For a golf swing motion as shown in the following, I receive an overloaded muscle configuration near the end of the swing (late follow through phase). Do you think according to the motion type, It is logical to get overloaded muscle error?
1- I suppose that the problem is not from the GRF since when I load the model without the muscles, there is no problem in joint moment calculation.
2- Ankle flexion is between 40 and 43 degrees in the overloaded muscle period. I tried to change the AnklePlantarFlexion range of motion to maximum value of 45 instead of 40 but was not successful.
3- My concern is that the problem may originate from a wrong modeling technique by me?! However, when I use PCSAfactor equal to 3 for the overloaded muscles, I do not receive error. Is it acceptable?
Any other suggestion to address the problem would be greatly appreciated.
A quick observation from me. The direction of the ground reaction force on the right leg does not look right to me. Would they not be pushing backwards with the foot (and not forward as the force indicates)? Could one or more of the measured forces or moments be named incorrectly?
Maybe the following animation can help more:
I think according to the motion it seems correct. However, It is difficult to say that it is correct for sure. Anyway, the overload muscle configuration starts many steps after the direction of the force changes from backward to forward.
Which forces do you mean? from C3d file?
Yes, I was talking about the forces and moments from the c3d file. It looks like the overloading occurs because the ground reaction force (GRF) creates a large ankle plantarflextion moment because of the horisontal component of the GRF. I am not a golf player, but it seems odd to me that such a large moment should occur on the foot during a swing.
That is why I was asking if some variables by mistake could be swapped in the c3d file.
Also, it also strikes me that the centers of pressure under both feet move outside the feet.
Actually, golf is a complex motion and it is not easy to say at which moment, what should be the direction of the GRF and this may vary from subject to subject. I have another subject with a different swing technique and for this subject, the GRF under the right foot is almost vertical. Maybe that is the nature of the golf and it produces large moment in the ankle joint. Unfortunately, ankle joint is not studied well in the literature and make it difficult to judge if the GRF and the corresponding moments in the ankle joint here are correct or not.
What is your opinion about this?
It stills seems strange to me that such large horisontal forces should occur on that leg for a golf swing, but it is not somrthing I know for sure. I would probably recommend to do some sanity checks on the force plates and check that under known load directions that you also get those all way into the AnyBody model.
I do not think increasing the PSCAfactor that much makes sense unless you can show that their ankle muscles are really that much stranger than average subjects.
The only other thing I can think of is that they could be relaying on the passive stiffness in the ankle. If that is the case, you may have to more accurately model this passive stiffness.
Thanks for your reply.
I think it is shown exaggerated by AnyBody but actually it is not a large force at that moment for the right foot (red arrow is x axis):
and there are some other youtube videos from other labs that show the same direction for the right GRF at this moment:
I think this GRF direction varies between different subjects with different golf swing techniques.
Additionally, as stated in the literature, Proneus Longus (one of the over loaded muscles in my study) is among the most active muscles during a golf swing.
Anyway, I think you are right and this force and its lever arm, causes overloaded muscle problem.
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