Leg muscles’ force as a system of levers

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Discussion Overview

The discussion revolves around the breakdown of total force exerted by leg muscles into individual forces for each muscle group, conceptualizing the leg as a system of levers. The scope includes aspects of biomechanics, muscle optimization, and the application of inverse dynamics.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant inquires about methods to decompose total force F exerted by the legs into forces from individual muscle groups, suggesting a lever system approach.
  • Another participant notes that the problem is underdetermined and emphasizes the need for an optimization criterion to achieve a unique solution, mentioning the use of inverse dynamics and muscle optimization.
  • Software tools like OpenSim are suggested for modeling and solving the problem, particularly if simplified to a 2D scenario with fewer muscles.
  • There are corrections regarding the terminology, with one participant pointing out the use of "undermined" instead of "underdetermined," and another participant acknowledging the correction.

Areas of Agreement / Disagreement

Participants generally agree on the need for an optimization criterion and the use of software tools for analysis. However, the discussion includes some confusion over terminology and the nature of the problem, indicating that not all aspects are fully resolved.

Contextual Notes

The discussion highlights limitations related to the complexity of the problem, the need for specific assumptions in modeling, and the potential for simplification in analysis.

Who May Find This Useful

This discussion may be useful for individuals interested in biomechanics, muscle dynamics, and those seeking to understand the application of inverse dynamics in analyzing human movement.

KataruZ98
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TL;DR
How can I calculate the force exerted by each muscle group in a jump?
If I know a person has exerted total force F with their legs and I’m interested in breaking down said force in smaller forces exerted for each involved muscle group - how can I do it? With a basic level of understanding of human anatomy I can divide the leg as a series of levers but how can I specifically find force exerted by each lever?

EDIT: I’m aware “smaller” is not the correct word, but still..
 
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KataruZ98 said:
If I know a person has exerted total force F with their legs and I’m interested in breaking down said force in smaller forces exerted for each involved muscle group - how can I do it? With a basic level of understanding of human anatomy I can divide the leg as a series of levers but how can I specifically find force exerted by each lever?
Note that this is an underdetermined problem, so you need to specify an optimization criterion to get a unique solution. You use inverse-dynamics to get the external joint torques from the ground reaction force, and then muscle optimization to get the muscle forces that balance these external torques.

You can use software for that:
https://simtk.org/projects/opensim

If you simplify it to 2D and just a few muscles, then you might get something that you can solve by hand.
 
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A.T. said:
Note that this is an undermined problem, so you need to specify an optimization criterion to get a unique solution. You use inverse-dynamics to get the external joint torques from the ground reaction force, and then muscle optimization to get the muscle forces that balance these external torques.

You can use software for that:
https://simtk.org/projects/opensim

If you simplify it to 2D and just a few muscles, then you might get something that you can solve by hand.
Ah, I see. Thank you very much, I’ll see what I’ll be able to do.
 
A.T. said:
undermined
I suspect that the correct word is underdetermined.

There are some nasty repetitions in there to entice the fingers to skip ahead in the sequence and no spell check to save you.
 
jbriggs444 said:
I suspect that the correct word is underdetermined.
Yes, thanks. Fixed it.
 
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