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Hi all, my current thoughts include
  • Experimentally filming and motion tracking people leaning on walls/pushing weights, then using k=f/(initial - final distance)
  • Energy methods: change in kinetic energy = potential energy (in a spring), then solve 1/2kx^2 = 1/2mv^2 for the stiffness, k.
  • An alternative energy method: Castigliano's theorem?
  • Spring tension = inertial forces (i.e. D'Alembert's Principle) + body force (i.e. weight)
  • Simulation using FEA, probably including multibody dynamics and rigid bodies for everything other than the arm.
Is there a method (of using any of the above) to understand the non-linearities that might be expected in a human ligament?
Please can I get any other suggestions you might have or comments on the above?
Many thanks,
Alex
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Hi Alexander,
I don't know the answer. When I clicked on questions this was one of the top ones and it took me back to my undergraduate days and I thought it was intriguing.
I completed a project and published a paper on the development of a Glenohumeral Test rig back then and I also know of other researchers who were working on similar bio-mechanical projects. I've attached the paper below and a few others. Maybe you could use them for reading, have a look at the referencing, it might provide you with useful papers related to your project. It might not, but I just thought it could be of some use to you.
Hope they might be of some use.
Best Regards
Martin
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Dear all,
I am looking for a research work that implemented an uncertainty or statistical framework to study the impact of the geometric parameters on the fracture response.
I appreciate any help.
Thank you in advance,
Moj Ab
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Whether Acoustic Vibrations can be used to damage / fracture the CORONA VIRUS (COVID-19) structure ?
Acoustics with resonance frequency of the COVID-19 can be used to prevent this Pandemic ?
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I am working on a project on designing and testing new materials and different structure(3D-infill) configurations as prototypes for the mid-sole of a running shoe.
I was wondering about the functional properties that would be required from the mid-sole of a shoe to optimize its performance.
Any leads regarding mechanical/functional properties of running shoes, midsoles or regarding mechanical testing of midsoles would be very helpful.
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weight acting capacity, stiffness, material, strength etc.
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Kicking ability represents the most important soccer-specific skill, since it is used not only in passes, crosses, clearances, and also to score goals.
The ability to kick equally with both the preferred and non-preferred leg leads to an advantage for soccer players, since it increases the number of scoring opportunities. In modern football, this ability is becoming even more important as there is less space and time for players to decide what we do with the ball. In fact, there is positive relationship between player’s salary and ability to use two feet in professional soccer.
However, ball velocity is significantly lower after a kick with the non-preferred leg in comparison to the preferred one.
It’s known that two-footedness can be developed, to some extent, by training. But it would be possible to develop two-footed players in soccer club academys? Why don't we teach our soccer players to use both feet equally well?
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It is not only possible but totally necessary: that the soccer player have high bilateral motor skills allows their technical executions to be better. This improvement in sports performance leads to a decrease in the incidence of injuries since by optimizing bilateral movement patterns we are avoiding positions or gestures prone to injury.
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Dear all,
I am trying to apply material mapping to the vertebral model. I exported image data and surface model (.stl) from the 3D slicer, but when the same are imported IA-Femesh, there is no overlap, so cannot apply the image intensity based properties.
Can you please help me to resolve this issue.
Is it possible to link the IA-FEMesh to 3D slicer?
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make more than one surface
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Hi all,
I'm trying to simulate a static load being applied into a hip geometry where femur bone (sphere geometry) and pelvis bone(hemisphere geometry) are having contact through a frictionless environment.
My Boundary Conditions are the following:
- Distributed force applied through a kinematic coupling constraint on a surface(pelvis).
- No translation or rotation allowed on a surface (femur)
- Surface-to-surface frictionless contact.
I'm using tetrahedral C3D10 elements with a fine mesh due to the irregular shape of the geometries and their difficulty to partition in order to obtain a structured mesh.
The main convergence problem is that ABAQUS reaches the maximum number of attempts (5) for an increment without finding a solution[cut-backs]. I've seen some advice where they suggest the following:
-Modifying a mesh to a structured one
- In case of tetrahedral elements, use a very fine mesh.
- Modify algorithm such as increment attempts, reducing time increment and on.
- Decompose my load into more steps to overcome the critical point.
I haven't been able to succeed yet by trying some of those. Does anyone has a particular suggestion?
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Dear Karthigeyan,
Many thanks for the advice. In fact my problem was that the forces were not in equilibrium in y static model, which caused convergence problems. As a I only needed my geometry to move in the direction of my force, I was able to solve the problem by using linear elements C3D4 instead of Quadratic. Thus, rotation was not allowed by using these elements without compromising the result.
Best!
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Hello All
I'm trying to synchronize imu sensor with the Motion Capture system. Is this possible? If so, how?
thanks for answering
Alireza
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Hi Alireza,
First, what is the type of motion capture system do you have? Most of them actually have their own synchronization box, which serve as trigger in or trigger out for other external device including IMU. However, if your IMU sensor is a standalone sensor without any base to connected, then you can try an option to synchronize it by using some movement that cause spike on IMU signal like jumping.
Hope this helps you
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I am looking to sync data across an ultrasound machine (Terason USmart 3300), Vicon motion capture, force plate, and Delsys EMG data. I have gotten the Vicon, force plate, EMG to sync within a Vicon program, but am looking to add ultrasound to it. Terason has told me it is not possible unless I alter the unit (which they will do and charge me for). I am hoping that it is possible to do it without that expense (since it is not just my lab's unit).
I am looking to see if anyone has done this? I was thinking I could maybe get a digital to analog converter that would allow me to connect it to the trigger that is already hooking up the other devices (Vicon only allows me to add a "generic analog device" in the program). This Terason unit is extremely clinical and does not have any wires that would allow me to hook it up. I have seen some "Trigno wire" devices that seem to fix that problem, but not sure if that would be enough of a solve.
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I am not familiar with that exact system, but if you have the option of recording ECG you could generate a timing signal and attach that to both the ECG and EMG sensors to use as a synchronisation signal. Just ensure you generate an appropriate voltage and current so as not to damage the equipment.
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Alginate is an anionic polymer and on the other hand Rhodamine B is a cationic dye. Theoretically these two should be boned by ionic bond. Does it happen? More suggestions and experience are greatly appreciated. Advanced thanks!!
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You might be able to couple the rhodamine carboxyl to an alginate hydroxyl with a water soluble diimide coupling reagent.
Or use a different dye....
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Have you, or anybody you can recommend, published applied biomechanics research conducted at least in part as an undergraduate?
If so, please get in touch or recommend others.
I'm asking for 5 mins to complete a survey on your experiences to help others.
I'll get in touch with the survey link (not posting publicly to ensure genuine responses / inclusion criteria are met).
Many thanks,
Stuart
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Great, thank you. I'll send you a message.
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I want an initial direction, like how can I use IMU sensors on knees (e.g upper leg and lower leg ) to estimate body state e.g running, walking, climbing, etc. The basic idea I have is to use 2 IMU sensors on knee position (upper and lower leg) , and to get data or make a data set of it. Then process it using deep learning e.g CNN or ANN etc. But point is..are there data sets available on which I can test CNN etc to see either it works or not. Need guidance about data sets, from where could I get IMU knee based data sets, so that I can focus on my algorithm only.
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It seems you are trying to solve a classic problem of human activity recognition based on body-worn sensors. A very good starting point for different datasets, mainly based on acceleration only, is this paper:
I wouldnt recommend using a naked CNN for testing. A classic machine learning approach with a proper preprocessing, some good extracted features (e.g. simpe statistical features, PCA or Codebook) and a classification that supports the understanding of the problem (e.g. kNN or SVM). Good luck and have fun trying :).
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Which two software of ADINA and ABAQUS are better for fluid structure interaction (FSI) simulation?
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Dear Mehdi,
I heard, for example, the power of ABAQUS in mesh generation is better than ADINA. A researcher told me that he had a 3D model and he couldn’t prepare a meshed model of it using ADINA and he had many errors and problems, but he prepares the meshed model of that 3D model very easy using ABAQUS. Do you agree with him?
