Questions: Muscle Design for Tug-of-War

A. Explore and edit OpenSim model, storage, and controls files

1. How many degrees of freedom are in the Tug_of_War_Millard.osim model? What are they?

2. What are the values of the four primary muscle parameters (maximum isometric force, optimal fiber length, tendon slack length, and pennation angle at optimal fiber length) for each muscle?

3. Which XML elements in the controls file (Tug_of_War_controls.xml) describe the excitation signals?

B.  Examine the effect of tendon-to-fiber length ratio on isometric contraction simulations

1. Plot the muscle force vs. time for all five tendon-to-fiber length ratios on a single set of axes.

2. Describe any differences you observe between the curves in terms of the rate of force development and the steady-state force achieved.

3. Using what you know about muscle mechanics and dynamics, explain the difference in muscle force response with respect to changes in tendon-to-fiber length ratio.

C.  Examine the effect of tendon-to-fiber length ratio on isokinetic contraction simulations

1. Plot the tendon force vs. time for all five tendon-to-fiber length ratios on a single set of axes.

2. Describe any differences you observe between the curves in terms of the rate of force development and the steady-state force achieved.

3. Using what you know about muscle mechanics and dynamics, explain the difference in muscle force response with respect to changes in tendon-to-fiber length ratio.

D.  Design your best Tug-of-War competitor

1. Before you begin designing, outline your strategy for building the best muscle.

2. During your testing phase, document your process and results.

3. Create a brief report (no more than 2 pages) describing your final result. Your report should include the following sections:

   1. Introduction

      • List the objectives of your design.

   2. Methods

      • Outline the steps you used in your design process.

   3. Results

      • Include mathematical analyses, parameter sensitivity studies, and/or results of prototype muscle simulations.

      • Describe the final muscle design, including a demonstration that each criterion is met.

   4. Discussion

      • Justify your final design.

      • Evaluate the strengths and potential weaknesses of your design (e.g., the conditions under which you expect your muscle to perform well/poorly).

   5. References, if any were used

Reflection

Provide some suggestions for future offerings of the course:

• Were any elements of this lab confusing? How could they be improved?

• What resources did you use? Was anything missing or unclear in the OpenSim documentation?

• What was the best part of this lab? What would you add to improve the lab?