Proactive and Reactive Mechanisms Play a Role in Stepping on Inverting Surfaces During Gait

2007 ◽  
Vol 98 (4) ◽  
pp. 2266-2273 ◽  
Author(s):  
P.H.J.A. Nieuwenhuijzen ◽  
J. Duysens
Keyword(s):  
Initial Contact ◽  
Reactive Control ◽  
Foot Placement ◽  
Trap Door ◽  
Leg Muscles ◽  
Short Latency Response ◽  
Latency Response ◽  
Functional Relevance ◽  
And Control ◽  
Gastrocnemius Lateralis

Ankle inversions have been studied extensively during standing conditions. However, inversion traumas occur during more dynamic conditions, like walking. Therefore in this study sudden ankle inversions were elicited in 12 healthy subjects who stepped on a trap door while walking on a treadmill. First, 10 control trials (0° of rotation) were presented. Then, 20 stimulus (25° of rotation) and control trials were presented randomly. EMG recordings were made of six lower leg muscles. All muscles showed a short-latency response (SLR) of about 40 ms and a late-latency response (LLR) of about 90 ms. The peroneal muscles showed the largest amplitudes in both responses. The functionally more important, larger, and more consistent LLR response was too late to resist the induced stretch during the inversion. The functional relevance of this response must lie after the inversion. During the first trial a widespread “startle-like” coactivation of the LLR was observed. The last trials showed only a recruitment of the peroneal muscles and, to a lesser extent, the gastrocnemius lateralis, which is seen as a switch from reactive control to more proactive adaptive strategies. These proactive strategies were investigated separately by comparing trials in which inversion was expected (but did not occur) with those in which subjects knew that no inversion would occur. Anticipation of a possible inversion was expressed in decreased tibialis anterior activity before initial contact, consistent with a more cautious and stable foot placement. Furthermore, immediately after landing, the peroneal muscles were activated to counteract the upcoming stretch.

Research Participation Experiences of Informants of Suicide and Control Cases

Crisis ◽  
2010 ◽  
Vol 31 (5) ◽  
pp. 238-246 ◽  
Author(s):  
Paul W. C. Wong ◽  
Wincy S. C. Chan ◽  
Philip S. L. Beh ◽  
Fiona W. S. Yau ◽  
Paul S. F. Yip ◽  
...  
Keyword(s):  
Ethical Issues ◽  
Research Participation ◽  
Self Report ◽  
Initial Contact ◽  
Psychological Autopsy ◽  
Autopsy Study ◽  
The People ◽  
And Control ◽  
The Impact

Background: Ethical issues have been raised about using the psychological autopsy approach in the study of suicide. The impact on informants of control cases who participated in case-control psychological autopsy studies has not been investigated. Aims: (1) To investigate whether informants of suicide cases recruited by two approaches (coroners’ court and public mortuaries) respond differently to the initial contact by the research team. (2) To explore the reactions, reasons for participation, and comments of both the informants of suicide and control cases to psychological autopsy interviews. (3) To investigate the impact of the interviews on informants of suicide cases about a month after the interviews. Methods: A self-report questionnaire was used for the informants of both suicide and control cases. Telephone follow-up interviews were conducted with the informants of suicide cases. Results: The majority of the informants of suicide cases, regardless of the initial route of contact, as well as the control cases were positive about being approached to take part in the study. A minority of informants of suicide and control cases found the experience of talking about their family member to be more upsetting than expected. The telephone follow-up interviews showed that none of the informants of suicide cases reported being distressed by the psychological autopsy interviews. Limitations: The acceptance rate for our original psychological autopsy study was modest. Conclusions: The findings of this study are useful for future participants and researchers in measuring the potential benefits and risks of participating in similar sensitive research. Psychological autopsy interviews may be utilized as an active engagement approach to reach out to the people bereaved by suicide, especially in places where the postvention work is underdeveloped.

scholarly journals Development of a Virtual Reality Simulator for an Intelligent Robotic System Used in Ankle Rehabilitation

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1537
Author(s):  
Florin Covaciu ◽  
Adrian Pisla ◽  
Anca-Elena Iordan
Keyword(s):  
Virtual Reality ◽  
Muscle Activity ◽  
Human Subject ◽  
Robotic System ◽  
Virtual Reality Simulator ◽  
Robotic Rehabilitation ◽  
Rehabilitation Process ◽  
Leg Muscles ◽  
Ankle Rehabilitation ◽  
And Control

