7.7 Modeling seated posture in a chair

Ergoniza Intelligent distinguishes between a posture seated on the floor and a posture seated on a chair. This distinction is necessary because, although the pelvis may be positioned low relative to the floor in both cases, the mechanical nature of the supports differs. Consequently, the method used to calculate the reactions at the supports and the loads on the lower-limb joints also differs.

When the model is seated on the floor, the reactions at the supports are calculated as described in Sections 7.5 and 7.6 for knee and hip contact with the floor. However, when the posture corresponds to sitting in a chair, Ergoniza Intelligent considers part of the body to be supported by an external surface other than the floor: the chair seat. Under these conditions, although the feet may remain in contact with the floor, the distribution of the reactions at the supports and the transmission of loads through the lower kinematic chain differ from those in bipedal stance or a kneeling posture.