The beating heart of a mechanical watch is a spring-mounted balance wheel making several oscillations every second at a constant rate, delicately poised on a wire-thin staff. This complex assembly should be safely boxed and placed somewhere undisturbed, but is instead worn on the wrist, exposed to the full range of the wearer’s physical activities. Shock resistance refers to various systems built into the movement to protect the balance from disruptive forces and impact, to deliver consistent oscillations without breaking.