The collagen molecule contains both rigid and flexible regions, and these may serve different purposes when the molecule is strained. It is thought that the more rigid sections transfer stress throughout the molecule, while the more flexible sections store elastic energy. The storage and dissipation of energy applied at joints is precisely what tendons and ligaments, which contain collagen, are meant to do. The observed elastic spring constant for collagen in humans is 3.7-4.0 GPa [4], but this value will change significantly with various factors, such as age (of the body the collagen was harvested from), and pH.