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I am planning a study on freezing in patients with Parkinson’s disease. I need basic parameters including and especially time taken to initiate walking.
What is the most affordable way to conduct such gait analysis? Insoles? Affordable gait mats?
Thanks for your response in advance,
Siddharth.
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The cheapest is likely to be either a 2D video camera and free software.
The trouble you will find is placing a camera in the correct location. Using a treadmill is unlikely to be a good move with this patient group, therefore you will need multiple cameras to catch more than a step or two initiation of gait.
You could try an app on a mobile phone, you can either find one that tracks movement or one that streams data via Bluetooth. Most phones have both at least one triaxial accelerometer and gyroscope included, so depending on your skills with signal processing this could be a reasonably cheap approach.
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Hi everybody
I'm using abaqus dynamic implicit solver to analyze hip joint. There is not problem like this with static step. but i have to use time depended loads. so when i use dynamic implicit; there are stresses only in force applied area but no stress or displacement in anywhere else. i also tried with dynamic explicit step and concentrated and pressure loads but the problem didnt solve.
i've used frictionless surface to surface contact and fixed a region far from load applied area. and material properties defined by mimics software.
i'll also add a photo and abaqus files fore details. thanks alot for your help.
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Chee Loong Chin Thanks a lot for your helpful answer.
Units were not consistent. The mimics soft had defined density in g/cm3 but because distances was in mm; the consistent unit for density was tonne/mm3.
Problem solved and thank you again.
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Hi.
Anybody has/had been working for the subject topic primarily for the FE/XFEM study and the associated software. Need suggestions for existing models/codes and/or review papers.
Thanking you,
Raees
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Muscle tissue does not normally produce electrical signals during rest. So its expected that the value Amplitude in mV will be roughly 0. However when muscles are stiff is when your muscles feel tight and you find it more difficult to move than usual, especially after rest. You may also have muscle pains, cramping, and discomfort. Cramps, which acts like muscle stiffness, can occur when muscles are unable to relax properly due to myosin fiber's not fully detaching from actin filaments. In skeletal muscle, ATP must attach to the myosin heads for them to disassociate from the actin and allow relaxation — the absence of ATP in sufficient quantities means that the myosin heads remains attached to actin. So will there be an expected amplitude in mV well greater than 0, maybe 3 to 5 mV range.
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The tibia is the most commonly broken major bone in the leg. Displaced distal tibia shaft fractures are effectively treated with standard plates or intramedullary nails. which one is more preferable?
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Please find attached some recent literature opinions
Effect of Locking Plate Fixation vs Intramedullary Nail Fixation on 6-Month Disability Among Adults With Displaced Fracture of the Distal Tibia
The UK FixDT Randomized Clinical Trial
Matthew L. Costa, PhD; Juul Achten, PhD; James Griffin, MSc; Stavros Petrou, PhD; Ian Pallister, MMedSci; Sarah E. Lamb, DPhil; Nick R. Parsons, PhD; for the FixDT Trial Investigators
JAMA. 2017;318(18):1767-1776
A comparison of the cost-effectiveness of intramedullary nail fixation and locking plate fixation in the treatment of adult patients with an extra-articular fracture of the distal tibia. Economic Evaluation Based on the FixDt Trial
M. Maredza, S. Petrou, M. Dritsaki, J. Achten, J. Griffin, S. E. Lamb, N. R. Parsons, M. L. Costa
Bone Joint J 2018;100-B:624–33.
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I am trying to model the behavior of a deformable object with a discrete rigid plate and am getting these warnings:
The master surface assembly_surf-plate does not exist.
Analysis Input File Processor exited with an error.
Does anyone know how to solve this?
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How have you defined the contacts?
Franco
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According to ISO 7206-12 standard, for acetabular shell deformation test, which material is more risky, having the smallest diameter or the biggest diameter?
Note: The thickness values are the same.
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I Think that your fatigue implants specimens diameters must modeling according the more risky case which is the smallest diameter
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What process or mechanism would be taken?
We want to identify people by their gait cycle video.
Do people have a unique gait cycle?
Is there any software to simulate the gait cycle and analyze it using a video of a person's walking cycle?
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I think that it is very interesting thought, and apparently I remember seeing that kind of scene from a movie (I cannot remember the title of movie...).
What process or mechanism would be taken?
Both kinematic and kinetic.
We want to identify people by their gait cycle video. Do people have a unique gait cycle?
I believe that people have a unique gait pattern. However, you should consider that each person have somewhat variability within their gait cycle. In other words, there are slight variations (wider/narrower/shorter/longer steps) within a person during step by step movement.
In my opinion, it is impossible but not feasible/efficient due to following reasons.
First, the variation (within person)/changes of gait cycle might be bigger than the fingerprints so that it may require constant update to an identification system. For example, a person's gait cycle can be changed due to different footwear, results of an injury, and aging. On the other hand, fingerprints are relatively stable to change (of course it changes/fades as time goes by...).
Second, fingerprints provide a reliable means of personal identification. To achieve the same level of reliability, thousands and thousands of people's gait cycle should be tested and analyzed to see the differences and similarity. Maybe at the end, you may conclude that the variation of gait cycle is not unique as much as the fingerprints (between persons).
In conclusion, I think that the combination of both can be beneficial for some closed/secured setting. To my knowledge, however, the gait cycle won't be able to completely replace the fingerprints identification.
Hope my answers are helpful to advance your thought.
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Hi!
I'm working on a biomechanical project. In fact I'm want to design a mechanical robot to simulate human gate in positions of walking and running. So I need to record human gate in different speeds and analyze the movement of COM and some specific joints and organs after that.
Can you suggest a required way (tools, devices, software or...) for this project?
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Tools required for Gait-Kinematics only:
  1. 3D Motion Tracker: It can be based on Optical Active Marker, Optical Passive Marker or Marker-less technology. Choice is based on available budget and other requirements (desired accuracy, speed, latency, environment etc.) and choice depends on many factors. There are other technology solutions for 3D Motion like Electromagnetic or Hybrid (Inertial, Accelerometer, Magnetometer) but in case you also need to track humanoid Robots (Metallic), these technologies are not suitable. These are fine for tracking humans.
  2. Biomechanical (Inverse Kinematics) modelling and analysis software: This component (software) will reduce the 3D Motion tracking data of markers/sensors (placed on body segments) from 3D Motion Trackers to motions of body segments. This will help model the body segments as per anthropocentric data of subject, localize joint centers and create a hierarchical , linked multi-body model to compute kinematics like joint angles, linear and angular velocities and accelerations. There are softwares that come with motion tracking system and there are 3rd Party softwares. 3rd party softwares generally provide more flexibility and control in modelling and analysis. Software can have real-time interface to motion tracking hardware or limited to off-line.
  3. 1 or 2 video cameras with synch capability to record reference videos are also good to have.
For kinematics, these will suffice. If you also need Inverse Dynamics (joint force, torques and power), then you will additionally need 6 component force platforms (1 or more) to record GRF and COP, and of course Inverse dynamics capability in the software.
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I am preparing electrospun nanofiber samples for mechanical analysis. The meshes are collected on Aluminum foil, and it is so difficult to detach them from it to proceed the analysis.
I have done many trials using adhesive tapes but the scaffolds didn't detach well from the Al foil. Moreover, I tried to hydrate the samples with physiological solution, waiting to dehydrate and then taking them off from Al foil, but also this technique didn't work because once the scaffold become dehydrated, it attached to the Al foil making its collection difficult.
Please can anyone give me any suggestion to solve this problem??
I would like to mention that I have 2 different types of scaffolds (randomly oriented and highly aligned fibers)
Thank you in advance
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Hello Mohammad.
In the past I have done some electrospinning on aluminium foil. To collect some samples I put thin glass coverslips on top which allowed me the collection of the sample (with the aid of a scalpel).
Also, you can try with some teflon tape on top of the aluminium foil, which should detach easily.
