1. Throwing a baseball overhead
A.
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 joint
Innervation: Axillary nerve
B.
Muscle: Pectoralis major
Action: As a whole, 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.
Muscle: Biceps femoris
Action: Flexes leg at knee joint and extends thigh at hip joint
Innervation: Tibial and fibular nerves from sciatic nerve
B.
Muscle: Semitendinosus
Action: Flexes leg at knee joint and extends thigh at hip joint
Innervation: Tibial nerve from sciatic nerve
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: Transversus abdominis
Action: Compresses abdomen
Innervation: Thoracic spinal nerves T8-T12, iliohypogastric nerve, and ilioinguinal 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: Internal intercostals
Action: Contraction draws adjacent ribs together to further decrease anteroposterior and lateral dimensions of thoracic cavity during forced exhalation
Innervation: Thoracic spinal nerves T2-T12