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. Deltoid
Action: Lateral fibers abduct arm at shoulder joint, anterior fibers flex and medially rotate arm at shoulder joint, and posterior fibers extend and laterally rotate arm at shoulder joint
Innervation: Axillary nerve
2. Kicking a ball
A. Biceps femoris
Action: Flexes leg at knee joint and extends thigh at hip joint
Innervation: Tibial and fibular nerves from sciatic nerve
B. Gluteus maximus
Action: Extends thigh at hip joint and laterally rotates thigh; helps lock knee in extension
Innervation: Inferior gluteal nerve
3. Doing sit-ups
A. Rectus abdominis
Action: Assists the flat muscles in compressing the abdominal viscera, stabilizes the pelvis during walking, and depresses the ribs
Innervation: Thoracoabdominal nerves (T7-T11)
B. Transverse abdominis
Action: Compresses and provides structural support to adjacent abdominal structures
Innervation: Thoracoabdominal nerves (T7-T11), Iliohypogastric nerve, and ilioinguinal nerve
4. Breathing
A. Diaphragm
Action: Primary muscle in inspiration, contracts and flattens during breathing
Innervation: Phrenic nerves and lower intercostal nerves
B. External intercostals
Action: Elevate ribs at their costovertebral joints and provide structural support to intercostal spaces
Innervation: Adjacent intercostal nerves (anterior rami of thoracic nerves)