Hi everyone,
I'm currently working on a project to try and calculate elastic power/energy in the plantarflexors in walking and running using OpenSim.
To calculate the power, I'm using the forces determined through static optimisation and the lengths determined through muscle analysis. However, when I compare the lengths of the muscle fibers and tendons to other in vivo studies, I have found the contribution of the muscle fibers to the change in MTU length is much greater than expected and attributed more towards muscles with long fibers and short, stiff tendons. As the plantarflexors consist of short fibres and long, compliant tendons, we would expect the tendons to contribute to the change in MTU length far greater than the fibers.
I was just wondering if anyone had a solution to my problem where I can tinker with OpenSim allowing the tendons to contribute to the change in MTU length instead of the muscle fibers. Thus I can use the tendon and fiber lengths to calculate the power contribution of each component.
Thank you all for your help.
Adrian
Tendon elastic energy
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Matthew Millard
- Posts: 24
- Joined: Fri Aug 01, 2008 7:17 am
Re: Tendon elastic energy
Hello,
Static optimization uses a rigid tendon muscle model exclusively, so none of the results using this tool will yield results that include tendon stretch. If you'd like to see how the tendon is stretching you will have to use CMC and one of the muscle models with an elastic tendon to compute your muscle forces.
If you don't have a deadline pressing it might be best to wait for the next release of OpenSim which should appear soon. This new release of OpenSim includes an overhauled Thelen2003Muscle model, new muscle models, and a much richer reporting of the internal muscle model quantities. Included in this new set of properties is tendon strain, tendon strain velocity, tendon potential energy, tendon power and tendon stiffness.
Matt
Static optimization uses a rigid tendon muscle model exclusively, so none of the results using this tool will yield results that include tendon stretch. If you'd like to see how the tendon is stretching you will have to use CMC and one of the muscle models with an elastic tendon to compute your muscle forces.
If you don't have a deadline pressing it might be best to wait for the next release of OpenSim which should appear soon. This new release of OpenSim includes an overhauled Thelen2003Muscle model, new muscle models, and a much richer reporting of the internal muscle model quantities. Included in this new set of properties is tendon strain, tendon strain velocity, tendon potential energy, tendon power and tendon stiffness.
Matt