hitch insert perpendicularly to one end of a 575mm steel extrusion.
At the other end, clamp a 300mm cylindrical steel footrest to the extrusion. Use a bandsaw to cut a rectangular 29 by 100mm steel bar to a length of approximately 160mm so that it weighs 3.6kg. Insert the steel bar at the back of the chassis to counterbalance the leg support attachment, and assemble the device.
Insert the clevis pins through the hitch and the hitch insert to connect the leg support. Then adjust the location of the clamp to the desired footrest height. Thread the rod into the base stud, such that approximately 35mm of the rod protrudes from the base, and insert the protruding rod into the desired curved base.
Apply the grip tape to the lid, and cover the device with the lid. To instrument the device, connect an inertial measurement unit and eight vibrating tachters to a microcontroller. Program the microcontroller such that it reads anteroposterior and mediolateral tilt angles from the inertial measurement unit, and turns the vibrating tachters on or off based on the tilt angles.
Secure the inertial measurement unit in the center of the chassis and arrange the vibrating tachters in a regular octagon with a radius of 10cm, centered 8cm anterior of the center of the chassis, so that they will lie under the seat of an average sized person. Then connect the microcontroller to a computer, and open the software user interface. To conduct the balance experiments, recruit consenting participants who are free of neurological and musculoskeletal disorders, and acute or chronic back pain, and record each participant's age, weight, and height.
Next, open the user interface. The compass graph shows the tilt angle of the device, plus half the tilt velocity of the device in the anteroposterior and mediolateral directions. Prior to each balance trial, instruct the participant to don noise-canceling headphones, fold their arms across their chest, maintain an upright posture as much as possible, and verbally cue when they are ready.
Use the dropdown menus in the trial parameter section of the user interface to label the current difficulty and eye condition, and click record to start the trial. For trials with eyes open, instruct the participant to focus on a fixed point straight ahead to help maintain balance. For trials with eyes closed, use a blindfold to ensure that the participant is completely deprived of visual feedback.
Perform 20 30 second seated balance trials in series, taking breaks as warranted to avoid fatigue, and stopping at any time if necessary. An algorithm will compute which anteroposterior and mediolateral feedback thresholds to use and display the thresholds in the Q3 column of the user interface. The vibrotactile feedback thresholds can be optimized to provide feedback cues on direction and timing that are tailored toward a given task or goal.
After four familiarization trials, copy the values in the Q3 column into the right column and click refresh to update the feedback thresholds shown on the compass graph based on the fourth familiarization trial. As the anteroposterior and mediolateral tilt angles are automatically stored in real time in a text file for analysis, analyze the anteroposterior and mediolateral signals to characterize the sitting performance for each of the experimental conditions. This table shows the postero-graphic measures derived from anteroposterior and mediolateral support surface tilts averaged for 144 balance trials, and performed by 12 participants under each experimental condition.
Observations of anteroposterior tilt were significantly different between the eye open and eye closed balance conditions for the root-mean-square, centroidal frequency, and frequency dispersion. Consistent with other reports, these postero-graphic measures can discriminate between balance tasks during trials in which the vibrotactile feedback system was active. The centroidal frequency of the anteroposterior tilt observations was significantly higher than during the control trials.
Consistent with other reports, this vibrotactile feedback protocol has a measurable effect on balance performance. All structural components have a corresponding solid model and drawing that are available for download and can be used to replicate the construction process. The procedure can be used to test hypotheses regarding the fundamental nature of dynamic upright sitting and the effectiveness of vibrotactile feedback as a balance training technique.
This research provides a critical foundation for future work on clinical assessment and training tools for populations with impaired seated balance to improve their quality of life. The power tools used to construct this device may cause bodily harm;please follow all safety protocols.
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Overview
A novel sitting platform has been developed to passively destabilize sitting posture, aiding in balance assessment and rehabilitation. The device utilizes an inertial measurement unit for motion tracking and provides feedback through vibrations.
Key Study Components
Area of Science
- Neuroscience
- Rehabilitation
- Balance assessment
Background
- Seated instability can affect functional independence.
- It may lead to secondary health complications.
- Existing balance tools are combined into a single device.
- The device is designed for clinical use and accessibility.
Purpose of Study
- To assess and improve balance during sitting.
