Figure 11. External equilibrium of a sauropod, depending on neck posture.

External equilibrium is determined by the moments of segment weights about the hind feet, which must be equal to the ground reaction force F_v1 or F_v2, respectively, exerted by the forefeet with a lever arm l_f (F_v * l_f). Note that the tail exerts a nose up-rotating torque, because of its negative lever arm (1₇) Low neck position gives the weight forces of head and neck (F₁, F₂) long lever arms (1₁, 1₂). By contrast, a high neck position entails shorter lever arms (1₃, 1₄) of the same weight forces as before (F₁ and F₂). This reduces the load on the forefeet: F_v2 in comparison to F_v1. The share of body weight carried by the hindlimbs (F_h1 or F_h2, respectively, is total body weight – F_v The elevation of the neck is equivalent to a shift of the CoM in dorsal and caudal direction.