Name: sit-to-stand-and-walk from 120% knee height: a novel approach to assess dynamic postural control independent of lead-limb
Uploaded: 2016-08-30T14:00:00.000+00:00
Duration: 8 min 24 s
Description: Watch this Scientific Journal Video about Sit-to-stand-and-walk from 120% Knee Height: A Novel Approach to Assess Dynamic Postural Control Independent of Lead-limb at JoVE.com

The authors would like to thank Tony Christopher, Lindsey Marjoram at King&#39;s College London and Bill Anderson at London South Bank University for their practical support. Thank you also to Eleanor Jones at King&#39;s College London for her help in collecting the data for this project.

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The authors have no competing financial interests to disclose.

The sit-to-stand-and-walk (STSW) protocol defined here can be used to test dynamic postural control during complex transitional movement in healthy individuals or patient groups. The protocol includes constraints that are designed to allow subjects with pathology to participate, and the inclusion of switching off the light means it is ecologically valid and goal-orientated. As it has been shown previously that lead-limb and rising from a high (120% KH) seat does not fundamentally affect task dynamics during STSW20</...

Clinical pathologies affecting the sensorimotor systems, for example upper motor neuron (UMN) injury following stroke, lead to functional impairments including weakness, loss of postural stability and spasticity, which can negatively affect locomotion. Recovery can be variable with a significant number of stroke survivors failing to achieve the functional milestones of safe standing or walking1,2.
The discrete practice of walking and sit-to-stand are common rehabilitative tasks after UMN pathology3,4, however transitional movements are frequently neglected. Sit-to-walk (STW) is a sequential postural-locomotor task incorporating sit-to-stand (STS), gait initiation (GI), and walking5.
Separation of STS and GI, reflective of hesitation during STW has been observed in patients with Parkinson&#39;s disease6 and chronic stroke7, in addition to older unimpaired adults8, but not in young healthy individuals9. Therefore sit-to-stand-and-walk (STSW) is commonly implemented within the clinical environment and is defined by a pause phase of variable length when standing. However, there are no published protocols to date defining STSW dynamics in a context suitable for patient populations.
Usually in STW studies the initial chair height is 100% of knee height (KH; floor-to-knee distance), foot-width and GI lead-limb are self-selected, arms are constrained across the chest and an ecologically meaningful task context is often absent5-9. However, patients find rising from 100% KH challenging10 and frequently adopt a wider foot position compared with healthy individuals11, initiate gait with their affected leg7, and use their arms to generate momentum7.
To initiate gait, a state change in whole-body movement in a purposeful direction is required12. This is achieved by uncoupling the whole-body center-of-mass (BCOM: the weighted average of all considered body segments in space13) from the center-of-pressure (COP: the position of the resultant ground reaction force (GRF) vector14). In the anticipatory phase of GI, rapid stereotypical posterior and lateral movement of the COP toward the limb to be swung occurs thereby generating BCOM momentum12,15. The COP and BCOM are thus separated, with the horizontal distance between them having been proposed as a measure of dynamic postural control16.
The calculation of COP-BCOM distance requires simultaneous measurement of the COP and BCOM positions. The standard calculation of COP is shown below in equation (1)17:
<img alt="Equation 1" src="/files/ftp_upload/54323/54323eq1.jpg" />
<img alt="Equation 2" src="/files/ftp_upload/54323/54323eq2.jpg" />
<img alt="Equation 3" src="/files/ftp_upload/54323/54323eq3.jpg" /> 
(1)
Where M and Force represent moments about the force platform axes and the directional GRF respectively. The subscripts represent axes. The origin is the vertical distance between the contact surface and the origin of the force platform, and is considered to be zero.
The kinematic method of deriving BCOM position involves tracking the displacement of segmental markers. A faithful representation of body-segment motion can be achieved by employing markers clustered on rigid plates placed away from bony landmarks, minimizing soft-tissue-artifact (CAST technique18). In order to determine BCOM position, individual body segment masses are estimated, based on cadaveric work19. Three-dimensional (3D) motion system proprietary software uses the coordinate positions of proximal and distal segment locations to: 1) determine segmental lengths, 2) arithmetically estimate segmental masses, and 3) compute segmental COM locations. These models are then able to provide estimates of 3D BCOM position at a given point in time based on the net summation of inter-segmental positions (Figure 1).
Thus, the purpose of this paper is first to present a standardized STSW protocol that is ecologically valid and includes rising from a high seat-height. It has been shown previously that STSW from 120% KH is biomechanically indistinct from 100% KH barring generation of lower BCOM vertical velocities and GRF&#39;s during rising20, meaning rising from 120% KH is easier (and safer) for compromised individuals. Second, to derive COP-BCOM horizontal distances to assess dynamic postural control during key milestones and transitions using 3D motion-capture. This approach, which in healthy individuals during STSW is independent of limb-lead20, offers the prospect of functional recovery evaluation. Finally, a preliminary STSW data set representative of young healthy individuals is presented, and intra and inter-subject variability in the group is defined in order to inform comparison with pathological individuals.
<img alt="Figure 1" src="/files/ftp_upload/54323/54323fig1.jpg" /> 
Figure 1. 2D BCOM calculation. For simplicity, the example is based on calculating whole-leg COM from a 3-linked mass in 2 dimensions, where coordinates of the respective COM positions (x,y), and segmental masses (m1, m2, m3) are known. Segment masses and location of segmental COM positions, with respect to the laboratory coordinate system (LCS; origin: 0, 0), are estimated by motion analysis system proprietary software using subject body mass and published anthropometric data (see main text). The x and y leg COM position, in this example of the 3-linked mass, is then derived using the formulae shown. <a href="https://jove.unicartagenaproxy.elogim.com/files/ftp_upload/54323/54323fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

