The authors acknowledge the funding of National Natural Science Fund of China (11572202, 11772201, and 31700815).

Prior to tests, the participants signed an informed consent after receiving information about the experimental process. This experiment has been approved by the ethics committee of Shanghai University of Sports.
1. Equipment setup
<ol>
	<li>Turn on the CDP system, complete self-calibration, and ensure that the instrument operates normally at 100 Hz sampling frequency. 
	NOTE: Each of the two installed independent force plates measures three forces (Fx, Fy, and Fz) and three moments (Mx, My, and Mz). The x-axis is in the left&#8211;right direction and is perpendicular to the sagittal plane. The y-axis is in the forward&#8211;backward direction and is perpendicular to the coronal plane. The z-axis is perpendicular to the horizontal plane. The origins are located at the centers of the force plates.</li>
	<li>Double-click Balance Manager System | Clinical Module, and then click New Patient and establish the patient ID. Input an accurate height, weight, and age. Select Sensory Organization Test, Unilateral Stance, Limits of Stability, Motor Control Test, and Adaption Test. 
	NOTE: Such demographic data are also used for age-matched normative diagnostic analysis.</li>
	<li>Turn on the surface electromyography (sEMG) system, and double click the EMG Motion Tools icon. Specify the trigger signal as Trigger In (Manual Stop), establish the participant ID, and match the measured muscles with the wireless electrode. The muscles of unstable lower limb are vastus medialis (VM), vastus lateralis (VL), biceps femoris (BF), tibialis anterior (TA), peroneal longus (PL), gastrocnemius medialis (GM), and gastrocnemius lateralis (GL). 
	NOTE: The phrase Trigger In (Manual Stop) indicates that CDP triggers the sEMG system to capture EMG data during tests, but the &#34;end&#34; flag requires manual clicking to stop the acquisition.</li>
	<li>Connect sEMG system with CDP system through the synchronization line. Adjust the camera of sEMG system to capture the signal indicator light of the CDP system. 
	NOTE: The video of the indicator light is collected synchronously with the CDP system and sEMG to cut the corresponding cycle of the EMG in accordance with the CDP tests. &#8220;Light on&#8221; indicates that the test is in progress, and &#8220;light off&#8221; indicates that the test is paused/stopped.</li>
</ol>
2. Participant selection and preparation
<ol>
	<li>Use the following inclusion criteria for CAI participants: (1) 35 male participants with regular daily activity, excluding professional athletes or sedentary participants; (2) 20&#8211;29 years old; (3) history of at least one significant ankle sprain, and the initial sprain must have occurred at least 12 months before enrollment in the study; (4) feelings of &#8220;giving away&#8221; of the injured ankle joint and/or recurrent sprain and/or &#8220;feeling of instability;&#8221; and (5) a Cumberland Ankle Instability Tool questionnaire score of less than 24 points16.
	<ol>
		<li>Exclude participants with a history of bilateral sprains, lower limb fracture, operation, nervous and vestibular system diseases, or allergy to taping. Additionally, recruit 35 male participants without CAI, whose demographic data matched with the CAI group, as the control group.</li>
	</ol>
	</li>
	<li>For preparation, fix the electrode piece on the belly of the measured muscles. Instruct the participants to wear a safety harness and stand barefoot on the force plates to face the visual surround.
	<ol>
