The direction of an explicitly applied distributed load must be given with reference to a local or global coordinate system in the spatial frame, but its magnitude must be with reference to the undeformed reference (or material) area. That is, the relation between the true force f acting on the current area da and the specified distributed load F acting on the material area dA is f da= FdA. When the solid is subjected to an external pressure, p, the true force on a surface element acts with magnitude p in the current area da in the normal direction n:

where both the normal n and area element da are functions of the current displacement field.

Another view of how to interpret the load, is to express it in the first Piola-Kirchhoff stress tensor P via the following formula:

where the normal n0 corresponds to the undeformed surface element. Such a force vector is often referred to as the nominal traction.