Calculation of CoM

[xiaoxia yan]

Hi,

Hope everything is going well with you.

I want to calculate the center of mass (CoM) for children during gait but have been unable to find any relevant code. Could you please assist me with this?

Best regards,
xia

[Matt Petrucci]

Hi Xia,

Hope you are well also.

We have some example Python code here to extract COM mass values. You can also use this Google Colab.

[xiaoxia yan]

Hi,

Thank you for your response, and I hope all is well with you.

With your assistance, I have managed to understand how to calculate the Center of Mass (CoM) in OpenCap, which involves segmental mass and the segmental CoM.

I am researching children's gait and need to calculate their CoM. The ratios of segmental weight to total body weight in children vary with age and differ significantly from those in adults. For instance, the proportion of head weight to total body weight in a 3-year-old child is different from that in a 40-year-old adult. Many studies have reported these variations. Understanding the principle of segmental mass is crucial for accurate CoM calculation. Once I grasp this concept, I intend to develop methods that adjust the segmental mass calculations based on the correlation between segmental mass and age to suit children better.

Could you please tell me how to solve this problem?

Best regards,
Xia

[Matt Petrucci]

Hi Xia, you could consider creating a model with the correct segment weights. Once you have a properly scaled model, you can then perform inverse kinematics in OpenSim using the marker data that you obtained from OpenCap.

There is documentation to get you started with scaling and inverse kinematics here: https://opensimconfluence.atlassian.net ... e+Dynamics