Hope it helps,
Hector
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We usually find many papers on theory or experimental researches about nano/microcantilever biosensors. Nevertheless, it is important for me to know which companies are working on it to improve this device for commercial goals?
Is there a final form of this device or technology?
Has this device ever been used in a clinic or hospital complex?
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Dear Saman ,
- There are several cantilever suppliers in EU and US as mentioned in the other answers.
- For cantilever based research, different groups normally using the simulation (FEM, ANSYS) to simulate and come up with their own cantilever designs. The variations are materials ( often are Si, low stress SiN, polysilicon, some polymers..), dimension, and even new cantilever formats (single, arrays, added materials ( often Au) for facilating the biding of receptors, new structuring...). In this way, they bring the added values in research and also make easy of later publishing the paper. This called custom-made designs.
- At Nanosens, we have been offering custom-made cantilevers for various customers (www.nanosens.nl). Most of the case we provide ultrathin ( down to 20 nm in thickness) low-stress SiN cantilvers. We are not often offer Si cantilevers as to make it we need to start from SOI wafers, and currently comercial available SOI , especially SOI with the device thickness in the micron range, has poor device thickness uniformity ( ca. 25% for 4 inc. wafer), subsequently lead to large variation in final cantilever thickness. Low-stress LPCVD SiN layer can be realized within 2 % of thickness variation.
Is there a final form of this device or technology?
No. As mentioned above, there are so much variations. Also, the cantilever forms depended on the measurement setup ( singles or arrays, range of frequency, static or dynamic modes, and recently coupling of opto + mechanics for optomechanical cantilevers...)
Has this device ever been used in a clinic or hospital complex?
Not yet. But I personally think it comes soon . You can take a look at the research group of Prof. Javier Tamayo and Montserrat Calleja , BioNanoMechnics Lab in Spain http://www.imm-cnm.csic.es/bionano/en
You may see that they have been making a great progress to push this device to practical applications.
- Finally, measurement setup is also a crucial important factor for the cantilever research. The Scala system from MECWINS is a personally recommended as its cost is acceptable, and simple in both operation and maitenance.
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Does anyone measure and analyse postural status of body with 2D camera system and how?
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I recommend using the CVMob free system available at https://sites.google.com/site/cvmobufba/ that has been validated for gait evaluation (http://dx.doi.org/10.17267/2238-2704rpf.v7i4.1648 ) and for postural evaluation (http://dx.doi.org/10.1097/JCE.0000000000000226).
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I ask about the convenient test to evaluate the leg power in sports, and the relationship between horizontal, vertical jump and leg power.
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The horizontal system in terms of power sharing is equal. Two joined company are able to maximize the resources on an equal level. However, Vertical system is mostly controlled by one party on the top.
If you're interested which system works based on your organization, and learn more cases in the marketing system. You can check out Career Academy. We use them for our office managers' training Project Management (Project Management, Business Skills, IT & CyberSec Online Certification Training)
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Osteoarthritis (OA) is a common occupational dangerous case for service members. I wanted to know how body borne load impacts knee biomechanics for participants who do and do not present varus thrust during running.
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I agree with Dr.Diachkova. Knee varus deformity predisposes to degenerative changes medially and progression.
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The test person’s right knee had a meniscal tear three times before the measurement. The last meniscal tear (always on the right knee) happened 2016.
Test person A: male, 25 years of age, 180cm, 89kg
The test person had to squat at a rhythm of 20 beats per minute (BPM). In other words, the participant had to perform one squat within 3 seconds. The measurement is finished till the test person is not able to keep the rhythm for his squats. This was the case after 103 squats. In addition to that, a chair was placed behind the participant as an orientation for the downward movement to squat always at the same height .
I'm trying to find out the differences in muscular activity and muscular fatigue during the same movement of m. rectus femoris / m. vastus lateralis of the test persons postsurgical and uninjured knee (leg). Maybe someone already has experience with these injuries.
I evaluated the measurement data (Matlab, STFT) from the EMG and they look like in the following way.
Vastus lateralis and rectus femoris from the right leg (postsurgical) occured to work in a much higher muscular frequency than the uninjured left leg. I'm not sure why this is the case and which role the meniscal tear takes in.
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I will suggest for power spectrum analysis on the data
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I currently want the measure the biomechanics of mice. Is there any available hardware / software to do so?
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CatWalk XT - a gait analysis system for rats and mice. 
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I need to know which sEMG descriptors are useful to determine motor unit recruitment or activation of a certain muscle. In our study, we want to see how the pattern of activation / recruitment differs between different inter-electrode distance (IED) and different intensities using an electrostimulator to cause muscle contraction.
In brief, we want to see if different intensities of electrostimulation (50, 75 and 100 mA) with different IED differ in the recruitment of motor units or something similar (i.e., any sEMG useful descriptor for this purpose).
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Does anyone have any data/research to the real intrarticular pressures in the ankle, particularly PSI. Not at the margin which is published at 10mpa. But within the joint and in the 9 different articular zones during phases of gait.
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Interesting but no experience
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we are writing a thesis on augmented eccentric loading's with additional isometric holds 
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fantastic - Thank you so much!!!
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What are the more important requirement needed during the measuring of the interface pressure for  the patient using ankle foot ortheses ?
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Thank you professor brain for all your expertise  informations its very interesting
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How can the modeling of the residual lower limb amputation be performed below the knee under consideration the effect of thermal distribution resulting from the tissues, muscles, veins and arteries as a heat source?
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Thank you sofia for your answer and attachment paper .
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I want to examine the efficacy of a lower limb stretching program on foot alignment or posture.
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You can use navicular drop or normalized truncated navicular height also according  to  your sample population
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Mostly in mathematical modelling of muscle strength by Marras and Granata this term PCSA has been used. I want to know how do we find the exact PCSA. or is it just an average from cadaver studies. 
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Imran, 
Oftentimes, mixed methods are employed.  For example, in a well-known study involving  R. Roy and V. Edgerton (1992), they estimated muscle volume from living subjects using serial axial view MRI scans.  However, the PCSA equation variables for muscle fiber length (i.e., muscle bundle length) and pennation angle were derived from their earlier cadaveric work from the seminal 1983 publication with Wickiewicz.  
Of course, there are other ways of accomplishing this task. More contemporary studies feature investigators that use imaging methods such as sonography to obtain in vivo estimates of muscle bundle length and pennation angle.  The brief list of links below highlight some of the classic methods and more recent techniques, along with some of the limitations associated with the imaging methods and PCSA estimates in general.
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I have a set of EMG data from incremental pedaling from the quadriceps muscles. I need to predict the  muscle fatigue from the analyses of EMG data. I could not find a change in parameters like median frequency or Zero crossing to identify fatigue threshold. I believe these are usual in Isometric contractions.
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The study of muscle fatigue with EMG can be done with the median frequency obtained from the power spectrum. However the EMG signal needs to be very stable and this only happens in an isometric contraction. In other words, the calculation of the median frequency of the EMG signal can not be done based on a dynamic muscle contraction. You can have a dynamic exercise which induces fatigue and two isometric contractions, for instance, before and after. In these two isometric contractions you can calculate the median frequency.
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I plan a study with a measurement of pressure firmness. Is there someone with experience with such a device?
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A lot of work on validating the Myoton has been carried out by Prof Maria Stokes and her team at Southampton Univesity - http://www.southampton.ac.uk/healthsciences/about/staff/mjs2.page
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Hi researchers,
I am working on gait analysis and I want to find joint angles of hip,knee and ankle.The only information I have is the markers position(x,y,z coordinates).Any help will be appreciated .
Thank you
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Hi , Srilakshmi
You asked how to calculate lower extremity kinematics using 3d coordinates. If you want hip I/E rotations, shank I/E rotations, Vaurus/valgus , and foot inversion/evertion as well you want 3d Angles.
The suggestion for inverse kinematics is mostly used in robotics where you know where the end effector is and you want to know what angles of arm segments would be to end up with the end effector in a certain position.  In your case the end effector is the foot. The solution given by Vijay is only 2d (I assume you want 3d) and it only provides two angles – the angle between the thigh and the horizontal (not really hip flexion) and the angle between the thigh and shank (knee angle). Inverse kinematics can yield different solutions.
