Possible error with Pmech calculation

Dear AnyBody,

I have created a simple elbow flexion with the Standing Model and looked at two cases, with and without a 100 N load at the hand in the -y direction. Please see the attached image. The Pmech output is the same in both cases and this seems like a mistake unless Pmech is only intended to account for inertial loads.

Thanks again,

Jeremy

Dear Jeremy,

If you only have changed the magnitude of the external force at the hand, then it seems that those two models have same kinematics.

Then it means that those two models have same mechanical energy(kinematic + potential) of the system(Emech value of AnyBodyStudy),
then those two models will have same mechanical power(Pmech) values.

If you are interested in the ‘sum of mechanical power from human muscles’,
then you should not use this Pmech value of AnyBodyStudy object because it considers all force elements in the system.

If you want to calculate the sum of mechanical power from only human muscles, then you should see the ‘Pmt’ value of AnyMuscle objects.

All human muscles in the AnyBody Human Model have beenderived from this AnyMuscle class, you can make your own script to sum all these Pmt values from individual muscles.

I hope this may be helpful to you.

Best regards,
Moonki

Moonki,

I think I understand and I have just one more quick question. My model has only torque muscles (moment generators at the joints) so my question is the following: Can I still get a useful Pmt value with these ‘torque muscles’? If not, that is okay - the Pmech value is still useful to us - as long as I fully understand what it is.

Hopefully I didn’t offend anyone by suggesting there might be error. I have been impressed with the help I’ve received thus far on the forum!

Thank you,

Jeremy

Hi Jeremy,

Of course you can calculate the mechanical power from ‘torque muscles’.
As we know we usually use AnyGeneralMuscle class object for that purpose.

But we have found some problem in Pmt value in case of AnyGeneralMuscle objects,
so we would like to suggest you an alternative way to do that.

Mechanical power is just product between torque and velocity.

Attached please find our example to help you understand this concept clear.

If you run the attached AnyScript model,
then you can find ‘muscle_mechanical_power_calculation’ AnyOutputFun in the AnyBoduStudy object.
Then I guess that you can understand how to calculate the mechanical power values from AnyGeneralMuscle objects.

If you have more questions, please ask to us here again.

Best regards,
Moonki

1 Like

Thanks for your considered answer to a dumb question :slight_smile: I could, of course, calculate power! I am sure this will be one of the easier issues to figure out…

Thanks again and have a good weekend,

Jeremy