We thank Angus Begg (The Bionics Institute) for his assistance in the video protocol. We acknowledge Dr. Sue Finch (Statistical Consulting Centre and Melbourne Statistical Consulting Platform, University of Melbourne) who provided statistical support. This work was supported by the funding through the National Health and Medical Research Council (1066565), the Victorian Lions Foundation, and The Victorian Government&#39;s Operational Infrastructure Support Program.

All methods described were reviewed and approved by the local human research ethics committee at Melbourne Health. Informed consent was obtained from the participant prior to the study.
1. Equipment setup
<ol>
	<li>Prepare the electromagnetic motion tracker with 3 miniature motion sensors as per the manufacturer&#39;s guidelines. Prior to data collection, ensure each sensor is sampled at a minimum 250 Hz, displacement is measured in millimeter units and rotations (pitch, roll, and yaw) are in degrees. Ensure that all internal filterings are disabled, and the position of the sensors set to reference a static origin (usually the electromagnetic transmitter).</li>
	<li>Affix a load cell (minimum tension range 100 N, S-type recommended) to the patient harness at shoulder-level using a rope with a minimum diameter of 10 mm. 
	NOTE: The harness system and rope are suitable for use in participants weighing up to 120 kg.</li>
	<li>Connect the load cell to data acquisition unit (A/D Converter).</li>
	<li>Connect the trigger output from the data acquisition unit into a trigger input of the motion tracker to ensure synchronized recording. Set data acquisition unit sampling rate to match the motion tracker and disable all filtering.</li>
	<li>Conduct the experiment in a quiet room to minimize distractions during the assessment. Allow enough space for participants to take several corrective steps to regain balance. 
	NOTE: Patients with Parkinson&#39;s disease and retropulsion are known to take 5-6 steps backward during the pull test.</li>
	<li>Place falls mat on the floor as a precautionary measure.</li>
	<li>Clean the harness, sensors, and wires with a hospital grade disinfectant wipe before testing each participant. 
	NOTE: Video recording (e.g., using a portable camera on a tripod) of the instrumented pull test procedure is recommended so that any irregularities during data processing can be referenced against the video data of a trial.</li>
</ol>
2. Participant selection and preparation
<ol>
	<li>Identify appropriate participants for study: participants can comprise a range of ages, disease conditions and severity where postural responses are of interest and balance assessment typically employs the clinical pull test. Ensure that participants can stand independently and generate a corrective balance response not requiring assistance to recover (i.e., up to Grade 1 postural instability according to the UPDRS).</li>
	<li>Exclude any persons with cardiovascular, vestibular, vision and musculoskeletal conditions (including persons requiring foot orthotics or splints), that may impair balance performance unless this is the subject of the investigation, those on contact precautions, and those on medication known to affect balance or attention (e.g., antidepressants, neuroleptics, benzodiazepines, antiepileptics, antiarrhythmics, and diuretics).</li>
	<li>Have the participant wear comfortable loose clothing on the day of the experiment and remove shoes prior to the pull test procedure.</li>
	<li>Assist the participant in putting on the customized trunk harness with the load cell. Click the buckles around the chest and waist. Ensure adjustment straps on the harness are tight but comfortable. Do not allow more than 50 mm of slack in the harness when pulling on the rope. In participants with known postural instability, ensure that an assistant is present when the harness is applied while the participant is standing.</li>
	<li>Attach motion sensors using medical tape to the sternal notch (at the level of the second and third thoracic vertebra), and on the feet at the right and left ankle malleolus. 
	NOTE: Apply the sensors on participants with known postural instability in sitting. All cables must be routed carefully to avoid trip hazards.</li>
	<li>Ask the participant to stand bare feet, in a comfortable stance (according to the participant&#39;s preferred base of support) along vertical and horizontal line markings on the floor. Note the participant&#39;s feet position. Ask the participant to also note their own feet position in order to revert to the same position after every pull. Monitor the participant&#39;s feet placement after every trial and ask the participant to return to the original feet position if any deviations are observed.</li>
