The splenius capitus muscle will be stretched most effectively by rotation of the head and neck. The splenius capitus is a broad, strap like muscle found at the posterior neck. It attaches at the base of the skull and inserts at the vertebrae of the cervical and upper thoracic spine. It is involved in head extension, in addition to lateral flexion and rotation of the cervical spine. 

The rectus abdominis muscle originates from the pubic crest and pubic symphysis and inserts into the cartilage of the fifth to seventh ribs and the xiphoid process. It functions as a flexor of the vertebral column, especially in the lumbar region and is capable of compressing the abdomen to aid in urination, defecation, forced exhalation, and childbirth.

The external oblique muscle bilaterally compresses the abdomen and flexes the vertebral column. Unilaterally it can laterally flex the vertebral column, particularly in the lumbar region, as well as rotate the column.

The internal oblique muscle normally has its origin from the iliac crest, inguinal ligament, and thoracolumbar fascia. Its insertion is into the cartilage of the last three or four ribs as well as the transverse processes of the first four lumbar vertebrae.

The transversus abdominis muscle originates from the iliac crest, inguinal ligament, lumbar fascia, and cartilages of the inferior six ribs. It inserts into the xiphoid process, linea alba, and pubis. It functions as a compressor of the abdomen.

The risorius muscle is primarily responsible for drawing the angle of the mouth laterally as in smiling. Major functions of the orbicularis oris and orbicularis oculi muscles include the shaping of the lips during speech and closing the eyes, respectively. The masseter muscle is the main muscle for mastication.  

The sternocleidomastoid muscle bilaterally causes flexion of the cervical vertebrae and extension of the head. Unilaterally, it can cause lateral flexion and rotation of the head to the side opposite of the contracting muscle. It originates on the sternum and clavicle and inserts onto the mastoid process.

The orbicularis oculi opens closes the eye. The muscle that opens the eye is called the levator palpebrae superioris.

The occipitofrontalis covers the skull from the occipital bone to the frontal bone. It is a muscle of facial expression.

Because it attaches superior to the hyoid bone, the geniohyoid does not depress the hyoid rather, it elevates it. The omohyoid (both inferior and superior bellies), the thyrohyoid, sternothyroid, and the sternohyoid muscles are collectively called the infrahyoid muscles, due to their attachments being inferior to the hyoid bone. Because of this attachment site, they depress the hyoid bone.