The traditional systems used in the physiotherapy rehabilitation process are evolving towards more advanced systems that use virtual reality (VR) environments so that the patient in the rehabilitation process can perform various exercises in an interactive way, thus improving the patient’s motivation and reducing the therapist’s work. The paper presents a VR simulator for an intelligent robotic system of physiotherapeutic rehabilitation of the ankle of a person who has had a stroke. This simulator can interact with a real human subject by attaching a sensor that contains a gyroscope and accelerometer to identify the position and acceleration of foot movement on three axes. An electromyography (EMG) sensor is also attached to the patient’s leg muscles to measure muscle activity because a patient who is in a worse condition has weaker muscle activity. The data collected from the sensors are taken by an intelligent module that uses machine learning to create new levels of exercise and control of the robotic rehabilitation structure of the virtual environment. Starting from these objectives, the virtual reality simulator created will have a low dependence on the therapist, this being the main improvement over other simulators already created for this purpose.

DECAFF: Experimental Study on Human Haptic Perception

2000 ◽  
Author(s):  
Scott L. Springer ◽  
Nicola J. Ferrier
Keyword(s):  
Interface Design ◽  
Haptic Perception ◽  
Human Perception ◽  
Initial Contact ◽  
Haptic Interfaces ◽  
Feed Forward ◽  
Feed Forward Control ◽  
Contact Distance ◽  
Traditional Approaches ◽  
And Control

Abstract DECAFF is a method for design and control of haptic interfaces that utilizes a DE-Coupled Actuator and Feed-Forward control. In this paper results of an experimental investigation are presented that quantify improved human haptic perception while using the DECAFF system, compared to the traditional haptic interface design and control systems. Perception improvements include the increased stability for rigid surfaces and increased ability of subjects to accurately identify initial contact with virtual surface boundaries. Traditional haptic interfaces employ an actuator directly coupled to the human operator that provides a force proportional to wall penetration distance and velocity. The DECAFF paradigm for design and control of haptic displays utilizes a de-coupled actuator and pre-contact distance sensing as a feed forward control term to improve stability and response performance. A human perception experiment has been performed that compares the touch sensation of the subjects for both the DECAFF system and traditional approaches to haptic display. In the human factors study the quality of rigid body display is evaluated in addition to the sensitivity of touch experienced by the subjects while making initial contact with virtual surfaces.

scholarly journals Temporal Evolution of “Automatic Gain-Scaling”

2009 ◽  
Vol 102 (2) ◽  
pp. 992-1003 ◽  
Author(s):  
J. Andrew Pruszynski ◽  
Isaac Kurtzer ◽  
Timothy P. Lillicrap ◽  
Stephen H. Scott
Keyword(s):  
Steady State ◽  
Muscle Activity ◽  
Temporal Evolution ◽  
Rapid Decrease ◽  
Short Latency ◽  
State Activity ◽  
Long Latency ◽  
Short Latency Response ◽  
Latency Response ◽  
Steady State Activity

The earliest neural response to a mechanical perturbation, the short-latency stretch response (R1: 20–45 ms), is known to exhibit “automatic gain-scaling” whereby its magnitude is proportional to preperturbation muscle activity. Because gain-scaling likely reflects an intrinsic property of the motoneuron pool (via the size-recruitment principle), counteracting this property poses a fundamental challenge for the nervous system, which must ultimately counter the absolute change in load regardless of the initial muscle activity (i.e., show no gain-scaling). Here we explore the temporal evolution of gain-scaling in a simple behavioral task where subjects stabilize their arm against different background loads and randomly occurring torque perturbations. We quantified gain-scaling in four elbow muscles (brachioradialis, biceps long, triceps lateral, triceps long) over the entire sequence of muscle activity following perturbation onset—the short-latency response, long-latency response (R2: 50–75 ms; R3: 75–105 ms), early voluntary corrections (120–180 ms), and steady-state activity (750–1250 ms). In agreement with previous observations, we found that the short-latency response demonstrated substantial gain-scaling with a threefold increase in background load resulting in an approximately twofold increase in muscle activity for the same perturbation. Following the short-latency response, we found a rapid decrease in gain-scaling starting in the long-latency epoch (∼75-ms postperturbation) such that no significant gain-scaling was observed for the early voluntary corrections or steady-state activity. The rapid decrease in gain-scaling supports our recent suggestion that long-latency responses and voluntary control are inherently linked as part of an evolving sensorimotor control process through similar neural circuitry.

