The authors acknowledge the design efforts of the undergraduate students Animesh Singh Kumawat, Kshitij Agarwal, Quinn Boser, Benjamin Cheung, Caroline Collins, Sarah Lojczyc, Derek Schlenker, Katherine Schoepp, and Arthur Zielinski.&#160;This study was partially funded through a Discovery Grant from the Natural Sciences and Engineering Research Council of Canada (RGPIN-2014-04666).

All methods described here have been approved by the Health Research Ethics Board of the University of Alberta.
1. Construction and Assembly of Structural Components
<ol>
	<li>Construct an attachment interface for interchangeable hemispherical bases: weld a base nut to a steel weld plate.&#160;</li>
	<li>Use a computer numerical controlled (CNC) milling machine to construct a cylindrical chassis, lid, and base from polyethylene as shown in Figure 1. Bolt the base plate to the base and the base to the chassis. 
	NOTE: The mill features for attachment of bolts and other parts are according to the drawing files and 3D solid model files provided (see Supplementary Files 1 and 2). All structural components have a corresponding solid model and drawing that are available for download and can be used to replicate the construction process.</li>
	<li>Use a milling machine to construct a cylindrical polyvinyl chloride sleeve that fits onto a threaded rod, as shown in Figure 1. Make the sleeve 37 mm long, with an outer diameter of 32 mm.</li>
	<li>Weld steel flanges to each side of a steel hitch, as shown in Figure 1. Bolt the hitch to the front of the base.</li>
	<li>Use a CNC turning machine to construct 5 identical cylinders from polyethylene, each with a height of 63 mm and a diameter of 152 mm. In the center of the top surface of each cylinder, cut a 32 mm hole to a depth of 38 mm so that it fits the cylindrical sleeve (see Step 1.3. above) with some interference.&#160;</li>
	<li>On the bottom surface of each cylinder, use a CNC turning machine to cut a uniformly curved base with a unique radius of curvature for each of the 5 cylinders, maintaining the overall height of 63 mm, as shown in Figure 2.&#160; 
	NOTE: The radius of curvature and height of the base determine the stability of the device. The suggested radii of curvature for this height are between 110 mm (very unstable) and 250 mm (slightly unstable), as shown in Table 1.</li>
	<li>Construct a leg support attachment as shown in Figure 3, by first welding a 70 mm steel hitch insert perpendicularly to one end of a 575 mm steel extrusion. At the other end, clamp a 300 mm cylindrical steel footrest to the extrusion.&#160; 
	NOTE: For detailed part dimensions, see Supplementary File 1 (drawings) and Supplementary File 2 (3D solid models).</li>
	<li>Use a bandsaw to cut a rectangular steel bar (29 mm by 100 mm) to a length of approximately 160 mm so that it weighs 3.6 kg. Insert the steel bar at the back of the chassis to counterbalance the leg support attachment, as shown in Figure 1.</li>
	<li>Assemble the device as shown in Figure 4. Connect the leg support by inserting clevis pins through the hitch and hitch insert. Adjust the location of the clamp to the desired foot rest height. Thread the rod into the base stud such that approximately 35 mm of the rod protrudes from the base.&#160; Insert the protruding rod into the desired curved base.&#160;</li>
	<li>Apply grip tape or another suitable upholstery to the lid. Put on the lid.&#160;</li>
</ol>
2. Instrumenting the Device
<ol>
	<li>Acquire a microcontroller (see the Table of Materials), an inertial measurement unit and eight vibrating tactors. Connect the inertial measurement unit and vibrating tactors to the microcontroller.</li>
	<li>Program the microcontroller such that it reads antero-posterior (AP) and medio-lateral (ML) tilt angles from the inertial measurement unit and turns the vibrating tactors on or off based on the tilt angles. See Supplementary File 3 (exemplary microcontroller script) and Step 2.2.1. 
	NOTE: Inertial measurement units that utilize accelerometers and gyroscopes are prone to error. Perform a positional calibration of the sensors: rest the device on a level surface and use this position as a baseline for all following measurements. Use a motion capture system or similar approach to validate the tilt angle measurements and ensure that they are sufficiently accurate throughout the expected range of use (spatial and temporal). Ensure the vibrating tactors operate at a frequency of no more than 200 Hz, so as to induce a one-to-one response of sensory receptors in human skin or muscle9.
	<ol>
		<li>Upload the microcontroller script that generates vibrotactile cues based on a feedback control signal that represents a weighted sum of AP (or ML) tilt angle and velocity. 
		NOTE: The computer activates three tactors closest to the left, right, front, or back of the surface when the control signal exceeds a threshold in that direction; or five tactors if an AP and ML threshold are surpassed simultaneously; none of the tactors are active when the control signal is below the threshold in both directions (i.e., in the no-feedback zone).</li>
	</ol>
	</li>
	<li>Secure the inertial measurement unit in the center of the chassis. Arrange the vibrating tactors on a regular octagon with a radius of 10 cm, centered 8 cm anterior of the center of the chassis so that they will lie under the seat of an average-sized person10. A photograph of one potential arrangement is shown in Figure 4. 
