8.2.1 Lower-limb joint loads in an unsupported model

When there is no contact with the floor, the model is unbalanced because no reaction forces at the supports counteract the effect of gravity.

A static analysis of the whole body cannot be performed under these conditions. However, Ergoniza Intelligent calculates and displays the joint loads by assuming that the pelvis remains fixed in space. The results are equivalent to those for a situation in which the model is held static by a rigid restraint applied at the pelvis, a circumstance that must be taken into account when interpreting them.

When the model remains unsupported, loads at the wrists, elbows, shoulders, and L5/S1 joint are calculated as described in Section 8.1. Lower-limb joint loads are calculated analogously, but starting at the ankles and proceeding upward through the knees to the hips.

This virtual fixation of the pelvis interrupts load transmission between the torso and the lower limbs. Consequently, the forces and moments calculated at the L5/S1 joint are not transmitted to the hips, and the loads on each leg are calculated independently.