I am using c3d files to determine joint forces for subjects during walking.
In my c3d files, there is body weight information (groups–processing–bodymass).
Can AnyBody use the weight information automatically? Ortherwise I have to change the body weight in TrialSpecificData (GaitLowerExtremity).
In the c3d file in GaitLowerExtremity, there is no information about body weight (GaitNormal0001 - 0003.c3d). So I guess I have to change the body weight information if I want to use this kind of data. Am I right?
Yes, you are right.
AnyBody does not use the body weight information in the C3D files.
So as you know, you have to input the real body weight in the TrialSpecificData file.
Although I need to modify the body weight by hand, I think there is no need to change the body length information in GaitLowerExtremity. Because GaitLowerExtremity optimize these information automatically. Am I right?
Besides the body weight, is there any other things I should care in order to run my own c3d files?
Another question:
My c3d files only have one force plate, meaning that the ground reaction force can only be applied to one foot (say the left foot). During swing phase of the same foot (left foot), no ground reaction force is applied to the other foot (right). Does this affect the hip joint force of the left foot? In other words, does the ground reaction force information of one foot affects the hip joint force of the other foot?
Just a quick comment. In the TrialSpecificData file, it is possible to make a reference to the body mass information in the c3d file so you do not have to copy it manually for every subject. Just write the appropriate reference in the TrialSpecificData file.
You may have to adjust the initial segment lengths for each subject if the optimizer has trouble finding a solution. This is typically necessary if the subject’s segments are much smaller or larger than the ones specified in the TrialSpecificData file.
Best regards
Michael Skipper Andersen
The AnyBody Research Group
From my understanding, the ‘pelvis residuals’ are caused by the unballanced measured ground reaction force and the body weight (upper body). The ground reaction force transmitted to the plevis cannot offset the upper body weight, causing the residuals. Am I right?
Does these residuals affect the hip joint forces which are my research emphasis? If so, could you explain the reason. Because I really cannot understand how can the ground reaction force on one foot affect the hip joint force of the other foot in inverse dynamics.
And if the hip joint force is not accurate due to the lackage of the other one force plate, is there anything I can do to enhance the accuracy? Now all of my data contain only one force plate. I think it is better for me to just modify the codes in GaitLowerExtremity.