	NOTE: If the vibrating tactors are not powerful enough to vibrate the user, improve the interface between tactor and skin by cutting holes into the lid and fixating the vibrators to rest flush with the surface. If the method used to secure the vibrators in place causes dampening of the vibration, consider using a two-part mounting enclosure with a loose-fit locating pin, as shown in Figure 5.</li>
	<li>Connect the microcontroller to a laptop or desktop computer via a universal serial bus (USB) or other suitable communication method. Open the user interface, shown in Figure 6. 
	NOTE: Alternatively, connect the microcontroller to a battery or other power source. This improves the portability of the device, but precludes a user interface.</li>
</ol>
3. Exemplary Assessment and Training Protocol
<ol>
	<li>Recruit consenting participants who are free of neurological or musculoskeletal disorders and acute or chronic back pain. Record each participant&#8217;s age, weight, and height. Then, for each participant, carry out the following procedure.</li>
	<li>Open the user interface (Figure 6). The compass graph shows the device&#8217;s tilt angle plus half its tilt velocity in the AP direction (vertical axis) and ML direction (horizontal axis).</li>
	<li>Prior to each balance trial, instruct the participant to don noise-cancelling headphones, fold his or her arms across the chest, maintain an upright posture as much as possible, and verbally cue the experimenter of being ready.</li>
	<li>Perform twenty 30 second seated balance trials in series11, taking breaks as warranted to avoid fatigue, stopping at any time if necessary.
	<ol>
		<li>Sequence the trials as follows (example only): randomly select one of two &#8220;base stability level/eye condition&#8221; combinations, hereafter called balance conditions (more difficult base and eyes open; or less difficult base and eyes closed)12. Perform four trials of the first balance condition to familiarize the participant with the task and to identify appropriate control signal thresholds for the vibrating tactors in the seat (see Step 3.4.5 below). 
		NOTE: It is more difficult to maintain balance on a base with a small radius of curvature than on a base with a large radius of curvature (Table 1 shows the relative stability of all five interchangeable bases). Four trials have been found to be sufficient to achieve a stable performance of the balance task2.</li>
		<li>Randomly select three of the next six trials to be control trials: switch the vibrating tactors off for the duration of these trials. To turn the vibrational feedback on or off, toggle the Feedback slider to the desired setting in the user interface. Repeat this sequence of ten trials for the second balance condition.</li>
		<li>Label the current difficulty and eye condition by selecting from the drop-down menus in the Trial Parameters section of the user interface. Click Record to start the trial. 
		NOTE: The participants&#8217; safety is paramount. The experimenter should supervise all balance activities and be prepared to assist in the event of balance loss. Clear the area of any potential hazards and be aware of local emergency protocols.</li>
		<li>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. 
		NOTE: For balance paradigms where the movement of the feet should be restricted, attach the foot support and insert the counterbalance beneath the lid.</li>
		<li>An algorithm computes which AP and ML feedback thresholds to use and displays them in the Q3 column of the user interface. After four familiarization trials, copy the values shown in the Q3 column into the Write Column, and then click Refresh to update the feedback thresholds shown on the compass graph (pink) based on the fourth familiarization trial. 
		NOTE: The computed threshold values displayed in the Q3 column of the interface are equal to the third quartile for each tilt direction (AP, ML) during the previous trial. This feedback scheme is based on the notion that balance function is improved when feedback is optimized for each individual13,14, while providing too much feedback may detriment learning15. Once the two threshold values have been selected for a given individual, they can be kept constant for that individual to be able to assess improvements over time or with an intervention.</li>
	</ol>
	</li>
	<li>As the AP and ML tilt angles are automatically stored, in real-time, in a text file for analysis, analyze the AP and ML signals to characterize sitting performance for each of the experimental conditions.
	<ol>
		<li>In time domain, calculate the following posturographic measures from each time series8: root-mean-square (a measure of the variance of the motion) and the mean velocity (a measure of the average angular speed of the motion).</li>
		<li>In frequency domain, calculate the following posturographic measures from each time series8: centroidal frequency (a measure of the motion&#8217;s overall frequency) and frequency dispersion (a measure of the variance in the motion&#8217;s frequency)8.</li>
	</ol>
	</li>
	<li>Use a linear mixed model to estimate and characterize the effects of two fixed-effects factors, (1) the balance condition (stability level and eye condition combined) and (2) vibrotactile feedback, on each of the posturographic measures (dependent variables), considering the correlation of repeated measurements from each participant16 (one random-effects factor).
	<ol>
		<li>Test for significance of the fixed effects by computing the ratio of the variance between the group means to the variance of the residuals, and comparing the result to an F-distribution.</li>
	</ol>
	</li>
</ol>