<table><tbody><tr><td>Motion Tracking Cameras</td><td>Qualysis&amp;nbsp; (Qualysis AB Gothenburg, Sweden)</td><td>Oqus 300+</td><td>n= 8</td></tr><tr><td>Qualysis Track Manager (QTM)</td><td>Qualysis&amp;nbsp; (Qualysis AB Gothenburg, Sweden)</td><td>QTM 2.9 Build No: 1697</td><td>Proprietary tracking software&amp;nbsp;</td></tr><tr><td>Force Platform&amp;nbsp; Amplifier</td><td>Kistler Instruments, Hook, UK</td><td>5233A</td><td>n= 4</td></tr><tr><td>Force Platform</td><td>Kistler Instruments, Hook, UK</td><td>9281E</td><td>n= 4</td></tr><tr><td>AD Converter</td><td>Qualysis&amp;nbsp; (Qualysis AB Gothenburg, Sweden)</td><td>230599</td><td></td></tr><tr><td>Light-Weight Wooden Walkway Section</td><td>Kistler Instruments, Hook, UK</td><td>Type 9401B01&amp;nbsp;</td><td>n= 2</td></tr><tr><td>Light-Weight Wooden Walkway Section</td><td>Kistler Instruments, Hook, UK</td><td>Type 9401B02&amp;nbsp;</td><td>n= 4</td></tr><tr><td>4 Point &quot;L-Shaped&quot; Calibration Frame</td><td>Qualysis&amp;nbsp; (Qualysis AB Gothenburg, Sweden)</td><td></td><td></td></tr><tr><td>&quot;T-Shaped&quot; Wand</td><td>Qualysis&amp;nbsp; (Qualysis AB Gothenburg, Sweden)</td><td></td><td></td></tr><tr><td>12 mm Diameter Passive Retro reflective Marker</td><td>Qualysis&amp;nbsp; (Qualysis AB Gothenburg, Sweden)</td><td>Cat No: 160181</td><td>Flat Base</td></tr><tr><td>Double Adhesive Tape</td><td>Qualysis&amp;nbsp; (Qualysis AB Gothenburg, Sweden)</td><td>Cat No: 160188</td><td>For fixing markers to skin</td></tr><tr><td>Height-Adjustable Stool</td><td>Ikea, Sweden</td><td>Svenerik</td><td>Height 43 - 58 cm with ~ 10cm customized height extension option at each leg</td></tr><tr><td>Circular (Disc) Pressure Floor Pad</td><td>Arun Electronics Ltd, Sussex, UK</td><td>PM10</td><td>305 mm Diameter, 3 mm thickness, 2 wire</td></tr><tr><td>Lower Limb Tracking Marker Clusters</td><td>Qualysis&amp;nbsp; (Qualysis AB Gothenburg, Sweden)</td><td>Cat No: 160145</td><td>2 Marker clusters, lower body with 8 markers (n= 2)</td></tr><tr><td>Upper Limb Tracking Marker Clusters</td><td>Qualysis&amp;nbsp; (Qualysis AB Gothenburg, Sweden)</td><td>Cat No: 160146</td><td>2 Marker clusters, lower body with 6 markers (n= 2)</td></tr><tr><td>Self-Securing Bandage</td><td>Fabrifoam, PA, USA</td><td></td><td>3&#039;&#039; x 5&#039;</td></tr><tr><td>Cycling Skull Cap</td><td>Dhb</td><td>Windslam</td><td></td></tr><tr><td>Digital Column Scale</td><td>Seca</td><td>763 Digital Medical Scale w/ Stadiometer</td><td></td></tr><tr><td>Measuring Caliper</td><td>Grip-On</td><td>Grip Jumbo Aluminum Caliper - Model no. 59070</td><td>24 in. Jaw</td></tr><tr><td>Extendable Arm Goniometer</td><td>Lafayette Instrument</td><td>Model 01135</td><td>Gollehon</td></tr><tr><td>Light Switch</td><td></td><td></td><td>Custom made</td></tr><tr><td>Visual3D Biomechanics Analysis Software</td><td>C-Motion Inc., Germantown, MD, USA</td><td>Version 4.87</td><td></td></tr></tbody></table>

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.

