1. Throwing a Baseball Overhead
Muscle 1: Deltoid (Anterior)
Action: Flexes and medially rotates the arm.
Innervation: Axillary nerve (C5, C6).
Muscle 2: Triceps Brachii
Action: Extends the forearm at the elbow.
Innervation: Radial nerve (C6, C7, C8).
2. Kicking a Ball
Muscle 1: Quadriceps Femoris
Action: Extends the knee and flexes the hip.
Innervation: Femoral nerve (L2, L3, L4).
Muscle 2: Gluteus Maximus
Action: Extends and laterally rotates the thigh at the hip.
Innervation: Inferior gluteal nerve (L5, S1, S2).
3. Doing Sit-ups
Muscle 1: Rectus Abdominis
Action: Flexes the vertebral column, bringing the chest toward the pelvis.
Innervation: Thoracoabdominal nerves (T6-T12).
Muscle 2: Iliopsoas (Psoas Major and Iliacus)
Action: Flexes the hip.
Innervation: Lumbar plexus (L1-L3); Femoral nerve (L2-L4).
4. Breathing
Muscle 1: Diaphragm
Action: Contracts and flattens during inhalation.
Innervation: Phrenic nerve (C3, C4, C5).
Muscle 2: External Intercostals
Action: Elevates the ribs during inhalation.
Innervation: Intercostal nerves (T1-T11).