Either of the two protein fragments produced when the muscle protein myosin is digested by the enzyme trypsin. Light meromyosin forms the tail portion of the myosin molecule, while heavy meromyosin contains the head regions that bind actin and hydrolyse ATP during muscle contraction. Studying these fragments helped scientists unravel how muscles contract at the molecular level, revealing the sliding-filament mechanism. In meat science, understanding myosin and its breakdown products matters because post-mortem changes in these proteins govern meat tenderness: the state of the contractile proteins determines whether meat is tender or tough, and ageing allows enzymes to modify them favourably.