The cosign formula from Mustafa will work but it gives the absolute 3d angle between two vectors and if the vectors are not in the same plane this angle is not necessarily the same as the clinical joint angle you want – maybe not a problem if hip and shank are in same plane – but like for the upper arm movements relative to the trunk it is problematic.
The preferred method used by most motion capture systems is to calculate the Euler Angles based on the local coordinate frames for each segment. Too much to explain here, but you should look up Euler angle calculation which you can do or get matlab or even excel programs to do. There are some caveat’s with them, but you can also reference several authors as well as ISB recommendations for their calculations
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Pressure insoles (or force insoles) are devices made to measure the reaction forces of the ground. They are built to measure how much pressure does the body produce and how its distributed on the surface of the device, when the foot contacts the ground, and this allows to measure balance with specific parameters like the Center Of Pressure (COP).
Some studies have used these devices to meassure the COP on static(Standing position) and dynamic balance(Walk, jump, run). Activities like Walking, and running have some phases on its movements when one foot (or even both of them) is not doing contact with the ground, but still the insoles record some residual pressure in this moment. Depending on how much time are we recording, does it imply that the residual pressure recorded is going to change the outcome in a significative way? if this happens, should researchers delete this remaining data?
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From my empirical knowledge all data should be taken into consideration. This type of study, that implies the use of an insole, could offer information over a larger range of anthologies, because it can measure in close and open chain.
Only if the data is beyond normal limits it should be used a threshold. In this direction there is a lot to talk about because I haven't heard of such normal limits, they depend on the situation of analysis environment. All that we know is that friction is given by friction coefficient multiplied by N and the ground reaction force is mass multiplied by acceleration plus any external or internal forces that might appear. It would be interesting to find a relation between this parameters that could offer a coefficient to calculate the limits of the forces considering age, mass, and different anthropometrical values.
In conclusion, I would use those values obtained from the opened swing phase of locomotion.
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The center of pressure (COP) is the point on a surface where the total sum of the resultant forces can act with the same magnitude of the force which is distribuited on the surface of an object. Measuring the COP has been used in biomechanics as a way to measure the postural balance in humans. There's been created variables or parameters related to the COP, in order to measure postural balance (e.g. COP Velocity, COP Displacement, COP Trayectory). Some studies have used one or more of this parameters with the purpose of investigate postural balance. But Which of this COP parameters is more usefull to reflect the COP behavior? Are there better parameters than others or maybe each parameter is better measuring balance in an specific task or context?
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I think it all comes down to matching your outcome measure to your research question. For instance, if you want to look at variability of a dataset, perhaps the standard deviation of the COP or even a nonlinear approach such as approximate entropy to look at the randomness within a sample.
Another example is using fractal dimension, which looks at the 'predictability' of a given path, where one would assume a more complex path represents either an altered postural control strategy, or perhaps dysfunction of the sensorimotor system.
I suggest reading this article by Prieto et al, 1996, regarding various COP outcomes, and it includes the calculations for each: http://www.ncbi.nlm.nih.gov/pubmed/9214811
Within my lab, we use time-to-boundary, which is a derived signal that looks at the direction and velocity of the COP signal with respect to the borders of the foot. See Hertel et al, 2006: http://www.ncbi.nlm.nih.gov/pubmed/16760569 There are other outcomes like this, and this would represent the amount of time it would take for an individual's COP to pass outside the borders of their foot (base of support), thus the assumption is made they would lose balance or be in a compromised position.
The 95% confidence ellipse is also a popular outcome, representing the locations of the COP, or another measure of COP area, if you want to look at the area of COP displacement.
Ultimately, my first point will help you best. Figure out which outcome will tell you most about your population or your balance task, and then use it. 
I hope this helps,
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Prefer an exhaustive text book which is written as an introductory text and explain the concept of strain energy in details and multiple models, derivation and limitations.
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Hi,
I am not sure you will find easily this information on text books, however, I am sure you can find few PhD thesis using hyperelastic models for soft biological tissues. You can nevertheless find easily hyperelastic theory for polymers (which is the same theory)
Some key aspects of this are :
- Usual strain energy derives from classical thermoelasticity for hyperelastic materials.
- limitations are based on the fact that hyperelastic behavior depends on identification parameters on simple test such as simple tension or biaxial tension not valid on complex load scenarios
Application to soft tissue depends on two factors : (i) hypothesis of homogeneity of the structure, (ii) validity of tissue microstructureal behavior to the model you use.
Regards,
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I want to process biomedical data on LABview 8.5. I tried to download the VI's but they don't work. Are they only for the newer versions of LABview. If they are: Can I get such a toolkit for my version?
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What VI´s did you download? Why didn´t worked? If it was because of the newer version you can ask for a version conversion in the forums of NI (first link). All the compatibles toolkits available for that version are listed in the second link. I´m sure you can process biomedical data on labview 8.5, the question is, how are you gonna acquire the data. Also, you can download the evaluation softtware of labview (newer version) directly from NI. Best regards.
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In several studies which aim is to test or evaluate static or dynamic balance, is usual that the measuring tool are force plates, platforms or pressure insoles. In order to perform the balance recording, the researchers have to set the appropiate settings, which includes the sampling rate. Some studies had reported sampling rates ranging from 200 to 1000 Hz or more, depending on the tool.
Having in count that each one of the main sensory systems involved is supose to react and modulate balance at very low frequencies (compared to the sampling rate that the measuring tools usually have in most of the studies), is it really necessary to set the sampling rate to high?
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The Nyquist sampling theorem dictates your sampling frequency. You first must determine the highest frequency intrinsic to the process you are trying to record. The Nyquist theorem states that your sampling frequency must be at least twice that of the highest intrinsic frequency. If you don't, aliasing will occur. Often, the ideal sampling frequency may be more like ten times that of the highest intrinsic frequency. 
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There are lots of papers about researchers which investigated how does the COP behave in some postures (like unipedal or bipedal standing), and functional activities (like walking) on healthy population. Another activity related to the daily living is going up and down stairs, which of course allow us to get to some point (high or down in a building, for example) in case there is not an elevator or other devices that allow us to get there. Furthermore most of the buildings around us (even our own houses) have stairs on them, so we have to deal with that structure.
There are some studies which have investigated the kinetic and kinematic parameters, angles and other properties related to the stair descent. I´m interested in knowing how the COP parameters (Ap/Ml Displacement, Velocity, and trace length) behaves in this activity
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HUMOS 2 model is developed under a European Framework program and used in numerous publications since early 2000's. Unfortunately, I could not find a reference on how the model it self can be accessed. Any help is appreciated.
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Unfortunately no, I could not find the Humos 2 hbm model on a public source. To be honest I did not contact ESI either. 
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I am working on a thesis about how different hand tool designs affect the pressure distribution over the palm of the hands. However, it is somewhat difficult to get references about how excessive pressures may impair the use of a product and what are its implications on hands, in a physiological level (like schemias, calluses, etc.). I found only very sparse mentions of pressure in some texts, like Cacha and Tichauer and Gage. One reference that may be helpful is the one listed below, but I can't get my hands on it:
Mechanical considerations of skin in work. AMERICAN JOURNAL OF INDUSTRIAL MEDICINE. Volume 8, Issue 4-5, 1985, Pages: 463–472, Thomas J. Armstrong
Article first published online : 11 JAN 2007, DOI: 10.1002/ajim.4700080428
Does someone have it or know any reference that may help me in this way?
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Paul W. Brand, FRCS, and the bioengineers with whom he worked at the US Public Hearth Service, Carville, LA (USA) did considerable research regarding soft tissue response to stress.   The tree editions of his book, Clinical Mechanics of the Hand, contain synopses of this research.  Although these books are out of print, they continue to be highly regarded and prized in the hand/upper extremity surgery and rehabilitation fields.  You may be able to locate one or all of these books through your medical library; or the Internet.  Below are a few of Brand's journal publications that may pertain:
Brand, P. W. (2006). Pressure sore--the problem. J Tissue Viability, 16(2), 9-11.
