During an contraction, the muscle develops tension without changing in length. An isometric contraction occurs at the of a muscle contraction and during prolonged activities. During an isotonic contraction, the muscle shortens even though the level of is maintained. During an isotonic contraction, a can be moved. The act of a muscle maintaining tension while it lengthens is called an isotonic contraction. During an isotonic eccentric contraction, a muscle is allowed to without going limp.