		<li>Adjust the alignment of the feet on the force plates. Align the malleolus medialis with the horizontal line and lateral edge of foot with the corresponding computer-generated height line (S, M, and T lines). Turn off the screen embedded in the visual surround (Figure 1). 
		NOTE: These guidelines are based on the following heights. &#8220;S&#8221; means &#8220;small&#8221; and includes heights ranging from 76 cm to 140 cm. &#8220;M&#8221; means &#8220;medium&#8221; and includes heights ranging from 141 cm to 165 cm. &#8220;T&#8221; means &#8220;tall&#8221; and includes heights ranging from 166 cm to 203 cm. The screen may produce learning effects, because it can provide real-time visual feedback. Thus, the screen should remain closed during the test, except during the limit of stability (LOS) test17.</li>
	</ol>
	</li>
</ol>
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/61592/61592fig01.jpg" /> 
Figure 1: Participant preparation for measurement.&#160;The participants stand upright barefoot to face the visual surround, wear safety harness, correctly align their feet with the force plates, and fix the wireless EMG electrodes on their legs. <a href="https://www.jove.com/files/ftp_upload/61592/61592fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
3. Measurement procedures
<ol>
	<li>CDP measurement
	<ol>
		<li>Sensory organization test
		<ol>
			<li>Instruct the participants to stand upright and to keep their COG as stable as possible to cope with the interference from vision, somatosensory, and vestibular sensation (singly or combined) (Table 1). Complete the measurements of conditions 1&#8211;6. Each test lasts for 20 s. Repeat the procedure thrice for each condition.</li>
		</ol>
		</li>
		<li>Unilateral stance
		<ol>
			<li>Instruct the participants to place their hands on the anterior superior iliac spine with their eyes open/closed. Consider the unstable ankle side as the support leg. Fully extend their knee joint, and bend the knee of their non-supporting leg by approximately 30&#176;. Allow the participants to remain standing stably for 10 s. Repeat the procedure thrice for each visual condition.</li>
		</ol>
		</li>
		<li>Limit of stability
		<ol>
			<li>Instruct the participants to maintain their COG in the central area. Upon hearing the ring, lean their body and shift their COG quickly into the targeted frame in the screen. Instruct the participants to remain steady for 10 s. Complete the eight directional shifting of their COG (forward, forward-right, right, right-backward, backward, backward-left, left, and left-forward). 
			NOTE: In the process of COG shifting, the body is kept straight, the heel or toes are not far from the force plates, and the hip joint is not bent.</li>
		</ol>
		</li>
		<li>Motor control test
		<ol>
			<li>Instruct the participants to respond effectively to restore body stability and to cope with the unexpected slipping of the force plates. Repeat the procedure thrice for each slip condition. 
			NOTE: The force plates are slipped with small/medium/large amplitude in the anterior/posterior direction. According to the participant&#8217;s height, the slip amplitude of the force plates is automatically adjusted. Standard procedures must be followed to align the foot position on the force plates. Random delay exists between trials.</li>
		</ol>
		</li>
		<li>Adaption test
		<ol>
			<li>Instruct the participants to respond effectively to restore body stability and to cope with five consecutive unexpected rotations at a velocity of 20&#176;/s. Direct the toes upward or downward.</li>
		</ol>
		</li>
	</ol>
	</li>
</ol>
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Condition</td>
			<td>Eyes</td>
			<td>Force plates</td>
			<td>Visual surround</td>