	<li>Instruct the participant to focus on artwork 1.5 m ahead at the eye level with hands by their side to minimize distractions between pulls.</li>
</ol>
3. Instrumented pull test procedure
<ol>
	<li>Perform the instrumented pull test in accordance with the clinical pull test guidelines described by the UPDRS5.</li>
	<li>Explain the test procedure, and let the participant know that stepping is allowed to regain balance following the backward pull. Discourage anticipatory responses such as forward trunk flexion, stiffening in posture or knee flexion prior to the pull. Note these responses if they occur during the experiment.</li>
	<li>Prior to each pull, ensure the participant is attentive by asking the participant to focus on a picture hanging on the wall. Ensure the participant is standing upright, with eyes open, hands by their side, and their feet placed on the designated markers in a comfortable stance.</li>
	<li>Stand behind the participant. Apply a brisk pull of sufficient force to generate a trunk and step response via the rope and load cell held perpendicular to the shoulder level of the participant.</li>
	<li>After each pull ensure the participant returns to the original feet positioning. Reset the position back to designated markers on the floor and repeat 35 times. 
	NOTE: The number of trials can be varied according to the experimental design and clinical population.</li>
	<li>Allow participants a short rest of 2 min after every 10 trials or as required to reduce the effects of fatigue and ensure attention is focused on the task. Participants can choose to sit or stand. Request that participants refrain from talking in between pulls unless requesting a break or expressing discomfort during the procedure.</li>
	<li>As an additional safety precaution, ensure that the assessor and assistant are standing with their backs close to a wall while allowing enough room for the participant to take several steps backward. 
	NOTE: The assessor must always be prepared to catch the patient. An assistant is required for safety when participants with known postural instability are assessed.</li>
	<li>Detach sensors and assist the participant out of the harness following completion of the instrumented pull test procedure.</li>
</ol>
4. Signal processing
NOTE: Use a suitable data science platform such as MATLAB, R, or Python. Commands shown here are for MATLAB and example code is available as Supplementary File.
<ol>
	<li>Import data recorded during step 3.4 into a suitable data science platform: csvread().</li>
	<li>Align the motion tracker and load cell data using trigger signals and resample to a higher sampling rate: 1 kHz resample() function if required.</li>
	<li>High-pass filter all motion tracking and load cell data with a 0.05 Hz cut-off frequency to remove base-line drift: butter() and filtfilt().</li>
	<li>Double differentiate the trunk motion tracking displacement data to obtain trunk velocity and acceleration: diff().</li>
	<li>Using either the trigger signal or a peak-detection algorithm applied to the load cell data, slice recordings to obtain epochs of each individual pull test trial: findpeaks() function.</li>
	<li>Detect and reject trials with the anticipatory truncal movement. A forward trunk displacement immediately prior to the pull administration usually presents as a peak at least three standard deviations above the baseline mean of the trunk sensor: std() and mean().</li>
	<li>Determine postural reaction time as the difference between the onset of trunk displacement (3 standard deviations above baseline mean) following the pull and the turning point of the trunk velocity curve (indicating the beginning of trunk deceleration): differentiate, diff(), and use zero crossing detector, zcd().</li>
	<li>Determine the magnitude of the postural response as the peak deceleration of the trunk: min() or max().</li>
	<li>Calculate the step reaction time as the difference between the onset of truncal displacement (as per 4.7) to the initial movement of the stepping limb: 3 standard deviations above the baseline mean.</li>
	<li>Determine the step response magnitude by calculating the total displacement of the foot in millimeters (mm), from initial foot lift-off to contact of the stepping limb arresting backward retropulsion. Exclude steps less than 50 mm, as the change in the base of support is considered negligible24: min() or max().</li>
	<li>Calculate the peak pull force and rate of force development from the load cell: max() for pull; max() and diff() for rate of force. 
	NOTE: The peak pull force indicates the instantaneous maximum force delivered, whereas the force rate is the slope of the force versus time curve indicating how rapidly the force was generated.</li>
</ol>

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No conflicts of interest, financial or otherwise, are declared by the authors.

