What function does the sternocleidomastoid muscle have?

The sternocleidomastoid muscle plays a crucial role in neck movement, specifically in neck flexion and rotation. When this muscle contracts on one side, it causes the head to tilt towards that side while simultaneously rotating it to the opposite side. This allows for a greater range of motion as it helps to turn the head and flex the neck forward when both sides contract together. Understanding the anatomical position and function of the sternocleidomastoid is essential for correctly assessing neck injuries and for therapeutic exercises in chiropractic practices, making it vital for chiropractic assistants to know this muscle's role. The other options reference functions that are not associated with the sternocleidomastoid; thus, recognizing its specific purpose helps clarify how neck dynamics work during various movements.