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The authors have nothing to disclose.

Methods for constructing a portable, instrumented, sitting device are presented. The device is portable and durable, building on previous studies of wobble chairs2,4 and vibrational feedback5,6,7 to make the benefits of these tools more powerful and accessible. Follow the assembly protocol in reverse to prepare the device for transportation or storage. The difficulty of ...

Upright sitting is a prerequisite for other human sensorimotor functions, including skilled movements (e.g., typing) and perturbed balance tasks (e.g., riding on a train). To rehabilitate and improve sitting and related functions, modern balance training techniques are used: unstable surfaces perturb sitting1,2 and motion tracking quantifies balance proficiency3,4. Balance training outcomes improve when vibration is delivered to the body using patterns that match performance5. Such sensory feedback is evidently effective as a rehabilitation and training method; yet, current sensory feedback methods are geared towards standing balance and require laboratory-based equipment6,7.
The purpose of the work presented here is to build a portable device that can be sat upon and passively destabilized to various degrees while built-in instruments record its position and deliver vibrational feedback to the sitting surface. This combination of tools integrates previous work on wobble chairs2,4 and vibrational feedback5,6,7, making the benefits of these tools more powerful and accessible. Also presented are a procedure to train upright sitting and an analysis of the quantitative outcomes, following the established literature on posturographic measures8. These methods are appropriate for studying the effects of sitting balance exercise with an unstable surface when combined with vibrational feedback. Anticipated applications include sports training, general improvement of motor coordination, assessment of balance proficiency, and rehabilitation following skeletal, muscular, or neurological injury.

