Buck: the energy that transforms stiffness into (stiff) movement. In bucks, not only the characteristic stiff-legged movement displays this energy, but the stiff projections from the head (called antlers). Note that in both cases, either in approach or flight, stiffness precedes movement. They are the same. In other words, buck energy is a way of harnessing the fluidity of muscle to the ability to hold ground. They are in continuous tension.