RRA and residual forces with weight lifting

[John De Witt]

I am doing an anlaysis of persons performing squat exercises using about 80kg of load. When I look at residual loads at the pelvis, they are rather large. If I run and RRA analysis (I am using Arnold's 2 legs + torso model scaled to my subject), I get reductions in mass of most segments to about 50% of their original mass.

Is this occurring because the RRA is assuming that the only load on the person is their body weight? If so, how to I tell the model about the load on the person's back. I thought this was accounted for in the GRF, but I am wondering if perhaps the large residuals are due to the external weight issue.

John