MacMoran, J. W., & Brand, P. W. (1987). Bone loss in limbs with decreased or absent sensation: ten year follow-up of the hands in leprosy. Skeletal Radiol, 16(6), 452-459.
Brand, P. W. (1979). Management of the insensitive limb. Phys Ther, 59(1), 8-12.
Brand, P. W., & Ebner, J. D. (1969). Pressure sensitive devices for denervated hands and feet. A preliminary communication. J Bone Joint Surg Am, 51(1), 109-116.
Brand, P. W., & Ebner, J. D. (1969). A pain substitute pressure assessment in the insensitive limb. Am J Occup Ther, 23(6), 479-486.
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Chapter 4: Simulation of a Lumbar Motion Segment
vertebral_body_input.dat -- Input file for the lumbar motion segment simulation.
vertebral_body.cdb -- Common database file for the lumbar motion segment model (called by the vertebral_body_input.dat file).
The files are available in the td-10 folder. See Obtaining the Input Files for more information.
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Thank You Rayudu Nithin manohar
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 side deviations For line work Force leads to weakness in the Force while running and throwing during movement
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Dear my  colleague Hamdy,
I hope the following papers help you.
Buller, P. F., & McEvoy, G. M. (2012). Strategy, human resource management and performance: Sharpening line of sight. Human Resource Management Review. http://doi.org/10.1016/j.hrmr.2011.11.002
Cholewicki, J., & McGill, S. M. (1996). Mechanical stability of the in vivo lumbar spine: Implications for injury and chronic low back pain. Clinical Biomechanics, 11(1), 1–15. http://doi.org/10.1016/0268-0033(95)00035-6
Colloca, C. J., Keller, T. S., Harrison, D. E., Moore, R. J., Gunzburg, R., & Harrison, D. D. (2006). Spinal manipulation force and duration affect vertebral movement and neuromuscular responses. Clinical Biomechanics, 21(3), 254–262. http://doi.org/10.1016/j.clinbiomech.2005.10.006
Danion, F., & Sarlegna, F. R. (2007). Can the human brain predict the consequences of arm movement corrections when transporting an object? Hints from grip force adjustments. The Journal of Neuroscience : The Official Journal of the Society for Neuroscience, 27(47), 12839–12843. http://doi.org/10.1523/JNEUROSCI.3110-07.2007
Dulhunty, J. (2002). A simplified conceptual model of the human cervical spine for evaluating force transmission in upright static posture. Journal of Manipulative and Physiological Therapeutics, 25(5), 306–317. http://doi.org/10.1067/mmt.2002.124421
Flanagan, J. R., & Wing, a M. (1997). The role of internal models in motion planning and control: evidence from grip force adjustments during movements of hand-held loads. The Journal of Neuroscience : The Official Journal of the Society for Neuroscience, 17(4),
Han, J. S., Goel, V. K., & Kumar, S. (1991). A nonlinear optimization force model of the human lumbar spine. International Journal of Industrial Ergonomics, 8(3), 289–301. http://doi.org/10.1016/0169-8141(91)90039-O
Hansen, L., de Zee, M., Rasmussen, J., Andersen, T. B., Wong, C., & Simonsen, E. B. (2006). Anatomy and biomechanics of the back muscles in the lumbar spine with reference to biomechanical modeling. Spine, 31(17), 1888–99.
Keenan, K. G., Santos, V. J., Venkadesan, M., & Valero-Cuevas, F. J. (2009). Maximal voluntary fingertip force production is not limited by movement speed in combined motion and force tasks. The Journal of Neuroscience : The Official Journal of the Society for Neuroscience, 29(27), 8784–8789. http://doi.org/10.1523/JNEUROSCI.0853-09.2009
Lackner, J. R., & Dizio, P. (1994). Rapid adaptation to Coriolis force perturbations of arm trajectory. J Neurophysiol, 72(1), 299–313. http://doi.org/citeulike-article-id:450102
Ledet, E. H., Tymeson, M. P., DiRisio, D. J., Cohen, B., & Uhl, R. L. (2005). Direct real-time measurement of in vivo forces in the lumbar spine. Spine Journal, 5(1), 85–94. http://doi.org/10.1016/j.spinee.2004.06.017
Luinge, H. J., & Veltink, P. H. (2004). Inclination measurement of human movement using a 3-D accelerometer with autocalibration. IEEE Transactions on Neural Systems and Rehabilitation Engineering : A Publication of the IEEE Engineering in Medicine and Biology Society, 12(1), 112–121. http://doi.org/10.1109/TNSRE.2003.822759
Shirazi-Adl, A., & Parnianpour, M. (1993). Nonlinear response analysis of the human ligamentous lumbar spine in compression. On mechanisms affecting the postural stability. Spine, 18(1), 147–58. http://doi.org/10.1097/00007632-199301000-00021
Shirazi-Adl, A., Sadouk, S., Parnianpour, M., Pop, D., & El-Rich, M. (2002). Muscle force evaluation and the role of posture in human lumbar spine under compression. European Spine Journal, 11(6), 519–526. http://doi.org/10.1007/s00586-002-0397-7
Shum, G. L. K., Crosbie, J., & Lee, R. Y. W. (2005). Symptomatic and asymptomatic movement coordination of the lumbar spine and hip during an everyday activity. Spine, 30(23), E697–702. http://doi.org/10.1097/01.brs.0000188255.10759.7a
Teo, E. C., & Ng, H. W. (2001). Evaluation of the role of ligaments, facets and disc nucleus in lower cervical spine under compression and sagittal moments using finite element method. Medical Engineering and Physics, 23(3), 155–164. http://doi.org/10.1016/S1350-4533(01)00036-4
Vaz, G., Roussouly, P., Berthonnaud, E., & Dimnet, J. (2002). Sagittal morphology and equilibrium of pelvis and spine. European Spine Journal, 11(1), 80–87. http://doi.org/10.1007/s005860000224
Wada, O., Tateuchi, H., & Ichihashi, N. (2014). The correlation between movement of the center of mass and the kinematics of the spine, pelvis, and hip joints during body rotation. Gait and Posture, 39(1), 60–64. http://doi.org/10.1016/j.gaitpost.2013.05.030
Wu, B., Wang, C., Krug, R., Kelley, D. A., Xu, D., Pang, Y., … Zhang, X. (2010). 7T human spine imaging arrays with adjustable inductive decoupling. IEEE Transactions on Bio-Medical Engineering, 57(2), 397–403. http://doi.org/10.1109/TBME.2009.2030170
Regards, 
Abdel-Rahman
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Man of 58 years-old with trauma (D12 vertebral fracture, fractured left shoulder blade, multiple rib fractures on the left). The scapular fracture treated with immobilization for 30 days (orthopedic). The patient has undergone neurosurgery of reduction / stabilization of the fracture with screws transpedicular D12 D11-D12 L1e kyphoplasty (duration surgery - 1 hour and 25 minutes, anesthesia duration - 2 hours and 15 minutes). The patient was placed in the prone position with the head resting on blankets and turned to the left. Immediately after the operation, during arousal, the patient experienced pain in the left eye, edema and amaurosis. He underwent angiography which showed signs of retinopathy in both eyes and a central retinal artery occlusion in the left eye (CRAO).The patient is diabetic with insulin pump therapy, hyperlipidemic (rosuvastatina), hypertension, occasional smoker or former smoker, hyperhomocysteinemia, assumes Cardioaspirin. The doppler has revealed a thickening of the left carotid artery with a fibro-calcific plaque without significant impairment of flow. In addition, both the CT that the brain MRI showed multiple small areas of gliosis of the white matter, as from vascular cerebral disease. According to your experience, could the prone position to have been the only cause of ocular damage? 
