Myosin heavy chains are the heavy-chain isoforms of myosin, the principal contractile protein of muscle. They constitute the head region of the myosin molecule, the part that binds actin and hydrolyses ATP during the contraction cycle, while the tail regions assemble into the thick filaments of the myofibril. In meat science they play a particularly important role in the heat-induced gelation of myosin: on heating, the heavy chains unfold and cross-link into the three-dimensional network that gives cooked sausages, frankfurters, and restructured meats their firm, elastic texture. Also known as heavy meromyosin, these isoforms vary between muscle types and species, influencing the gelling behaviour, water-holding capacity, and final bite of processed meat products. Understanding heavy-chain composition helps manufacturers select raw materials and set salt, pH, and cooking schedules for consistent product quality.