Figure 9 plots the ground forces on the real ant in the Z (vertical up) direction during the stance stage. For the front leg, the force magnitude present small variations during the whole stance stage. For the middle leg, the force magnitude increases initially, remains stable and decreases when the stance stage comes to the end. This creates a parabolic curve of the force profile. For the back leg, it presents a distinct peak during the first half of the stance stage, which is in consistent with the torque results in the simulation case.