what form of exercise does the muscle contract and does not lengthen nor shorten
Muscle contraction An isometric contraction of a muscle generates tension without changing length.[1][3][4][5] An example can be found when the muscles of the hand and forearm grip an object; the joints of the hand do not move, but muscles generate sufficient force to prevent the object from being dropped.
Myofibril Myofibrils are composed of long proteins including actin, myosin, and titin, and other proteins that hold them together. These proteins are organized into thick and thin filaments called myofilaments, which repeat along the length of the myofibril in sections called sarcomeres. Muscles contract by sliding the thick (myosin) and thin (actin) filaments along each other.