1. Throwing a baseball overhead
a) Muscle: Latissimus dorsi; Action: Extends, adducts, and medially rotates arm at shoulder joint; draws arm inferiorly and posteriorly. RMA: Elevates vertebral column and torso; Innervation: Thoracodorsal nerve
b) Muscle: Deltoid; Action: Lateral fibers abduct arm at shoulder joint; anterior fibers flex and medially rotate arm at shoulder joint; posterior fibers extend and laterally rotate arm at shoulder join; Innervation: Axillary nerve
2. Kicking a ball
a) Muscle: Tensor fasciae latae; Action: Flexes and abducts thigh at hip joint; Innervation: Superior gluteal nerve
b) Muscle: Piriformis; Action: Laterally rotates and abducts thigh at hip join; Innervation: Sacral spinal nerves S1 or S2, mainly S1
3. Doing sit-ups
a) Muscle: 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) Muscle: External oblique; Action: Acting together (bilaterally), compress abdomen and flex vertebral column; acting singly (unilaterally), laterally flex vertebral column, especially lumbar portion, and rotate vertebral column; Innervation: Thoracic spinal nerves T7–T12 and the iliohypogastric nerve
4. Breathing
a) Muscle: 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) Muscle: 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