<table><tbody><tr><td>&lt;strong&gt;&lt;em&gt;Chassis&lt;/em&gt;&lt;/strong&gt;</td><td>McMaster-Carr</td><td>8657K421</td><td>Moisture-Resistant LDPE Polyethylene Sheet 1-1/2&quot; Thick, 24&quot; X 24&quot;</td></tr><tr><td>&lt;strong&gt;&lt;em&gt;Lid&lt;/em&gt;&lt;/strong&gt;</td><td>McMaster-Carr</td><td>8657K414</td><td>Moisture-Resistant LDPE Polyethylene Sheet 1/4&quot; Thick, 24&quot; X 24&quot;</td></tr><tr><td>&lt;strong&gt;&lt;em&gt;Base&lt;/em&gt;&lt;/strong&gt;</td><td>McMaster-Carr</td><td>8657K414</td><td>Moisture-Resistant LDPE Polyethylene Sheet 1/4&quot; Thick, 24&quot; X 24&quot;</td></tr><tr><td>&lt;strong&gt;&lt;em&gt;Grip-Tape&lt;/em&gt;&lt;/strong&gt;</td><td>McMaster-Carr</td><td>6243T471</td><td>Nonabrasive Antislip Tape, Textured, 6&quot; Wide Strip, 2&#039; Long, Black</td></tr><tr><td>&lt;strong&gt;&lt;em&gt;Base Nut&lt;/em&gt;&lt;/strong&gt;</td><td>McMaster-Carr</td><td>90596A039</td><td>Steel Round-Base Weld Nut, 5/8&quot;-11 Thread Size</td></tr><tr><td>&lt;strong&gt;&lt;em&gt;Weld Plate&lt;/em&gt;&lt;/strong&gt;</td><td>McMaster-Carr</td><td>1388K142</td><td>Low-Carbon Steel Sheet 1/16&quot; Thick, 3&quot; X 3&quot;, Ground Finish</td></tr><tr><td>&lt;strong&gt;&lt;em&gt;Threaded Rod&lt;/em&gt;&lt;/strong&gt;</td><td>McMaster-Carr</td><td>90322A170</td><td>3&quot; 5/16&quot;-18 Medium-Strength Alloy Steel Threaded Stud</td></tr><tr><td>&lt;strong&gt;&lt;em&gt;Sleeve&lt;/em&gt;&lt;/strong&gt;</td><td>McMaster-Carr</td><td>8745K19</td><td>Chemical-Resistant PVC (Type I) Rod 1-1/4&quot; Diameter</td></tr><tr><td>&lt;strong&gt;&lt;em&gt;Square Flange&lt;/em&gt;&lt;/strong&gt;</td><td>McMaster-Carr</td><td>8910K395</td><td>Low Carbon Steel Bar, 1/8&quot; Thick, 1&quot; Wide</td></tr><tr><td>&lt;strong&gt;&lt;em&gt;Hitch&lt;/em&gt;&lt;/strong&gt;</td><td>McMaster-Carr</td><td>4931T123</td><td>Bolt-Together Framing Heavy-Duty Steel, 1-1/2&quot; Square</td></tr><tr><td>&lt;strong&gt;&lt;em&gt;Curved Base&lt;/em&gt;&lt;/strong&gt;</td><td>McMaster-Carr</td><td>8745K48</td><td>PVC Rod, 6&quot; Diameter</td></tr><tr><td>&lt;strong&gt;&lt;em&gt;Hitch Insert&lt;/em&gt;&lt;/strong&gt;</td><td>McMaster-Carr</td><td>6535K313</td><td>Bolt-Together Framing Heavy-Duty Steel, 1&quot; Square</td></tr><tr><td>&lt;strong&gt;&lt;em&gt;Extrusion&lt;/em&gt;&lt;/strong&gt;</td><td>McMaster-Carr</td><td>6545K7</td><td>1045 Cold Drawn Steel Square Bar Stock, 1&#039; X 1&quot; Wide, Unpolished</td></tr><tr><td>&lt;strong&gt;&lt;em&gt;Clamp&lt;/em&gt;&lt;/strong&gt;</td><td>Vlier</td><td>TH103A</td><td>Adjustable Torque Knob</td></tr><tr><td>&lt;strong&gt;&lt;em&gt;Footrest&lt;/em&gt;&lt;/strong&gt;</td><td>McMaster-Carr</td><td>6582K431</td><td>4130 Steel Tubing, 1&quot; X 1&quot; Wide, 0.065&quot; Wall Thickness, Unpolished Mill Finish</td></tr><tr><td>&lt;strong&gt;&lt;em&gt;Counterwieght&lt;/em&gt;&lt;/strong&gt;</td><td>McMaster-Carr</td><td>8910K67</td><td>Low-Carbon Steel Rectangular Bar 1-1/8&quot; Thick, 4&quot; Width</td></tr><tr><td>&lt;strong&gt;&lt;em&gt;Clevis Pin&lt;/em&gt;&lt;/strong&gt;</td><td>McMaster-Carr</td><td>97245A616</td><td>Zinc-Plated Steel Clevis Pin with Hairpin Cotter Pin, 3/16&quot; Diameter, 1-9/16&quot; Usable Length</td></tr><tr><td>&lt;strong&gt;&lt;em&gt;Microprocessor&lt;/em&gt;&lt;/strong&gt;</td><td>Arduino</td><td>MEGA 2560</td><td>Microcontroller board with 54 digital I/O pins and USB connection</td></tr><tr><td>&lt;strong&gt;&lt;em&gt;Inertial Measurement Unit&lt;/em&gt;&lt;/strong&gt;</td><td>x-io Technologies Ltd.</td><td>x-IMU</td><td>Inertial Measurement Unit and Attitude Heading Reference System with enclosure</td></tr><tr><td>&lt;strong&gt;&lt;em&gt;Vibrating Tactor&lt;/em&gt;&lt;/strong&gt;</td><td>Precision Microdrives</td><td>DEV-11008</td><td>Lilypad Vibe Board, available from SparkFun Electronics</td></tr></tbody></table>

a vibrotactile feedback device for seated balance assessment and training

Postural perturbations, motion tracking, and sensory feedback are modern techniques used to challenge, assess, and train upright sitting, respectively. The goal of the developed protocol is to construct and operate a sitting platform that can be passively destabilized while an inertial measurement unit quantifies its motion and vibrating elements deliver tactile feedback to the user. Interchangeable seat attachments alter the stability level of the device to safely challenge sitting balance. A built-in microcontroller allows fine-tuning of the feedback parameters to augment sensory function. Posturographic measures, typical of balance assessment protocols, summarize the motion signals acquired during timed balance trials. No dynamic sitting protocol to date provides variable challenge, quantification, and sensory feedback free of laboratory constraints. Our results demonstrate that non-disabled users of the device exhibit significant changes in posturographic measures when balance difficulty is altered or vibrational feedback provided. The portable, versatile device has potential applications in rehabilitation (following skeletal, muscular, or neurological injury), training (for sports or spatial awareness), entertainment (via virtual or augmented reality), and research (of sitting-related disorders).

