A bar’s metallurgical properties are the primary determining factors in the mechanical properties of the bar, or in more practical terms, how the bar behaves in the lifter hands against gravity and the force generated. The yield strength of the metal determines how much stress it can take before permanent deformation, while the tensile strength measures its breaking, or fracture point. The softer, or lower strength a bar is - the more it bends under load. The harder, or higher yield/tensile strength a bar is - the less it bends under load. Each of these options varies the feel or oscillation of a bar under load, and the art of bar design comes in determining the fine dance between the bars properties and how it behaves under load, against gravity. One downside of higher tensile strength is brittleness, or catastrophic failure (not bending, but cracking under tension).