Here, we have demonstrated the protocol for instrumentation of the clinical pull test, taking a method widely used in clinical practice and yielding an objective measurement of postural responses in addition to the important aspect of the pull administration. Using semi-portable motion tracking, this method offers a means of measurement that is more accessible compared to conventional laboratory techniques28. Using this method, researchers can explore characteristics of postural responses to a top...

An erratum was issued for: <a href="https://www.jove.com/video/59309/an-instrumented-pull-test-to-characterize-postural-responses">An Instrumented Pull Test to Characterize Postural Responses</a>.&#160; Author&#160;affiliations were&#160;updated.
The affiliations for Joy Tan were updated from:
1. Department of Medical Bionics, The University of Melbourne&#160; 
2. Department of Neurology, The Royal Melbourne Hospital
to:
1.&#160;Department of Medical Bionics, The University of Melbourne&#160; 
2.&#160;Department of Neurology, The Royal Melbourne Hospital 
4. The Bionics Institute
The affiliations for Thushara&#160;Perera&#160;were updated from:
1. Department of Medical Bionics, The University of Melbourne&#160; 
3. Department of Neurology, Austin Hospital
to:
1.&#160;Department of Medical Bionics, The University of Melbourne&#160; 
4. The Bionics Institute

An erratum was issued for: <a href="https://www.jove.com/video/59309/an-instrumented-pull-test-to-characterize-postural-responses">An Instrumented Pull Test to Characterize Postural Responses</a>.&#160; The affiliation section&#160;was updated.

Erratum: An Instrumented Pull Test to Characterize Postural Responses

Postural reflexes act to maintain&#160;balance and upright stance in response to perturbations1. Impairment of these postural responses in disorders such as Parkinson&#39;s disease results in postural instability, and commonly leads to falls, reduced walking confidence and diminished quality of life2,3,4. In clinical practice, postural reflexes are typically assessed with the pull test, where an examiner briskly pulls the patient backward at the shoulders and visually grades the response5,6,7,8. Postural instability is usually scored using the Unified Parkinson&#39;s Disease Rating Scale (UPDRS) (0 - normal to 4 - severe), as published by the International Movement Disorder Society5. This method has been used extensively in the assessment of individuals with Parkinson&#39;s disease but suffers poor reliability and very limited scaling (score/4)6,7,9. Pull test scores often do not correlate with important clinical endpoints such as falls and the integer-based rating lacks sensitivity to detect fine postural changes10,11.
Laboratory-based objective measures offer precise information about the nature of balance response by quantifying kinetic (e.g., the center of pressure), kinematic (e.g., joint goniometry/limb displacement) and neurophysiological (e.g., muscle recruitment) endpoints12. These methods may identify abnormalities before postural instability is clinically evident and track changes over time, including responses to treatment13,14.
Tools for Quantifying Postural Instability
Conventional techniques of dynamic posturography commonly employ moving platforms. Resulting postural responses are quantified using a combination of posturography, electromyography (EMG), and accelerometry12,15,16. However, the bottom-up responses of platform perturbations - which evoke a response like slipping on a wet floor, are fundamentally different from the top-down postural responses of the clinical pull test - as may occur when being bumped in a crowd. Emerging evidence suggests truncal perturbations yield different postural characteristics to those of moving platforms17,18,19. Accordingly, others have attempted truncal perturbations in the laboratory using complex techniques including motors, pulleys, and pendulums15,20,21,22. Methods of measurement are often expensive and inaccessible and comprise of video-based motion capture that requires dedicated space in specialized laboratories20,21. Ideally, an objective method to characterize pull test responses should have excellent psychometric properties, be easy to administer, simple to operate, widely accessible, and portable. This is important to facilitate widespread adoption of the technique as an alternative assessment tool to assess postural responses within research and potentially, clinical settings.
The Instrumented Pull Test 
The aim of this protocol is to offer researchers a technique for objective assessment of postural responses to the pull test. A semi-portable and widely available electromagnetic motion capture system underpins the technique. The perturbation involves manual pulls that do not require specialized mechanical systems. This method has sufficient sensitivity to detect small differences in postural reaction times and response amplitudes; therefore, it is suited to capturing potential abnormalities rated from normal up to grade 1 postural instability according to the UPDRS (postural instability with unassisted balance recovery)5. This method may also be utilized to explore the effects of therapy on postural instability. The protocol described here is derived from that in Tan et al.23.