Table 2 shows, for each experimental condition, the posturographic measures derived from observations of the AP and ML support surface tilts, averaged over 144 balance trials performed by 12 participants (2 x 2 x 3 trials per participant).
Effect of Changing the Balance Condition: The base condition was chosen to be dependent on the eye condition (i.e., when the eyes were closed, the ba...

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A Vibrotactile Feedback Device for Seated Balance Assessment and Training

A sitting platform has been developed and assembled that passively destabilizes sitting posture in humans. During the user&#39;s stabilizing task, an inertial measurement unit records the device&#39;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.

Postural perturbations, motion tracking, and sensory feedback are modern techniques used to challenge, assess, and train upright sitting, respectively. ...

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Universidad de Cartagena UDEC

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JoVE Journal

Behavior

6.3K Views.  University of Alberta. 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.

Video: A Vibrotactile Feedback Device for Seated Balance Assessment and Training

Computerized Dynamic Posturography for Postural Control Assessment in Patients with Intermittent Claudication

Computerized dynamic posturography with the EquiTest is an objective technique for measuring postural strategies under challenging static and dynamic conditions. As part of a diagnostic assessment, the early detection of postural deficits is important so that appropriate and targeted interventions can be prescribed. The Sensory Organization Test (SOT) on the EquiTest determines an individual&#39;s use of the sensory systems (somatosensory, visual, and vestibular) that are responsible for postural control. Somatosensory and visual input are altered by the calibrated sway-referenced support surface and visual surround, which move in the anterior-posterior direction in response to the individual&#39;s postural sway. This creates a conflicting sensory experience. The Motor Control Test (MCT) challenges postural control by creating unexpected postural disturbances in the form of backwards and forwards translations. The translations are graded in magnitude and the time to recover from the perturbation is computed.
Intermittent claudication, the most common symptom of peripheral arterial disease, is characterized by a cramping pain in the lower limbs and caused by muscle ischemia secondary to reduced blood flow to working muscles during physical exertion. Claudicants often display poor balance, making them susceptible to falls and activity avoidance. The Ankle Brachial Pressure Index (ABPI) is a noninvasive method for indicating the presence of peripheral arterial disease and intermittent claudication, a common symptom in the lower extremities. ABPI is measured as the highest systolic pressure from either the dorsalis pedis or posterior tibial artery divided by the highest brachial artery systolic pressure from either arm. This paper will focus on the use of computerized dynamic posturography in the assessment of balance in claudicants.

Individuals with intermittent claudication exhibit poor balance compared to healthy controls. Computerized dynamic posturography is an objective method for measuring an individual's postural responses to balance disturbances. This provides an objective reflection of the person&#x2019;s ability to respond to situations under which sensory stimuli are altered and unexpected perturbations occur.

Computerized dynamic posturography with the EquiTest is an objective technique for measuring postural strategies under challenging static and dynamic ...

Medicine

A Modified Lean and Release Technique to Emphasize Response Inhibition and Action Selection in Reactive Balance

Assessment of reactive balance traditionally imposes some type of perturbation to upright stance or gait followed by measurement of the resultant corrective behavior. These measures include muscle responses, limb movements, ground reaction forces, and even direct neurophysiological measures such as electroencephalography. Using this approach, researchers and clinicians can infer some basic principles regarding how the nervous system controls balance to avoid a fall. One limitation with the way in which these assessments are currently used is that they heavily emphasize reflexive actions without any need to revise automatic postural reactions. Such an exclusive focus on these highly stereotypical reactions would fail to adequately address how we can modify these reactions should the need arise (e.g., avoiding an obstacle with a recovery step). This would appear to be a glaring omission when one considers the enormous complexity of the environments we face daily. Overall, the status quo when evaluating the neural control of balance fails to truly expose how higher brain resources contribute to preventing falls in complex settings. The present protocol offers a way to require suppression of automatic, but inappropriate corrective balance reactions, and force a selection among alternative action choices to successfully recover balance following postural perturbation.

Here we offer a protocol that allows the user to selectively change affordances and/or constraints on movements that are relevant for recovering balance after postural perturbation.

Assessment of reactive balance traditionally imposes some type of perturbation to upright stance or gait followed by measurement of the resultant ...

