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I conducted OpenSim CMC to obtain hamstring forces for drop landing using OpenSim’s example gait2392_simbody.osim model. The muscle force values from my CMC results are much greater than the estimated forces from previous researches (inverse dynamics and EMG).

Peak hamstring forces/(body weight) :
Semimembranosus 2.168
Semitendinosus 1.203
Biceps femoris mlh 2.352
Biceps femoris msh 1.5

I need your help:
1. How to change the input CMC settings that will result in smaller or greater hamstring forces?
2. Provide any hamstring force data for comparison.

Thank you in advance,
Di-An

Hi Di-An,

Can you provide more information about the your height and type of landing? I mean if it was both legs or one leg.

Please look at your quad forces as well. what are their values in terms of B.W? also look at your GRF if they have been applied correctly.

If you give me more information about these parameters I can give you better answer.

Regards,
Hossein

Hossein,

Please see the following information:

Subjects performed bilateral drop landings from a height of 40 cm. GRFs from both left and right forceplates were applied correctly in OpemSim.

Peak forces/(body weight) :

GRF (Right+Left) 6.32
Rectus femoris 4.41
Vastus medialis 2.05
Vastus intrmedius 2.10
Vastus lateralis 2.16

Thank your for your help.
Di-An

Di-An,

They may look great value. But you should check if you reserve actuators are small or not.

Tim has said that:

"Check the reserves in _CMC_Actuation_force.sto file. If reserves are significant (>2N/2Nm) "

then these actuators are acting to compensate for insufficient muscle strength to achieve desired kinematics tracking. You could either increase muscle strength, or penalize reserve actuators higher (reduce optimal_force value for the actuator)."

Hope this may help. If not, please let's know if you have changed any parameters in actuator files for muscles, reserve and residuals.

BTW, Which EMG papers do you compare your results with?

Cheers,