<table><tbody><tr><td>Analog to Digital Convertor &amp;amp; Software</td><td>CED</td><td>Micro 1401-3</td><td>Any suitable digital acquisition system can be used</td></tr><tr><td>Load Cell</td><td>Omegadyne</td><td>LCM201-100N</td><td></td></tr><tr><td>MATLAB Software</td><td>MathWorks Inc.</td><td>NA</td><td>Any data science platform can be used</td></tr><tr><td>Motion Sensor</td><td>Ascension</td><td>6DOF, type-800</td><td></td></tr><tr><td>Motion Tracker</td><td>Ascension&amp;nbsp;</td><td>3D Guidance trakSTAR</td><td>Mid-range transmitter</td></tr><tr><td>S&amp;amp;F Technical Harness and Belt</td><td>Lowepro</td><td>LP36282</td><td></td></tr></tbody></table>

an instrumented pull test to characterize postural responses

Impairment of postural reflexes, termed postural instability, is a common and disabling deficit in Parkinson's disease. To assess postural reflexes, clinicians typically employ the pull test to grade corrective responses to a backward perturbation at the shoulders. However, the pull test is prone to issues with reliability and scaling (score/4). Here, we present an instrumented version of the pull test to more precisely quantify postural responses. Akin to the clinical test, pulls are manually administered except pull force is also recorded. Displacements of the trunk and feet are captured by a semi-portable motion tracking system. Raw data represent distance traveled (in millimeter units), making subsequent interpretation and analysis intuitive. The instrumented pull test also detects variabilities influencing pull test administration, such as pull force, thereby identifying and quantifying potential confounds that can be accounted for by statistical techniques. The instrumented pull test could have application in studies seeking to capture early abnormalities in postural responses, track postural instability over time, and detect responses to therapy.

The instrumented pull test (Figure 1) was used to investigate trunk and step responses in a young, healthy cohort23. Thirty-five trials were presented serially, with an auditory stimulus delivered concurrently with each pull (Figure 2). The auditory stimulus was either 90 dB (normal) or 116 dB (loud). The loud stimulus has been demonstrated as sufficient to trigger StartReact effects, where pre-prepared re...

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An Instrumented Pull Test to Characterize Postural Responses

Impairment of postural reflexes, termed postural instability, is difficult to quantify. Clinical assessments such as the pull test suffer issues with reliability and scaling. Here, we present an instrumented version of the pull test to objectively characterize postural responses.

Impairment of postural reflexes, termed postural instability, is a common and disabling deficit in Parkinson's disease. To assess postural reflexes, ...

an-instrumented-pull-test-to-characterize-postural-responses

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Education

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Equilibrium of a Rigid Body

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10.7K Views.  The University of Melbourne. Het algemene doel van deze procedure is om posturale reacties nauwkeuriger te beoordelen met behulp van een geinstrumenteerde versie van de klinische pull-test. Dit wordt bereikt door gebruik te maken van een semi-draagbaar, motion-tracking systeem om posturale reacties op een handmatige achterwaartse pull vast te leggen. Breng eerst het harnas aan en bevestig sensoren op de romp en voeten.De volgende stap is om ervoor te zorgen dat de deelnemer staat in comfortabele houding langs lijn...

