Throwing a baseball overhead
Muscle 1: Pectoralis major
Action: As a whole, adducts and medially rotates arm at shoulder joint
Innervation: Medial and lateral pectoral nerves
Muscle 2: Deltoid
Action: Extends forearm at elbow joint
Innervation: Radial nerve
Kicking a ball
Muscle 1: Quadratus femoris
Action: Extends leg at the knee joint and flexes thigh at the hip joint
Innervation: Nerve to quadratus femoris
Muscle 2: Biceps Femoris
Action: Flexes leg at knee joint and abducts thigh at hip joint
Innervation: Tibular and fibular nerves from sciatic nerve
Doing sit-ups
Muscle 1: External oblique
Action: Trunk flexion; compresses abdominal viscera
Innervation: Intercoastal nerves, subcostal nerves, iliohypogastric nerve
Muscle 2: Rectus abdominus
Action: Trunk flexion; flexes vertebral column and compresses abdomen
Innervation: Intercoastal and subcostal nerves
Breathing
Muscle 1: Diaphragm
Action: Contraction of this muscle causes it to flatten; primary muscle of breathing
Innervation: Phrenic nerves
Muscle 2: Intercostal muscles
Action: Mechanical support to the thoracic cage
Innervation: Intercostal nerves