Quantitative Static and Dynamic Assessment of Balance Control in Stroke Patients

In patients with stroke, damage to the central nervous system (CNS) can affect the postural stability and increase the risk of falling. Therefore, accurately assessing the balance is important to understand the type, extent, and causes of balance deficit, and to identify individualized interventions. Clinical assessment methods for balance function can be broadly divided into observation, scale assessment, and balance instrument testing. Here, a clinical protocol is presented for static and dynamic balance assessment in stroke patients, which includes three semiquantitative balance function scale assessments (i.e., Berg Balance Scale, Timed Up and Go Test, and Fugl-Meyer Assessment) and three quantitative instrumental balance evaluation (i.e., Stability Assessment Module, Proprioceptive Assessment Module, and Limit of Stability Module). It is recommended that clinicians consider the use of both classic clinical balance scales and instrumental balance measurements when assessing stroke patients to improve the accuracy of assessments, leading to a better individualized treatment plan.

Presented here is a quantitative, clinical balance assessment method suitable for stroke patients with balance disorders.

In patients with stroke, damage to the central nervous system (CNS) can affect the postural stability and increase the risk of falling. Therefore, ...

Training Persons with Spinal Cord Injury to Ambulate Using a Powered Exoskeleton

Powered exoskeletons have become available for overground ambulation in persons with paralyses due to spinal cord injury (SCI) who have intact upper extremity function and are able to maintain upright balance using forearm crutches. To ambulate in an exoskeleton, the user must acquire the ability to maintain balance while standing, sitting and appropriate weight shifting with each step. This can be a challenging task for those with deficits in sensation and proprioception in their lower extremities. This manuscript describes screening criteria and a training program developed at the James J. Peters VA Medical Center, Bronx, NY to teach users the skills needed to utilize these devices in institutional, home or community environments. Before training can begin, potential users are screened for appropriate range of motion of the hip, knee and ankle joints. Persons with SCI are at an increased risk of sustaining lower extremity fractures, even with minimal strain or trauma, therefore a bone mineral density assessment is performed to reduce the risk of fracture. Also, as part of screening, a physical examination is performed in order to identify additional health-related contraindications. 
Once the person has successfully passed all screening requirements, they are cleared to begin the training program. The device is properly adjusted to fit the user. A series of static and dynamic balance tasks are taught and performed by the user before learning to walk. The person is taught to ambulate in various environments ranging from indoor level surfaces to outdoors over uneven or changing surfaces. Once skilled enough to be a candidate for home use with the exoskeleton, the user is then required to designate a companion-walker who will train alongside them. Together, the pair must demonstrate the ability to perform various advanced tasks in order to be permitted to use the exoskeleton in their home/community environment.

Training a person with paralysis to ambulate using a powered exoskeleton may present challenges. The goals are to present the candidate selection criteria and the training procedures for exoskeletal-assisted walking and other mobility skills that can be progressed as the participant's skill level improves.

Powered exoskeletons have become available for overground ambulation in persons with paralyses due to spinal cord injury (SCI) who have intact upper ...

Bioengineering

A Method for Evaluating Timeliness and Accuracy of Volitional Motor Responses to Vibrotactile Stimuli

Artificial sensory feedback (ASF) systems can be used to compensate for lost proprioception in individuals with lower-limb impairments. Effective design of these ASF systems requires an in-depth understanding of how the parameters of specific feedback mechanism affect user perception and reaction to stimuli. This article presents a method for applying vibrotactile stimuli to human participants and measuring their response. Rotating mass vibratory motors are placed at pre-defined locations on the participant's thigh, and controlled through custom hardware and software. The speed and accuracy of participants' volitional responses to vibrotactile stimuli are measured for researcher-specified combinations of motor placement and vibration frequency. While the protocol described here uses push-buttons to collect a simple binary response to the vibrotactile stimuli, the technique can be extended to other response mechanisms using inertial measurement units or pressure sensors to measure joint angle and weight bearing ratios, respectively. Similarly, the application of vibrotactile stimuli can be explored for body segments other than the thigh.

This article describes a technique for applying vibrotactile stimuli to the thigh of a human participant, and measuring the accuracy and reaction time of the participant&#39;s volitional response for various combinations of stimulation location and frequency.

Artificial sensory feedback (ASF) systems can be used to compensate for lost proprioception in individuals with lower-limb impairments.  Effective design ...