Video: An Instrumented Pull Test to Characterize Postural Responses

Sit-to-stand-and-walk from 120% Knee Height: A Novel Approach to Assess Dynamic Postural Control Independent of Lead-limb

Individuals with sensorimotor pathology e.g., stroke have difficulty executing the common task of rising from sitting and initiating gait (sit-to-walk: STW). Thus, in clinical rehabilitation separation of sit-to-stand and gait initiation - termed sit-to-stand-and-walk (STSW) - is usual. However, a standardized STSW protocol with a clearly defined analytical approach suitable for pathological assessment has yet to be defined.
Hence, a goal-orientated protocol is defined that is suitable for healthy and compromised individuals by requiring the rising phase to be initiated from 120% knee height with a wide base of support independent of lead limb. Optical capture of three-dimensional (3D) segmental movement trajectories, and force platforms to yield two-dimensional (2D) center-of-pressure (COP) trajectories permit tracking of the horizontal distance between COP and whole-body-center-of-mass (BCOM), the decrease of which increases positional stability but is proposed to represent poor dynamic postural control.
BCOM-COP distance is expressed with and without normalization to subjects&#39; leg length. Whilst COP-BCOM distances vary through STSW, normalized data at the key movement events of seat-off and initial toe-off (TO1) during steps 1 and 2 have low intra and inter subject variability in 5 repeated trials performed by 10 young healthy individuals. Thus, comparing COP-BCOM distance at key events during performance of an STSW paradigm between patients with upper motor neuron injury, or other compromised patient groups, and normative data in young healthy individuals is a novel methodology for evaluation of dynamic postural stability.

Here, we present a novel protocol to measure positional stability at key events during the sit-to-stand-to-walk using the center-of-pressure to the whole-body-center-of-mass distance. This was derived from the force platform and three-dimensional motion-capture technology. The paradigm is reliable and can be utilized for the assessment of neurologically compromised individuals.

Individuals with sensorimotor pathology e.g., stroke have difficulty executing the common task of rising from sitting and initiating gait (sit-to-walk: ...

Tilt Testing with Combined Lower Body Negative Pressure: a "Gold Standard" for Measuring Orthostatic Tolerance

Orthostatic tolerance (OT) refers to the ability to maintain cardiovascular stability when upright, against the hydrostatic effects of gravity, and hence to maintain cerebral perfusion and prevent syncope (fainting). Various techniques are available to assess OT and the effects of gravitational stress upon the circulation, typically by reproducing a presyncopal event (near-fainting episode) in a controlled laboratory environment. The time and/or degree of stress required to provoke this response provides the measure of OT. Any technique used to determine OT should: enable distinction between patients with orthostatic intolerance (of various causes) and asymptomatic control subjects; be highly reproducible, enabling evaluation of therapeutic interventions; avoid invasive procedures, which are known to impair OT1.
In the late 1980s head-upright tilt testing was first utilized for diagnosing syncope2. Since then it has been used to assess OT in patients with syncope of unknown cause, as well as in healthy subjects to study postural cardiovascular reflexes2-6. Tilting protocols comprise three categories: passive tilt; passive tilt accompanied by pharmacological provocation; and passive tilt with combined lower body negative pressure (LBNP). However, the effects of tilt testing (and other orthostatic stress testing modalities) are often poorly reproducible, with low sensitivity and specificity to diagnose orthostatic intolerance7.
Typically, a passive tilt includes 20-60 min of orthostatic stress continued until the onset of presyncope in patients2-6. However, the main drawback of this procedure is its inability to invoke presyncope in all individuals undergoing the test, and corresponding low sensitivity8,9. Thus, different methods were explored to increase the orthostatic stress and improve sensitivity.
Pharmacological provocation has been used to increase the orthostatic challenge, for example using isoprenaline4,7,10,11 or sublingual nitrate12,13. However, the main drawback of these approaches are increases in sensitivity at the cost of unacceptable decreases in specificity10,14, with a high positive response rate immediately after administration15. Furthermore, invasive procedures associated with some pharmacological provocations greatly increase the false positive rate1.
Another approach is to combine passive tilt testing with LBNP, providing a stronger orthostatic stress without invasive procedures or drug side-effects, using the technique pioneered by Professor Roger Hainsworth in the 1990s16-18. This approach provokes presyncope in almost all subjects (allowing for symptom recognition in patients with syncope), while discriminating between patients with syncope and healthy controls, with a specificity of 92%, sensitivity of 85%, and repeatability of 1.1&plusmn;0.6 min16,17. This allows not only diagnosis and pathophysiological assessment19-22, but also the evaluation of treatments for orthostatic intolerance due to its high repeatability23-30. For these reasons, we argue this should be the "gold standard" for orthostatic stress testing, and accordingly this will be the method described in this paper.