All subjects rose with their feet placed on the twin force platforms, leading with their non-dominant limb as instructed. Normal gait was observed with subjects stepping cleanly onto the other platforms and 3D optical-based motion analysis successfully tracked whole body movement during 5 repeated goal-orientated STSW tasks rising from 120% KH. Simultaneous COP and BCOM mediolateral (ML) and anteroposterior (AP) displacements between seat-off and IC2 (100% STSW cycle) comprising: rise, pa...

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

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: ...

sit-to-stand-walk-from-120-knee-height-novel-approach-to-assess

Universidad de Cartagena UDEC

Research

JoVE Journal

Behavior

10.2K Views.  King's College London. 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.

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

Substantiating Appropriate Motion Capture Techniques for the Assessment of Nordic Walking Gait and Posture in Older Adults

Nordic walking (NW) has become a safe and simple form of exercise in recent years, and in studying this gait pattern, various data collection techniques have been employed, each with positives and negatives. The aim was to determine the effect of NW on older adult gait and posture and to determine optimal use of different data collection systems in both short and long duration analysis. Gait and posture during NW and normal walking were assessed in 17 healthy older adults (age: 69 &#177; 7.3). Participants performed two trials of 6 Minute Walk Tests (6MWT) (1 with poles (WP) and 1 without poles (NP)) and 6 trials of a 5m walk (3 WP and 3 NP). Motion was recorded using two systems, a 6-sensor accelerometry system and an 8-camera 3-dimensional motion capture system, in order to quantify spatial-temporal, kinematic, and kinetic parameters.
With both systems, participants demonstrated increased stride length and double support and decreased gait speed and cadence WP compared to NP (p &#60;0.05). Also, with motion capture, larger single support time was found WP (p &#60;0.05). With 3-D capture, smaller hip power generation and moments of force were found at heel contact and pre-swing as well as smaller knee power absorption at heel contact, pre-swing, and terminal swing WP compared to NP, when assessed over one cycle (p &#60;0.05). Also, WP yielded smaller moments of force at heel contact and terminal swing along with larger moments at mid-stance of a gait cycle (p &#60;0.05). No changes were found for posture.
NW seems appropriate for promoting a normal gait pattern in older adults. Three-dimensional motion capture should primarily be used during short duration gait analysis (i.e. single gait cycle), while accelerometry systems should be primarily employed in instances requiring longer duration analysis such as during the 6MWT.

The aim was to substantiate optimal use of data collection techniques for Nordic walking gait and posture analysis. Three-dimensional motion capture should be used during short duration analysis (i.e. single gait cycle), while accelerometry should be employed for longer duration analysis (i.e. repeated cycles) like a 6 Minute Walk Test.

Nordic walking (NW) has become a safe and simple form of exercise in recent years, and in studying this gait pattern, various data collection techniques ...

Movement Retraining using Real-time Feedback of Performance

Any modification of movement - especially movement patterns that have been honed over a number of years - requires re-organization of the neuromuscular patterns responsible for governing the movement performance. This motor learning can be enhanced through a number of methods that are utilized in research and clinical settings alike. In general, verbal feedback of performance in real-time or knowledge of results following movement is commonly used clinically as a preliminary means of instilling motor learning. Depending on patient preference and learning style, visual feedback (e.g. through use of a mirror or different types of video) or proprioceptive guidance utilizing therapist touch, are used to supplement verbal instructions from the therapist. Indeed, a combination of these forms of feedback is commonplace in the clinical setting to facilitate motor learning and optimize outcomes.
Laboratory-based, quantitative motion analysis has been a mainstay in research settings to provide accurate and objective analysis of a variety of movements in healthy and injured populations. While the actual mechanisms of capturing the movements may differ, all current motion analysis systems rely on the ability to track the movement of body segments and joints and to use established equations of motion to quantify key movement patterns. Due to limitations in acquisition and processing speed, analysis and description of the movements has traditionally occurred offline after completion of a given testing session.
This paper will highlight a new supplement to standard motion analysis techniques that relies on the near instantaneous assessment and quantification of movement patterns and the display of specific movement characteristics to the patient during a movement analysis session. As a result, this novel technique can provide a new method of feedback delivery that has advantages over currently used feedback methods.

Retraining abnormal movement patterns following injury or disease is a key component of physical rehabilitation. Recent advances in technology have permitted accurate assessment of movement during a variety of tasks, with near instantaneous quantification of results. This provides new opportunities for modification of faulty movement patterns in real time.

Any modification of movement - especially movement patterns that have been honed over a number of years - requires re-organization of the neuromuscular ...

Medicine

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.

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, ...

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, ...

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

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 ...