			<td>Interference</td>
			<td>Anticipated Response</td>
		</tr>
		<tr>
			<td>1</td>
			<td>Open</td>
			<td>Fix</td>
			<td>Fix</td>
			<td></td>
			<td>Somatosensory</td>
		</tr>
		<tr>
			<td>2</td>
			<td>Close</td>
			<td>Fix</td>
			<td>Fix</td>
			<td>Vision</td>
			<td>Somatosensory</td>
		</tr>
		<tr>
			<td>3</td>
			<td>Open</td>
			<td>Fix</td>
			<td>Sway-reference</td>
			<td>Vision</td>
			<td>Somatosensory</td>
		</tr>
		<tr>
			<td>4</td>
			<td>Open</td>
			<td>Sway-reference</td>
			<td>Fix</td>
			<td>Somatosensory</td>
			<td>Vision, vestibular</td>
		</tr>
		<tr>
			<td>5</td>
			<td>Close</td>
			<td>Sway-reference</td>
			<td>Fix</td>
			<td>Somatosensory, vision</td>
			<td>Vestibular</td>
		</tr>
		<tr>
			<td>6</td>
			<td>Open</td>
			<td>Sway-reference</td>
			<td>Sway-reference</td>
			<td>Somatosensory, vision</td>
			<td>Vestibular</td>
		</tr>
	</tbody>
</table>
Table 1: Different interference and corresponding anticipated response in sensory organization test. The term &#8220;sway-referenced&#8221; means that the movement of the force plates and visual surround follows the participant&#8217;s COG sway.
<ol start="2">
	<li>sEMG measurement and data process
	<ol>
		<li>After triggering by CDP system during SOT, US, LOS, MCT and ADT, start the automatic acquisition of lower-limb muscle activity raw data. Manually stop the acquisition during the sEMG system when the light is off. The sample size is 1000 Hz.</li>
		<li>Enter the processing window of the sEMG software. Import the C3d file of the EMG raw data and mp4 file of the light video. Cut the trial cycle when the light is on.</li>
		<li>In the &#8220;processing pipeline&#8221; operations, include the following options in the run pipeline: Butterworth filter with low-pass (450 Hz, 2. Order) and high-pass (20 Hz, 2. Order); notch filter at 50 Hz; and root mean square smoothing window of 100 ms. 
		NOTE: Choose the Butterworth filter with low-pass (450 Hz, 2. Order) and high-pass (20 Hz, 2. Order) to filter out unwanted low and high-frequency components. Set the notch filter at 50 Hz to remove 50 Hz interference from the main power. Use the root mean square smoothing window of 100 ms to smooth the noisy signal.</li>
		<li>In the Generate Events options, include the following events in the run pipeline. &#8220;muscle on&#8221; is defined as &#8220;all channels go above 5x baseline noise standard deviations for at least 50 ms&#8221;. &#8220;muscle off&#8221; is defined as &#8220;all channels drop below 5x standard deviations over baseline for at least 50 ms &#8221;.</li>
		<li>In the Generate Parameters options, include the following parameters in the run pipeline: integral electromyography (iEMG); root mean square (RMS); mean power frequency (MPF); medium frequency (MDF); and co-activation ratio. 
		NOTE: The following are the referenced calculation formulas for the above parameters (Equations 1&#8211;4): 
		<img alt="Equation 1" src="/files/ftp_upload/61592/61592equ01v2.jpg" /> 
		<img alt="Equation 2" src="/files/ftp_upload/61592/61592equ02v2.jpg" /> 
		<img alt="Equation 3" src="/files/ftp_upload/61592/61592equ03v2.jpg" /> 
		<img alt="Equation 4" src="/files/ftp_upload/61592/61592equ04v2.jpg" /></li>
		<li>Normalize the RMS values of the SOT, US, LOS, MCT and ADT trials with the RMS values of maximal voluntary isometric contraction (MVIC) for each muscle (Equation 5). 
		<img alt="Equation 5" src="/files/ftp_upload/61592/61592eq5v3.png" /> 
		NOTE: MVIC indicates the maximum force contraction of each muscle for participants in the standard posture for 5 s (Supplementary file 1)18.</li>
	</ol>
	</li>
</ol>

