1. Throwing a baseball overhead
A. Upper Trapezius
Action: upward rotation of the scapula
Innervation: anterior rami of the spinal nerves C3 and C4, spinal accessory nerve (cranial nerve XI)
B. Anterior Deltoid
Action: contraction in the wind-up phase, moving arm forward
Innervation: axillary nerve
2. Kicking a ball
A. Quadriceps
Action: extend the leg at the knee joint, flex the thigh at the hip joint
Innervation: femoral nerve
B. Gluteus medius
Action: hip extension, lateral abduction during whip-up
Innervation: superior gluteal nerve
3. Doing sit-ups
A. Internal Obliques
Action: flexes the trunk by drawing the pubis towards the xiphoid
Innervation: lower six thoracic spinal nerves (T7-T12)
B. Rectus abdominis
Action: flexes torso
Innervation: thoracoabdominal nerves
4. Breathing
A. Diaphragm
Action: contracts and flattens chest cavity
Innervation: phrenic nerve
B. External intercostals
Action: lifts and expands rib cage (exhalation)
Innervation: anterior rami on spinal nerves T1-T11