Implementing Vestibular Disorder Screening Tests

Screening People on Standing Balance with Romberg Testing and Walking Balance with Tandem Walking

The goal of this protocol is to inform readers about the exact procedures to use to perform two screening tests for vestibular disorders: tandem walking (TW) with eyes closed, also known as heel-toe walking, and the Clinical Test of Sensory Integration and Balance (CTSIB), which is also known as the modified Romberg. The study describes the steps for performing each test and each of the three CTSIB subtests so that the reader will be able to replicate the test conditions for use in the clinic, in the clinical laboratory, or in any other situation needing valid and reliable screening for balance skill which might be affected by changes in vestibular system function. The procedures detailed here can be easily administered and take less than 1 min per trial. References to published papers with normative data are provided. The representative results section includes examples of data collected with these screening tests.

Author Spotlight: Developing Low-Tech Balance Assessment Methods for Broad-Spectrum Healthcare Applications 

This article describes procedures for screening people for standing and walking balance impairments using two normed, rapid, low-tech balance tests.

The goal of this protocol is to inform readers about the exact procedures to use to perform two screening tests for vestibular disorders: tandem walking ...

Quantifying Arms and Legs Contributions during Repetitive Electrically-Assisted Sit-To-Stand Exercise in Paraplegics: A Pilot Study

Execution of Sit-to-Stand (SitTS) in incomplete spinal cord injury (SCI) patients involves motor function in both upper and lower extremities. The use of arm support, in particular, is a significant assistive factor while executing SitTS movement in SCI population. In addition, the application of functional electrical stimulation (FES) onto quadriceps and gluteus maximus muscles is one of the prescribed management for incomplete SCI to improve muscle action for simple lower limb movements. However, the relative contribution of upper and lower extremities during SitTS has not been thoroughly investigated. Two motor incomplete SCI paraplegics performed repetitive SitTS to fatigue exercise challenge. Their performance was investigated as a mixed-method case-control study comparing SitTS with and without the assistance of FES. Three sets of SitTS tests were completed with 5-min resting period allocated in between sets, with mechanomyography (MMG) sensors attached over the rectus femoris muscles bilaterally. The exercise was separated into 2 sessions; Day 1 for voluntary SitTS and Day 2 for FES-assisted SitTS. Questionnaires were conducted after every session to gather the participants&#39; input about their repetitive SitTS experience. The analysis confirmed that a SitTS cycle could be divided into three phases; Phase 1 (Preparation to stand), Phase 2 (Seat-off), and Phase 3 (Initiation of hip extension), which contributed to 23% &#177; 7%, 16% &#177; 4% and 61% &#177; 6% of the SitTS cycle, respectively. The contribution of arms and legs during SitTS movement varied in different participants based on their legs&#39; Medical Research Council (MRC) muscle grade. In particular, the applied arm forces start to increase clearly when the leg forces start to decline during standing. This finding is supported by the significantly reduced MMG signal indicating leg muscle fatigue and their reported feeling of tiredness.

Arms contribution in Sit-To-Stand (SitTS) is determined by the legs' muscle condition. Several compensating strategies were discovered in efforts to achieve complete SitTS cycles. These findings triangulate the spinal cord injury (SCI) persons' biomechanical measures with their subjective feeling of load borne by both their limbs throughout the SitTS approaches.

Execution of Sit-to-Stand (SitTS) in incomplete spinal cord injury (SCI) patients involves motor function in both upper and lower extremities. The use of ...

Engineering

A Human-machine-interface Integrating Low-cost Sensors with a Neuromuscular Electrical Stimulation System for Post-stroke Balance Rehabilitation

A stroke is caused when an artery carrying blood from heart to an area in the brain bursts or a clot obstructs the blood flow to brain thereby preventing delivery of oxygen and nutrients. About half of the stroke survivors are left with some degree of disability. Innovative methodologies for restorative neurorehabilitation are urgently required to reduce long-term disability. The ability of the nervous system to reorganize its structure, function and connections as a response to intrinsic or extrinsic stimuli is called neuroplasticity. Neuroplasticity is involved in post-stroke functional disturbances, but also in rehabilitation. Beneficial neuroplastic changes may be facilitated with non-invasive electrotherapy, such as neuromuscular electrical stimulation (NMES) and sensory electrical stimulation (SES). NMES involves coordinated electrical stimulation of motor nerves and muscles to activate them with continuous short pulses of electrical current while SES involves stimulation of sensory nerves with electrical current resulting in sensations that vary from barely perceivable to highly unpleasant. Here, active cortical participation in rehabilitation procedures may be facilitated by driving the non-invasive electrotherapy with biosignals (electromyogram (EMG), electroencephalogram (EEG), electrooculogram (EOG)) that represent simultaneous active perception and volitional effort. To achieve this in a resource-poor setting, e.g., in low- and middle-income countries, we present a low-cost human-machine-interface (HMI) by leveraging recent advances in off-the-shelf video game sensor technology. In this paper, we discuss the open-source software interface that integrates low-cost off-the-shelf sensors for visual-auditory biofeedback with non-invasive electrotherapy to assist postural control during balance rehabilitation. We demonstrate the proof-of-concept on healthy volunteers.