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A., Hertel, J., Plisky, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Using+the+Star+Excursion+Balance+Test+to+assess+dynamic+postural-control+deficits+and+outcomes+in+lower+extremity+injury:+a+literature+and+systematic+review.">Using the Star Excursion Balance Test to assess dynamic postural-control deficits and outcomes in lower extremity injury: a literature and systematic review.</a> Journal of Athletic Training. 47 (3), 339-357 (2012).</li></ol>

The authors have nothing to disclose.

The presented protocol is used to measure dynamic postural control and related muscle activity in individuals with CAI by synchronizing CDP with sEMG. CDP traces the trajectory of the COP and COG and provides insight into the interaction between sensory information (visual, somatosensory, and vestibular sensation) input and the external environment8,21,22. It is an effective tool for the diagnosis of the functional activity limi...

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 (COP) and the center of gravity (COG). COG is the vertical projection of the center of mass (COM), whereas COM is the point equivalent of the total body mass in the global reference system. COP is the point location of the vertical ground reaction force vector. It represents a weighted average of all the pressures over the surface of the contact area with the ground1. Postural stability is the ability to maintain the COM within the base of support in a given sensory environment. It reflects neuromuscular control ability that coordinates the central nervous system with the afferent sensory system (vision, proprioception, and vestibular sensation) and motor command output2.
Previous evaluation methods for postural control, such as the time for a single-leg stance and the reach distance for Y-balance tests, are results-oriented and cannot be used to objectively evaluate the coordination between sensory systems and motor control3. In addition, some studies used portable computerized wobble board, which quantified dynamic balance performances out of laboratory settings4,5,6. CDP differs from the abovementioned test methods, because it can be applied to the analysis of the proportion of vision, proprioception, and vestibular sensation in postural stability maintenance and to the evaluation of the proportion of motor strategy, such as ankle or hip dominant strategy. It has been viewed as a gold standard for postural control measurement7 because of its accuracy, reliability, and validity8.
Chronic ankle instability (CAI) is characterized by persistent ankle pain, swelling, and feeling of &#8220;giving way&#8221;; it is one of the most common sports injuries9. CAI originates mostly from lateral ankle sprains, which destroy the integrity and stability of the lateral ankle ligament complex. The proprioception, fibular muscle strength, and normal trajectory of talus are impaired10,11. The deficiencies of the weak ankle segment can result in deficient postural control and muscle activation in individuals with CAI12. However, few studies have investigated the postural stability of individuals with CAI by using CDP3,13. Current measurements could rarely analyze the posture control deficiency of CAI from the perspective of sensory analysis. Therefore, the ability of sensory organization and postural strategy of CAI to maintain postural stability needs further exploration.
Muscle activity is an important component of neuromuscular control that affects the regulation of postural stability14,15. However, CDP only monitors the interrelationship between COP and COG through force plates, and its application to the observation of the specific activation level of lower limb muscles in individuals with CAI is difficult. Currently, few studies have evaluated the postural stability of individuals with CAI through a method that combines CDP with electromyography (EMG).
Therefore, the developed protocol aims to explore postural control and related muscle activity by combining CDP and surface electromyography system (sEMG). This protocol provides a novel approach to investigate neuromuscular control, including sensory organization, postural control, and related muscle activity, for participants with CAI.

<table><tbody><tr><td>NeuroCom Balance Manager SMART EquiTest</td><td>Natus Medical Incorporated, USA</td><td></td><td>Its major components include: NeuroCom Balance Manager Software Suite, dynamic dual force plate (rotate &amp;amp; translate), moveable visual surround with 15&amp;rdquo; LCD display (it could provide a real time display of the subject&amp;rsquo;s center of gravity shown as a cursor during the task) and illumination, overhead support bar with patient harness, computer and other parts.</td></tr><tr><td>wireless Myon 320 sEMG system</td><td>Myon AG</td><td></td><td>The system consists of 16 parallel channels of transmitter signals, receiver, &quot;EMG motion Tools&quot; and &quot;ProEMG&quot; software,computer and other parts.</td></tr></tbody></table>

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.

Representative CDP Results 
Sensory organization test 
The system evaluates the participant&#8217;s ability to maintain COG in the predetermined target area, when the environment changes as the peripheral signal input. Equilibrium score (ES) is the score under conditions 1&#8211;6 that reflects the ability to coordinate the sensory system to maintain postural stability (Equation 6). The composite score (COMP) is the weighted average score of al...

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

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 ...

evaluating-postural-control-lower-extremity-muscle-activation

Research

JoVE Journal

Neuroscience

8.3K Views.  Tongji University. Dit protocol presenteert een nieuwe aanpak voor de evaluatie van de coördinatie van de visuele somata sensorische en vestibulaire systemen, en de bijbehorende spieractivering die nodig is om posturale stabiliteit te behouden. Deze techniek kan worden gebruikt om een uitgebreid onderzoek van de neuromusculaire controle voor chronische enkelinstabiliteit uit te voeren door de combinatie van geautomatiseerde dynamische posturografie, en verwante spieractiviteit. Deze methode kan ook worden gebr...

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

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: ...

Behavior

Using Gold-standard Gait Analysis Methods to Assess Experience Effects on Lower-limb Mechanics During Moderate High-heeled Jogging and Running

