Tires â Retreading is less expensive than new tires and is a large portion of this cost. Although mere pennies per mile, an average tire can cost over $250 and annual tire expenses can exceed $4,000 ($0.03 per mile), enough to purchase 16 new tires annually, but still not enough to replace every tire of an 18-wheeler.
With the head in a forward position, a passive tensile force is created in the hyoid muscles resulting in hyoid muscle tension, causing the mandible to be depressed and translated posteriorly. The patient is therefore forced to contract the temporalis and masseter muscles to keep the mouth closed.
The muscle lies deep to the sternocleidomastoid in its superior portion, and deep to trapezius in its inferior portion. The muscle acts as a shaker of the head, it causes neck extension and lateral flexion. Other muscles that extend and rotate the head include the semispinalis capitis and semispinalis cervicis (also laterally flexes the head). The superior portion of trapezius also acts as a lateral flexor of the neck.