muscle contact forces

ARFA Essosnam · Post by **ARFA Essosnam** » Thu Mar 31, 2016 2:09 am

Hello everyone,
What can I Find the contact forces at the level of anchor points of muscles?
I Have done an inverse dynamics but I don't have this information.
Thanks.

jimmy d · Post by **jimmy d** » Thu Mar 31, 2016 8:10 am

It's unclear what you are asking for. Can you please further explain?

ARFA Essosnam · Post by **ARFA Essosnam** » Fri Apr 01, 2016 2:09 am

Ok. I will try to be clear enough.
Supposing that a muscle is fixed for example with a ground and a body.
how can I determine the force that muscles will apply to body and ground during the body movement?
do you think that inverse dynamics can deal with that? if not how can I do that? Thanks.

Dimitar Stanev · Post by **Dimitar Stanev** » Fri Apr 01, 2016 2:18 am

Hi,

Inverse dynamics solves for the joint torques given a motion. What you are interested is static optimization, which for a given motion computes the muscle forces and activations to achieve the motion.

On the other hand if you don't have a concrete motion and you are running your simulation in a forward manner (forward dynamics), you can interrupt the simulation at some intervals and get the muscle force. If this is what you want I would suggest you to see the API examples:

http://simtk-confluence.stanford.edu:80 ... I+Examples

Regards

ARFA Essosnam · Post by **ARFA Essosnam** » Fri Apr 01, 2016 2:36 am

thanks jim, your answer is very helpful.
I Have a specific movement. So I Will use static optimization to find muscle forces and activations.
Now, I want to know the relation between Inverse kinematics, Inverse Dynamics and Forward dynamics?
I think that we need motion from IK tools to perform Inverse Dynamics and then we need joints torques from Inverse dynamics and eventually muscle forces from static Optimization to perform a forward dynamic. am I right?

Dimitar Stanev · Post by **Dimitar Stanev** » Fri Apr 01, 2016 3:58 am

Hi,

You can check the user guide, it explains everything (how to use the tools, the theory, examples):

http://simtk-confluence.stanford.edu:80 ... %27s+Guide

IK transforms your recorded motion to joint space coordinates (time series of angles).
ID solved the equation of motion for the acting torques given position, velocity and acceleration of the general coordinates (the product of IK).
FD integrates the equation of motion for given input force and predicts what will be the motion trajectory.

F = ma -> ID
a = F / m -> integration with initial conditions you get v, x -> FD

ARFA Essosnam · Post by **ARFA Essosnam** » Fri Apr 01, 2016 5:28 am

thanks jim.

muscle contact forces

muscle contact forces

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Re: muscle contact forces