A limited number of studies have explored lower-limb biomechanics during high-heeled jogging and running, and most studies have failed to clarify the wearing experience of subjects. This protocol describes the differences in lower-limb kinematics and ground reaction force (GRF) between experienced wearers (EW) and inexperienced wearers (IEW) during moderate high-heeled jogging and running. A three-dimensional (3D) motion analysis system with a configured force platform was used to synchronously capture lower-limb joint movements and GRF. 36 young females volunteered to participate in this study and were asked about high-heeled shoe-wearing experience, including frequency, duration, heel types, and heel heights. Eleven who had the experience of 3 to 6 cm heels for a minimum of three days per week (6 h per day) for at least two years and eleven who wore high heels less than twice per month participated. Subjects performed jogging and running at comfortable low and high speeds, respectively, with the right foot completely stepping onto a force platform when passing by along a 10 m walkway. EW and IEW adopted different biomechanical adaptations while jogging and running. IEW exhibited a generally larger range of joint movement, while EW showed a dramatically larger loading rate of GRF during running. Hence, further studies on the lower-limb biomechanics of high-heeled gait should strictly control the wearing experience of the subjects.

This study investigated lower-limb kinematics and ground reaction force (GRF) during moderate high-heeled jogging and running. Subjects were divided into groups of experienced wearers and inexperienced wearers. A three-dimensional motion analysis system with a configured force platform captured lower-limb joint movements and GRF.

A limited number of studies have explored lower-limb biomechanics during high-heeled jogging and running, and most studies have failed to clarify the ...

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 ...

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 ...

Diagnosis of Musculus Gastrocnemius Tightness - Key Factors for the Clinical Examination

Common foot and ankle pathologies have been linked to isolated Musculus gastrocnemius tightness (MGT). Various examination techniques have been described to assess MGT. Still, a standardized examination procedure is missing. Literature argues for weightbearing examination but the degree of knee flexion needed to eliminate the restraining effect of the M. gastrocnemius on ankle dorsiflexion (ADF) is unknown. This manuscript investigates the effect of knee flexion on ankle dorsiflexion and provides a detailed description of a standardized examination protocol. Examination on 20 healthy individuals revealed, that 20&#176; of knee flexion is sufficient to fully eliminate the influence of the M. gastrocnemius on ADF. This builds the prerequisite for a standardized examination for MGT. Non-weightbearing and weightbearing examination of ADF has to be conducted with the knee fully extended and at least 20&#176; flexed. Two investigators should conduct non-weightbearing testing with the subject in supine position. In order to obtain reliable results, the axis of the fibula should be marked. One examiner can conduct weightbearing examination with the subject in lunge stance. Isolated MGT is present if ADF is impaired with the knee fully extended and knee flexion results in a significant ADF increase. The herein presented standardized examination is the prerequisite for future studies aiming at establishing norm values.

Diagnosis of Musculus Gastrocnemius Tightness - Key Factors for the Clinical Examination

Isolated Musculus gastrocnemius tightness is a common cause for foot and ankle pathologies. Currently no standardized examination procedure exists. This manuscript demonstrates that 20 degree of knee flexion eliminates the restraining effect of the M. gastrocnemius on ankle dorsiflexion and presents a video description of a standardized examination protocol.

Common foot and ankle pathologies have been linked to isolated Musculus gastrocnemius tightness (MGT). Various examination techniques have been described ...

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

Postural Organization of Gait Initiation for Biomechanical Analysis Using Force Platform Recordings

Gait initiation (GI), the transient phase between orthograde posture and steady-state locomotion, is a functional task and an experimental paradigm that is classically used in the literature to obtain insight into the basic postural mechanisms underlying body motion and balance control. Investigating GI has also contributed to a better understanding of the physiopathology of postural disorders in elderly and neurological participants (e.g., patients with Parkinson&#39;s disease). As such, it is recognized to have important clinical implications, especially in terms of fall prevention.
This paper aims to provide scholars, clinicians, and higher education students information on the material and method developed to investigate GI postural organization via a biomechanical approach. The method is based on force platform recordings and the direct principle of mechanics to compute the kinematics of the center of gravity and center of pressure. The interaction between these two virtual points is a key element in this method since it determines the conditions of stability and whole-body progression. The protocol involves the participant initially standing immobile in an upright posture and starting to walk until the end of an at least 5 m track.
It is recommended to vary the GI velocity (slow, spontaneous, fast) and the level of temporal pressure - gait may be initiated as soon as possible after the deliverance of a departure signal (high level of temporal pressure) or when the participant feels ready (low level of temporal pressure). Biomechanical parameters obtained with this method (e.g., duration and amplitude of anticipatory postural adjustments, step length/width, performance, and stability) are defined, and their computation method is detailed. In addition, typical values obtained in healthy young adults are provided. Finally, critical steps, limitations, and significance of the method with respect to the alternative method (motion capture system) are discussed.

