Motion capture with Body weight support harness

[Jacob Wells]

Does anybody have any experience of collected 3D data from participants wearing a body weight suport harness?
We woud usually use vicon lower limb PIG but I have concerns over the placements of the ASIS & PSIS in relation to the harness.

If anyone has any tips or advice I'd be very happy to hear them.

Thanks

[Colin Bond]

Re: Motion capture with Body weight support harness

I have done this before with hockey players skating on a treadmill. You are right that the straps from most styles of harness tend to run directly over the ASISs, which is an issue for modeling techniques like PiG. I have tried a couple approaches to address this, some of which would take you away from using PiG:
1) If you are going to continue using a regression equation technique to estimate hip joint center location:
a) Capture calibration with ASIS markers on. Remove them for the motion trials and than virtually recreate their positions assuming you have 3+ additional markers on pelvis segment. You would have to add either a cluster over the sacrum and/or iliac crest markers to the PiG model. You could then continue using PiG pipelines to calculate joint centers and kinematic, or which ever regression technique you end up using.
b) Same process as above but instead of placing real markers on the ASIS for calibration, use a digitizing pointer to identify the ASIS location during a calibration.
2) Use a functional hip joint estimation technique, though you would need several additional markers compared to PiG.

3) If a full harness is not absolutely critical, just use an upper body/chest only one but put it on your participant backwards so that the connection for the carabiner is in the back.

[Edmund Cramp]

Re: Motion capture with Body weight support harness

I have no current experience with this but the issue is, are the markers in the correct location and can they be seen by the motion capture system? So I think your choices are to use a harness that does not cover the marker sites, or place the markers on the harness over the locations. If you go with the later approach them you will have to make sure that the harness does not change the marker locations by sliding to one side or the other during the trial.