Fig. 4. A vector field plot of forces at nodes computed after the cell moved two body lengths. The interior node forces (red) are applied to the substrate; the cell body interface node forces (blue) are applied throughout the substrate beneath the cell body. The magnitude of the forces are proportional to the lengths of the arrows. The forces applied to the center of the cell body interface are 100 pN. The total forward translocation force on the cell body is 1000 pN. The traction forces at the rear of the lamellipod are 10 pN per node. Because of the strong substrate adhesion and because there is no gradient in the bundling stress, the traction forces decrease to 1 pN per node at the leading edge. There is also no noticeable anisotropy in the traction forces.