The Sternocleidomastoid (SCM) muscle has two heads—sternal and clavicular—that contribute to different tension lines depending on the direction of movement and posture. Here are the typical tension lines: 1. Sternal Head: • Tension tends to run vertically along the neck from the sternum (manubrium) up to the mastoid process behind the ear. • Activities like forward head posture or excessive neck flexion can increase tension along this line. 2. Clavicular Head: • The tension follows a more obliqu