A novel low-cost human-machine interface for interactive post-stroke balance rehabilitation system is presented in this article. The system integrates off-the-shelf low-cost sensors towards volitionally driven electrotherapy paradigm. The proof-of-concept software interface is demonstrated on healthy volunteers.

A stroke is caused when an artery carrying blood from heart to an area in the brain bursts or a clot obstructs the blood flow to brain thereby preventing ...

Neuroscience

Exergaming in Older People Living with HIV Improves Balance, Mobility and Ameliorates Some Aspects of Frailty

Approximately 1.2 million people in the United States live with HIV infection. Medical advancements have increased the life expectancy and this cohort is aging. HIV-positive individuals have a high incidence of frailty (~20%) characterized by depression and sedentary behavior. Exercise would be healthy, but due to the frail status of many HIV-positive individuals, conventional exercise is too taxing. The aim of this study was to evaluate the effectiveness and acceptability of a novel game-based training program (exergame) in ameliorating some aspects of frailty in HIV-infected individuals. Ten older people living with HIV were enrolled in an exergame intervention. Patients performed balance exercises such as weight shifting, ankle reaching, and obstacle crossing. Real-time visual/audio lower-extremity joint motion feedback was provided using wearable sensors to assist feedback and encourage subjects to accurately execute each exercise task. Patients trained twice a week for 45 min for 6 weeks. Changes in balance, gait, psychosocial parameters and quality of life parameters were assessed at the beginning, midterm and at conclusion of the training program. Ten patients completed the study and their results analyzed. The mean age was 57.2 &#177; 9.2 years. The participants showed a significant reduction in center of mass sway (78.2%, p = .045) during the semi-tandem balance stance with eyes closed and showed a significant increase in gait speed during a dual task motor-cognitive assessment (9.3%, p = .048) with an increase in stride velocity of over 0.1 m/sec. A significant reduction in reported pain occurred (43.5%, p = .041). Preliminary results of this exergame intervention show promise in improving balance and mobility while requiring older people living with HIV to be more active. The exergame can be continued at home and may have long term as well as short-term benefits for ameliorating frailty associated with HIV infection.

Persons infected with HIV are often frail, depressed and live a sedentary lifestyle for which conventional exercise is too taxing. Here, we present an exercise protocol that ameliorates aspects of frailty in HIV-infected persons. An exergame integrating cognitive control was developed using biosensors that measured balance, weight-shifting and obstacle crossing.

Approximately 1.2 million people in the United States live with HIV infection. Medical advancements have increased the life expectancy and this cohort is ...

Evaluating Postural Control and Lower-extremity Muscle Activation in Individuals with Chronic Ankle Instability

Computerized dynamic posturography (CDP) is an objective technique for the evaluation of postural stability under static and dynamic conditions and perturbation. CDP is based on the inverted pendulum model that traces the interrelationship between the center of pressure and the center of gravity. CDP can be used to analyze the proportions of vision, proprioception, and vestibular sensation to maintain postural stability. The following characters define chronic ankle instability (CAI): persistent ankle pain, swelling, the feeling of &#8220;giving way,&#8221; and self-reported disability. Postural stability and fibular muscle activation level in individuals with CAI decreased due to lateral ankle ligament complex injuries. Few studies have used CDP to explore the postural stability of individuals with CAI. Studies that investigate postural stability and related muscle activation by using synchronized CDP with surface electromyography are lacking. This CDP protocol includes a sensory organization test (SOT), a motor control test (MCT), and an adaption test (ADT), as well as tests that measure unilateral stance (US) and limit of stability (LOS). The surface electromyography system is synchronized with CDP to collect data on lower limb muscle activation during measurement. This protocol presents a novel approach for evaluating the coordination of the visual, somatosensory, and vestibular systems and related muscle activation to maintain postural stability. Moreover, it provides new insights into the neuromuscular control of individuals with CAI when coping with real complex environments.

Individuals with chronic ankle instability (CAI) exhibit postural control deficiency and delayed muscle activation of lower extremities. Computerized dynamic posturography combined with surface electromyography provides insights into the coordination of the visual, somatosensory, and vestibular systems with muscle activation regulation to maintain postural stability in individuals with CAI.

Computerized dynamic posturography (CDP) is an objective technique for the evaluation of postural stability under static and dynamic conditions and ...