EMG

Hello!

I have uploaded a new file EMG.zip with matlab figures of Elbow Flexion
movement. There is one without loads and one with 4kg load. I am wondering about
the result of the activity of the Biseps Caput Breve. In the figure representing
the motion with loads in the hands it seem quite reasonable. But without any
loads in the hands the inverse dynamic analysis gives funny results of the
Biseps muscle activity. You cannot see any cyclic pattern that follows the
motion. The MaxMuscleActivity for the hole system, (is not in the figures), is
almost constant about 0.24 for the motion without loads. If the Biceps is the
major muscle force for the motion, the MaxMuscleActivity and the Activity of the
Biceps should look similar, right?

Can you take a look at the EMG.zip and tell me what is wrong with the muscle
activity?

I have not been able to use the latest Repository 5, because then I need to
update my AnyBody licence. But I think I can get enough results out of the
version I have, so far.

Thanks for all help

Best Regards
Signe


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Hi Signe

The activities you get for the model with no load on looks a very
jumpy, you are right.

This is most likely due to numeric unstability which is caused by
the low load on the model. I have tried to add a small linear
penalty to the model (RecruitmentLpPenalty=1e-4) this is done in
the main file in the study folder. This means that if a muscle is
active it will always contribute to the objective function of the
recruitment solver due to this penalty factor.
The penalty solved the jumpy behaviour of the biceps muscle and i
obtained a clear pattern like the one you have for the model with
load in the hands.

You can read more about the LpPenalty in reference manual, please
try to play around with the size of it, it should in general be as
small as possible, while retaining the effect of removing the
jumps.

I still think you should run the model for a shorter time period
while using the same amount of time steps.

Best regards
Søren AnyBody Support

I have tried to run your model with different settings

— In anyscript@yahoogroups.com, Signe Jeppesen <signejeppesen@…>
wrote:
>
> Hello!
>
> I have uploaded a new file EMG.zip with matlab figures of Elbow
Flexion movement. There is one without loads and one with 4kg load.
I am wondering about the result of the activity of the Biseps Caput
Breve. In the figure representing the motion with loads in the hands
it seem quite reasonable. But without any loads in the hands the
inverse dynamic analysis gives funny results of the Biseps muscle
activity. You cannot see any cyclic pattern that follows the motion.
The MaxMuscleActivity for the hole system, (is not in the figures),
is almost constant about 0.24 for the motion without loads. If the
Biceps is the major muscle force for the motion, the
MaxMuscleActivity and the Activity of the Biceps should look
similar, right?
>
> Can you take a look at the EMG.zip and tell me what is wrong
with the muscle activity?
>
> I have not been able to use the latest Repository 5, because
then I need to update my AnyBody licence. But I think I can get
enough results out of the version I have, so far.
>
> Thanks for all help
>
> Best Regards
> Signe
>
>
>
>
> ---------------------------------
> Brings words and photos together (easily) with
> PhotoMail - it’s free and works with Yahoo! Mail.
>
> [Non-text portions of this message have been removed]
>