Design and Control of an Assistive Bionic Joint for Leg Muscle Rehabilitation

2017 ◽  
Author(s):  
Vincent Nagel ◽  
Sarah Chu ◽  
Jack Forney ◽  
Lyle Kosinski ◽  
Vimal Viswanathan
Keyword(s):  
Response Time ◽  
Sensor Data ◽  
Full Extension ◽  
Rehabilitation Process ◽  
Leg Muscles ◽  
Finite Control ◽  
Recovery Times ◽  
Sensor Signals ◽  
Leg Muscle ◽  
And Control

This project aims to create an electronically powered and controlled knee brace to aid stroke victims with partial paralysis with their leg muscle rehabilitation process. The newly designed assistive bionic joint takes the functionality of the existing assistive knee braces to the next level by incorporating a control algorithm that uses sensor signals gathered from the patient’s leg muscles. Electromyography (EMG) is used for gathering impulse signals from electrodes placed on key muscles as inputs for the device. The action of each major leg muscle is replicated using a set of fluidic muscles that mimic the functionality of the actual leg muscles. A microcontroller is used to interpret sensor data and adjust the contraction length of the muscles, thereby providing the wearer with augmented strength and mobility. Initial testing of a proof-of-concept prototype has led to finite control over muscle contraction length based on sensor data and has a response time of 280ms from full extension to contraction. Further testing of the brace assembly, fluidic muscles and control system is conducted and the results indicate a 600ms response time due to a step input. This personalized, powered brace has many implications for the enrichment of muscle rehabilitation such as higher patient morale, more muscle activity, and shortened recovery times.

scholarly journals Impact of Experimental Tonic Pain on Corrective Motor Responses to Mechanical Perturbations

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Elodie Traverse ◽  
Clémentine Brun ◽  
Émilie Harnois ◽  
Catherine Mercier
Keyword(s):  
Sensory Feedback ◽  
Pain Model ◽  
Voluntary Response ◽  
Long Latency ◽  
Short Latency Response ◽  
Latency Response ◽  
Tonic Pain ◽  
Underlying Mechanisms ◽  
The Impact ◽  
Muscle Responses

Movement is altered by pain, but the underlying mechanisms remain unclear. Assessing corrective muscle responses following mechanical perturbations can help clarify these underlying mechanisms, as these responses involve spinal (short-latency response, 20-50 ms), transcortical (long-latency response, 50-100 ms), and cortical (early voluntary response, 100-150 ms) mechanisms. Pairing mechanical (proprioceptive) perturbations with different conditions of visual feedback can also offer insight into how pain impacts on sensorimotor integration. The general aim of this study was to examine the impact of experimental tonic pain on corrective muscle responses evoked by mechanical and/or visual perturbations in healthy adults. Two sessions (Pain (induced with capsaicin) and No pain) were performed using a robotic exoskeleton combined with a 2D virtual environment. Participants were instructed to maintain their index in a target despite the application of perturbations under four conditions of sensory feedback: (1) proprioceptive only, (2) visuoproprioceptive congruent, (3) visuoproprioceptive incongruent, and (4) visual only. Perturbations were induced in either flexion or extension, with an amplitude of 2 or 3 Nm. Surface electromyography was recorded from Biceps and Triceps muscles. Results demonstrated no significant effect of the type of sensory feedback on corrective muscle responses, no matter whether pain was present or not. When looking at the effect of pain on corrective responses across muscles, a significant interaction was found, but for the early voluntary responses only. These results suggest that the effect of cutaneous tonic pain on motor control arises mainly at the cortical (rather than spinal) level and that proprioception dominates vision for responses to perturbations, even in the presence of pain. The observation of a muscle-specific modulation using a cutaneous pain model highlights the fact that the impacts of pain on the motor system are not only driven by the need to unload structures from which the nociceptive signal is arising.