- To provide training techniques for individuals with muscular impairments.
- To investigate balance control mechanisms.
Methods Used
- Development of a portable sitting platform.
- Use of an inertial measurement unit for motion recording.
- Vibrating elements for performance feedback.
- Application in rehabilitation and training paradigms.
Main Results
- The device effectively challenges and assesses seated balance.
- It provides valuable feedback to users.
- Potential to enhance rehabilitation outcomes.
- Accessible for clinical applications.
Conclusions
- The sitting platform is a promising tool for balance assessment.
- It can aid in the rehabilitation of individuals with balance issues.
- Further research may optimize sensory feedback methods.
Frequently Asked Questions
Executive Industry Relevance
This protocol addresses a critical gap in preclinical and translational research by providing a portable, quantifiable system to assess and train seated balance—a functional endpoint relevant to neurological, musculoskeletal, and vestibular disorders. By integrating real-time motion tracking with closed-loop vibrotactile feedback, the device enables mechanistic de-risking of sensorimotor interventions prior to costly in vivo studies. Its adaptability supports early-stage target validation and phenotypic screening in disease-relevant models of postural control.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Scientific Value: Enables interrogation of therapeutic hypotheses related to sensorimotor integration and postural control pathways.
- Operational Value: Provides quantitative, reproducible posturographic outputs (e.g., root-mean-square tilt, centroidal frequency) to objectively measure target engagement.
- Predictive Value: Supports biological de-risking by quantifying how genetic or pharmacological manipulations affect balance performance under controlled sensory conditions.
Screening & Assay Development
- Assay Readiness: Generates standardized, real-time anteroposterior and mediolateral tilt data suitable for high-content screening of compounds affecting vestibular or cerebellar function.
- Quantitative Output: Delivers continuous motion metrics that enable dose-response analysis and threshold-based feedback optimization.
- Scalability: Portable design allows deployment across multiple sites for cross-laboratory reproducibility in target validation campaigns.
Translational & Preclinical Research
- Disease Relevance: Models sitting-related balance deficits seen in Parkinson’s, MS, TBI, and muscular dystrophy, supporting preclinical continuity.
- Mechanistic De-risking: Isolates the contribution of vibrotactile feedback to motor learning, enabling prioritization of neuromodulation targets with higher predictive confidence.
- Translational Biomarker Alignment: Posturographic measures serve as functional biomarkers correlating with clinical balance scales, aiding go/no-go decisions.
Pipeline & Workflow Integration
The device fits within the discovery-to-preclinical continuum, supporting hypothesis testing in early discovery, assay standardization in screening, and functional validation in translational research.
- Discovery Biology: Facilitates pathway clarification by isolating the effects of sensory feedback on motor output during perturbed sitting.
- Screening: Enables assay readiness through standardized, quantifiable tilt measurements that detect subtle changes in postural stability.
- Analytics: Provides real-time motion data and derived metrics (e.g., frequency dispersion) for statistical comparison across experimental conditions.
- Translational Research: Bridges discovery and preclinical work by validating balance improvements in a disease-relevant, ecologically relevant sitting paradigm.
- Enterprise Reuse: Reusable platform design supports longitudinal studies and cross-functional teams in neuroscience and rehabilitation research.
Operational & Enterprise Impact
- Scientific Value: Increases predictive confidence in target validation by reducing ambiguity in sensorimotor mechanism interpretation.
- Operational Value: Ensures reproducibility through standardized feedback thresholds and motion tracking protocols.
- Strategic Value: Improves go/no-go decisions by providing objective, quantifiable balance outcomes prior to animal testing.
- Portfolio Impact: Enables risk-adjusted prioritization of neuromodulation or rehabilitative candidates based on functional sitting performance.
Implementation Considerations
- Requires expertise in biomechanics, neuroscience, or rehabilitation engineering for setup and data interpretation.
- Depends on inertial measurement units, microcontrollers, and vibratory actuators for closed-loop feedback functionality.
- Necessitates cross-team standardization of feedback thresholds and trial parameters for multi-site reproducibility.
- Adaptation across model systems may require scaling of platform dimensions and feedback intensity.
- Practical limitations include dependency on user compliance with posture instructions and environmental vibration interference.
