The large mouth bass has more than a big mouth. It’s fast and powerful. Oomph! That vacuum cleaner action, it’s made possible by the way muscles and bones are arranged — bear with me now — in a four bar linkage with three degrees of freedom. It’s not as complicated as it sounds. A four bar linkages just means four rigid bars linked together in a loop. Four bar linkages are very familiar to engineers. And once you start looking for them, you find them everywhere. In bicycles, for instance, they translate pedaling motion to forward motion. The same arrangement gives oil pumps the power to push oil up from deep in the earth And what about those degrees of freedom? Basically that describes how the joints connecting the bars move. Three degrees of freedom in a bass jaw allows for fine tuned strikes in any direction. But why study a bass? I study how the bones in fish heads move because fish heads are a great model system for understanding how joints work and how bones move. The human knee has a four bar linkage. That allows a transfer of power from muscles in the hip and pelvis to the leg. That’s the same maximization of muscle power that’s going on in the bass’s mouth. But how did we look inside? Researchers at Brown University used X-ray video and motion capture animation. And they came up with the most exact representation, so far, of how that fishy four bar linkage works. For now, this is basic science, but it could one day be useful to you and me, at least if your knees are anything like mine.