This paper describes the material and method developed to investigate the postural organization of gait initiation. The method is based on force platform recordings and on the direct principle of mechanics to compute center of gravity and center of pressure kinematics.

Gait initiation (GI), the transient phase between orthograde posture and steady-state locomotion, is a functional task and an experimental paradigm that ...

Evaluating Brain Activation by fNIRS During a Lower Limb Robotic Therapy Session

An Experiment Using Functional Near-Infrared Spectroscopy and Robot-Assisted Multi-Joint Pointing Movements of the Lower Limb

Stroke affects approximately 17 million individuals worldwide each year and is a leading cause of long-term disability. Robotic therapy has shown promise in helping stroke patients regain lost motor functions. One potential avenue for increasing the understanding of how motor recovery occurs is to study brain activation during the movements that are targeted by therapy in healthy individuals. Functional Near-Infrared Spectroscopy (fNIRS) has emerged as a promising neuroimaging technique for examining neural underpinnings of motor function. This study aimed to investigate fNIRS neural correlates of complex lower limb movements in healthy subjects. Participants were asked to perform cycles of rest and movement for 6 min using a robotic device for motor rehabilitation. The task required coordinated knee and ankle joint movements to point to targets displayed on a computer screen. Two experimental conditions with different levels of movement assistance provided by the robot were explored. The results showed that the fNIRS protocol effectively detected brain regions associated with motor control during the task. Notably, all subjects exhibited greater activation in the contralateral premotor area during the no-assistance condition compared to the assisted condition. In conclusion, fNIRS appears to be a valuable approach for detecting changes in oxyhemoglobin concentration associated with multi-joint pointing movements of the lower limb. This research might contribute to the understanding of stroke motor recovery mechanisms and might pave the way for improved rehabilitation treatments for stroke patients. However, further research is needed to fully elucidate the potential of fNIRS in studying motor function and its applications in clinical settings.

Author Spotlight: Assessing Brain Activity in Robotic-Assisted Lower Limb Rehabilitation Using fNIRS

It is estimated that 1 in 6 individuals worldwide will have a stroke in their lifetime, causing long-term disability, whose rehabilitation mechanisms are still poorly understood. This study proposes a protocol to evaluate brain activation by functional near-infrared spectroscopy (fNIRS) during a lower limb robotic therapy session.

Stroke affects approximately 17 million individuals worldwide each year and is a leading cause of long-term disability. Robotic therapy has shown promise ...

A Mouse Model of Ankle-Subtalar Complex Joint Instability

Ankle sprains are perhaps the most common sports injuries in daily life, often resulting in instability of the ankle-subtalar complex joint (ASCJ), and can eventually lead to post-traumatic osteoarthritis (PTOA) in the long term. However, due to the complexity of the injury mechanism and the clinical manifestations, such as ecchymosis, hematoma, or tenderness in the lateral foot, there is no clinical consensus on diagnosing and treating ASCJ instability. Since the musculoskeletal structure of the bones and ligaments of the mouse hindfoot is comparable to that of humans, an animal model of ASCJ instability in mice was established by the transection of ligaments around the ASCJ. The model was well-validated through a series of behavioral tests and histological analyses, including a balance beam test, a footprint analysis (an assessment of exercise level and balance ability in mice), a thermal nociception assessment (an assessment of foot sensory function in mice), micro-computed tomography (CT) scanning, and section staining of the articular cartilage (an assessment of articular cartilage damage and degeneration in mice). The successful establishment of a mouse model of ASCJ instability will provide a valuable reference for clinical research on the injury mechanism and result in better treatment options for ankle sprain.

The ankle-subtalar complex joint (ASCJ) is the core of the foot and plays a key role in balance control in daily activities. Sports injuries often lead to instability in this joint. Here, we describe a mouse model of ligament transection-induced instability of the ASCJ.

Ankle sprains are perhaps the most common sports injuries in daily life, often resulting in instability of the ankle-subtalar complex joint (ASCJ), and ...

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

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