The trapezius muscle refers to a broad, flat muscle that spans the posterior of the neck and upper thoracic region. This muscle is known by several synonyms, including the "trap muscle," the "ascending muscle," and the "descending muscle." Additionally, the trapezius muscle is sometimes referred to as the "triangular muscle" due to its shape, which resembles an upside-down triangle. The trapezius muscle helps to support the neck and head, as well as to control movements of the shoulder blades and upper back. Regular exercise, including strength training, stretching, and mobility work, can help to keep the trapezius muscle healthy and functioning properly.