1. THROWING A BASEBALL OVERHEAD
a. Latissimus dorsi
Action: Extends, adducts, and medially rotates arm at shoulder joint; draws arm inferiorly and posteriorly.
Innervation: Thoracodorsal nerve
b. Pectoralis Major
Action: Adducts and medially rotates arm at shoulder joint; clavicular head flexes arm, and sternocostal head extends flexed arm to side of trunk.
Innervation: Medial and lateral pectoral nerves.
2. KICKING A BALL
a. Quadriceps femoris
- Rectus femoris
- Vastus lateralis
- Vastus medialis
- Vastus intermedius
Action: All four heads extend leg at knee joint; rectus femoris muscle acting alone also flexes thigh at hip joint.
Innervation: Femoral nerve
b. Biceps Femoris
Action: Flexes leg at knee joint and extends thigh at hip joint.
Innervation: Tibial and fibular nerves from sciatic nerve
3. SIT-UPS
a. Rectus Abdominis
Action: Flexes vertebral column, especially lumbar portion, and compresses abdomen to aid in defecation, urination, forced exhalation, and childbirth. RMA: Flexes pelvis on the vertebral column.
Innervation: Thoracic spinal nerves T7–T12.
b. Transversus abdominis
Action: Compresses abdomen
Innervation: Thoracic spinal nerves T8–T12, iliohypogastric nerve, and ilioinguinal nerve.
4. BREATHING
a. Diaphragm
Action: Contraction of diaphragm causes it to flatten and increases vertical dimension of thoracic cavity, resulting in inhalation; relaxation of diaphragm causes it to move superiorly and decreases vertical dimension of thoracic cavity resulting in exhalation.
Innervation: Phrenic nerve, which contains axons from cervical spinal nerves (C3–C5).
b. External intercostals
Action: Contraction elevates ribs and increases anteroposterior and lateral dimensions of thoracic cavity, resulting in inhalation; relaxation depresses ribs and decreases anteroposterior and lateral dimensions of thoracic cavity, resulting in exhalation.
Innervation: Thoracic spinal nerves T2–T12.