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Bone fracture, post op immobilisation , DM , hyperlipidaemia, carotid plaque etc has the potentiality to develop thrombus and or embolus which can cause blockage of arteriole on their  circulating path way. We ophthalmologist often keep our patient in prone position following VR surgery. There is hardly any report  of CRAO following such procedure. I also agree w other responder that positioning of the patient has not caused CRAO. 
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I need to a) know if its built-in hardware circuit network amplify the raw signal and b) if its built-in hardware circuit network convert the raw signal to an average root-mean-square (rms).
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Many thanks for your help. Your comments have helped me a lot as I could not find that information anywhere.
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Suppose I am given a motion data file (say AMC) that is without the translation/rotation of the overall skeleton. If I only know the joint angles, how do I compute the overall translation and orientations of the figure? I have some idea. To calculate walking distance for example, I would need to calculate the stride length (how to determine a stride?) and the number of strides per unit time. To calculate the body orientation, I should compute the length and orientation of the leg limb at the point of foot-ground contact, and to calculate the body position during the flight phase (in running), I will need the velocity of the feet upon take-off and compute the force. But I'm interested to know if there's certain subtlety or if there is is some explanation or example calculations anywhere. Thanks.
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The Book by David Tittertoin "Strapdown Inertial Navigation Technology" is a very usful reference for that kind of work also.
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Currently most of the material models available for bone are linear elastic with E nd v. Are there any better models available for representing bone in Abaqus like concrete damage plasticity etc.
Do all bones have same material properties or are these very site specific.
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Thank You Abdul Aziz , Prasannah , Navid and Zdenka for your suggestions.
Based on the literature survey i found that most of the works on different bones have used Linear models for static studies and other constitutive models such as concrete damage plasticity, hyperfoam , power law models etc for dynamic studies.
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I am developing a FE model of lumbar spine. Has anyone developed a model using tetrahedral mesh. Most of the papers which I read have used hex mesh. I wanted to know the advantage and disadvantages of both the meshes while developing a model. 
Also I want to know how to go about in making the inter vertebral disc. I have read about mesh interpolation techniques which are used for this , I guess it wont work with tet mesh.
thanks and regards
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Hi I Wayan Sadwika
Can you tell me your stage of model building. so that we can share the problems and the people who have built the model can guide us in the same.
I am stuck at creating the disc.
I am trying to extract the geometry from the mesh file and trying to loft it. But then I m not able to build the bulge of disc.
Is there any easy method to go about the same.
PFA the pictures of the process.
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There are more studies explaining about chronic pain and inability of patient to repeat the Joint Re position test in both cervical and Lumbar region. I would like to know how can we measure it precisely in clinical set up. Any reliable scale to grade the error?
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Hello, some articles that can help you, kings regards.
1. Arch Phys Med Rehabil. 1994 Aug;75(8):895-9.
Changes in cervicocephalic kinesthesia after a proprioceptive rehabilitation
program in patients with neck pain: a randomized controlled study.
Revel M(1), Minguet M, Gregoy P, Vaillant J, Manuel JL.
Author information:
(1)Laboratoire d'Explorations Fonctionnelles de l'Appareil locomoteur et
d'évaluation du handicap, Hôpital Cochin, Paris, France.
Head repositioning accuracy (HRA) after full range active motion was evaluated in
60 cervicalgic patients. The mean angular error was 7.7 degrees +/- 3.3 (mean +/-
SD) and 82% were outside a threshold value of 4.5 degrees. After randomization 30
patients followed a rehabilitation program based on eye-head coupling (RG) and 30
served as a control group (CG). At 10 week follow-up, a greater gain in HRA was
observed in the RG (2 degrees +/- 2.7, mean +/- SD) than in the CG (0 +/- 2.6,
mean +/- SD) (p = 0.005). Clinical parameters (pain, drug intake, range of
motion, and self assessed functional improvement) were also more improved in the
RG than in the CG. These data emphasize the role of a neck proprioception
alteration in chronic neck pain and suggest that a rehabilitation program based
on eye-head coupling should be included in most medical management of cervicalgic
patients.
PMID: 8053797 [PubMed - indexed for MEDLINE]
2. Arch Phys Med Rehabil. 1991 Apr;72(5):288-91.
Cervicocephalic kinesthetic sensibility in patients with cervical pain.
Revel M(1), Andre-Deshays C, Minguet M.
Author information:
(1)Department de Reeducation, Clinique de Rhumatologie, Hopital COCHIN, Paris,
France.
Head orientation in space makes use of multiple sensory afferents, among which
the cervical proprioceptive cues could play a predominant role. To quantify the
alteration of neck proprioception in patients with cervical pathology, we
proposed a test for the clinical evaluation of the ability to relocate the head
on the trunk after an active head movement, for 30 healthy subjects and 30
patients with cervical pain. The data demonstrated that this ability was
significantly poorer in the patient group, indicating an alteration in neck
proprioception. This test permits a discriminant classification of healthy and
sick subjects, justifies proprioceptive rehabilitation programs, and allows a
quantitative evaluation of their results.
3. Physiother Theory Pract. 2008 Sep-Oct;24(5):380-91. doi:
10.1080/09593980701884824.
Test-retest reliability of cervicocephalic relocation test to neutral head
position.
Pinsault N(1), Fleury A, Virone G, Bouvier B, Vaillant J, Vuillerme N.
Author information:
(1)Laboratoire TIMC-IMAG, UMR UJF CNRS 5525, Grenoble, France.
Considering the important role of the cervical joint position sense on control of
human posture and locomotion, accurate and reliable evaluation of neck
proprioceptive abilities appears of great importance. Although the
cervicocephalic relocation test (CRT) to the neutral head position (NHP) usually
is used for both research and clinical purposes, its test-retest reliability has
not been clearly established yet. The purpose of the present experiment was to 1)
evaluate the test-retest reliability of the CRT to NHP and 2) to determine the
number of trial recordings required to ensure reliable measurements. To this aim,
40 young healthy adults performed the CRT to NHP on two separate occasions. Ten
trials were performed for each rotation side. Absolute and variable errors,
processed along their horizontal, vertical, and global components, were used to
assess the cervical joint repositioning accuracy and consistency, respectively.
Mean difference between test and retest with 95% confidence interval, intraclass
correlation coefficient, and Bland and Altman graphs with limits of agreement
were used as statistical methods for assessing test-retest reliability. Results
show that the CRT to NHP when executed in its original form (i.e., 10 trials) has
a fair to excellent reliability (ICC ranged from 0.52 to 0.81 and from 0.49 to
0.77, for absolute and variable errors, respectively); the test-retest
reliability of this test increases as the number of trials used to establish
subject's repositioning errors increases; and using the mean of eight trials is
sufficient to ensure fair to excellent reliability of the measurements (ICC
ranged from 0.39 to 0.78 and from 0.44 to 0.78, for absolute and variable errors,
respectively).
PMID: 18821444 [PubMed - indexed for MEDLINE]
4. Ann Readapt Med Phys. 2008 May;51(4):257-62. doi: 10.1016/j.annrmp.2008.02.004.
Epub 2008 Apr 29.
[Impact of nociceptive stimuli on cervical kinesthesia].
[Article in French]
Vaillant J(1), Meunier D, Caillat-Miousse JL, Virone G, Wuyam B, Juvin R.
Author information:
(1)Centre de recherche et d'innovation en kinésiologie, kinésiopathologie et
kinésithérapie, institut universitaire professionnalisé en ingénierie de la
santé, BP 217, 38049 Grenoble cedex 09, France. JVaillant@chu-grenoble.fr
The goal of this study was to evaluate the impact of nociceptive stimuli upon the
cervical proprioception ability.METHOD: Thirty healthy young subjects performed a
cervicocephalic relocation test (CRT) in two random conditions: the first one was
based on a nociceptive electric stimulation called condition "pain", whereas the
second one was targeting a painless electric condition called condition
"control". The CRT consisted of repositioning the head on the trunk, after an
active transversal movement of the head in the transverse field with closed eyes.
The pointing was recorded at the beginning and at the end of each rotation using
a custom video acquisition system.
