Trunk Rotation Muscles (PDF)

# 28th lecture Theoretical Part: Trunk Rotation. ## Objectives At the end of this lecture the student will be able to: 1. Identify the primary muscles involved in trunk rotation. 2. Identify the range of motion of trunk rotation. ## Content 1. Primary muscles involved in trunk rotation. 2. Rang...

# 28th lecture Theoretical Part: Trunk Rotation. ## Objectives At the end of this lecture the student will be able to: 1. Identify the primary muscles involved in trunk rotation. 2. Identify the range of motion of trunk rotation. ## Content 1. Primary muscles involved in trunk rotation. 2. Range of motion of trunk rotation. ## Trunk Rotation Motion ### Primary Muscle: a. External oblique muscle. b. Internal oblique muscle. ### Accessory Muscles: a. Latissimus dorsi. b. Semispinalis. c. Multifidus. d. Rectus abdominis ## Range of motion & fixation: In back lying position, rotation of thorax is possible until scapula on side of forward shoulder is raised from table as shown in figure 1. ## Factors limiting motion: 1. Tension of annulus fibrosus between vertebrae. 2. Tension of oblique abdominal muscles on side opposite those being tested 3. In thoracic area, tension of costovertebral ligaments. ## Anatomy of external oblique muscle. ### Origin: Anterior angles of lower eight ribs (Fig. 2). ### Insertion: a. Outer anterior half of iliac crest. b. Inguinal ligament. c. Public tubercle and crest. d. It interlaces with aponeurosis of opposite muscle forming Linea alba, extending from xiphoid process to symphysis pubis. ### Action: a. It rotates trunk. b. It supports abdominal wall and assists forced expiration, aids raising intraabdominal pressure. ### Nerve supply: Anterior primary rami (T7-12) ## Anatomy of Internal oblique muscle: ### Origin: - Lumbar fascia. - Anterior two thirds of iliac crest. - Lateral two thirds of inguinal ligament (Fig. 3). ### Insertion: a. Costal cartilages of 8th to 12th ribs. b. Crest of pubis and medial part of pectineal line. c. Lina alba. ### Action: a. It rotates trunk. b. It supports abdominal wall and assists forced expiration, aids raising intraabdominal pressure. ### Nerve supply: Anterior primary rami (T7-12) ## Image Descriptions **Figure 1: Trunk rotation motion.** Shows a person laying supine with their legs extended and their left shoulder raised, illustrating trunk rotation. **Figure 2: External oblique muscle.** A skeletal illustration highlighting the external oblique muscle. The muscle is shown with its origin at the lower 8 ribs and insertion at the iliac crest, the inguinal ligament, and the pubic crest. **Figure 3: Internal oblique muscle.** A skeletal illustration highlighting the internal oblique muscle. The muscle is shown with its origin at the iliac crest and the inguinal ligament and insertion at the costal cartilages of the 8th to 12th ribs, the crest of pubis, and the linea alba.