Phase-dependent reflex reversal in human leg muscles during walking

1990 ◽  
Vol 63 (5) ◽  
pp. 1109-1117 ◽  
Author(s):  
J. F. Yang ◽  
R. B. Stein
Keyword(s):  
Stimulus Intensity ◽  
Rectus Femoris ◽  
Leg Muscles ◽  
Middle Latency Response ◽  
Reflex Pathways ◽  
Activation Level ◽  
Reflex Reversal ◽  
Latency Response ◽  
Middle Latency ◽  
Stimulation Of

1. Reflex responses during walking were elicited in humans by stimulation of the tibial nerve at the ankle. The stimulus intensity was controlled by monitoring the M-wave from an intrinsic foot muscle. Responses were observed in the ipsilateral tibialis anterior (TA), soleus (SO), and rectus femoris (RF) muscles. The most reproducible responses were observed at a middle latency between 50 and 90 ms. The responses were most likely of cutaneous origin, because they closely resembled the responses to stimulation of a purely cutaneous nerve, the sural nerve. 2. A reversal in the direction of the middle latency response from excitation to inhibition was observed for the first time within single muscles during walking. Evidence for a reversal was seen in all three muscles examined and in all seven subjects. 3. The reflex reversal could not be elicited in standing. An inhibition whose amplitude varied in a linear fashion with stimulus intensity and background activation level was always observed at middle latency. The responses elicited during standing resembled those during the stance phase of walking. The two tasks shared some common movement goals and appeared to make use of similar reflex pathways.

Optimum Reactive Control and Control by Latching of a Wave-Absorbing Semisubmerged Heaving Sphere

2002 ◽  
Author(s):  
Jo̸rgen Hals ◽  
Torkel Bjarte-Larsson ◽  
Johannes Falnes
Keyword(s):  
Phase Control ◽  
Energy Output ◽  
Reactive Control ◽  
Wave Energy Converters ◽  
Submerged Sphere ◽  
Sphere Radius ◽  
Absorbed Power ◽  
S Period ◽  
And Control ◽  
Incident Waves

The theoretical potential for maximising energy output of wave-energy converters by means of optimum control is quantified for a heaving semi-submerged sphere on deep water. The heave amplitude is constrained to not exceed 0.6 units of the radius. Sinusoidal incident waves of amplitudes up to 3 m and period in the range of 6 s to 12 s are considered, when the sphere radius is 5 m. Optimum reactive control, contrary to sub-optimal latching phase control, requires ability for reversing the energy flow through the power take-off machinery. Computed results show that, for a typical wave of 0.5 m amplitude and 9 s period, the maximum absorbed power is 24, 137, and 172 kW for the cases of no phase control (passive system), sub-optimal latching control, and ideally optimal reactive control, respectively. The ratio between the maximum/minimum instantaneous power and the average absorbed power is 2/0, 4.1/0 and 11.0/-9.0, respectively, for the three different strategies.

scholarly journals Transcriptome-wide assessment of the m6A methylome of intestinal porcine epithelial cells treated with deoxynivalenol

2020 ◽  
Author(s):  
Zhengchang Wu ◽  
Chao Xu ◽  
Haifei Wang ◽  
Song Gao ◽  
Shenglong Wu ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Mammalian Cells ◽  
Tumor Necrosis ◽  
Cytotoxic Compound ◽  
Wide Range ◽  
Food And Feed ◽  
Functional Relevance ◽  
And Control ◽  
Necrosis Factor

Abstract Background: Deoxynivalenol (DON) is a cytotoxic compound found in various food and feed products. N6-Methyladenosine (m6A) is a highly abundant epitranscriptomic marker that modifies a wide range of mRNA molecules in mammalian cells. However, the role of the m6A methylome in DON-induced damage remains poorly understood.Results: In this study, we assessed the transcriptome-wide m6A profile of intestinal porcine epithelial cells (IPEC-J2) treated with 1000 ng/mL DON by m6A sequencing and RNA sequencing. Overall, 5406 new m6A peaks appeared with the disappearance of 2615 peaks in DON-treated IPEC-J2 cells. Genes that were uniquely m6A-modified following DON treatment were found to be associated with the tumor necrosis factor (TNF) signaling pathway. On comparing DON-treated and control cells, we identified 733 differentially expressed mRNAs bearing hyper- or hypomethylated m6A peaks. Further experimental data suggested that METTL3-dependent m6A methylation might also play a role in DON-induced inflammatory response, and CSF2 marker is key functional relevance in the context of DON-induced toxicity. Conclusions: This is the first study to perform a transcriptome-wide assessment of the m6A methylome of IPEC-J2 cells treated with DON. We believe that our findings should be useful for identifying mechanisms whereby m6A modifications influence the outcomes of DON exposure.

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