RESULTS: The average mean of error repositioning was worth 3.98+/-0.99 degrees
(average mean, standard deviation) in the condition "pain", and 1.75+/-0.37
degrees in the condition "control" (p<0.01).
CONCLUSION: Acute pain provokes a disturbance of the cervical proprioception
ability without damaging the anatomic structure. This observation suggests the
interest of an early follow-up of the pain to avoid sensory disturbances, as well
as the establishment of a cervical proprioceptive rehabilitation program after an
algic event.
5. Phys Ther Sport. 2010 May;11(2):66-70. doi: 10.1016/j.ptsp.2010.02.004. Epub 2010
Mar 15.
Cervical joint position sense in rugby players versus non-rugby players.
Pinsault N(1), Anxionnaz M, Vuillerme N.
Author information:
(1)Ecole de kinésithérapie du CHU de Grenoble, France; TIMC-IMAG laboratory AFIRM
and AGIM3 teams, UMR UJF-CNRS 5525, Grenoble, France. npinsault@chu-grenoble.fr
OBJECTIVE: To determine whether cervical joint position sense is modified by
intensive rugby practice.
DESIGN: A group-comparison study.
SETTING: University Medical Bioengineering Laboratory.
PARTICIPANTS: Twenty young elite rugby players (10 forwards and 10 backs) and 10
young non-rugby elite sports players.
INTERVENTIONS: Participants were asked to perform the cervicocephalic relocation
test (CRT) to the neutral head position (NHP) that is, to reposition their head
on their trunk, as accurately as possible, after full active left and right
cervical rotation. Rugby players were asked to perform the CRT to NHP before and
after a training session.
MAIN OUTCOME MEASUREMENTS: Absolute and variable errors were used to assess
accuracy and consistency of the repositioning for the three groups of Forwards,
Backs and Non-rugby players, respectively.
RESULTS: The 2 groups of Forwards and Backs exhibited higher absolute and
variable errors than the group of Non-rugby players. No difference was found
between the two groups of Forwards and Backs and no difference was found between
Before and After the training session.
CONCLUSIONS: The cervical joint position sense of young elite rugby players is
altered compared to that of non-rugby players. Furthermore, Forwards and Backs
demonstrated comparable repositioning errors before and after a specific training
session, suggesting that cervical proprioceptive alteration is mainly due to
tackling and not the scrum.
PMID: 20381004 [PubMed - indexed for MEDLINE]
6. Spine (Phila Pa 1976). 2010 Feb 1;35(3):294-7. doi: 10.1097/BRS.0b013e3181b0c889.
Degradation of cervical joint position sense following muscular fatigue in
humans.
Pinsault N(1), Vuillerme N.
Author information:
(1)AFIRM Team, TIMC-IMAG Laboratory, UMR UJF CNRS 5525, La Tronche, France.
STUDY DESIGN: Before and after intervention trials.
OBJECTIVE: To investigate the effect of cervical muscular fatigue on joint
position sense.
SUMMARY OF BACKGROUND DATA: Although fatigue-related degradation of
proprioceptive acuity at lower and upper limbs is well documented, to date no
study has investigated whether muscular fatigue induced at the neck could modify
joint position sense.
METHODS: A total of 9 young healthy adults were asked to perform the
cervicocephalic relocation test to the neutral head position, that is, to
relocate the head on the trunk, as accurately as possible, after full active
cervical rotation to the left and right sides. This experimental task was
executed in 2 conditions of No fatigue and Fatigue of the scapula elevator
muscles. Absolute and variable errors were used to assess the cervical joint
repositioning accuracy and consistency, respectively.
RESULTS: Less accurate and less consistent repositioning performances were
observed in Fatigue relative to No fatigue condition, as indicated by increased
absolute and variable errors, respectively.
CONCLUSION: Results of the present experiment evidence that cervical joint
position sense, assessed through the cervicocephalic relocation test to the
neutral head position, is degraded by muscular fatigue.
PMID: 20075783 [PubMed - indexed for MEDLINE]
7. Arch Phys Med Rehabil. 2008 Dec;89(12):2375-8. doi: 10.1016/j.apmr.2008.06.009.
Cervicocephalic relocation test to the neutral head position: assessment in
bilateral labyrinthine-defective and chronic, nontraumatic neck pain patients.
Pinsault N(1), Vuillerme N, Pavan P.
Author information:
(1)Laboratoire TIMC-IMAG, UMR CNRS 5525, Grenoble, France.
OBJECTIVE: To determine whether vestibular or cervical proprioceptive information
influence the cervicocephalic relocation test to the neutral head position, by
comparing head repositioning errors obtained in asymptomatic, unimpaired control
subjects with those obtained in bilateral labyrinthine-defective patients and
chronic, nontraumatic neck pain patients.
DESIGN: A group-comparison study.
SETTING: University medical bioengineering laboratory.
PARTICIPANTS: Labyrinthine-defective patients (n=7; mean age+/-SD, 67+/-15 y),
nontraumatic neck pain patients (n=7; 56+/-9 y), and asymptomatic, unimpaired
control subjects (n=7; 64+/-12 y).
INTERVENTIONS: Participants were asked to relocate the head on the trunk, as
accurately as possible, after full active cervical rotation to the left and right
sides. Ten trials were performed for each rotation side.
MAIN OUTCOME MEASURES: Absolute and variable errors were used to assess accuracy
and consistency of the repositioning, respectively.
RESULTS: No significant difference in repositioning errors was observed between
labyrinthine-defective patients and control subjects, whereas nontraumatic neck
pain patients demonstrated significantly increased absolute errors in horizontal
and global components and higher variable errors in horizontal component.
CONCLUSIONS: These findings suggest that the vestibular system is not involved in
the performance of the cervicocephalic relocation test to neutral head position,
and further support this test as a measure of cervical proprioceptive acuity.
PMID: 19061750 [PubMed - indexed for MEDLINE]
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Looking for a start up to quantify the harmony between a carrying system (e.g. leaf blower) using acceleration sensors. In a first approach a attached a sensor to the sternum and a second sensor close to the centre of mass of the device. Both sonsor's coordinate systems have had teh same orientation. Analysis of the signals came up with questions such as "How can a improve the position of the sensors?" and " Which parameter is suitable for the assessment of a comfortable fit"? Thanks for any help.
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This article is very useful thx.
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how does the modulus of elasticity for entire tree trunks vary with tree age? Where are data on this?
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There are a suite of papers centred on the work of Mike Watt in NZ around the relationship between slenderness and MOE.
Watt, Michael S., et al. "Modelling environmental variation in Young's modulus for Pinus radiata and implications for determination of critical buckling height." Annals of botany 98.4 (2006): 765-775.
Lasserre, Jean-Pierre, et al. "Influence of initial planting spacing and genotype on microfibril angle, wood density, fibre properties and modulus of elasticity in Pinus radiata D. Don corewood." Forest Ecology and Management 258.9 (2009): 1924-1931.
There is also a lot of detailed within-tree variation in wood property data based around the SilviScan technology and the work of Rob Evans. e.g 
Medhurst, Jane, et al. "Intra-specific competition and the radial development of wood density, microfibril angle and modulus of elasticity in plantation-grown Eucalyptus nitens." Trees 26.6 (2012): 1771-1780.
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Hi,
I am looking at an innovative way to present some data for a article I am currently writing. I have measured the impact point between a putter and golf ball using a mechanical putting robot, whereby stroke kinematics are standardised. Along with human participants where variation has occurred with stroke kinematics. To present the differences between the two I'd like to map them through a stereographic projection. I don't have access to MATLAB unfortunately so am looking for alternative methods to complete this if possible.
Thanks 
Ashley
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Hi Ashley,
May I suggest you to use Scilab (http://www.scilab.org/), which is a FREE computation software initially  developed by the French Research Institute on Artificial Intelligence (INRIA) and which is quite as powerful as Matlab ?
Best regards,
Philippe.
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I assessed biomechanical parameters during running and I would like to estimate joint stiffness. Is it possible? If yes, how should I do it?
