what is the origin of the primary muscle used in a chin up
Chin-up Both pull-ups and chin-ups are among the best[citation needed] exercises for back and overall upper body conditioning. However, they target the muscles a bit differently. Both exercises will work the latissimus dorsi and biceps, but standard chin-ups—with an underhand grip—place more emphasis on the biceps.
Pectoralis major muscle The pectoralis major (/ˌpɛktəˈreɪlɪs ˈmeɪdʒər/) (from Latin: pectus, breast) is a thick, fan-shaped muscle, situated at the chest (anterior) of the human body. It makes up the bulk of the chest muscles and lies under the breast. Below (deep to) the pectoralis major is the pectoralis minor, a thin, triangular muscle. In sports as well as bodybuilding, the pectoral muscles may colloquially be referred to as "pecs", "pectoral muscle" or "chest muscle" due to its being the larger and most superficial muscle in the chest area.