I have an undergrad degree in Physics from U of Toronto, but university physics is unnecessary to analyse figure skating bio-mechanics. A basic understanding of geometry and conservation laws comes in handy to build technique. Sustained lean is not possible without motion and is a fundamental of figure skating. In physics terms, "lean" involves the spatial orientation of the centre of mass compared to the point of contact with the ice. The relationship of lean, speed, arc, and rotation is of paramount importance to distinguish the sport and underpin its beauty. Those four concepts are related through the law of conservation of angular momentum. Other concepts of physics such as friction, leverage, the gravitational and centripetal forces, energy, and Newton's third law are helpful to gain insight.