Human locomotion is typically more complex than insect locomotion. Humans use what are known as dynamically stable gates. When the center of mass is plotted as a human walks, it looks like an inverted pendulum motion. Potential energy at the peak is converted into kinetic energy in the next step, the the kinetic energy is recovered and converted back into potential energy again. This is visible in figure 1. Even when a human is standing still they are not very stable. They are using their muscles to insure that they remain balanced on their feet. If they did not, then the slightest perturbation would knock them over and they would fall. So humans maintain stability by constantly adjusting the muscles of their body to insure that they do not fall. This is what is meant by dynamic stability.