We describe a "gold standard" for evaluating orthostatic tolerance (OT) using tilt testing with combined lower body negative pressure (LBNP). This can be combined with non-invasive evaluations of cardiovascular reflex control. Normal and abnormal responses are defined.

Orthostatic tolerance (OT)  refers to the ability to maintain cardiovascular stability when upright,  against the hydrostatic effects of gravity, and ...

Medicine

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).

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. ...

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 ...

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, ...

Standing Neurophysiological Assessment of Lower Extremity Muscles Post-Stroke

Transcranial magnetic stimulation (TMS) is a common tool used to measure the behavior of motor circuits in healthy and neurologically impaired populations. TMS is used extensively to study motor control and the response to neurorehabilitation of the upper extremities. However, TMS has been less utilized in the study of lower extremity postural and walking-specific motor control. The limited use and the additional methodological challenges of lower extremity TMS assessments have contributed to the lack of consistency in lower extremity TMS procedures within the literature. Inspired by the decreased ability to record lower extremity TMS motor evoked potentials (MEP), this methodological report details steps to enable post-stroke TMS assessments in a standing posture. The standing posture allows for the activation of the neuromuscular system, reflecting a state more akin to the system's state during postural and walking tasks. Using dual-top force plates, we instructed participants to equally distribute their weight between their paretic and non-paretic legs. Visual feedback of the participants' weight distribution was provided. Using image guidance software, we delivered single TMS pulses via a double-cone coil to the participants' lesioned and non-lesioned hemispheres and measured the corticomotor response of the paretic and non-paretic tibialis anterior and soleus muscles. Performing assessments in the standing position increased the TMS response rate and allowed for the use of the lower stimulation intensities compared to the standard sitting/resting position. Utilization of this TMS protocol can provide a common approach to assess the lower extremity corticomotor response post-stroke when the neurorehabilitation of postural and gait impairments are of interest.

This protocol describes the process for performing a neurophysiological assessment of the lower extremity muscles, tibialis anterior and soleus, in a standing position using TMS in people post-stroke. This position provides a greater probability of eliciting a post-stroke TMS response and allows for the use of reduced stimulator power during neurophysiological assessments.

Transcranial magnetic stimulation (TMS) is a common tool used to measure the behavior of motor circuits in healthy and neurologically impaired ...

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

Experimental Methods to Study Human Postural Control

Many components of the nervous and musculoskeletal systems act in concert to achieve the stable, upright human posture. Controlled experiments accompanied by appropriate mathematical methods are needed to understand the role of the different sub-systems involved in human postural control. This article describes a protocol for performing perturbed standing experiments, acquiring experimental data, and carrying out the subsequent mathematical analysis, with the aim of understanding the role of musculoskeletal system and central control in human upright posture. The results generated by these methods are important, because they provide insight into the healthy balance control, form the basis for understanding the etiology of impaired balance in patients and the elderly, and aid in the design of interventions to improve postural control and stability. These methods can be used to study the role of somatosensory system, intrinsic stiffness of ankle joint, and visual system in postural control, and may also be extended to investigate the role of vestibular system. The methods are to be used in the case of an ankle strategy, where the body moves primarily about the ankle joint and is considered a single-link inverted pendulum.

This article presents an experimental/analytic framework to study human postural control. The protocol provides step-by-step procedures for performing standing experiments, measuring body kinematics and kinetics signals, and analyzing the results to provide insight into the mechanisms underlying human postural control.

Many components of the nervous and musculoskeletal systems act in concert to achieve the stable, upright human posture. Controlled experiments accompanied ...

Bioengineering

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 ...

An Instrumented Pull Test to Characterize Postural Responses

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