OpenSim

Introduction to OpenSim

OpenSim is Stanford's open source software for biomechanical modeling, simulation, and analysis of the musculoskeletal system. For this assignment, we used version 4.5. In OpenSim, we opened the model and under the Coordinates tab, we could change the angle of certain parts. I made changes to hip_flexion_r for the thigh to be parallel to the ground, knee_angle_r for the shin to be perpendicular to the thigh, and ankle_angle_r for the foot to flex up.

OpenSim Tutorial 1

I followed this tutorial

1. Degrees of Freedom

a. Use the Coordinates panel to view the degrees of freedom of the model. How many degrees of freedom, in total, does the model have? List the degrees of freedom of the right leg

Counting all of the slides under the coordinates panel, the model as 23 degrees of motion while the right leg has 6.

b. All models are approximations. Compare the degrees of freedom in the model to the degrees of freedom in your lower limbs. Give an example of a joint motion in the model that has been simplified. Give an example of a motion that is not included in this model.

OpenSim's model shows fewer degrees of freedam than what is actually present in the human body. For example, the knee only moves like a hinge in OpenSim, while I am able to slightly rotate it in real life.

3. Modeling Limitations

a. Zoom in on the right hip, and display only the glut_max3_r muscle (right hip extensors group). Examine this muscle for the full range of hip flexion angles. What problems do you see with the path of glut_max3_r through the range of motion? In what ways are point-to-point representations of muscle paths a simplification of musculoskeletal geometry?

Stretching gluteus maximus

Positive rotation

Flexion the other way

Negative rotation

Adduction positive

Adduction negative

I noticed that some of the motions were not realistic, where it did not follow the natural way of anatomy. The muscles are also unusually straight, where it should be curved in real life. For the the path of Glut_Max3_R, it's definitely oversimplified

Fiber Length vs. Joint Angle

4. Muscle Fiber Length vs. Joint Angle

a. Study the plot of muscle fiber length vs. knee angle. For each of the rectus femoris and vastus intermedius, do you expect the fiber-length curve be different if the right hip was flexed? Why or why not?

I would expect it to be different. If the right hip is flexed, the rectus femoris will be stretched more because the distance between the pelvis and the tibia increases, causing the muscle fibers to elongate. However, The vastus intermedius fiber-length curve would not be significantly different if the right hip was flexed because this muscle only crosses the knee joint.

b. In the Coordinates window, adjust the model's right hip flexion to 45 degrees (save the pose as r_hip_flex_45), add rectus femoris and vastus intermedius fiber-length curves for 45º hip flexion. Compare the muscle curves for the model with an unflexed hip you plotted previously to the curves for the model that you just plotted. How have the curves changed? Explain your findings. How can bi-articular muscles complicate analysis?

The graph reflect what I thought, where the the rectus femoris changes when the hip is flexed and the vastus intermedius fiber-length curve remaining unchanged because it only crosses the knee joint.

Crouch Gait Simulation

Normal gait model navigation window

Normal next to crouch gait model

Comparing the walking knee angle of the two gaits

6. Range of Motion

b. Label the times at which heel strike and toe-off occur, and the stance and swing intervals.

c. What is the range of motion for knee flexion during stance phase for normal gait?

Flexion ranges from about 0° (full extension) to 15-20° of flexion

d. How does knee flexion range of motion for crouch gait compare to that of normal gait?

In crouch gait, the range of knee flexion is significantly greater than in normal gait. While normal gait involves knee flexion ranging from 0° to 60°, crouch gait is seen to involve knee flexion between 60-70° or.

IMG_2690.mp4

Normal gait walking

IMG_2692.mp4

Crouch gait walking

IMG_2693.mp4

Both gaits walking in sync

OpenSim Tutorial 2

I followed this tutorial

Seeing the muscle properties before surgery

Selected the muscle point and the name ECU_pre-surgery shows up

Muscle post surgery

1. Which motion is expressed in positive angles: wrist flexion or wrist extension?

Wrist Flexion

2. Which motion is expressed in positive angles: radial deviation or ulnar deviation?

Radial Deviation

3. What are the functions of the Extensor Carpi Ulnaris (ECU) muscle? Check or circle all that apply.

Ο wrist extension Ο wrist flexion Ο radial deviation Ο ulnar deviation Ο hip extension

4. What are the functions of the Extensor Carpi Radialis Brevis (ECRB)? Check or circle all that apply.

Ο wrist extension Ο wrist flexion Ο radial deviation Ο ulnar deviation Ο hip extension

5. In these plots, given how the model defines the wrist flexion degree of freedom, is wrist extension moment denoted by positive or negative values?

Wrist extension moment can be denoted by positive or negative values based on the adopted sign convention of the model.

6. What happens to the maximum moment of the wrist extensors if the ECU muscle is transferred to the ECRB? Hint: Remember, one of the goals of the surgery is to increase wrist extension strength.

Transferring the Extensor Carpi Ulnaris (ECU) muscle to the Extensor Carpi Radialis Brevis (ECRB) location would increase the maximum isometric extension moment of the wrist extensors, shifting the deviation moment from ulnar to radial.

7. In these plots, is the sign of an ulnar deviation moment positive or negative?

Negative

8. What happens to the maximum moment of the ulnar deviators if the ECU muscle is transferred to the ECRB location?

It shifts the maximum moment of the ulnar deviators from ulnar to radial deviation

9. One goal of this tendon transfer surgery is to decrease excessive ulnar deviation. Has your simulated surgery achieved this goal? Why or why not?

Yes

10. What is the peak value of the ECU extension moment before transfer? At what flexion angle does it occur? Note: Remember, extension moments are negative on the plots.

(-70, -0.76)

11. What is the peak value of the ECU extension moment after transfer? At what flexion angle does it occur?

(-0.707, -1.93)

OpenSim Soccer Kicking Contest

Soccer Kick

For the contest, we were challenged to adjust the property values of the leg muscles and angle the body is oriented in to get the maximum velocity. We began by running the default and getting a max speed of 9. Then we tried to maximize each muscle individually while keeping the others at default, just to see what happened. We found that the hamstrings would hold back the speed, while the Soleus muscle contributes most to speed. So, we made hamstrings 0 and everything else 9000, the maximum. This brought our max speed to 10.57. Then, we started changing the angle, because we thought doing it at a diagonal would allow the ball to gather more momentup and go faster. That seemed to work. where it got us into the 13 range. Playing around more, the max we got it to was 13.6.

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