1. Throwing a baseball overhead
Muscle 1: Deltoids
Action: Shoulder flexion; medial rotation
Innervation: Axillary nerve (C5, C6)
Muscle 2: Triceps Brachii
Action: Elbow extension
Innervation: Radial nerve (C6-C8)
2. Kicking a ball
Muscle 1: Rectus Femoris
Action: Knee extension; hip flexion
Innervation: Femoral nerve (L2-L4)
Muscle 2: Gluteus Maximus
Action: Hip extension; external rotation
Innervation: Inferior gluteal nerve (L5-S2)
3. Doing sit-ups
Muscle 1: Rectus Abdominis
Action: Trunk flexion
Innervation: Thoracoabdominal nerves (T7-T11)
Muscle 2: External Oblique
Action: Flexion of the trunk; rotation to opposite sides
Innervation: Thoracoabdominal nerves (T7-T11)
4. Breathing
Muscle 1: Diaphragm
Action: Primary muscle of respiration; expansion of thoracic cavity
Innervation: Phrenic nerve (C3-C5)
Muscle 2: Intercostal muscles (External Intercostals)
Action: Elevation of ribs during inspiration
Innervation: Intercostal nerves (T1-T11)