Is there some paper talking about this?
Thank you very much!
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I recall reading some of Neville Hogan's papers on joint stiffness which could be relevant and helpful to answering your question.  Those works were done at MIT in 80's.
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We conducted a study, where three investigators with different experience levels measured joint range of motions. We calculated the ICC an 95% for each combination of the there investigators (s. table). We found significant differences when looking at the 95% CI. (do you know a test to calculate?)
We now want to calculate norm values. Should we use the mean values of the three investigators with different skill sets or the mean of the two investigators with the highest ICC scores (All vs. HP-SFB)?
Thank you very much for your help!
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To calculate norms, you want to use the most accurate scores. In your situation, these would be the scores from the experienced tester/s. If you have gross differences between testers, was this random error or systematic error (did you use 1-way or 2-way ICC? Did you compare means with an F-test?). One almost has to assume, barring evidence to the contrary, that disagreement was due to the inexperienced tester.
Was the highest ICC between the two more experienced testers? I'm not sure about your last question - what is HP-SFB?
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Hello researchers,
I would like to know about various researches happening around the world to determine maximum torque that can be exerted by human hands to rotate a hand wheel. 
The result of one such research is provided in the link below:
Any update on same type of research is appreciated.
Thank you in advance.
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Dear all,
  Greetings, I am interested in creating a full body model for Vicon (With Marker set) using the clusters to find the joint center unlike the plug in gait model which has got individual and wand markers.
The idea is to find the reliable joint center for all the major joints thereby reducing the error percentage in the 3D motion analysis (especially in terms of angle interpretations).
While post capturing the same data can be imported into matlab to find the angles and associated graphs for the same.
I will be more than happy to go on with a collaborative study on this. 
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Vasanth,
The marker placement strategy can certainly dictate how you determine the underlying skeletal kinematics.  There are, for example, the point cluster method by Andriacchi et al and minimum marker (less than 3 per body segment) method we developed which would use mathematical optimization to enforce the rigidity of underlying linkage.  Hope this helps.
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According to strain-stress diagram of the Achilles tendon, one can consider one linear and one nonlinear part before rupture. It is important to see which of these two area should be considered in vibration analysis. 
Is there any study (book, paper, etc) reporting that how much strain (what percent) occurs during running? 
Thank you in advance
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Hi Arash, the following may give you some idea altough its quite difficult to determine the strain using ultrasound during dynamic activities such as running
J Exp Biol. 2014 Sep 1;217(Pt 17):3159-68. doi: 10.1242/jeb.100826. Epub 2014 Jun 19.
Tendon elastic strain energy in the human ankle plantar-flexors and its role with increased running speed.
Lai A1, Schache AG1, Lin YC1, Pandy MG2.
Cheers
Steve
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Please advise.
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Hi Angadkumar,
Here are some links that may help you with gait data on impaired and non-impaired individuals. On the Hicks and colleagues paper see the "Appendix A. Supplementary materials".
Good luck!
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Hello everybody,
I want to work on human motion using three-axis acceleration, but I do not have a standard dataset. Do you know any dataset in this feild?
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Hi Vahid
See if this can help you; multi-sensing data from a variety of daily activities:
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I have to setup a lab for gait analysis . Please suggest me what are the tools required for the same and which color background i should go for ( green, black or blue) . 
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Dear Mr Prakash,
Are you talking about a full gait analysis lab with 3D motion capture (for kinematics), forceplates (for dynamics), electromyography, etc..., or maybe only electronic walkway and/or video? Is it mainly a clinical gait lab or not?
The answers to your request (which material) will depend on your needs. Please give some more details. 
Regarding color background,
if you are using mocap system with passive markers (reflective), as Vicon system, better way is to try to reduce the reflectance value of your environment (i.e. laminate floor, walls), even if recent cameras and software allow to deal with reflectance. So a choice of matte color is surely better.
For the color itself, it depends your feelings. It only has to allow you to get a good color contrast for video quality purpose. You can look at usual choice of color in clinical settings and effect of colors on mood and behavior.
I hope this will help you in your thinking.
Best regards,
AG.
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I am trying to measure plantar pressure in badminton players when they make the shift to the net for linking with lower body injuries and need to have speed variable at which they are shifting around the court. Does anyone have a similar laboratory study with which to help me?
Thanks in advance
Raúl
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Hi Raul,
In addition to using such cameras, one can also utilize an accelerometer together with the tracker to measure speed and change in direction.
You can then also download and use the simple free software of Kinovea to see the analysis that you want.
Hope this helps.
Regards,
Habib
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I'm interested in this product by XSens for sports kinematics analysis, and I'm looking for feedback from users of this system in a context of biomechanical research :
I'm aware that inertial systems are prone to serious limitations compared to optical motion capture, including positional drift and magnetic disturbance. Do we have to (re)calibrate (too) often ?
Moreover, I guess it is not trivial to transfer from the XSens "functional axes" to true anatomical axes ?
And finally, what are your experience with the new wireless XSens Awinda system ? Do you experience instabilities or dropouts during the acquisitions ?
Thank you very much
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Hello Félix ,
I am a Master students and I am using that system for my research. As you say they are prone to drift and magnetic disturbances. 
I use them inside of a Human Motion Lab therefore magnetic disturbances are high. You are suppose to use the KiC no magnetometers when you expect non-homogeneus disturbances, however switching to that fusion engine didn´t help much because then drift is worse than magnetic distortions. One way around it is to find a "magnetically safe" spot and calibrate it always there. I find the need to calibrate them on top of  a 40cm high wooden step to avoid disturbances from the ground.
That is the main issue I've found. If you use them outside the lab it might get better, I cannot give you feedback about that. 
Regarding the wireless system I haven't had problems with that. I record about 3hours per experiment but I do notice that instabilities are  more likely to occur when battery is about 50%, so you kind of have to hurry up with your experiments.
I think it is a usefull technology, once you find the tricks to make the best out of it. 
I hope this is helpful.
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i have a clubfoot model and a corrective orthosis (special shoe) model i designed. i want to simulate the deformation of the foot due to the forces that act on it while its inside this orthosis.
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The first studies in which the characterisation and simulation of the lower limbs and the interconnection of the skeletal and muscular behaviours were attempted, were those by (Hoy, Zajac and Gordon 1990), who developed a musculoskeletal model of the human lower extremity to allow computer simulation. This model incorporates the salient features of muscle and tendon, specifies the musculoskeletal geometry and musculotendon parameters of 18 musculotendon actuators, and defines the active isometric moment about the knee and ankle joints. In (Tang and Hui 2007), the effect of the human foot’s tendons on the deformation of the foot surface was analysed. This stresses the importance that modelling has, not only of muscles and bones, but tendons as well as there are also certain forces that have effects on the system’s modelling and simulation, affecting the final foot surface deformation. Later research by these authors (Tang and Hui 2009) widened ligament-tendon modelling using forces related to curves and mass-springs that deform the foot surface, simulating the tendon’s position. There are contributions related to the simulation of plantar pressures obtained through the application of force on a foot (Antunes et al. 2007) in which, through finite element techniques, a foot is modelled according to the pressures measured on the foot plantar area, taking the influence of the foot’s bones and the application of a certain force into account.
These models are difficult to apply in the industry. In the previously mentioned models, the anatomical information of the bone structure of the limb to be deformed is needed, including the muscular-tendon representation of the foot, and this requires high cost equipment to be available, such as a CT scanner, as well as the software for the reconstruction and later linking of the geometry represented by the skeleton and the foot surface in order to carry out the deformation. It is therefore necessary to include the following constraints in the definition of the model: Efficiency, in the acquisition of the foot geometry with a short timeframe and at a low cost; Effectiveness, for the application of deformation techniques that make the deformation and positioning of the foot possible with the available information and subject to the previous constraint.
In the attached link you will find a paper where we present a cage-based model to simulate the deformation process of the foot. This model is efficient and precise for the requiriments of the foottwear industries.  I hope this paper will be useful to you.