Adding Mass to a body doesn't affect the fibre force after simulation of the arm26 model

[Chiedozie Okefienam]

Hello

Please I'm trying to do a biomechanical analysis of the biceps brachii when a mass of 4kg and 12kg dumbbell is added during the dumbbell curl exercises.

Upon adding the mass, I realized that the fibre force doesn't change after simulation.

Mass was added to the radius_ulna_hand body to reflect the weight of the dumbbell before simulation by changing the mass of the body from 1.5kg to 5.5kg, the same method was used to add a mass of 12kg which changed the new mass to 13.5kg

After performing inverse kinematics with the new mass, the fibre forces doesn't change

I'll like to enquire if there's a better way to add mass in such a way that it reflects on the fibre force after simulation and inverse kinematics is carried out.

Thank you for your time.

[Mohammadreza Rezaie]

After performing inverse kinematics with the new mass, the fibre forces doesn't change

Hi, Inverse Kinematics (IK) tool only computes joints angles. I suspect that you are observing muscles forces via Plotter tool. Segments masses don't have any effect on IK and Plotter/Y-Quantity/*fiber-force results. You may want to use Static Optimization or Computed Muscle Control (CMC) tools to compute muscles forces.

Some examples can be found here: https://simtk-confluence.stanford.edu:8 ... +Tutorials

Hope this helps.